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Fibre metal laminate (FMLs) are hybrid composite materials which consisted of metallic layers and fibre-reinforced polymer. Currently, FMLs are becoming increasingly utilized in a wide range of applications, such as aircraft, automotive, marine, sporting goods and medical due to their specific mechanical properties like superior impact resistance and fatigue resistance. ARALL (Aramid-Reinforced Aluminium Laminate), which is based on aramid fibres, GLARE (Glass Reinforced Aluminium Laminate), which is based on high-strength glass fibres and CARALL (Carbon Reinforced Aluminium Laminate), which is based on carbon fibres, are the most commercial products FMLs. This article analyzes pertinent literature associated with experimental work on FMLs and their constituent materials subjected to impact loading. It reviewed the mechanical properties, impact performance indices, crushing behavior, failure modes, and failure mechanisms of various FML structures with different variables (impact energy, fibre orientation, layup configuration, stacking sequence, metal arrangement, direction and type of reinforcement, laminate thickness, metal thickness) under impact conditions (lateral and axial impacts). Overall, the literature on the response of FML flat plate structures to axial impact loads is unreported, and the most current research focusing on the axial crushing of FML tubes. Hence, further studies are required to increase the applicability of FMLs in applications that may be impacted under axial loading. more...

The transient impact load during the launch of a rocket at sea threatens the safety of the launcher and the deck structure of the launch platform. In view of the impact resistance of the offshore rocket launcher system, this paper takes the real-scale rocket launcher system as the research object and establishes the analysis model of the fiber-reinforced composite rocket launcher based on the finite element method. Then, we explore the factors of the thickness by finite element simulation method and the angle and the position of IM7 fiber-reinforced composite, which influence the impact resistance property of the rocket launcher. The results show that the fiber-reinforced composite rocket launcher can effectively reduce the impact response of the structure and improve the impact resistance of the structure. The best laying scheme is to lay four layers of IM7 fiber material on both sides of the panels of the fixed bracket and the webs of the erector, respectively, with a single layer thickness of 0.75 mm and a laying angle of [90°/∓45°/90°]. more...

This study investigated the impact response behaviours of pineapple leaf fibre (PALF)/carbon hybrid laminate composites for different ply orientations and stacking sequences. The laminates were manufactured using a vacuum infusion approach with various stacking sequences and ply orientations classified as symmetric quasi-isotropic, angle-ply symmetric, and cross-ply symmetric. The laminates were analysed using an IMATEK IM10 drop weight impact tester with an increment of 5 J until the samples were perforated. This investigation reveals that the overall impact properties of PALF and carbon as reinforcements were improved by a beneficial hybridised effect. The laminates with an exterior carbon layer can withstand high impact energy levels up to 27.5 J. The laminate with different stacking sequences had a lower energy transfer rate and ruptured at higher impact energy. The laminates with ply orientations of [0°/90°] and [±45°]8 exhibited 10% to 30% better energy absorption than those with ply orientations of [±45°2, 0°/90°2]s and [0°/90°2, ±45°2]s due to energy being readily transferred within the same linear ply orientation. Through visual inspection, delamination was observed to occur at the interfaces of different stacking sequences and ply orientations. more...

High-fall accidents refer to accidents where construction personnel, building materials, and equipment fall from a height, usually resulting in serious casualties and significant economic losses. This paper proposes a high-fall flexible protection system and its design approach with a tensile yield energy-consuming mechanism to solve high-fall accidents. The design approach based on component characteristics that obtained through tests contains energy matching, component internal force balance, and a two-level energy consumption mechanism. Component tests were conducted with mesh bursting tests and energy dissipator static tensile tests to obtain the characteristics of the intercepting net under the flexible boundary condition, and the force-displacement model of the ring-type energy dissipater. Combined with an actual project, we designed a high-fall flexible protection system with a protection energy level of 800 kJ for the core tube of an ultra-high-rise building construction using this method. The impact of dynamic response under multiple cases including the overall fall of the construction formwork was analyzed by dynamical numerical calculation models. The result shows that the system can effectively intercept high-falling objects and exhibit good two-stage energy dissipation characteristics to consume the impact energy. Compared with the protection system without an energy consumption mechanism, the internal force response of the steel wire rope and the suspended frame reduce by about 60%, and the energy consumption capacity increase more than six times. The protection technique proposed in this paper can effectively solve the problem of high-level impact protection such as falling construction formwork equipment, and improve construction safety. more...

Civil infrastructure O&M requires intelligent monitoring techniques and control methods to ensure safety. Unfortunately, tedious modeling efforts and the rigorous computing requirements of large-scale civil infrastructure have hindered the development of structural research. This study proposes a method for impact response prediction of prestressed steel structures driven by digital twins (DTs) and machine learning (ML). The high-fidelity DTs of a prestressed steel structure were constructed from the perspective of both a physical entity and virtual entity. A prediction of the impact response of prestressed steel structure’s key parts was established based on ML, and a structure response prediction of the parts driven by data was realized. To validate the effectiveness of the proposed prediction method, the authors carried out a case study in an experiment of a prestressed steel structure. This study provides a reference for fusion applications with DTs and ML in impact response prediction and analysis of prestressed steel structures. more...

Piezoelectric energy harvesting (PEH) is studied in the case of a low-velocity impact of a rigid mass on a composite beam. A methodology is outlined, encompassing modelling of the open-circuit impact response in a finite element (FE) package, formulation of a lumped parameter (LP) model for the piezoelectric transducer connected with the harvesting circuit, and experimental verification of the impact using a custom portable configuration with impactor motion control. The subcircuit capacitor charging effect, the impactor mass and velocity on the harvesting subcircuit response, and the obtained output power are quantified. The results indicate that the current methodology can be used as a design tool for the structure and the harvesting circuit to achieve power output from composite beams with piezoelectric patches under impact conditions. more...

This paper presents the results of a current study on the development and impact response of composite plates manufactured by injection overmolding on the two sides of a single reinforcement fibre mat. The injection polymer is a talc-filled polypropylene, nowadays used for structural purposes. Three configurations with different insert fibre mats were used: Kevlar, biaxial and multiaxial glass fibre mats. The parameters studied were the fibre mat type and the impact energy. For single impact tests, it was concluded that the highest impact energy required to achieve impactor perforation is obtained with Kevlar insert, while the highest percentage of energy recovered is achieved with biaxial glass fibre netting. Kevlar insert also allows for the maximum impact stiffness. For the multi-impact tests, the recovered energy and the dynamic stiffness show the same tendencies of the single impact tests. On low energy impacts, the effect of the insert fibre and of the previous impact are quite reduced, while for impact energies above 6J, previous impacts reduce significantly the recovered energy and the impact energy for which the perforation was achieved. more...

Up to this moment, there is no guideline regarding the materials to produce mouthguards. The most used is Ethylene-Vinyl Acetate (EVA). Studies indicate that laminating EVA sheets with rigid components could increase the protection capacities of the mouthguards whereas other studies suggest that only replacement of the material within it structure can increase energy absorption. The aim of this work is to evaluate the impact response of four different foils when compared to a 4 mm thickness EVA sheet. Five groups of different materials were subjected to impact tests with energies of 1.72 J, 2.85 J and 4.40 J. In this context was considered the following materials: EVA foils (G1), EVA foils with an EVA foam core (G2), EVA foils with an acetate core (G3), Foils of Erkoloc-pro (G4) and Foils of Ortho IBT resin (G5). Comparisons between the materials were made by qualitative analysis of the average energy-time and load-displacement curves, as well as by comparison of the peak load, maximum displacement, contact time and absorbed energy using the Kruskal-Wallis test. It was possible to conclude that statistically significant differences were found in the energy absorbed (p=0.001). Laminated foils with a soft core (G2) are a good option to produce mouthguards, while EVA foils with an acetate core (G3) and foils of Ortho IBT resin (G5) were declared unsuitable. more...

In this paper, we design a new three-dimensional honeycomb with a negative Poisson’s ratio. A honeycomb cell was first designed by out-of-plane stretching a re-entrant honeycomb and the honeycomb is built by spatially combining the cells. The in-plane response and energy absorption characteristics of the honeycomb are studied through the finite element method (FEM). Some important characteristics are studied and listed as follows: (1) The effects of cell angle and impact velocity on the dynamic response are tested. The results show that the honeycomb exhibits an obvious negative Poisson’s ratio and unique platform stress enhancement effect under the conditions of low and medium velocity. An obvious necking phenomenon appears when the cell angle parameter is 75°. (2) Based on the one-dimensional shock wave theory, the empirical formula of the platform stress is proposed to predict the dynamic bearing capacity of the honeycomb. (3) The energy absorption in different conditions are investigated. Results show that as the impact velocity increases, the energy absorption efficiency gradually decreases. In addition, with the increase of cell angle, the energy absorption efficiency is gradually improved. The above study shows that the honeycomb has good potential in using in vehicle industry as an energy absorption material. It also provides a new strategy for multi-objective optimization of mechanical structure design. more...

Despite the growing diffusion of composite materials in automotive and aerospace sectors, a standard procedure for testing their crashworthiness has not been developed yet. At present, the international standards for testing composite materials under impact conditions are not adequate to test their crush behavior. In this paper, a procedure for measuring the energy absorption due to the compressive crushing of a composite flat specimen, along its mid plane, is proposed. The experimental setup requires a fixture to hold the specimen and to avoid its buckling and an instrumented drop weight tower to obtain the force-displacement curves with the aim of calculating the Specific Energy Absorption. The paper will describe the adopted test procedure and some of the features of the newly developed experimental setup. The effectiveness of the procedure is demonstrated by testing several glass fiber-epoxy specimens under different impact energies. more...

Bird impact on fan blades poses a serious threat to the operational safety of aircraft engines.In this study, a real bird model of mallard duck was developed using the smooth particle hydrodynamics method based on a CT scan of a mallard duck.The accuracy of the real bird model was verified by comparing the simulation results of the impact on a plate of real bird model and simplified traditional bird model with the results of Wilbeck's tests.The transient impact responses of bird body and fan blade as the bird was striking a static and a rotating fan blade were comparatively analyzed.To study the effect of fan rotational speed on the bird-impact process, 836r/min, 1984r/min, 3344r/min, and 3772r/min were selected as fan rotational speed.To study the effects of impact location on the bird-impact process, 1/6, 2/6, 3/6, 4/6 and 5/6 of the blade height were selected as impact locations.The results show that blade rotation has a direct impact on the number of bird block cuts, the mass of a single bird block, and the number of impacted blades.Without considering the blade rotation conditions, the contact force, blade root stress, and blade leading edge stress are significantly lower than that when the blade rotation conditions are considered, which makes the prediction of blade stress and damage conservative and inadequate for use in the design of blade strength.Therefore, the blade rotation motion should be considered in the study of bird impact.The interaction mode between the bird and blade at 836r/min speed obviously differs from that at other rotational speeds.The kinetic energy of the bird decreases at a rotational speed of 836r/min, and increases at other rotational speeds, and the increment of the kinetic energy of the bird increases with increases in rotational speed.The leading-edge peak stress at 836r/min is greater than that at 1984r/min;at other rotational speeds, the peak stress of the leading edge increases with increases in the rotational speed.The contact force and blade root stress increase with increases in the rotational speed.With increases in the impact height, the contact force, kinetic-energy increment of the bird body, peak stress of the blade root, kinetic energy of the bird body, and the stress on the leading edge of blade all increase first and then decrease under the combined action of the relative velocity of the impact point and twist angle of the blade.The peak stress of the leading edge and the increment of the kinetic energy of the bird are greatest when impact occurs at 3/6 blade height, and the peak stress of the blade root and the contact force are greatest when impact occurs at 4/6 blade height. more...

Bird impact on fan blades poses a serious threat to the operational safety of aircraft engines.In this study, a real bird model of mallard duck was developed using the smooth particle hydrodynamics method based on a CT scan of a mallard duck.The accuracy of the real bird model was verified by comparing the simulation results of the impact on a plate of real bird model and simplified traditional bird model with the results of Wilbeck's tests.The transient impact responses of bird body and fan blade as the bird was striking a static and a rotating fan blade were comparatively analyzed.To study the effect of fan rotational speed on the bird-impact process, 836r/min, 1984r/min, 3344r/min, and 3772r/min were selected as fan rotational speed.To study the effects of impact location on the bird-impact process, 1/6, 2/6, 3/6, 4/6 and 5/6 of the blade height were selected as impact locations.The results show that blade rotation has a direct impact on the number of bird block cuts, the mass of a single bird block, and the number of impacted blades.Without considering the blade rotation conditions, the contact force, blade root stress, and blade leading edge stress are significantly lower than that when the blade rotation conditions are considered, which makes the prediction of blade stress and damage conservative and inadequate for use in the design of blade strength.Therefore, the blade rotation motion should be considered in the study of bird impact.The interaction mode between the bird and blade at 836r/min speed obviously differs from that at other rotational speeds.The kinetic energy of the bird decreases at a rotational speed of 836r/min, and increases at other rotational speeds, and the increment of the kinetic energy of the bird increases with increases in rotational speed.The leading-edge peak stress at 836r/min is greater than that at 1984r/min;at other rotational speeds, the peak stress of the leading edge increases with increases in the rotational speed.The contact force and blade root stress increase with increases in the rotational speed.With increases in the impact height, the contact force, kinetic-energy increment of the bird body, peak stress of the blade root, kinetic energy of the bird body, and the stress on the leading edge of blade all increase first and then decrease under the combined action of the relative velocity of the impact point and twist angle of the blade.The peak stress of the leading edge and the increment of the kinetic energy of the bird are greatest when impact occurs at 3/6 blade height, and the peak stress of the blade root and the contact force are greatest when impact occurs at 4/6 blade height. more...

In the process of coal mining, the canopy and column play an important role in the safety support of hydraulic support. However, due to the complex and changeable coal seam conditions, the hydraulic support is significantly affected by the impact load. This paper aims to reveal the dynamic characteristics of canopy and column under impact load. Firstly, the dynamic model of hydraulic support is established, and the impact response of each hinge point of the canopy is analyzed. Secondly, based on the fluid–structure interaction (FSI) theory, the two-way FSI model of the column is established, and the structural change of the column and the flow field characteristics in the cylinder under the impact load are analyzed. The results show that the front column hinge is more prone to impact failure under impact load. The impact load has a significant impact on the two-level cylinder, the pressure in the cylinder increases, and an eddy current occurs on both sides of the bottom of the cylinder. The research results can provide references for the structural optimization of the hydraulic support with anti-impact load and the strength design of the column. more...

Banana fiber has a high potential for use in fiber composite structures due to its promise as a polymer reinforcement. However, it has poor bonding characteristics with the matrixes due to hydrophobic&ndash, hydrophilic incompatibility, inconsistency in blending weight ratio, and fiber length instability. In this study, the optimal conditions for a banana/epoxy composite as determined previously were used to fabricate a sandwich structure where carbon/Kevlar twill plies acted as the skins. The structure was evaluated based on two experimental tests: low-velocity impact and compression after impact (CAI) tests. Here, the synthetic fiber including Kevlar, carbon, and glass sandwich structures were also tested for comparison purposes. In general, the results showed a low peak load and larger damage area in the optimal banana/epoxy structures. The impact damage area, as characterized by the dye penetration, increased with increasing impact energy. The optimal banana composite and synthetic fiber systems were proven to offer a similar residual strength and normalized strength when higher impact energies were applied. Delamination and fracture behavior were dominant in the optimal banana structures subjected to CAI testing. Finally, optimization of the compounding parameters of the optimal banana fibers improved the impact and CAI properties of the structure, making them comparable to those of synthetic sandwich composites. more...

The study of processes characterized by impulsive nature (i.e. impacts) can be considered of great interest in both physics and engineering disciplines: in the geotechnical field, for instance, their effect on the interaction between soil and structures need to be investigated. The present work aims at the validation, by means of two-dimensional finite element simulations, of a methodology of force calibration which uses results obtained from three-dimensional discrete element analysis for predicting the stress at the base of a granular bed, retained by a movable wall, arising when the system is hit by a projectile. To approach this problem, the low-velocity impact has been modeled as a punctual impulsive force on a granular packing. more...

The main goal of this study is to investigate the effectiveness of seismic retrofit using CFRP wrapping in reducing the damage and preventing the failure of RC bridge piers under vehicular impacts. This paper reports the results of an experimental investigation on the performance of cantilever CFRP-wrapped circular RC columns under lateral low-velocity impact. To this aim, a total of nine 1/3-scale cantilever columns without axial load, comprising three types of shear-deficient RC columns with different reinforcement layout, were tested in a horizontal collision facility at two different impact velocities. The columns were tested in plain configuration (0 plies) and two wrapped configurations with 2 and 4 plies of CFRP. Generally, for plain columns, brittle shear-type damage was observed. Larger damage was obtained by increasing the impact velocity and decreasing the amount of transverse reinforcements while the variation of the amount of longitudinal steel bars has a negligible effect. The experimental results demonstrate that seismic retrofit using CFRP can provide an effective solution to convert the failure mechanism under lateral impact loading, from shear- to flexural-dominated, with a reduction of the impact damage. This strategy has a beneficial effect given sufficient bending capacity of the plain RC column. more...

In order to obtain the effect of porosity on the dynamic mechanical properties and impact response characteristics of high aluminum content PTFE/Al energetic materials, PTFE/Al specimens with porosities of 1.2%, 10%, 20%, and 30% were prepared by adding additives. The dynamic compression properties and impact response characteristics of high aluminum content PTFE/Al energetic materials with porosity were studied by using a split Hopkinson pressure bar (SHPB) impact loading experimental system. Based on the one-dimensional viscoplastic hole collapse model, an impact temperature rise analysis model including melting effects was used, and corresponding calculation analysis was performed. The results show that with the increase of porosity, the yield strength and compressive strength of the material will decrease. Under dynamic loading, the reaction duration of PTFE/Al energetic materials with different porosities generally shows a tendency to become shorter as the porosity increases, while the ignition delay time is basically unchanged. In this experiment, the material response has the optimal porosity with the lowest critical strain rate, the optimal porosity for PTFE/Al energetic materials with different porosity and high aluminum content (50/50 mass ratio, size of specimens &Phi, 8 &times, 5 mm) is 10%. The research results can provide an important reference for the engineering application of PTFE/Al energetic materials. more...

Bird-strike failure of fan blades is one of the basic challenges for the safety of aircraft engines. Simplified slender blade-like plates are always used to evaluate the impact-induced damage mechanism at design stage. One undesirable issue is the failure at the root of clamped slender plates, which cannot recover the real case of twisted blades. For this purpose, three different strategies were exploited to obtain desirable deformation and stress responses, namely the impact location, additional weight, and the boundary condition. Numerical models of the simplified slender blade and the bird projectile were constructed by using finite element method (FEM) and smoothed particle hydrodynamics (SPH) approaches. The impact deformations and stress distributions were comparatively investigated in detail. The numerical results show that changing the boundary condition is the most effective way to obtain preferable impact responses for further failure analysis of real fan blades. Present results will be useful to future experimental design of simplified bird-strike testing. more...

Aerospace composites are susceptible to barely visible impact damage (BVID) produced by low-velocity-impact (LVI) events. Fibre Bragg grating (FBG) sensors can detect BVID, but often FBG sensors are embedded in the mid-plan, where residual strains produced by impact damage are lower, leading to an undervaluation of the damage severity. This study compares the residual strains produced by LVI events measured by FBG embedded at the mid-plan and other through-thickness locations of carbon fibre reinforced polymer (CFRP) composites. The instrumented laminates were subjected to multiple low-velocity impacts while the FBG signals were acquired. The FBG sensor measurements allowed not only for the residual strain after damage to be measured, but also for a strain peak at the time of impact to be detected, which is an important feature to identify the nature and presence of BVID in real-life applications. The results allowed an adequate optical fibre (OF) embedding location to be selected for BVID detection. The effect of small- and large-diameter OF on the impact resistance of the CFRP was compared., This research was funded by the European Regional Development Fund, grant number NORTE-01-0145-FEDER-000015, and the APC was funded by the European Space Agency’s Network/Partnering Initiative Program, with contract number 4000123315. more...

The effectiveness of Carbon Fiber Reinforced Polymer (CFRP) seismic-retrofit of circular Reinforced Concrete (RC) bridge piers under vehicular lateral impact loading is addressed in the present work performing experimental tests. Sixteen 1 / 3 scale RC bridge piers with circular cross-sections characterized by three different configurations of longitudinal and transverse reinforcements were tested with and without CFRP seismic-retrofit. In the first case, tested columns represent common shear-deficient RC bridge piers designed with obsolete design practice or for non-seismic areas. In the second case, CFRP wrapping is applied according to common seismic-retrofit practices to increase the shear capacity and ductility of columns. Experimental tests were carried out under static and lateral impact loading with propped cantilever conditions reproducing a typical short-span viaduct bridge pier configuration. In the static tests, the lateral load was applied monotonically through a hydraulic jacket under equivalent impact conditions. In impact tests, the lateral impact load was applied through a colliding truck equipped with a rigid hammer at the typical vehicular impact location adopting two different impact velocities (3 and 4.5 m / s ). A critical investigation of the transient dynamic characteristics, damage evolution, and post-impact damage is conducted by comparing the results obtained with and without CFRP seismic-retrofit, and under static and dynamic loading conditions. It is shown that CFRP seismic-retrofitting of circular RC bridge pier can also be effective in reducing the vulnerability under lateral impact loading. The CFRP-retrofit approach adopted in this study meets the requirement of multi-hazard prevention improving the robustness of the bridge. Finally, a semi-empirical equation for predicting the maximum displacement under impact loading is derived based on experimental results. The proposed equation adopts the results of a static test as a proxy for assessing the dynamic behavior allowing for the design of the required shear and flexural load-carrying capacity. more...

While the separate design of functionally graded and fractal self-similarity structures had shown to be effective in improving the energy absorption capacities of honeycombs, their combined effect is still unknown. Hence, in this study, a series of novel fractal honeycombs are proposed based on the combination of functionally gradient with fractal self-similarity features, which are constructed by varying the fractal parameter in each layer of the traditional self-similar honeycombs. Two graded fractal honeycombs with symmetric gradient and another two with asymmetric gradient are presented, and their dynamic crushing behaviors are numerically investigated. The numerical approach is first validated by comparing against theoretical and experimental data. Subsequently, it is demonstrated that the SG-I honeycomb can present the best energy absorption behavior (89% higher than traditional honeycomb) for low-velocity impact, while SG-II honeycomb performs the best for specific energy absorption (17% larger than traditional honeycomb) for high-velocity impact. Furthermore, deformation patterns under dynamic crushing can be controlled through the introduction of different gradient distributions. The graded fractal honeycombs present significant improvements to the absorbed energy and mean crushing force over traditional honeycombs, offering a new route to the design and optimization of future lightweight energy absorption systems with improved safety protection performance. Nanyang Technological University National Research Foundation (NRF) Accepted version The authors would like to thank the Singapore Centre for 3D Printing, which is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Medium‐Sized Centre funding scheme, as well as the internal funding by Nanyang Technological University 04INS000329C160 and 04INS000453C160. more...

We built a three-dimensional finite element (FE) model to investigate the impact response of fiber-metal laminates (FMLs). This FE model comprises two metal layers as facesheets and a carbon woven fabric-reinforced plastic laminate as inner core. Simulation was performed on ABAQUS/Explicit platform, and stiffness progressive degeneration criteria were implemented to evaluate damages in composites. The Johnson-Cook model was selected to calculate failures in metal, while surface-based cohesive behavior was adopted to simulate the delamination phenomenon. We studied the fiber stacking sequence, panel thickness, and incident angle effect on the impact behavior of FMLs. The critical penetration energy of the FMLs was determined, and the impact parameter history was discussed. more...

The present study delved into the effect of impactor diameter on low velocity impact response and damage characteristics of CFRP. Moreover, the phased array ultrasonic technique (PAUT) was adopted to identify the impact damages based on double-sided scanning. Low-velocity impact tests were carried out using three hemispherical impactors with different diameters. The relationship of impact response and impactor diameters was analyzed by ultrasonic C-scans and S-scans, combined with impact response parameters. Subsequently, the damage characteristics were assessed in terms of dent depth, delamination area and extension shape via the thickness, and the relationships between absorbed energy, impactor displacement, dent depth and delamination area were elucidated. As revealed from experiment results, double-sided PAUT is capable of representing the internal damage characteristics more accurately. Moreover, the impactor diameter slightly affects the impact response under small impact energy, whereas it significantly affects the impact response under large impact energy. more...

As an effective strategy to enhance the energy absorption and impact resistance capacities of foam materials, density-gradient design has been widely proposed as a viable solution. However, the influence of thermal environment on the impact response and energy absorption of functionally graded foam still remains unclear. In the present paper, an analytical model based on the double shock wave theory is presented to examine the impact performance of density-graded foam rods under temperature gradient environments. A density-graded foam with one end supported and the other end struck by a block of mass is presented to evaluate their impact performances. Both the positive and negative density-gradient models with power-law profiles along the axial direction of the foam rod are considered. The proposed theoretical representation is validated against several previous models, including a finite element (FE) simulation. It is demonstrated that the temperature gradient may lead to transformations in the deformation pattern for the positive and negative density-graded foams. Moreover, the temperature gradient can enlarge the impact resistance property in most cases and can reduce the energy absorption capacity of density-graded foams. Nanyang Technological University Accepted version The authors appreciate the support of a start-up grant from Nanyang Technological University. more...

BISS Pvt. Ltd. Bangalore;Blue Star Engineering and Electonics Ltd.;DRDO India;Edu-Tek;EduTech 2nd International Conference on New Frontiers in Engineering, Science and Technology, NFEST 2019 -- 18 February 2019 through 22 February 2019 -- -- 150584 The aim of this work was to study the energy absorption of composite pipesunder different level of low velocity impact test. The basalt fiber is used for making filament wound composite pipe. Because it offer more strength and a reduction in density when compared to existing fibres such as glass fibres, carbon fibre and etc. Moreover the fibre has higher breaking strength compare to other fibre. The basalt composite pipe is manufactured under filament winding process with the help of epoxy resin and undergoesimpact tests. The pipe is manufactured with 100mm diameter, 6mm thickness and filament winding angle is set as 55degree. In this pipes are tested under drop weight low velocity impact machine and strength of the pipe was examined in different energy level. Impact force, displacement, energy absorption were measured. © 2019 IOP Publishing Ltd. All rights reserved. more...

Nowadays, scientific and technological efforts are being carried out to diminish serious ecological problems caused by indiscriminate use of non-biocompostable polymers in the packaging industry. In this sense, novel biodegradable blends of different composition based on poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) and tributyrin (TB) are developed and here proposed as an eco-friendly alternative. Materials are characterized by fracture experiments under quasi-static and biaxial impact loading. Fracture behavior is analyzed together with thermal, tensile and water permeation properties to evaluate their potential in-service performance. TB_PLA/PHB blends with 15 wt% TB exhibit better permeation and fracture toughness than currently used bio-based polymers, being in the range of polyethylene properties. Results highlight the potential of these new blends broadening the current application field of PLA. Fil: Iglesias Montes, Magdalena Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Cyras, Viviana Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Manfredi, Liliana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina more...

This work focuses on the experimental investigation of the residual flexural strength of hemp/epoxy, basalt/epoxy and hybrid (hemp-basalt)/epoxy composite laminates subjected to low velocity impact damage at different temperatures. These specimens were subjected to a low velocity impact of 1.5 m/s with an incident impact energy of 2.17 J using an instrumented drop weight impact tester at three different temperatures of 30 °C, 50 °C and 65 °C. The residual flexural strength of the post impacted specimens were measured by the conduction of three point bending test in a 100 kN universal testing machine with acoustic emission monitoring. The effects of temperature and basalt fiber hybridisation on the damage initiation, propagation and onset of failure were investigated using the magnitude of AE cumulative counts at different stages of loading. The results show a reduction in impact strength and residual flexural strength after impact at elevated temperatures. Lower impact resistance shown in the impact test results for all three types of composites at elevated temperatures indicate the effect of temperature which leads to inferior impact properties. It was evidenced from the impact and dynamic mechanical analysis (DMA) carried out on the composites that hybrid composites have better residual flexural strength and impact properties compared to non-hybrid composites. more...

In order to study the base pounding effects of base-isolated structure under earthquake excitations, a base pounding theoretical model with a linear spring-gap element is proposed. A finite element analysis program is used in numerical simulation of seismic response of based-isolated structure when considering base pounding. The effects of the structure pounding against adjacent structures are studied, and the seismic response of a base-isolated structure with lead-rubber bearing and a base-isolated structure with friction pendulum isolation bearing are analyzed. The results indicate that: the model offers much flexibility to analyze base pounding effects. There is a most clearance unfavorable width between adjacent structures. The structural response increases with pounding. Significant amplification of the story shear-force, velocity, and acceleration were observed. Increasing the number of stories in a building leads to an initial increase in impact force, followed by a decrease in such force. As a result, it is necessary to consider base pounding in the seismic design of base-isolated structures. more...

A key aspect in the design of mega bridge structures across navigable waterways is to ensure bridge safety with respect to accidental ship collisions. Special attention has been paid to providing sufficient impact resistance for bridge sub-structures including piers and pylons. However, the collision design of bridge super-structures such as bridge girders is commonly neglected. In this paper, high-fidelity finite element models of a ship bow and a bridge girder are established. Numerical simulations are conducted to study the structural response of the bridge girder subjected to impact from the ship forecastle. Based on the simulation results, design considerations of bridge girders against ship forecastle collision loads are discussed. The effects of the impact location and relative structural strength are also investigated. A simple but effective strengthening method is proposed to increase the collision resistance of steel bridge girders. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). more...

本研究では，AFRPシートを接着した曲げ補強RC梁の，耐衝撃挙動を適切に評価可能な数値解析モデルの構築を最終目的として，衝突速度の異なる RC梁を対象に三次元弾塑性衝撃応答解析を実施し，別途実施した実験結果との比較により，解析手法の妥当性を検討した。その結果，（1）提案の解析手法を用いることにより，最大変位およびひび割れ分布性状を概ね再現可能であること，（2）一方，シート破断を生じた試験体の場合は，最大変位を過小評価することが明らかになった。 more...

Annual Conference on Experimental and Applied Mechanics, 2016, 6 June 2016 through 9 June 2016, Poly ethylene terephthalate (PET) is considered one of the most important engineering polymers for the last two decades due to its rapid growth of usage, aesthetic appearance, good light transmittance, and smooth surface. It is highly preferable for the food and soft drink bottle packaging industry because of its low gas permeability and recycling potential. For this reason, vast amount of PET’s is used daily and mandates an effective recycling process. The recycling of PET can be performed using two different methods, which are chemical and mechanical methods. In this study, chemical recycling method was chosen as a recycling method. Waste PET bottle evaluated as a binder for composite materials. Obtained glycolized products and binder are characterized by OH number (hydroxyl), acid number and FTIR. Then E-glass/recycle resin composite plates were manufactured via Vacuum Assisted Resin Transfer Molding (VARTM). Drop weigh tests were applied to measure the general mechanical and damage behavior of these composites. © The Society for Experimental Mechanics, Inc. 2017. more...

© 2016 Elsevier Ltd. Ballistic tests were performed on two types of polyethylene core sandwich structures (AA6082/LDPE/AA6082 and AA6082/UHMWPE/AA6082) to investigate their perforation resistance. Bulging and dishing deformation of layered plates were compared under low-velocity impact by hemispherical-nosed projectiles. Different impact failure mechanisms leading to perforation were revealed for laminates composed of a pair of aluminum alloy face sheets separated by a polyethylene interlayer. Using the finite element code Abaqus/Explicit, the perforation behavior and distribution of energy dissipation of each layer during penetration were simulated and analysed. The deformation resistance and anti-penetration properties of polyethylene core sandwich structures were compared with those of monolithic AA6082-T6 plates that had the same areal density. Although the polyethylene interlayer enlarged the plastic deformation zone of the back face, the polyethylene core sandwich structure was a little less effective than the monolithic Al alloy target at resisting hemispherical-nosed projectile impact. more...

Natural fibers combine technological, economic and ecological aspects. However, a major restriction on their successful use in long term composite applications is their high moisture absorption and poor dimensional stability. This paper is aimed at establishing a link between the mats grammage and the mechanical properties of the epoxy/jute fibers laminates. Composites reinforced by coarse, medium and fine (C, M and F) mats were processed by vacuum bagging. Some batches were immersed in water up to 60 days in order to study the hydro-degradation. Mechanical tests were performed to obtain the bending strength and impact response. The mechanical response to bending and impact loadings was conditioned not only by the percentage of fiber, but also by the thickness of the specimens, which leads to composites F having lower strength than composites C despite having a higher percentage of fiber. Immersion in water causes a marked loss of mechanical properties in the first days of immersion, especially for thinner fiber grammage composites. A strong influence of the mats grammage on the impact response was observed. Increasing mats grammage promotes a strong increase in peak load, restored energy and impact energy for perforation and also a marked reduction of the deformation. more...

The present experimental investigation deals with the impact responses of hybrid composites (carbon-glass fiber/epoxy) under various temperatures. A number of samples were subjected to increasing impact energy at the temperature range of -20 to 60°C until complete perforation of samples. With this use of increasing impact energies, it was possible to examine the impact response and failure mechanisms of hybrid composites until perforation of sample. An Energy Profiling Diagram (EPD) was used to obtain the penetration and perforation thresholds of hybrid composites. Besides, the temperature effects on impact characteristics such as load, contact time and permanent deflection were also presented in figures. Test results showed that temperature variations affect the impact characteristics of hybrid composites and they get their maximum values at -20°C or 60°C. © 2012 Elsevier Ltd. All rights reserved. more...

The effect of mechanical shock impacts is a key factor in the reliability of modern handheld products. Due to differences in product enclosures, impact orientations, strike surfaces and mountings of component boards, the loading conditions induced in a true product drop differ from those encountered in standardized board-level tests. In order to better understand the correlation between board-level drop testing and actual drops of a complete device, series of board and product-level drop tests were conducted using specialized test boards. The mechanical shock impact response of the commercial handheld device component board was characterized with the help of acoustic excitation laser vibrometry and finite element analysis. The results were used to design the mechanically compatible specialized test board for both 4-point supported board-level and unsupported product-level drop tests. Special care was taken to ensure that the vibration behavior of the test board accurately represented the vibration behavior of the commercial component board. Additional board-level drop tests were conducted using a JEDEC JESD22-B111 compliant component board for comparison. The drop test results showed that, even though the test board design and supporting method have a marked influence on the strain conditions and lifetime of solder interconnections, the primary failure mode and mechanism under the product-level drop tests is comparable to that typically encountered in the standard JEDEC JESD22-B111 board-level drop tests. More detailed analyses suggest that the comparability of the shock impact loading conditions affecting solder interconnections can be characterized using three metrics: (1) the maximum component board strain rate, (2) the maximum board strain amplitude and (3) the damping of the component board. more...

Rotor rubbing is a common fault of rotating machinery, and usually induced by other faults, such as bending, clearance, unbalance and so on. The essential characteristic of this fault is the impact and friction between rotor and stator, so this paper puts forward a method for representing the rubbing fault by identifying the suffered dynamic load of rotor and stator. The basic formula of load identification is built, and the measured impact response is used to replace the system real impulse response function. The experiment results show that the proposed method can effectively extract the impact components of rotor and stator, and detecting stator vibration signal is more effective to represent rubbing fault than that of rotor, and the analysis result has clear credibility. Meanwhile, the proposed method is convenient for practical engineering application. more...

In this paper, in order to accumulate a basic knowledge for establishing rational performance-based impact resistant design procedure for the RC type rock-sheds, casting a 2/5 scale model of RC type rock-shed, the falling-weight impact test for the structure without sand cushion is conducted using 2 ton heavy weight. From this study, following results are obtained: (1) the model is failed in the punching shear mode when surcharged at the center of roof slab; and (2) the impact resistant capacity of the free edges of the model may be greater than that at the center because the free edges can more flexibly behave and more absorb the impact energy than the center of the roof slab. more...

In order to establish performance-based impact resistant design procedure for RC rock-sheds, falling-weight impact test of small Rahmen-type RC models with/without sand cushion was conducted. And its numerical simulation was performed by means of three-dimensional elasto-plastic finite element method and its applicability was investigated comparing with experimental results. The results obtained from this study are as follows: 1) absorbing effects of the sand cushion are significant but dynamic response characteristics of the model can't be much affected by sand cushion; 2) dynamic response characteristics of the RC model are similar to those under static loading; and 3) dynamic response behavior of the RC model under falling-weight impact loading can be better simulated by using proposed numerical analysis method. more...

In this study, the impact response of unidirectional glass/epoxy laminates has been investigated by considering energy profile diagrams and associated load-deflection curves. Damage modes and the damage process of laminates under varied impact energies are discussed. Two different stacking sequences, [0/90/0/90]s and [0/90/+45/-45]s, were chosen in tests for comparison. An alternative method, based on variation of the excessive energy (Ee) versus impact energy (Ei), is presented to determine penetration threshold (Pn). The penetration threshold for stacking sequence [0/90/+45/-45]s is found to be smaller than that of [0/90/0/90]s. The primary damage mode was found to be fiber fracture for higher impact energies; whereas, it was indentation resulting in delamination and matrix cracks for smaller impact energies. Contour plots of the overall damage areas are also depicted for several impact energies. © 2008 Elsevier Ltd. All rights reserved. 104M426 Financial support for this study was provided by The Scientific and Technological Research Council of Turkey (TÜBİTAK), (Project Number: 104M426). Partial financial support by Izoreel firm, in Izmir-Turkey, is also gratefully acknowledged. more...

In the present paper, the problem of low-velocity impact of an elastic sphere against a viscoelastic Timoshenko-type beam is studied considering the extension of its middle surface. The viscoelastic features of the beam out of the contact domain are governed by the standard linear solid model with derivatives of integer order, while within the contact domain the fractional derivative standard linear solid model is utilized, in so doing rheological constants of the material in both models are the same. However the presence of the additional parameter, i.e. fractional parameter which could vary from zero to unit, allows one to vary beam’s viscosity, since the structure of the beam’s material within this zone may be damaged, resulting in the decrease of the beam material viscosity in the contact zone. Consideration for transient waves (surfaces of strong discontinuity) propagating in the target out of the contact zone via the theory of discontinuities and determination of the desired values behind the surfaces of discontinuities upto the contact domain with the help of ray series, as well as the utilization of the Hertz theory in the contact zone allow one to obtain a set of two integro-differential equations, which govern the desired values, namely: the local bearing of the target and impactor’s materials and the displacement of the beam within the contact domain. more...

An analytical model of the dynamic properties is established for a piezoelectric structure under impact load, without considering noise and perturbations in this paper. Based on the general theory of piezo-elasticity and impact mechanics, the theoretical solutions of the mechanical and electrical fields of the smart structure are obtained with the standing and traveling wave methods, respectively. The comparisons between the two methods have shown that the standing wave method is better for studying long-time response after an impact load. In addition, good agreements are found between the theoretical and the numerical results. To simulate the impact load, both triangle and step pulse loads are used and comparisons are given. Furthermore, the influence of several parameters is discussed so as to provide some advices for practical use. It can be seen that the proposed analytical model would benefit, to some extent, the design and application (especially the airport runway) of the related smart devices by taking into account their impact load performance. more...

The processing characteristics and mechanical properties of glass fabric reinforcements coated with graphene nanoparticles were investigated. Graphene was coated onto either one or both sides of a plain weave glass fabric. The coated fabrics were investigated to measure key process characterization parameters used for vacuum assisted resin transfer molding (VARTM) process which are, reinforcement compaction response, in-plane, and transverse permeability. It was found that graphene coated glass reinforcements were stiffer than the pure glass reinforcements which will have direct influence on final fiber volume fraction obtained during VARTM processing. The permeability measurement results show that the graphene coated reinforcements filled relatively slower compared with the pure glass samples. Composite samples were then tested for flexural and low velocity impact. The initial results show that the flexural modulus did not change as the wt % of graphene increases. However, a decrease in flexural strength with increasing wt % of graphene was observed. It was also observed that the coating of graphene on glass reinforcements caused delamination between plies and resisted localized damage under low velocity impact as compared to pure glass samples. more...

This experimental study deals with the impact response of composite plates manufactured with stitch-bonded non-crimp glass fiber fabrics. Three kinds of fabrics – biaxial, triaxial, and quadraxial – are used as reinforcing material. Polyester resin is used as a matrix material in the composition of composite plates. An instrumented drop weight impact testing machine, Instron-Dynatup 9250 HV, is used for impact testing. Impact tests are performed under various impact energies, ranging from damage initiation to final perforation. An energy profiling method, showing the relation between impact energy and absorbed energy, was used together with load-deflection curves to determine the penetration and perforation thresholds of those composites. The failure processes of damaged specimens for different impact energies were evaluated by comparing load-deflection curves and images of damaged samples taken from the impacted and non-impacted sides. All types of composites have obvious penetration and perforation thresholds. The perforation threshold of triaxial/polyester composite is approximately 27% and 22% higher than that of the quadraxial and biaxial/polyester composites, respectively. more...

This article presents a new multiscale modeling approach proposed to predict the impact response of a biomedical niobium-zirconium alloy by incorporating both geometric and microstructural aspects. Specifically, the roles of both anisotropy and geometry-based distribution of stresses and strains upon loading were successfully taken into account by incorporating a proper multiaxial material flow rule obtained from crystal plasticity simulations into the finite element (FE) analysis. The simulation results demonstrate that the current approach, which defines a hardening rule based on the location-dependent equivalent stresses and strains, yields more reliable results as compared with the classical FE approach, where the hardening rule is based on the experimental uniaxial deformation response of the material. This emphasizes the need for proper coupling of crystal plasticity and FE analysis for the sake of reliable predictions, and the approach presented herein constitutes an efficient guideline for the design process of dental and orthopedic implants that are subject to impact loading in service. Copyright © Materials Research Society 2014. more...

This study investigates the performance of particulate-filled thermoplastic fluoropolymer coatings under both dynamic impact tests and static indentation tests. An instrumented impact testing rig was used to measure the impact energy, impact velocity, acceleration and impact force during the impact tests. Coating samples with different thicknesses of coating layers and steel substrate were impact tested to investigate the effect of coating and substrate thickness on the impact response and damage to the coatings. The data obtained from the dynamic tests were used to calculate the Meyer hardness values of the coating and compared with the Meyer hardness results obtained from Brinell indentation tests on the coating. The Meyer index m was similar under dynamic impact and static indentation testing conditions. The Meyer hardness calculated from the impact tests does not change markedly as a function of depth of penetration normalised to the thickness of coating, whereas the Brinell hardness increases with the depth of penetration to coating thickness ratio. For a given value of indentation strain, the Meyer hardness calculated from the maximum force measured in the impact test is approximately 2.5 times that resulting from the Brinell test. This reflects the fact that the higher strain rate in the impact test would give rise to a higher flow stress and thus hardness. School of Engineering Sciences, University of Southampton and BP Exploration, Sunbury-on-Thames, UK. more...

Polyvinylidene fluoride (PVDF) is popular sensing material because of its unique piezoelectric characteristics. In this work an impact sensor was prepared from a sandwiched structure PVDF film, and the related detection circuits were presented. The dependence of the PVDF sensors’ response on the elasticity of the supporting materials was examined and discussed. Here two response indexes were discussed, which were the peak-to-peak voltage (Vpp) and the recovery time. Firstly, falling impact experiments were executed on desk-supported PVDF sensors (100 mm PVDF film) using free falls of different weights from different heights. Then the same shock experiments were repeated on the same sensor, but changing the backstops to a sponge and rubber, respectively. On the desk, the values of Vpp were bigger than when the other two backstops were used, but the changes of the impact energy could not be reflected by the PVDF sensor when it was supported by a hard material. It was found that the biggest sensitivity of the voltage response (about 96.62 V/J) was obtained by the sponge-supported sensor, for the same sensor, when it was supported by rubber, the slope was 82.26 V/J. Moreover, the recovery time for the desk-supported sensor was almost constant, varying from 0.15 to 0.18 s, while for the same sensor supported by sponge or rubber, its recovery time changed with the shifting of the impact energy in the range of 0.02~0.36 s, but no pattern could be found in the recovery-time characteristics. more...

In this study an experimental investigation is performed on the impact response of non-crimp fabric composite plates at room temperature. Chopped strand mat combi is used as reinforcing material and two kinds of matrix; epoxy and polyester, are also used as resin material in the composite plates. All specimens used in experiments are manufactured by vacuum assisted resin infusion method at Atard Defence and Aerospace Advanced Technology Application Research and Development Inc. An instrumented drop weight impact testing machine Instron-Dynatup 9250 HV is used for impact testing. Impact tests are performed under various impact energies ranging from initiation of damage to final perforation. Damage processes of the samples are analyzed from cross-examining load deflection curves, energy profiling method and damaged specimens. more...

The objective of this paper is to present the effect of gaps and overlaps on the mechanical properties of an AFP manufactured 24-plies quasi-isotropic carbon/epoxy composite. Tests are carried out using 7 defect configurations in Open Hole Compression (OHC) specimens (ASTM D 6484) and 4 defect configurations in drop weigh impact tests specimens (ASTM D7136). Ultrasonic C-scan observations and compression after impact tests (ASTM D7137) were performed on impacted specimen. Tests results show that 90° defects have the most important effect on OHC strength (between 7% and 13% strength reduction for 90° gaps) due to 45° plies waviness whereas specimen with 0° gaps or 0° overlaps have a maximum strength variation of 7%. It is also observed that AFP defects have a local effect on composite impact response but they do not have a significant effect on coupons impact response. An analytical model which predicts the effect of 0° defects on the compressive properties is proposed in this paper. Using classical laminate theory, this model recalculates the material's properties considering the effect of the defect on the global mechanical properties of the specimen. The prediction of the model show very good agreement with the experimental results and demonstrate that 0° defects do not create stress concentrations which lead to specimen failure., 26th Annual Technical Conference of the American Society for Composites 2011 and the 2nd Joint US-Canada Conference on Composites, 26 September 2011 through 28 September 2011, Montreal, QC more...

The aim of the study is to lay bare the impact behavior of filled composite plates experimentally. The woven glass/polyester-matrix composite plates filled with 0% (unfilled), 10%, and 20% SiCp ceramic particles were manufactured by hand lay-up method. The low velocity drop impact testing is conducted to the composite samples subjected to increasing impact energies that were ranged from approximately 2.5 to 22.5 J. With this use of increasing impact energies, it was possible to examine the impact response and damage mechanism until perforation of the composite plates. An energy profiling method was used in order to identify the perforation thresholds of composites. It is concluded that addition of particles to resin, until a certain ratio, increases the perforation thresholds of the woven glass/polyester. The perforation threshold of 10% filled composite is about 37% higher than that of the 20% filled composite and 6% higher than ones of the unfilled composite. POLYM. COMPOS., 32: 1125-1133, 2011. (C) 2011 Society of Plastics Engineers more...