Search

This paper reports on a study that examined the quality of the learning environment of sandwich programmes in Ghana. The study used a sequential explanatory mixed method design and focused on tutors and 400 students of the programme. The Total Quality Management Theory, Expectation Confirmation/Disconfirmation Theory, Context, Input, Process, and Product Evaluation Model underpined the study. A disproportional stratified selection method was used to select 1,000 students and 50 tutors from each of the four teaching centres. While a purposive sampling method was employed to select 12 students and eight tutors involved in sandwich programmes for follow-up interviews. The data were collected using a questionnaire and an interview guide. The quantitative data was analysed using means and standard deviation, while the qualitative data were subjected to thematic analysis. These findings revealed that the tutors show concern for the welfare of the students and offer chances for student-teacher contact. However, big class sizes limit how much faculty can customise the learning environment. Also, students were friendly, helpful, cooperative, and supported one another during activities. The study recommended that the management of the Institute of Education and centre coordinators make every effort to secure spacious classrooms to help reduce large class sizes and increase opportunities for student-teacher interactions, cohesiveness, and students' participation in the classroom. In addition, tutors should foster an atmosphere that invites student interaction and identify students' strengths and weaknesses.

This paper reports on a study that examined the quality of the learning environment of sandwich programmes in Ghana. The study used a sequential explanatory mixed method design and focused on tutors and 400 students of the programme. The Total Quality Management Theory, Expectation Confirmation/Disconfirmation Theory, Context, Input, Process, and Product Evaluation Model underpined the study. A disproportional stratified selection method was used to select 1,000 students and 50 tutors from each of the four teaching centres. While a purposive sampling method was employed to select 12 students and eight tutors involved in sandwich programmes for follow-up interviews. The data were collected using a questionnaire and an interview guide. The quantitative data was analysed using means and standard deviation, while the qualitative data were subjected to thematic analysis. These findings revealed that the tutors show concern for the welfare of the students and offer chances for student-teacher contact. However, big class sizes limit how much faculty can customise the learning environment. Also, students were friendly, helpful, cooperative, and supported one another during activities. The study recommended that the management of the Institute of Education and centre coordinators make every effort to secure spacious classrooms to help reduce large class sizes and increase opportunities for student-teacher interactions, cohesiveness, and students' participation in the classroom. In addition, tutors should foster an atmosphere that invites student interaction and identify students' strengths and weaknesses.

In steel structures, a lot of attention is paid to lightweight structures, i.e. reduction of dead load without compromising structural safety, integrity and performance. Thanks to modern steel aluminium foam sandwich panel manufacturing technology a new possibility became available for lightweight structural design. Assessment and understanding of the behaviour of this sandwich panel under in-plane compression or flexure is crucial before its application in steel structures. Column buckling theory is considered and applied to the steel aluminium foam sandwich panel to evaluate its behaviour under in-plane compressive load. In this work, various assumptions are made to generalise Euler's buckling formula. The generalisation requires modification of the buckling stiffness expression to account for sandwich panel composite properties. The modified analytical expression is verified with finite element simulation employing various material models specific to steel face-plates and aluminium foam as well as various geometric imperfections. Based on this study, it can be concluded that Euler's buckling formula can be successfully modified and used in the prediction of the load-carrying capacity of a sandwich panel., Engineering Structures

The disruption of thyroid hormone homeostasis by hexabromocyclododecane (HBCD) in rodents is hypothesized to be due to HBCD increasing the hepatic clearance of thyroxine (T4). The extent to which these effects are relevant to humans is unclear. To evaluate HBCD effects on humans, the activation of key hepatic nuclear receptors and the consequent disruption of thyroid hormone homeostasis were studied in different human hepatic cell models. The hepatoma cell line, HepaRG, cultured as two-dimensional (2D), sandwich (SW) and spheroid (3D) cultures, and primary human hepatocytes (PHH) cultured as sandwich were exposed to 1 and 10 µM HBCD and characterized for their transcriptome changes. Pathway enrichment analysis showed that 3D models, followed by SW, had a stronger transcriptome response to HBCD, which is explained by the higher expression of hepatic nuclear receptors but also greater accumulation of HBCD measured inside cells in these models. The Pregnane X receptor pathway is one of the pathways most upregulated across the three hepatic models, followed by the constitutive androstane receptor and general hepatic nuclear receptors pathways. Lipid metabolism pathways had a downregulation tendency in all exposures and in both PHH and the three cultivation modes of HepaRG. The activity of enzymes related to PXR/CAR induction and T4 metabolism were evaluated in the three different types of HepaRG cultures exposed to HBCD for 48 h. Reference inducers, rifampicin and PCB-153 did affect 2D and SW HepaRG cultures’ enzymatic activity but not 3D. HBCD did not induce the activity of any of the studied enzymes in any of the cell models and culture methods. This study illustrates that for nuclear receptor-mediated T4 disruption, transcriptome changes might not be indicative of an actual adverse effect. Clarification of the reasons for the lack of translation is essential to evaluate new chemicals’ potential to be thyroid hormone disruptors by altering thyroid hormone metabolism.

Given the increasing importance of sustainability in product design, tools for designing products with low environmental impact are important for tackling problems in the future. One important measure of environmental impact is life cycle energy (LCE), which uses the cumulative amount of energy a product consumes over its’ lifetime as a proxy for environmental impact. In this work, the core topology and face sheet thickness of a sandwich beam are optimized for different material compositions with the goal to minimize the life cycle energy of the beam. A constraint on the mean compliance of the beam is used as a proxy for functional requirements. The problem is solved using a mixed-integer programming extension of the established Topology Optimization of Binary Structures (TOBS) method. Numerical examples indicate that the method is able to find feasible minimum LCE solutions with varying topologies and face sheet thicknesses., Part of proceedings: DOI 10.29327/566492, QC 20220906

A thin Lie algebra is a Lie algebra, graded over the positive integers, with its first homogeneous component of dimension two and generating, and such that each non-zero ideal of lies between consecutive terms of its lower central series. All homogeneous components of a thin Lie algebra have dimension one or two, and the two-dimensional components are called diamonds. Suppose the second diamond of (that is, the next diamond past) occurs in degree. We prove that if 5$]]>, then for some non-zero element of. In characteristic different from two this means is a sandwich element of. We discuss the relevance of this fact in connection with an important theorem of Premet on sandwich elements in modular Lie algebras.

This study investigates the influence of design parameters on the impact mitigation capacity of a new meta-panel that leveraged the coupled mechanisms of plastic deformation and local resonance to absorb energy from impact loading. The main objective is to minimize the force to be transmitted to the protected structures through mitigating the stress wave propagation by using local resonators. The meta-panel demonstrates the capability of filtering out the stress wave induced by impact loading with frequencies falling in its bandgaps. A numerical model is built and verified by the analytical solution with a good agreement in terms of the predicted frequency bandgaps. The meta-panel shows a substantial reduction in the mid-span deflection of the facesheets and an increase in the impact energy absorption as compared with the conventional sandwich panels. The peak reaction force of the meta-panel transmitted to the protected structure is also reduced significantly by more than 47% compared to its conventional counterparts. Furthermore, parametric studies are conducted to investigate the effects of the thickness of the hollow-truss bar, core material properties, and impact velocity on the meta-panels impact-resistant behaviour.

Honeycomb sandwich structures are widely used for cabin interior components in passenger aircrafts. The load introduction into the sandwich structure proves to be particularly critical. However, the verification takes place based on non-standardized tests abstracted from the application so that influences caused by boundary conditions and multiple load introduction points cannot be investigated. Moreover, these tests also do not allow comparisons of different designs. The variety of different test setups on component level has made the comparability of published results more difficult. This paper summarizes the state of the art of existing component tests. Based on that and using the example of an aircraft cabin partition, the existing test setups are checked for their suitability to cover all given load cases. New test setups with extended boundary conditions and several load introduction points are developed. For one test setup, test results are shown and compared to a conventional component test., Bundesministerium für Wirtschaft und Klimaschutz (BMWK)

aortic aneurysms involving the renal and visceral arteries are endovascular challenges, especially for emergencies. We report a case of ruptured thoracoabdominal aortic aneurysm (TAAA) in a morbidly obese 71-year-old man. The patient was admitted with a stable hemodynamic state. A computed tomography angiogram (CTA) revealed a contained ruptured TAAA with an occluded celiac trunk and left renal artery due to previous nephrectomy. Due to the emergency and his comorbidities, we performed an endovascular aortic repair with the sandwich technique and 2 chimneys. Two bridging stents (chimneys) were deployed between the aorta and the target vessels (superior mesenteric and right renal arteries) in a space created in-between 2 aortic straight endografts. Ten days postoperative, acute renal failure appeared and right renal stent occlusion was diagnosed on CTA. Unfortunately, no adequate kidney revascularization could be obtained, requiring permanent hemodialysis. At a 3-month follow-up visit, the patient did well with stable aneurysm dimensions. encouraging outcomes of chimney-EVAR techniques, comparable to those in published reports of fenestrated-EVAR and branched-EVAR, support this procedure as a valid off-the-shelf available alternative in emergency situations. Nevertheless, only few midterm results achieved are actually available and long-term outcomes are actually unknown.

Legislative demands force the automotive industry to reduce greenhouse gas (GHG) emissions. At the same time, crashworthiness must not be compromised. A ve-hicle’s GHG emissions, such as carbon dioxide, is dependent on its fuel consump-tion. Lowering the vehicle weight, reducing fuel consumption, will therefor reduce emissions. Thus, high performance lightweight materials and structures are on demand. Several methods for achieving high-performance lightweight components are available. One of the most successful approaches has been replacing mild steels with press-hardened steels, e.g. ultra high strength steels (UHSS). In the press-hardening process, a low-alloyed boron steel blank is austenitized followed by simultaneously forming and cooling. By controlling cooling rates, a martensitic microstructure can be obtained, resulting in components with superior properties compared to mild steels. Other methods of achieving lightweight components in-clude the usage of sandwich structures where stiff skins are bonded to a low-density core. In the present thesis, several types of sandwich structures are studied both numerically and experimentally. A UHSS sandwich with a bidirectionlly corru-gated core, intended for stiffness application, is manufactured and evaluated in three-point bending. Finite element models are utilized to recreate the three-point bend test. A large amount of finite elements are required for precise discretization of the core. The number of finite elements are reduced by replacing the sandwich with an homogeneous, equivalent model with input data obtained from analyzing representative volume elements (RVEs) of the core, subjected to periodic and ho-mogeneous boundary conditions. Good agreement is found between experiments and finite element models. A UHSS sandwich with a partly perforated core is evaluated numerically for energy absorption applications. Several hole configu-rations for the core are evaluated with respect to specific energy absorption.

Discrete material optimization (DMO) is a method, which was originally developed for designing composite structures via multi-material topology optimization principles. Current study applies DMO to sandwich structures with variable thickness in the core and face sheets. Each layer contains design variables for available materials. Materials are combined through interpolation schemes to define properties of the layer. The objective function (mass of the structure) and the failure constraints are interpolated via Rational Approximation of Material Properties (RAMP) in order to calculate with smooth variables, but achieve discrete results. This enables gradient optimization via Interior Point Optimizer (IPOPT) with constraints on maximum stress, wrinkling, and crimping. Structure is modeled by the finite element method, which calculates element forces and moments repeatedly as the stiffness of the structure changes during optimization. Element loads are used by the first-order shear deformation theory to evaluate the stresses in the layers to obtain failure constraints requested in each iteration by the gradient optimizer. Solution is demonstrated on the plate examples showing material distribution and discreteness level. In addition, constraint aggregation by Kreisselmeier-Steinhauser (KS) function was utilized to decrease the number of constraints in the optimization.

Discrete material optimization (DMO) is a method, which was originally developed for designing composite structures via multi-material topology optimization principles. Current study applies DMO to sandwich structures with variable thickness in the core and face sheets. Each layer contains design variables for available materials. Materials are combined through interpolation schemes to define properties of the layer. The objective function (mass of the structure) and the failure constraints are interpolated via Rational Approximation of Material Properties (RAMP) in order to calculate with smooth variables, but achieve discrete results. This enables gradient optimization via Interior Point Optimizer (IPOPT) with constraints on maximum stress, wrinkling, and crimping. Structure is modeled by the finite element method, which calculates element forces and moments repeatedly as the stiffness of the structure changes during optimization. Element loads are used by the first-order shear deformation theory to evaluate the stresses in the layers to obtain failure constraints requested in each iteration by the gradient optimizer. Solution is demonstrated on the plate examples showing material distribution and discreteness level. In addition, constraint aggregation by Kreisselmeier-Steinhauser (KS) function was utilized to decrease the number of constraints in the optimization.

Discrete material optimization (DMO) is a method, which was originally developed for designing composite structures via multi-material topology optimization principles. Current study applies DMO to sandwich structures with variable thickness in the core and face sheets. Each layer contains design variables for available materials. Materials are combined through interpolation schemes to define properties of the layer. The objective function (mass of the structure) and the failure constraints are interpolated via Rational Approximation of Material Properties (RAMP) in order to calculate with smooth variables, but achieve discrete results. This enables gradient optimization via Interior Point Optimizer (IPOPT) with constraints on maximum stress, wrinkling, and crimping. Structure is modeled by the finite element method, which calculates element forces and moments repeatedly as the stiffness of the structure changes during optimization. Element loads are used by the first-order shear deformation theory to evaluate the stresses in the layers to obtain failure constraints requested in each iteration by the gradient optimizer. Solution is demonstrated on the plate examples showing material distribution and discreteness level. In addition, constraint aggregation by Kreisselmeier-Steinhauser (KS) function was utilized to decrease the number of constraints in the optimization.

Legislative demands force the automotive industry to reduce greenhouse gas (GHG) emissions. At the same time, crashworthiness must not be compromised. A ve-hicle’s GHG emissions, such as carbon dioxide, is dependent on its fuel consump-tion. Lowering the vehicle weight, reducing fuel consumption, will therefor reduce emissions. Thus, high performance lightweight materials and structures are on demand. Several methods for achieving high-performance lightweight components are available. One of the most successful approaches has been replacing mild steels with press-hardened steels, e.g. ultra high strength steels (UHSS). In the press-hardening process, a low-alloyed boron steel blank is austenitized followed by simultaneously forming and cooling. By controlling cooling rates, a martensitic microstructure can be obtained, resulting in components with superior properties compared to mild steels. Other methods of achieving lightweight components in-clude the usage of sandwich structures where stiff skins are bonded to a low-density core. In the present thesis, several types of sandwich structures are studied both numerically and experimentally. A UHSS sandwich with a bidirectionlly corru-gated core, intended for stiffness application, is manufactured and evaluated in three-point bending. Finite element models are utilized to recreate the three-point bend test. A large amount of finite elements are required for precise discretization of the core. The number of finite elements are reduced by replacing the sandwich with an homogeneous, equivalent model with input data obtained from analyzing representative volume elements (RVEs) of the core, subjected to periodic and ho-mogeneous boundary conditions. Good agreement is found between experiments and finite element models. A UHSS sandwich with a partly perforated core is evaluated numerically for energy absorption applications. Several hole configu-rations for the core are evaluated with respect to specific energy absorption.

Methods for reducing weight of structural elements are important for a sustainable society. Over the recent years ultra high strength steel (UHSS) has been a successful material for designing light and strong components. Sandwich panels are interesting structural components to further explore areas where the benefits of UHSS can be utilized. The specific properties of sandwich panels make them suitable for stiffness applications and various cores have been studied extensively. In the present work, bidirectionally corrugated UHSS cores are studied experimentally and numerically. A UHSS core is manufactured by cold rolling and bonded to the skins by welding. Stiffness is evaluated experimentally in three-point bending. The tests are virtually reproduced using the finite element method. Precise discretization of the core requires large amounts of computational power, prolonging lead times for sandwich component development, which in the present work is addressed by homogenization, using an equivalent material formulation. Input data for the equivalent models is obtained by characterizing representative volume elements of the periodic cores under periodic boundary conditions. The homogenized panel reduces the number of finite elements and thus the computational time while maintaining accuracy. Numerical results are validated and agree well with experimental testing. Important findings from experimental and simulation results show that the suggested panels provide superior specific bending stiffness as compared to solid panels. This work shows that lightweight UHSS sandwiches with excellent stiffness properties can be manufactured and modeled efficiently. The concept of manufacturing a UHSS sandwich panel expands the usability of UHSS to new areas., Validerad;2020;Nivå 2;2020-05-14 (alebob)

Methods for reducing weight of structural elements are important for a sustainable society. Over the recent years ultra high strength steel (UHSS) has been a successful material for designing light and strong components. Sandwich panels are interesting structural components to further explore areas where the benefits of UHSS can be utilized. The specific properties of sandwich panels make them suitable for stiffness applications and various cores have been studied extensively. In the present work, bidirectionally corrugated UHSS cores are studied experimentally and numerically. A UHSS core is manufactured by cold rolling and bonded to the skins by welding. Stiffness is evaluated experimentally in three-point bending. The tests are virtually reproduced using the finite element method. Precise discretization of the core requires large amounts of computational power, prolonging lead times for sandwich component development, which in the present work is addressed by homogenization, using an equivalent material formulation. Input data for the equivalent models is obtained by characterizing representative volume elements of the periodic cores under periodic boundary conditions. The homogenized panel reduces the number of finite elements and thus the computational time while maintaining accuracy. Numerical results are validated and agree well with experimental testing. Important findings from experimental and simulation results show that the suggested panels provide superior specific bending stiffness as compared to solid panels. This work shows that lightweight UHSS sandwiches with excellent stiffness properties can be manufactured and modeled efficiently. The concept of manufacturing a UHSS sandwich panel expands the usability of UHSS to new areas., Validerad;2020;Nivå 2;2020-05-14 (alebob)

[ES] En el presente proyecto, se van a desarrollar materiales compuestos tipo sándwich mediante la técnica de moldeo por contacto de laminación manual. Para la obtención de las capas exteriores emplearán tejidos de carbono, lino y kevlar y para la parte interna, se ha fabricarán núcleos con la tecnología de impresión 3D (FDM) con material base de poliamida aditivada con carbono (ONYX) y reforzados con fibras continuas. La tecnología 3D de FDM (Fusion Deposition Modeling) consiste en utilizar un filamento termoplástico suministrado por un carrete o bobina que se funde por medio de un cabezal calefactado hasta el punto de fusión. El material fundido es suministrado a la plataforma de trabajo mediante una boquilla extrusora que se desplaza en los ejes X e Y. La plataforma, que se desplaza en Z, desciende un nivel cada vez que se aplica una capa, hasta finalizar la pieza. Además, en esta tecnología se puede incorporar fibras continuas con el fin de reforzar las estructuras. De esta forma se han conseguido obtener núcleos con estructuras hexagonales y reforzados con fibras continuas para mejorar las propiedades de resistencia mecánica y ligereza. Una vez fabricados los prototipos, se llevará a cabo una completa caracterización mecánica tanto a temperatura ambiente como a bajas temperaturas, y se complementará el proyecto con la evaluación del comportamiento al fuego de los distintos materiales obtenidos.

[ES] En el presente proyecto, se van a desarrollar materiales compuestos tipo sándwich mediante la técnica de moldeo por contacto de laminación manual. Para la obtención de las capas exteriores emplearán tejidos de carbono, lino y kevlar y para la parte interna, se ha fabricarán núcleos con la tecnología de impresión 3D (FDM) con material base de poliamida aditivada con carbono (ONYX) y reforzados con fibras continuas. La tecnología 3D de FDM (Fusion Deposition Modeling) consiste en utilizar un filamento termoplástico suministrado por un carrete o bobina que se funde por medio de un cabezal calefactado hasta el punto de fusión. El material fundido es suministrado a la plataforma de trabajo mediante una boquilla extrusora que se desplaza en los ejes X e Y. La plataforma, que se desplaza en Z, desciende un nivel cada vez que se aplica una capa, hasta finalizar la pieza. Además, en esta tecnología se puede incorporar fibras continuas con el fin de reforzar las estructuras. De esta forma se han conseguido obtener núcleos con estructuras hexagonales y reforzados con fibras continuas para mejorar las propiedades de resistencia mecánica y ligereza. Una vez fabricados los prototipos, se llevará a cabo una completa caracterización mecánica tanto a temperatura ambiente como a bajas temperaturas, y se complementará el proyecto con la evaluación del comportamiento al fuego de los distintos materiales obtenidos.

[ES] En el presente proyecto, se van a desarrollar materiales compuestos tipo sándwich mediante la técnica de moldeo por contacto de laminación manual. Para la obtención de las capas exteriores emplearán tejidos de carbono, lino y kevlar y para la parte interna, se ha fabricarán núcleos con la tecnología de impresión 3D (FDM) con material base de poliamida aditivada con carbono (ONYX) y reforzados con fibras continuas. La tecnología 3D de FDM (Fusion Deposition Modeling) consiste en utilizar un filamento termoplástico suministrado por un carrete o bobina que se funde por medio de un cabezal calefactado hasta el punto de fusión. El material fundido es suministrado a la plataforma de trabajo mediante una boquilla extrusora que se desplaza en los ejes X e Y. La plataforma, que se desplaza en Z, desciende un nivel cada vez que se aplica una capa, hasta finalizar la pieza. Además, en esta tecnología se puede incorporar fibras continuas con el fin de reforzar las estructuras. De esta forma se han conseguido obtener núcleos con estructuras hexagonales y reforzados con fibras continuas para mejorar las propiedades de resistencia mecánica y ligereza. Una vez fabricados los prototipos, se llevará a cabo una completa caracterización mecánica tanto a temperatura ambiente como a bajas temperaturas, y se complementará el proyecto con la evaluación del comportamiento al fuego de los distintos materiales obtenidos.

Este vídeo didáctico tiene como objetivo principal describir las etapas del proceso de fabricación de materiales compuestos tipo sándwich mediante infusión de resina asistida por vacío (VARIM) con núcleo permeable.

Este vídeo didáctico tiene como objetivo principal describir las etapas del proceso de fabricación de materiales compuestos tipo sándwich mediante infusión de resina asistida por vacío (VARIM) con núcleo permeable.

Crack root rotation is a measure of deviation from clamped boundary conditions of region in front of the crack tip. The root rotation depends on the shear force and bending moment acting at the crack tip. Such rotation significantly affects the compliance and energy-release rate. Crack root rotation analysis of Single Cantilever Beam (SCB) sandwich specimens is presented here. Closed-form solutions for the root rotation angle obtained from the foundation analysis are compared to finite element analysis (FEA) predictions. The derived expressions closely match for a range of sandwich configurations. An expression for the energy-release rate, derived from the foundation analysis was found to agree with FEA predictions over a large range of face-to-core modulus ratios. Energy-release rate and mode mixity phase angle increased with decreasing crack length due to the transverse shear effects. At longer crack lengths, both energy-release rate and phase angle reached a value independent of crack length. The foundation model is used to derive a simple expression for the offset crack length for the SCB sandwich fracture test. It is shown that the obtained formulation agrees closely well with both numerical and experimental values. In addition, SCB fracture tests performed using an in-house built translatable rig showed close relation to both analytical and numerical compliance results.

The single cantilever beam sandwich specimen has been proposed, as a fracture test standard for mode I peel loading. Critical parameters, including specimen dimensions, determine whether the crack propagates along the face/core interface in mode I during the fracture test. This paper outlines a parametric study based on a numerical method to examine local mode mixity conditions for a wide array of sandwich systems by varying several geometrical and material parameters. The thickness and modulus of the face sheet were seen to influence the mode mixity for most sandwich systems. Core Poisson’s ratio was shown to influence the local mode mixity and has the capability of driving the crack along the interface or into the core. The effect of the intact specimen length was analyzed and presented from a mode mixity perspective based on various elastic foundation modulus expressions. Reinforcement of the single cantilever beam specimen with stiff layers was also investigated numerically and compared with a similar analysis in the literature. The analysis presented in this paper shows that, despite reducing the global shear component, the local mode mixity condition deviated away from the mode I regime for several sandwich specimens. An appropriate foundation model along with a minimum loading rod length was one of the recommendations provided from the analyses, which may supplement the ASTM International standardization efforts.

This paper experimentally investigates the effects of low temperature on fracture toughness and fatigue debond growth rate in foam core sandwich composites. Mixed-mode bending specimens were statically and cyclically tested inside a climatic chamber at a low temperature (−20°C) and at room temperature (23°C) as a reference. Testing was conducted in mode I (opening) and mixed-mode I/II (opening-sliding) mode mixities. The fatigue tests results are presented according to the modified Paris–Erdogan relation. Results showed substantial fracture toughness reduction due to low temperature. Low temperature furthermore elevated the cyclic crack growth rate.

Este vídeo didáctico tiene como objetivo principal describir las etapas del proceso de fabricación de materiales compuestos tipo sándwich mediante infusión de resina asistida por vacío (VARIM) con núcleo permeable.

Los procedimientos de homogeneización han ido ganando cada vez más énfasis en el campo del análisis numérico de los materiales compuestos. Un procedimiento de homogenización se basa sobre la hipótesis de que existe un set de ecuaciones o un elemento de volumen representativo que puede proporcionar una respuesta equivalente a la del material real. Un procedimiento de homogeneización multiescala será enseñado donde el comportamiento del material compuesto se obtiene a través de un estudio en su microescala donde la interacción entre sus materiales componentes con sus respectivas propiedades se modeliza a través de un modelo RVE. La formulación propuesta utiliza una función de activación del modelo nolineal en la escala estructural y su objetivo es evaluar si un punto de material está en el rango elástico o nolineal. Como consecuencia, la metodología desarrollada únicamente resuelve el problema microscópico de condición en la frontera en aquellos elementos de volumen representativo (RVE) que están en el rango nolineal. El procedimiento se usará para la simulación nolineal de un material compuesto tipo sándwich formado por eco-composites, ensayado en un test de flexión a cuatro puntos., This work has been supported by the Spanish Ministerio de Economia y Competividad through the project BIAS2015-67807-R(RESCICLO) and by European Union EU-H2020 (Agreement No 690638)and the People’s Republic of China (Agreement No [2016]92)(ECOCOMPASS). All this support is gratefully acknowledged., Peer Reviewed, Postprint (published version)

Fracture testing of aerospace grade honeycomb core sandwich composites is carried out using the Double Cantilever Beam specimen loaded with Uneven Bending Moments, and a Double Cantilever Beam–Uneven Bending Moment test rig capable of applying pure moments is utilized. Specimens with carbon fiber-reinforced plastic face sheets are employed with a range of honeycomb core grades comprising of Nomex® and Kevlar paper. The sandwich specimens are reinforced with steel doublers to reduce excessive rotation of the face sheets. The mode mixity phase angle pertaining to a particular ratio of moments between the two arms of the Double Cantilever Beam specimen is determined using the numerical mode mixity method—Crack Surface Displacement Extrapolation method. For Nomex® honeycomb core sandwich specimens, it is observed that the mode I interface fracture toughness increases with increase in core density. The interface fracture toughnesses for Nomex®-based honeycomb cores are also compared against specimens with Kevlar paper-based honeycomb cores. Crack propagation is observed at the interface just beneath the meniscus layer for the majority of the tested specimen configurations. The Double Cantilever Beam–Uneven Bending Moment test methodology with the concept of direct application of moments on both crack flanks has proven to have a significant potential for mixed mode face/core fracture characterization of aerospace grade sandwich composites.

The decohesion of coatings, thin films, or layers used to protect or strengthen technological and structural components causes the loss of their functions. In this paper, analytical, computational, and semi-analytical 2D solutions are derived for the energy release rate and mode-mixity phase angle of an edge-delamination crack between a thin layer and an infinitely deep substrate. The thin layer is subjected to general edge loading: axial and shear forces and bending moment. The solutions are presented in terms of elementary crack tip loads and apply to a wide range of material combinations, with a large mismatch of the elastic constants (isotropic materials with Dundurs’ parameters −1≤α≤1 and −0.4≤β≤0.4 ). Results show that for stiff layers over soft substrates ( α→1 ), the effects of material compressibility are weak, and the assumption of substrate incompressibility is accurate; for other combinations, including soft layers over stiff substrates ( α→−1 ), the effects may be relevant and problem specific. The solutions are applicable to edge- and buckling-delamination of thin layers bonded to thick substrates, to mixed-mode fracture characterization test methods, and as benchmark cases.

[ES] La actual búsqueda de materiales de alto rendimiento, tanto en el ámbito de la mecánica como en el de aislamiento o resistencia a ambientes desfavorables, ha llevado al estudio y desarrollo de productos con composiciones variadas que sean capaces de satisfacer todos estos aspectos. Actualmente, en el mercado ya existen compuestos con características muy destacables, sin embargo, en muchos de los casos la contaminación que conlleva el procesado y obtención de estas materias es demasiado elevada. Este proyecto se ha centrado en la obtención de materiales de altas prestaciones desde un punto de vista respetuoso con el medio ambiente. Se han utilizado materias primas como refuerzos de origen natural o resinas ecológicas para conseguir un producto final a la altura de las necesidades actuales. Concretamente, se ha enfocado este trabajo en el estudio y manejo de materiales tipo sándwich. Este tipo de materiales compuestos están basados en la combinación de núcleos y refuerzos exteriores, por lo que se ha llevado a cabo la utilización diversas estructuras con la intención de encontrar una combinación de materias primas, según la cual, se consiga un producto resultante con características competentes. El tipo de núcleo utilizado para este estudio pertenece la familia de núcleos permeables. Con características de alta resistencia a la compresión. Este tipo de material permite realizar las infusiones a través de sí mismo, por lo que son necesarios menos utensilios para realizar el proceso y por lo tanto menos productos contaminantes. Además, está compuesto a base de poliéster, que se recicla con relativa facilidad, puede ser de origen BIO e incluso biodegradable. El estudio se ha abordado analizando los materiales actuales y las posibilidades que estos ofrecen, investigando nuevos procesos de infusión de alto rendimiento y bajo impacto medioambiental, así como analizando las propiedades que ofrecen los materiales resultantes de esta combinación y caracterizándolos técnic, [EN] The current search for high performance materials, both in the field of mechanics and in isolation or resistance to unfavorable environments, has led to the study and development of products with varied compositions that are capable of satisfying all these aspects. Currently, in the market there are already compounds with very remarkable characteristics, however, in many cases the contamination that comes with processing and obtaining these materials is too high. This project has focused on obtaining high performance materials from an environmentally friendly point of view. Raw materials such as natural origin reinforcements or ecological resins have been used to achieve a final product that meets current needs. Specifically, this work has focused on the study and manufacture of sandwich materials. These types of composite materials are based on the combination of cores and external reinforcements, so various structures have been used with the intention of finding a combination of raw materials, according to which, a resulting product with competent characteristics is achieved. The type of core used for this study belongs to the permeable core family. With characteristics of high compressive strength. This type of material allows the infusions to be made through itself, so less tools are needed to make the process and therefore fewer polluting products are generated. In addition, it is composed of polyester, which is recycled with relative ease, can be of BIO origin and even biodegradable. The study has been carried out by analyzing the current materials and the possibilities they offer, investigating new infusion processes of high performance and low environmental impact, as well as analyzing the properties offered by the materials resulting from this combination and characterizing them technically. Thus, each of these steps has been studied comparing the results with other materials and procedures already existing in the market.¿

Potential energy surfaces of borazine-benzene and borazine-borazine stacking interactions were studied by performing DFT, CCSD(T)/CBS and SAPT calculations. The strongest borazine-benzene stacking was found in a parallel-displaced geometry, with a CCSD(T)/CBS interaction energy of -3.46 kcal mol-1. The strongest borazine-borazine stacking has a sandwich geometry, with a CCSD(T)/CBS interaction energy of -3.57 kcal mol-1. The study showed that borazine forms significant stacking interactions at large horizontal displacements (over 4.5), with energies of -2.20 kcal mol-1 for the borazine-benzene and -1.96 kcal mol-1 for the borazine-borazine system. The strength of interactions and their geometrical preferences can be rationalized by observing the electrostatic potentials of borazine and benzene, which is in agreement with SAPT analysis showing that electrostatics is the most important energy component for borazine stacking. All the interactions found in crystal structures of borazine and related compounds were identified either as potential curve minima or the geometries obtained from their optimizations. We also report a new dihydrogen bonding dimer with a CCSD(T)/CBS interaction energy of -2.37 kcal mol-1, which is encountered in the borazine crystal structures and enables the formation of additional simultaneous interactions that contribute to the overall stability of the crystals.

Potential energy surfaces of borazine-benzene and borazine-borazine stacking interactions were studied by performing DFT, CCSD(T)/CBS and SAPT calculations. The strongest borazine-benzene stacking was found in a parallel-displaced geometry, with a CCSD(T)/CBS interaction energy of -3.46 kcal mol-1. The strongest borazine-borazine stacking has a sandwich geometry, with a CCSD(T)/CBS interaction energy of -3.57 kcal mol-1. The study showed that borazine forms significant stacking interactions at large horizontal displacements (over 4.5), with energies of -2.20 kcal mol-1 for the borazine-benzene and -1.96 kcal mol-1 for the borazine-borazine system. The strength of interactions and their geometrical preferences can be rationalized by observing the electrostatic potentials of borazine and benzene, which is in agreement with SAPT analysis showing that electrostatics is the most important energy component for borazine stacking. All the interactions found in crystal structures of borazine and related compounds were identified either as potential curve minima or the geometries obtained from their optimizations. We also report a new dihydrogen bonding dimer with a CCSD(T)/CBS interaction energy of -2.37 kcal mol-1, which is encountered in the borazine crystal structures and enables the formation of additional simultaneous interactions that contribute to the overall stability of the crystals.

[ES] La actual búsqueda de materiales de alto rendimiento, tanto en el ámbito de la mecánica como en el de aislamiento o resistencia a ambientes desfavorables, ha llevado al estudio y desarrollo de productos con composiciones variadas que sean capaces de satisfacer todos estos aspectos. Actualmente, en el mercado ya existen compuestos con características muy destacables, sin embargo, en muchos de los casos la contaminación que conlleva el procesado y obtención de estas materias es demasiado elevada. Este proyecto se ha centrado en la obtención de materiales de altas prestaciones desde un punto de vista respetuoso con el medio ambiente. Se han utilizado materias primas como refuerzos de origen natural o resinas ecológicas para conseguir un producto final a la altura de las necesidades actuales. Concretamente, se ha enfocado este trabajo en el estudio y manejo de materiales tipo sándwich. Este tipo de materiales compuestos están basados en la combinación de núcleos y refuerzos exteriores, por lo que se ha llevado a cabo la utilización diversas estructuras con la intención de encontrar una combinación de materias primas, según la cual, se consiga un producto resultante con características competentes. El tipo de núcleo utilizado para este estudio pertenece la familia de núcleos permeables. Con características de alta resistencia a la compresión. Este tipo de material permite realizar las infusiones a través de sí mismo, por lo que son necesarios menos utensilios para realizar el proceso y por lo tanto menos productos contaminantes. Además, está compuesto a base de poliéster, que se recicla con relativa facilidad, puede ser de origen BIO e incluso biodegradable. El estudio se ha abordado analizando los materiales actuales y las posibilidades que estos ofrecen, investigando nuevos procesos de infusión de alto rendimiento y bajo impacto medioambiental, así como analizando las propiedades que ofrecen los materiales resultantes de esta combinación y caracterizándolos técnic, [EN] The current search for high performance materials, both in the field of mechanics and in isolation or resistance to unfavorable environments, has led to the study and development of products with varied compositions that are capable of satisfying all these aspects. Currently, in the market there are already compounds with very remarkable characteristics, however, in many cases the contamination that comes with processing and obtaining these materials is too high. This project has focused on obtaining high performance materials from an environmentally friendly point of view. Raw materials such as natural origin reinforcements or ecological resins have been used to achieve a final product that meets current needs. Specifically, this work has focused on the study and manufacture of sandwich materials. These types of composite materials are based on the combination of cores and external reinforcements, so various structures have been used with the intention of finding a combination of raw materials, according to which, a resulting product with competent characteristics is achieved. The type of core used for this study belongs to the permeable core family. With characteristics of high compressive strength. This type of material allows the infusions to be made through itself, so less tools are needed to make the process and therefore fewer polluting products are generated. In addition, it is composed of polyester, which is recycled with relative ease, can be of BIO origin and even biodegradable. The study has been carried out by analyzing the current materials and the possibilities they offer, investigating new infusion processes of high performance and low environmental impact, as well as analyzing the properties offered by the materials resulting from this combination and characterizing them technically. Thus, each of these steps has been studied comparing the results with other materials and procedures already existing in the market.¿

[ES] La actual búsqueda de materiales de alto rendimiento, tanto en el ámbito de la mecánica como en el de aislamiento o resistencia a ambientes desfavorables, ha llevado al estudio y desarrollo de productos con composiciones variadas que sean capaces de satisfacer todos estos aspectos. Actualmente, en el mercado ya existen compuestos con características muy destacables, sin embargo, en muchos de los casos la contaminación que conlleva el procesado y obtención de estas materias es demasiado elevada. Este proyecto se ha centrado en la obtención de materiales de altas prestaciones desde un punto de vista respetuoso con el medio ambiente. Se han utilizado materias primas como refuerzos de origen natural o resinas ecológicas para conseguir un producto final a la altura de las necesidades actuales. Concretamente, se ha enfocado este trabajo en el estudio y manejo de materiales tipo sándwich. Este tipo de materiales compuestos están basados en la combinación de núcleos y refuerzos exteriores, por lo que se ha llevado a cabo la utilización diversas estructuras con la intención de encontrar una combinación de materias primas, según la cual, se consiga un producto resultante con características competentes. El tipo de núcleo utilizado para este estudio pertenece la familia de núcleos permeables. Con características de alta resistencia a la compresión. Este tipo de material permite realizar las infusiones a través de sí mismo, por lo que son necesarios menos utensilios para realizar el proceso y por lo tanto menos productos contaminantes. Además, está compuesto a base de poliéster, que se recicla con relativa facilidad, puede ser de origen BIO e incluso biodegradable. El estudio se ha abordado analizando los materiales actuales y las posibilidades que estos ofrecen, investigando nuevos procesos de infusión de alto rendimiento y bajo impacto medioambiental, así como analizando las propiedades que ofrecen los materiales resultantes de esta combinación y caracterizándolos técnic, [EN] The current search for high performance materials, both in the field of mechanics and in isolation or resistance to unfavorable environments, has led to the study and development of products with varied compositions that are capable of satisfying all these aspects. Currently, in the market there are already compounds with very remarkable characteristics, however, in many cases the contamination that comes with processing and obtaining these materials is too high. This project has focused on obtaining high performance materials from an environmentally friendly point of view. Raw materials such as natural origin reinforcements or ecological resins have been used to achieve a final product that meets current needs. Specifically, this work has focused on the study and manufacture of sandwich materials. These types of composite materials are based on the combination of cores and external reinforcements, so various structures have been used with the intention of finding a combination of raw materials, according to which, a resulting product with competent characteristics is achieved. The type of core used for this study belongs to the permeable core family. With characteristics of high compressive strength. This type of material allows the infusions to be made through itself, so less tools are needed to make the process and therefore fewer polluting products are generated. In addition, it is composed of polyester, which is recycled with relative ease, can be of BIO origin and even biodegradable. The study has been carried out by analyzing the current materials and the possibilities they offer, investigating new infusion processes of high performance and low environmental impact, as well as analyzing the properties offered by the materials resulting from this combination and characterizing them technically. Thus, each of these steps has been studied comparing the results with other materials and procedures already existing in the market.¿

Projektet syftar till att föreslå en rimlig riktning för hur additiva produktionsmetoder, alltså tillverkningsmetoder som använder lager-på-lager-teknik, kan tänkas påverka arkitekturen, att försöka sätta sig in i teknikerna och komma fram till vilken riktning som upplevs mest givande eller gångbar. Hur ska man nyttja potentialen med den nya tekniken på ett bra sätt? Jag har försökt ta fram en produkt som nyttjar potentialen hos de additiva produktionsmetoderna och som upplevs tänkbar för fullskalig realisering i byggsektorn i en närliggande framtid. Produkten består av en metod för framställning av en sandwichkonstruktion med hög trähalt och troligen lång livslängd. Metoden minskar byggsektorns klimatbelastning och kan ge stora rumsliga kvaliteter och formgivningsmöjligheter. Jag har genom fysiska experiment och utforskande av olika digitala fabrikationsmetoder försökt att visualisera och identifiera möjligheter med dessa nya tekniska hjälpmedel. Genom praktiska tester har jag prövat mina föreställningar av hur dessa metoder kan användas på effektiva sätt. Projektet vidga-des från att initialt omfatta additiva produktionsmetoder till att senare under tillämpningsfasen även omfatta digitala hjälpmedel såsom fotogrammetri och verktyg för parametrisk design. Projektet har resulterat i ett tillvägagångsätt för printning av cellulosabaserade sandwichkonstruktioner i printade formverk av återvinningsbar biokomposit., The project aims to propose a direction for how additive manufacturing methods can influence architecture, to study the techniques and find out which direction could be perceived as most rewarding or viable. How to use the potential of the new technology in a good way? I have tried to develop a product that utilizes the potential of the additive manufacturing methods and which is conceivable for full-scale realization in the construction sector in the near future. The product consists of a method for producing long lasting sandwich constructions with high wood content. The method reduces the building industry's climate impact and can provide great spatial qualities and design possibilities. Through physical experiments and exploration of various digital fabrication methods, I have tried to visualize and identify possibilities with these new technological aids. Through practical tests, I have tested my ideas of how these methods can be used effectively. The project was expanded from initially studying additive production methods to, later during the application phase, also include digital aids such as photogrammetry and tools for parametric design. The project has resulted in a strategy for printing cellulose-based sandwich constructions in printed molds of recyclable biocomposite.

Projektet syftar till att föreslå en rimlig riktning för hur additiva produktionsmetoder, alltså tillverkningsmetoder som använder lager-på-lager-teknik, kan tänkas påverka arkitekturen, att försöka sätta sig in i teknikerna och komma fram till vilken riktning som upplevs mest givande eller gångbar. Hur ska man nyttja potentialen med den nya tekniken på ett bra sätt? Jag har försökt ta fram en produkt som nyttjar potentialen hos de additiva produktionsmetoderna och som upplevs tänkbar för fullskalig realisering i byggsektorn i en närliggande framtid. Produkten består av en metod för framställning av en sandwichkonstruktion med hög trähalt och troligen lång livslängd. Metoden minskar byggsektorns klimatbelastning och kan ge stora rumsliga kvaliteter och formgivningsmöjligheter. Jag har genom fysiska experiment och utforskande av olika digitala fabrikationsmetoder försökt att visualisera och identifiera möjligheter med dessa nya tekniska hjälpmedel. Genom praktiska tester har jag prövat mina föreställningar av hur dessa metoder kan användas på effektiva sätt. Projektet vidga-des från att initialt omfatta additiva produktionsmetoder till att senare under tillämpningsfasen även omfatta digitala hjälpmedel såsom fotogrammetri och verktyg för parametrisk design. Projektet har resulterat i ett tillvägagångsätt för printning av cellulosabaserade sandwichkonstruktioner i printade formverk av återvinningsbar biokomposit., The project aims to propose a direction for how additive manufacturing methods can influence architecture, to study the techniques and find out which direction could be perceived as most rewarding or viable. How to use the potential of the new technology in a good way? I have tried to develop a product that utilizes the potential of the additive manufacturing methods and which is conceivable for full-scale realization in the construction sector in the near future. The product consists of a method for producing long lasting sandwich constructions with high wood content. The method reduces the building industry's climate impact and can provide great spatial qualities and design possibilities. Through physical experiments and exploration of various digital fabrication methods, I have tried to visualize and identify possibilities with these new technological aids. Through practical tests, I have tested my ideas of how these methods can be used effectively. The project was expanded from initially studying additive production methods to, later during the application phase, also include digital aids such as photogrammetry and tools for parametric design. The project has resulted in a strategy for printing cellulose-based sandwich constructions in printed molds of recyclable biocomposite.

Crushing behaviours of foam filled multi-layer truncated square pyramid (TSP) kirigami structures are studied experimentally and numerically in this study. Each layer of this TSP foldcore is folded using a single aluminium sheet with pre-cuts. Light weight foams are inserted into each unit cell of the TSP foldcore to enhance its loading and energy absorption capacity. The effects of the foam material, density and shapes of foam material on crushing resistance of the multi-layer folded structure are studied. Two foam materials, i.e. expanded polystyrene (EPS) foam with density of 13.5, 19 and 28 kg/m3; rigid polyurethane (PU) foam with density of 35 kg/m3 are used as foam infill for this multi-layer foldcore. Two shapes of PU foam infill are studied as well. Single layered TSP foldcores with foam infill are firstly studied under quasi-static crushing condition, then foam filled multi-layer TSP foldcores are crushed under dynamic loading conditions. Numerical models are verified with the experimental results, followed by intensive numerical simulations. Key parameters such as peak and average crushing resistance, densification strain and specific energy absorption are compared among the foldcores with different foam configurations. Comparing with other cellular structures, uniform collapsing of the proposed foldcore is observed under both quasi-static and dynamic loading conditions with the uniformity ratio ranging between 1.1 and 2.0. Significant increases in average crushing resistances ranging from 36.6% to 82% are also observed by adding foam fillers, while the mass only increases by 3.2% to 20.4%.

Potential energy surfaces of borazine-benzene and borazine-borazine stacking interactions were studied by performing DFT, CCSD(T)/CBS and SAPT calculations. The strongest borazine-benzene stacking was found in a parallel-displaced geometry, with a CCSD(T)/CBS interaction energy of -3.46 kcal mol-1. The strongest borazine-borazine stacking has a sandwich geometry, with a CCSD(T)/CBS interaction energy of -3.57 kcal mol-1. The study showed that borazine forms significant stacking interactions at large horizontal displacements (over 4.5), with energies of -2.20 kcal mol-1 for the borazine-benzene and -1.96 kcal mol-1 for the borazine-borazine system. The strength of interactions and their geometrical preferences can be rationalized by observing the electrostatic potentials of borazine and benzene, which is in agreement with SAPT analysis showing that electrostatics is the most important energy component for borazine stacking. All the interactions found in crystal structures of borazine and related compounds were identified either as potential curve minima or the geometries obtained from their optimizations. We also report a new dihydrogen bonding dimer with a CCSD(T)/CBS interaction energy of -2.37 kcal mol-1, which is encountered in the borazine crystal structures and enables the formation of additional simultaneous interactions that contribute to the overall stability of the crystals.

Taking advance of the fiber-reinforced polymer process, commonly used in the fabrication of polymer composites, in this work we used electrospun microfibers to reinforce self-healing ionomeric polymers producing sandwich-type composites. In particular, three-layer stack with poly(lactic acid), PLA, electrospun fibers in between two layers of commercial smart polymers has been obtained based on poly(ethylene-co-methacrylic acid) (EMAA) copolymers, well-know with the tradename of Nucrel® and Surlyn®, both of them manufactured by Dupont™ Company. Surlyn® is the corresponding ionomer of Nucrel® in which the MAA groups are partially neutralized with sodium ions. In general, one of the main problems of thermoplastic composites, that provoke a lower impregnation of the fiber, is the high viscosity of the molten matrix. Therefore, in this work, we used electrospun microfibers in order to solve impregnation problem, thus considering that electrospinning process is an accessible, versatile and low-cost technique for fibers formation in the range of micron and nanometers. In order to create the sandwich-type structure, firstly, the optimization of the processing window has achieved in order to maintain the randomly oriented fiber structure on the final composites. In particular, the creation of sandwich-type structure with Surlyn® reinforced with woven non-woven electrospun fibers based on PLA with enhanced mechanical as well as hardness and wear resistance can be used for future active packaging solutions.

Lightweight materials and structures are essential building blocks for a future with sustainable transportation and automotive industries. Incorporating lightweight materials and structures in today's vehicles, reduces weight and energy consumption while maintaining, or even improving, necessary mechanical properties and behaviors. Due to this, the environmental footprint can be reduced through the incorporation of lightweight structures and materials. Awareness of the negative effects caused by pollution from emissions is ever increasing. Legislation, forced by authorities, drives industries to find better solutions with regard to the environmental impact. For the automotive industry, this implies more effective vehicles with respect to energy consumption. This can be achieved by introducing new, and improve current, methods of turning power into motion. An additional approach is reducing weight of the body in white (BIW) while maintaining crash worthiness to assure passenger safety. In addition to the structural integrity of the BIW, passenger safety is further increased through electrical systems integrated into the modern vehicle. Besides these safety systems, customers are also able to choose from a long list of gadgets to be fitted to the vehicle. As a result, the curb weight of vehicles are increasing, partly due to customer demands. In order to mitigate the increasing weights the BIW must be optimized with respect to weight, while maintaining its structural integrity and crash worthiness. To achieve this, new and innovative materials, geometries and structures are required, where the right material is used in the right place, resulting in a lightweight structure which can replace current configurations. A variety of approaches are available for achieving lightweight, one of them being the press-hardening method, in which a heated blank is formed and quenched in the same process step. The result of the process is a component with greatly enhanced properties

Spherical ultrasonic motors (SUSMs) that can operate with multiple degrees of freedom (MDOF) using only a single stator have high holding torque and high torque at low speed, which makes reduction gearing unnecessary. The simple structure of MDOF-SUSMs makes them useful as compact actuators, but their development is still insufficient for applications such as joints of humanoid robots and other systems that require MDOF and high torque. To increase the torque of a sandwich-type MDOF-SUSM, we have not only made the vibrating stator and spherical rotor larger but also improved the structure using three design concepts: (1) increasing the strength of all three vibration modes using multilayered piezoelectric actuators (MPAs) embedded in the stator, (2) enhancing the rigidity of the friction driving portion of the stator for transmitting more vibration force to the friction-driven rotor surface, and (3) making the support mechanism more stable. An MDOF-SUSM prototype was tested, and the maximum torques of rotation around the X(Y)-axis and Z-axis were measured as 1.48 N?m and 2.05 N?m, respectively. Moreover, the values for torque per unit weight of the stator were obtained as 0.87 N?m/kg for the X(Y)-axis and 1.20 N?m/kg for the Z-axis. These are larger than values reported for any other sandwich-type MDOF-SUSM of which we are aware. Hence, the new design concepts were shown to be effective for increasing torque. In addition, we measured the transient response and calculated the load characteristics of rotation around the rotor’s three orthogonal axes.

Das Rollmaterial auf den Eisenbahnschienen ist in der Regel enorm schwer. Leichtere Waggons verringern nicht nur den Verschleiss von Radsätzen und Schienen, sondern benötigen auch weniger Traktionsenergie und reduzieren die CO2-Emissionen. Der Einsatz der modernen Sandwichbauweise ebnet den Weg hin zu diesen leichteren Schienenfahrzeugen.

Zwischen 1955 und 1985 entwickelten sich die Alu-Wagenkästen von der Bauweise „Flugzeug-Konstruktion“ über „Stahlbau in Aluminium“ und „Grossprofil-Technologie“ bis hin zur heute vorherrschenden spantenlosen „Integral-Bauweise“, hier Wagenkasten 4.0 genannt. Auf diesem Entwicklungsweg reduzierten sich die Fabrikations-Stunden markant. Gleichzeitig stieg aber das Kastengewicht kontinuierlich an. Im Zuge von zulassungsbedingten Gewichts-Limiten (z.B. Achslasten), der aktuellen Bestrebungen, den Radsatz- und Schienenverschleiss weiter zu minimieren sowie Traktions-Energie und damit CO2-Emissionen einzusparen, steht der Leichtbau von Schienenfahrzeugen wieder verstärkt im Fokus. Im neu entwickelten Wagenkasten 4.1 ersetzen deckschichtverschweisste Sandwich- Paneele in dafür geeigneten Bereichen die heute üblichen Integral-Hohlprofil-Strukturen. Bei unverändert hoher Struktursteifigkeit sind durch die neuartige Sandwichtechnologie Gewichtsreduktionen bis 10% realistisch, wenn Teile der Bodenplatte, des Daches und Bereiche der Seitenwand mit dieser Bauweise ausgeführt werden. Vergleichbare Konzepte wurden ansatzweise bereits früher umgesetzt, wie beispielsweise lasergeschweisste Sandwich-Paneele beim Transrapid oder geklebte Hybrid-Wagenkasten. Keine dieser Bauweisen hat sich jedoch durchgesetzt, sei es aus technischen oder aus wirtschaftlichen Gründen. Die neue Bauweise der Sandwich-Integration wurde an der ZHAW Zürcher Hochschule für Angewandte Wissenschaften zusammen mit 3A Composites als Strukturlieferant für Schienenfahrzeuge und der Rapid Technic AG als Spezialist für das Reibrührschweissen (Friction Stir Welding - FSW) entwickelt. Sie ermöglicht dank geschicktem Einsatz von FSW-Nähten das Verbinden von grossformatigen Sandwichplatten mit Randprofilen, welche dann mittels konventioneller MIG-Verfahren mit der Wagenkastenstruktur verbunden werden. Dieses Vorgehen ermöglicht eine vollständig geschweisste Integration von Sandwich-Paneelen mit Aluminium-Deckschichten in

Die Zürcher Hochschule für Angewandte Wissenschaften hat zusammen mit Airex Composite Structures und Rapid Technic eine Technologie zum Verbinden von Sandwichbauteilen und Strangpressprofilen mittels Rührreibschweißen entwickelt. Damit lassen sich leichtere Schienenfahrzeuge bauen, zulassungsrelevante Achslasten einhalten und Betriebskosten minimieren.

Spherical ultrasonic motors (SUSMs) that can operate with multiple degrees of freedom (MDOF) using only a single stator have high holding torque and high torque at low speed, which makes reduction gearing unnecessary. The simple structure of MDOF-SUSMs makes them useful as compact actuators, but their development is still insufficient for applications such as joints of humanoid robots and other systems that require MDOF and high torque. To increase the torque of a sandwich-type MDOF-SUSM, we have not only made the vibrating stator and spherical rotor larger but also improved the structure using three design concepts: (1) increasing the strength of all three vibration modes using multilayered piezoelectric actuators (MPAs) embedded in the stator, (2) enhancing the rigidity of the friction driving portion of the stator for transmitting more vibration force to the friction-driven rotor surface, and (3) making the support mechanism more stable. An MDOF-SUSM prototype was tested, and the maximum torques of rotation around the X(Y)-axis and Z-axis were measured as 1.48 N?m and 2.05 N?m, respectively. Moreover, the values for torque per unit weight of the stator were obtained as 0.87 N?m/kg for the X(Y)-axis and 1.20 N?m/kg for the Z-axis. These are larger than values reported for any other sandwich-type MDOF-SUSM of which we are aware. Hence, the new design concepts were shown to be effective for increasing torque. In addition, we measured the transient response and calculated the load characteristics of rotation around the rotor’s three orthogonal axes.

Spherical ultrasonic motors (SUSMs) that can operate with multiple degrees of freedom (MDOF) using only a single stator have high holding torque and high torque at low speed, which makes reduction gearing unnecessary. The simple structure of MDOF-SUSMs makes them useful as compact actuators, but their development is still insufficient for applications such as joints of humanoid robots and other systems that require MDOF and high torque. To increase the torque of a sandwich-type MDOF-SUSM, we have not only made the vibrating stator and spherical rotor larger but also improved the structure using three design concepts: (1) increasing the strength of all three vibration modes using multilayered piezoelectric actuators (MPAs) embedded in the stator, (2) enhancing the rigidity of the friction driving portion of the stator for transmitting more vibration force to the friction-driven rotor surface, and (3) making the support mechanism more stable. An MDOF-SUSM prototype was tested, and the maximum torques of rotation around the X(Y)-axis and Z-axis were measured as 1.48 N?m and 2.05 N?m, respectively. Moreover, the values for torque per unit weight of the stator were obtained as 0.87 N?m/kg for the X(Y)-axis and 1.20 N?m/kg for the Z-axis. These are larger than values reported for any other sandwich-type MDOF-SUSM of which we are aware. Hence, the new design concepts were shown to be effective for increasing torque. In addition, we measured the transient response and calculated the load characteristics of rotation around the rotor’s three orthogonal axes.

Today, mainly man-made materials such as carbon and glass fibres are used to produce composite parts in aviation. Renewable materials such as natural fibres or bio-sourced resin systems have not found their way into aviation, yet. The project ECO-COMPASS aims to evaluate the potential applications of ecologically improved composite materials in the aviation sector in an international collaboration of Chinese and European partners. Natural fibres such as flax and ramie will be used for different types of reinforcements and sandwich cores. Furthermore, the bio-based epoxy resins to substitute bisphenol-A based epoxy resins in secondary structures are under investigation. Adapted material protection technologies to reduce environmental influence and to improve fire resistance are needed to fulfil the demanding safety requirements in aviation. Modelling and simulation of chosen eco-composites aims for an optimized use of materials while a life cycle assessment aims to prove the ecological advantages compared to synthetic state-of-the-art materials. In this paper, the status of selected ecologically improved materials will be presented with an outlook for potential application in interior and secondary structures., Postprint (author's final draft)

Die Zürcher Hochschule für Angewandte Wissenschaften hat zusammen mit Airex Composite Structures und Rapid Technic eine Technologie zum Verbinden von Sandwichbauteilen und Strangpressprofilen mittels Rührreibschweißen entwickelt. Damit lassen sich leichtere Schienenfahrzeuge bauen, zulassungsrelevante Achslasten einhalten und Betriebskosten minimieren.

Das Rollmaterial auf den Eisenbahnschienen ist in der Regel enorm schwer. Leichtere Waggons verringern nicht nur den Verschleiss von Radsätzen und Schienen, sondern benötigen auch weniger Traktionsenergie und reduzieren die CO2-Emissionen. Der Einsatz der modernen Sandwichbauweise ebnet den Weg hin zu diesen leichteren Schienenfahrzeugen.