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The use of composites has widely increased over the years. These structures have particularly attracted the attention of the aerospace industry where the low weight is one of the important features of structural design. Then, the composites have been started to use in sandwich panels. There have been many implementations of the composites in the sandwich panels due to their structural efficiency with the low weight. The aim of this research is to investigate a novel three-dimensional woven cellular core (3DWCC) for application in morphing wing for unmanned aerial vehicles. Polyester yarn is used as reinforcement and the epoxy as matrix. In order to characterise their mechanical properties, the composite cores are tested under compression in 1- and 3- directions. Then, the 3D woven composite core performance, which the cells lie in 1- direction (longitudinal), is investigated under four-point bending. The effect of skin thickness, the core topology and the core type are examined experimentally. One of the key results obtained from the experiments is that the 3DWCC, which the cells lie in 1-direction, recover their shape after the load is removed in both compression and flexural tests. In addition, the 3D woven cellular core (3DWCC) shows resistance to the bending without skin. The flexural behaviour of the sandwich panels is highly affected from the geometrical parameters of the core and skin. In this line, failure modes of the 3D woven cellular core panels and their limit loads are predicted analytically depending on variables: the skin thickness, core density, and loading configuration.

This thesis explores the use of lightweight composite materials in road freight trailer design as a means of reducing the emissions of the road freight industry. A comprehensive review of previous lightweight composite trailers and related projects was conducted; it concluded that the application of composites in trailers to-date has largely been limited by relatively high material and production costs. The review highlighted that the trailer industry could learn from the success of composites in the bridge construction industry. A statistical weight analysis of two road freight fleets and an energy consumption estimation, via a drive cycle analysis, were used to identify trailers that are particularly suited to lightweighting. Hardwood trailer decking was identified as a prime subcomponent for composite replacement. However, there is little literature on how conventional hardwood trailer decks react to in-service loadings. This problem was addressed through a comprehensive deck damage study, which was used to benchmark novel lightweight deck systems. Several lightweight replacement composite sandwich panels were designed, built and tested. Two different pultruded GFRP decks were also examined. While pultrusions do not offer the same level of weight savings as sandwich panels, the highly cost-driven nature of the trailer industry could dictate that their integration is the most reasonable first step to introducing composites into structural subcomponents. The final part of the thesis explores options for lightweighting the trailer chassis holistically. Trailer load cases were investigated through finite element modelling in Abaqus. A parametric model of a typical longitudinal trailer I-beam was developed using Python scripting and Abaqus. The model was expanded to analyse composite trailer structures. It showed that approximately 1,300 kg of weight could be saved by shape and material optimisation in a composite trailer. In summary, this research has shown that short-term trailer weight reductions can be effectively achieved through subcomponent replacement, while more significant reductions can be achieved in the long-term by a ‘clean slate’ composite redesign of the trailer chassis. The lightweighting strategies presented here are poised to have an increasingly important role in reducing the emissions of the road freight industry.

This thesis presents the results of research on sandwich panel construction, with the aims of developing tools for modelling sandwich panel fire performance and hence to use the tools to aid the development of sandwich panel construction with improved fire resistance. The research focuses on sandwich panels made of thin steel sheeting and a polyisocyanurate (PIR) foam core. For non-loadbearing sandwich panel construction, fire resistance is measured in terms of thermal insulation and integrity only. However, these two parameters are affected by mechanical performance of sandwich panel construction due to the high distortion and large deformation nature of sandwich panel construction under fire attack. Therefore, it is necessary to consider both thermal and mechanical performances of sandwich panels under fire conditions. The work in this thesis includes development of a thermal conductivity model for PIR foam as this thermal property is one of the key values in determining heat transfer through sandwich panels; this thermal conductivity model is based on the effective thermal conductivity of porous foams proposed by Glicksman (1994) and includes the effects of polymer decomposition and increases in foam cell size. It is validated against fire tests carried out on PIR sandwich panels 80mm and 100mm thick with steel facings of thickness 0.5mm. A large 3D sequentially coupled thermal-stress model of a full scale fire test has been developed in the commercial finite element analysis (FEA) software ABAQUS to provide insight into the way sandwich panels behave in a fire resistance test and also to assess different modelling techniques. Aspects and stages of the simulation that agree well with test data are explained. Limitations of the ABAQUS software for simulating sandwich panel fire tests are highlighted; namely, it is not possible to simulate the correct radiation heat transfer through panel joints, as cavity radiation cannot be specified in a fully coupled thermal-stress analysis. Joints are key components of sandwich panel construction. In order to obtain temperature development data for modelling joints, a number of fire tests have been carried out. These fire tests were conducted with different joint configurations and panel thicknesses under realistic fire conditions using timber cribs. The joint fire tests revealed significant ablation of the foam core within the joints of sandwich panels at high temperatures. At the beginning of fire exposure, the joint temperature on the unexposed surface was lower than that on the panel due to the better insulation property of air compared to the foam. However, as the joint gap increased due to ablation of the foam, the joint temperatures became higher than in the panel. A numerical simulation model has been created to investigate this behaviour. Using the aforementioned thermal model, numerical simulations have been carried out to examine the influences of possible changes to sandwich panel design on sandwich panel construction fire performance. It was suggested that if the maximum gap in the joints can be limited to 5mm, for example, by applying intumescent coating strips within the sandwich panel joints to counter the increasing gap formed due to core ablation, then the joint temperature on the unexposed surface would not exceed that of the panel surface, hence the joint would cease to be the weak link. To increase the panel fire resistance, the use of graphite particles in the PIR foam formulation may be considered to lower the contribution of radiative heat transfer within the foam cells by reducing the transmissivity of the cell walls. Graphite particles may offer considerable increases in the thermal resistance of PIR foam at high temperatures by limiting the radiation contribution which dominates heat transfer above 300oC.

Honeycomb sandwich panels, formed by bonding a core of honeycomb between two thin face sheets, are in wide use in aerospace, automotive and marine applications due to their well-known excellent density-specific properties. There are many technological methods of damping vibrations, including the use of inherently lossy materials such as viscoelastic materials, viscous and friction damping and smart materials such as piezoelectrics. Some have been applied to damping of vibrations, in particular to sandwich panel and honeycomb structures, including viscoelastic inserts in the cell voids. Complete filling of the cell with foam, viscoelastic or particulate fillers have all been demonstrated to improve damping loss in honeycombs. However, the use of an additional damping material inside the core of a sandwich panel increases its mass, which is often deleterious and may also lead to a significant change in dynamic properties. The work presented in this thesis explores the competing demands of vibration damping and minimum additional mass in the case of secondary inserts in honeycomb-like structures. The problem was tackled by initially characterising the main local deformation mechanism of a unit cell within a sandwich panel subjected to vibration. Out-of-plane bending deformation of the honeycomb unit cell was shown to be the predominant mode of deformation for most of the honeycomb cells within a sandwich panel. The out-of-plane bending deformation of the honeycomb cells results in relatively high in-plane deformation of the cells close to the skins of the sandwich panels. It was also highlighted that the magnitude and loading of the honeycomb unit cell are dependent on its location within the honeycomb or sandwich panel and the mode shape of the panel. An optimisation study was carried out on diverse honeycomb unit cell geometries to find locations at which the relative displacement between the honeycomb cell walls of the void is maximal under in-plane loadings. These locations were shown to be dependant of the nature of the loading, i.e. in-plane tension/compression or in-plane shear loading of the honeycomb unit cell and the unit cell geometry. Analytical expressions and finite element analyses were used to investigate the partial filling of the honeycomb unit cell with a damping material, in this case a viscoelastic elastomer, in the target locations identified previously where the relative displacement between the honeycomb cell walls is maximal. Damping inserts in the form of ligaments partially filling the honeycomb cell void have shown to increase the density-specific loss modulus by 26% compared to cells completely filled with damping material for in-plane tension/compression loading. The form of the damping insert itself was then analysed for enhancement of the dissipation provided by the damping material. The shear lap joint (SLJ) damping insert placed in the location where the relative displacement between the honeycomb cell walls of the void is maximal under in-plane loadings was characterised with very significant damping improvements compared to honeycomb cells completely filled with viscoelastic material. A case study of a cantilever honeycomb sandwich panel with embedded SLJ damping inserts demonstrated their efficiency in enhancing the loss factor of the structure for minimum added mass and marginal variation of the first modal frequency of the structure. Partial filling of the cells of the honeycomb core was shown to be the most efficient at increasing damping on a density basis.

Incremental sheet forming (ISF) is a flexible process where an indenter moves over the surface of a sheet of metal to form a 3D shell incrementally by a progression of localised deformation. Despite extensive research into the process, the deformation mechanics is not fully understood. This thesis presents new insights into the mechanics of ISF applied to two groups of materials: sheet metals and sandwich panels. A new system for measuring tool forces in ISF is commissioned. The system uses six loadcells to measure reaction forces on the workpiece frame. Each force signal has an uncertainty of ±15 N. This is likely to be small in comparison to tool forces measured in ISF. The mechanics of ISF of sheet metals is researched. Through-thickness deformation and strains of copper plates are measured for single-point incremental forming (SPIF) and two-point incremental forming (TPIF). It is shown that the deformation mechanisms of SPIF and TPIF are shear parallel to the tool direction, with both shear and stretching perpendicular to the tool direction. Tool forces are measured and compared throughout the two processes. Tool forces follow similar trends to strains, suggesting that shear parallel to the tool direction is a result of friction between the tool and workpiece. The mechanics of ISF of sandwich panels is investigated. The mechanical viability of applying ISF to various sandwich panel designs is evaluated by observing failure modes and damage under two simple tool paths. ISF is applicable to metal/polymer/metal sandwich panels. This is because the cores and faceplates are ductile and largely incompressible, and therefore survive local indentation during ISF without collapse. Through-thickness deformation, tool forces and applicability of the sine law for prediction of wall thickness are measured and compared for a metal/polymer/metal sandwich panel and a monolithic sheet metal. The mechanical results for ISF of sheet metals transfer closely to sandwich panels. Hence, established knowledge and process implementation procedures derived for ISF of monolithic sheet metals may be used in the future for ISF of sandwich panels.

This thesis documents the findings of a three year experimental investigation into the impact damage resistance and damage tolerance of composite honeycomb sandwich panels. The primary area of work focuses on the performance of sandwich panels under quasi-static and low-velocity impact loading with hemispherical and flat-ended indenters. The damage resistance is characterised in terms of damage mechanisms and energy absorption. The effects of varying the skin and core materials, skin thickness, core density, panel boundary conditions and indenter shape on the transverse strength and energy absorption of a sandwich panel have been examined. Damage mechanisms are found to include delamination of the impacted skin, core crushing, limited skin-core de bonding and top skin fibre fracture at high loads. In terms of panel construction the skin thickness is found to dominate the panel strength and energy absorption with core density having a lesser influence. Of the external factors considered the indenter noseshape has the largest effect on both failure load and associated damage area. An overview of existing analytical prediction methods is also included and the most significant theories applied and compared with the experimental results from this study. The secondary area of work expands the understanding obtained from the damage resistance study and assesses the ability of a sandwich panel to withstand in-plane compressive loading after sustaining low-velocity impact damage. The importance of the core material is investigated by comparing the compression-after-impact strength of both monolithic carbon-fibre laminates and sandwich panels with either an aluminium or nomex honeycomb core. The in-plane compressive strength of an 8 ply skinned honeycomb sandwich panel is found to be double that of a 16 ply monolithic laminate, with the type of honeycomb also influencing the compressive failure mechanisms and residual compressive strength. It is concluded that under in-plane loading the stabilising effect of the core opposes the de-stabilising effect of any impact damage.

This dissertation evaluates the behavior and capacity of single screw and adhesive anchors in thin concrete members that do not meet the minimum thickness requirements of current standards for anchorage. This dissertation focuses on the concept of full thickness embedment, wherein anchors are embedded through the entire thickness of the concrete member, and its implications. This is the first exclusive study on the concept of full thickness embedment anchors. In addition, this dissertation provides design models for single anchors in thin concrete members subjected to tension and shear loads. Three experimental programs were conducted to investigate the tensile and shear capacity of screw and adhesive anchors with a total of 350 tests. Variables included are concrete compressive strength, concrete thickness, anchor type, anchor diameter, screw and adhesive manufacturer, and edge distance for shear tests. Experimental data were used to develop the aforementioned design models for anchors in tension and shear. Consistent with modern standards for anchor design, the proposed design models are based on the 5% lower fractile and 90% confidence. It is shown that drilling through the concrete thickness causes the concrete to blowout at the back-face. The blowout is conical in shape with the depth of the blowout ranging from 0.65 to 0.96. This blowout affects the tensile capacity of screw anchors as the embedment depth is reduced by the depth of the blowout. However, back-face blowout effect was not noticeable in adhesive anchors as the adhesive fills the crack and fractures due to drilling. As a result, adhesive anchors have substantially higher tensile capacity compared to screw anchors. For example, typical adhesive anchor capacity in a 2-in. thick concrete member is almost four times larger than typical screw anchor capacity. In addition, adhesive anchors showed consistent performance independent of the adhesive supplier, unlike screw anchors wherein the failure mode and capacity were dependent on the product itself. Back-face blowout also affects shear capacity of screw anchors. However, the effect is less significant than on tension capacity. The reduction in the capacity (relative to adhesive anchors) is attributed to the reduction of the anchor stiffness due to the blowout. Modifications to the Concrete Capacity Design method are proposed to extend the method to full thickness embedment anchors in thin concrete members. To include the effect of back-face blowout on screw anchors in tension and shear, a reduced embedment depth and shear transfer length is proposed. In addition, a revised thickness modification factor is proposed for anchors subjected to shear loads.

This study focuses on structural optimization of the orthotropic sandwich cementitious composite systems. In order to develop a sandwich panel with high structural performance, design optimization techniques must be utilized to achieve full composite action as well as light weight, and high thermal insulation. This study involves both linear and nonlinear finite element analyses and parametric optimization. The verification and calibration of the numerical models will be based on the experimental results of numerous full-scale tests that were performed on two types of commercially produced sandwich panels under different loading scenarios at University of California Irvine. In order to minimize the number of design variables required for producing an optimum sandwich panel, the Taguchi statistical method for quality control is utilized. In this method, statistically planned experiments (or numerical simulation runs) are used to identify the settings of the sandwich panel design parameters that result in optimum design. Additionally, the Genetic Algorithm (GA) is used as an alternative approach for optimization, in order to evaluate the optimum design and build further confidence in our optimum design. GA combines Darwin's principle of survival of the fittest and a structured information exchange using randomized crossover operators to evolve an optimum design for the cementitious sandwich panel.Among the different initial parameters to be evaluated in the study are: (i) shear connectors’ geometry, volume fraction, and distribution; (ii) The thickness of exterior cementitious face sheets; (iii) The size and geometry of the exterior face sheets steel reinforcement details. Ultimately, the proposed optimization method reduced the Cost of Material of CSP by the by almost 48% using GA. In the same time, alternative design for CSP have been proposed where the optimization process increased the Thermal Resistance of the CSP by 40% compare to the conventional models currently available in the market while meeting the design Criteria’s based on the ACI Code. Pareto-optimal front and Pareto-optimal solutions have been identified. Correlation between the design variables of CSP is verified and design recommendation have been proposed for CSP manufacturers and structural designers.

Cellular core structures are the state-of-the-art technology for light weight structures in the aerospace industry. In an aerospace product, sandwich panels with cellular core represent the primary structural component as a given aerospace product may contain a large number of sandwich panels. This reveals the necessity of understanding the mechanical behavior of the cellular core and the impact of that behavior on the overall structural behavior of the sandwich panel, and hence the final aerospace product. As the final aerospace product must go through multiple qualification tests to achieve a final structure that is capable of withstanding all environments possible, analyzing the structure prior to testing is very important to avoid any possible failures and to ensure that the final design is indeed capable of withstanding the loads. To date, due to the lack of full understanding of the mechanical behavior of cellular cores and hence the sandwich panels, there still remains a significant lack of analytical capability to predict the proper behavior of the final product and failures may still occur even with significant effort spent on pre-test analyses. Analyzing cellular core to calculate the equivalent material properties of this type of structure is the only way to properly design the core for sandwich enhanced stiffness to weight ratio of the sandwich panels. A detailed literature review is first conducted to access the current state of development of this research area based on experiment and analysis. Then, one of the recently developed homogenization schemes is chosen to investigate the mechanical behavior of heavy, non-corrugated square cellular core with a potential application in marine structures. The mechanical behavior of the square cellular core is then calculated by applying the displacement approach to a representative unit cell finite element model. The mechanical behavior is then incorporated into sandwich panel finite element model and in an in-house code to test the predicted mechanical properties by comparing the center-of-panel displacement from all analyses to that of a highly detailed model. The research is then expanded to cover three cellular core shapes, hexagonal cores made of corrugated sheets, square cores made of corrugated sheets, and triangular cores. The expansion covers five different cell sizes and twenty one different core densities for each of the core shapes considering light cellular cores for space applications, for a total of 315 detailed studies. The accuracy of the calculated properties for all three core shapes is checked against highly detailed finite element models of sandwich panels. Formulas are then developed to calculate the mechanical properties of the three shapes of cellular cores studied for any core density and any of the five cell sizes. An error analysis is then performed to understand the quality of the predicted equivalent properties considering the panel size to cell size ratio as well as the facesheet thickness to core thickness ratio. The research finally expanded to understand the effect of buckling of the unit cell on the equivalent mechanical property of the cellular core. This part of the research is meant to address the impact of the local buckling that may occur due to impact of any type during the manufacturing, handling or assembly of the sandwich panels. The variation of the equivalent mechanical properties with the increase in transverse compression load, until the first folding of the unit cell is complete, is calculated for each of the three core shapes under investigation.

Sandwich panels constructed from honeycomb structures have been found to reduce sound transmission and improve vibration isolation. In this work, reiterated hierarchical honeycomb structures have been modeled for the core in sandwich panels and studied for sound transmission properties using finite element analysis. Several honeycomb unit cell geometries are considered, including, regular hexagonal, auxetic with properties of negative Poisson’s ratio, and different reiterated hierarchical structures. Previous studies have shown that auxetic honeycomb structures exhibit improved sound transmission loss compared to regular honeycomb sandwich panels. Two different orientations of the honeycomb unit cell geometry have been studied, namely, the zigzag and armchair configurations, which are, rotated 90 degrees. Both regular and auxetic honeycombs have been used in both these configurations. The finite element model of the panels are used to extract natural frequencies and mode shapes and to perform steady state frequency response dynamic analysis up to 1000 Hz. The transmitted sound pressure levels on the surface of each structure is extracted and compared to study the influence of the reiterated hierarchy on sound transmission characteristics. The influence of corner reinforcement constructed by subtracting interior high-level hierarchical structure except at the vertices of the underlying lower-level honeycomb unit cell was also studied. Furthermore, a study was conducted to quantify the effect of changing the ratio of cell-wall thickness between various levels of hierarchy. Special focus on the limiting case of level-1 hierarchy with zero level-0 thickness is also studied. In all cases, the total mass was kept constant in order to isolate only stiffness and mass distribution effects. The results show that introduction of reiterated hierarchy in level-1 structures reduced the sound transmission of honeycomb sandwich panels compared to parent level-0 geometry. Results also showed that the corner reinforcement does not influence the sound transmission characteristics significantly, but does change the stiffness of the structure. For regular hexagonal honeycombs, changing the ratio of thickness between various levels of hierarchy did not affect the sound transmission significantly but made the structure stiffer when the ratio was increased, and reduced the stiffness when the ratio was decreased. For auxetic honeycomb structure, increasing the ratio made the structure less stiff, but reducing the ratio did not change the stiffness significantly.

The present study focuses on the evaluation of the static and dynamic behavior of cementitious sandwich panels with parallel steel wire shear connectors. The study is divided into two parts: (i) large-scale experimental evaluation of different structural sandwich members subjected to different types of loading regimes, and (ii) analytical procedures to predict the behavior of such panels. However, and due to the lack of experimental data on the behavior of such sandwich panels, the emphasis of this study is on full-scale experimental evaluation. In the analytical part of the study, modified procedures, based on the experimental observations, following the general guidelines of the American Concrete Institute (ACI 318-11) were adopted. Also, the experimental program focused on assessing the out-of-plane flexural behavior of floor/roof sandwich slabs. Both simply supported and two-span continuous large-scale floor/roof slabs, with different boundary conditions and details, were evaluated. The experimental results were compared to the analytical predictions and well agreement between the results was achieved. The study also included several large-scale element experiments that were conducted on walls subjected to axial, shear, eccentric and flexural loadings conditions as well as exterior and interior corner connections. These tests are considered to be a pioneering research work that are not available to-date in published literature. A summary of the test setup, test procedures and experimental results that included quasi-static and cyclic load-displacement (P-δ) and Stress- Strain (σ−ε) curves are presented and discussed herein.The comprehensive experimental program provided much needed information to the structural engineers that lack the knowledge on the service and ultimate performance of this type of sandwich structural elements. For example, the experimental results provided important information on the suitability of the sandwich panels with parallel wire connectors for the use as floors and roof slabs. In addition, the experimental results identified the different failure modes that are not similar to those for solid concrete elements.The simplified analytical procedures that followed, in general, the requirements of ACI 318-11 with justifiable modifications succeeded to provide conservative estimates to the capacity of each structural sandwich element evaluated in this study. Numerical design examples for typical residential buildings that were performed using the proposed analytical procedures are also presented.Conclusions drawn from this pioneering study is summarized and recommendations for future research work is presented in this thesis.

Sandwich panel structures constructed with cellular honeycomb cores allow for control of acoustic performance due to their ability to optimize effective orthotropic material properties with changes in cell geometry. By modification of topology and geometric parameters of a unit cell, desirable effective properties can be obtained and used to design lightweight structures with reduced vibration and increased sound transmission loss properties. Thus investigating the relation between the geometric configuration of the honeycomb core and vibration and acoustic behavior is important to optimize design of sandwich panels. In this work, a finite element model is developed in MATLAB to evaluate the resonance frequencies, vibration frequency response and structural behavior of general honeycomb sandwich panels undergoing in-plane loading. Bernoulli-Euler beam element stiffness and mass matrices are computed with coordinate transformations to assemble for two-dimensional frame dynamic analysis. The developed MATLAB finite element program is written to allow the user to specify any unit cell geometry together with the number of repeated cells along the longitudinal and transverse direction of a honeycomb sandwich panel. This automation allows for rapid studies of the effects of the cell geometry and number of cells for optimization and parametric studies. In addition, the user can specify the size of elements for cell length subdivision to ensure mesh convergence analysis. The developed MATLAB code was verified by comparing dynamic results to finite element models created using the commercial software ABAQUS using both cubic Bernoulli-Euler and quadratic Timoshenko beam elements. Natural vibration frequencies of the structure and vibration amplitude frequency response for honeycomb structures are computed between 1~1000 Hz, corresponding to low to medium frequency ranges. In addition, the ABAQUS finite element model is used to simulate the acoustic behavior of the sandwich panel mounted in a rigid baffle resulting from an incident plane pressure wave. This required the coupling of an acoustic finite element model tied to the sandwich panel model to model sound radiation from the vibrating panel. To model the infinite acoustic region on one side of the sandwich panel, the acoustic finite element mesh is truncated using a founded ellipse non-reflecting boundary condition (NRBC). Previous studies used a circular nonreflecting boundary condition. The use of an ellipse for the NRBC allows for a reduced size computational region surrounding the elongated sandwich panel structure. The accuracy of the NRBC's was also studied as a function of distance from the vibrating panel source. Various core configurations of different geometric and effective material properties for regular and auxetic honeycomb cell geometries with two different orthogonal orientations were studied. Constant mass property is applied for sandwich panels with different number of longitudinal and transverse cell numbers to identify the effects of core geometry, cell truncation at face sheets, and effective properties on structural and acoustic behavior. Flexural and local dilatational vibration modes for the various configurations were identified. The influence of natural frequencies on the acoustic performance of the sandwich panels is also studied.

This research investigation explores the feasibility of implementing a laser welded sandwich steel panel bridge deck system as a viable alternative to standardized reinforced concrete bridge decks. Generally used in naval ship building applications, steel sandwich panels possess attractive characteristics towards the integration with bridge infrastructure such as service life in excess of 100 plus years, dead load reduction, rapid construction, decreased closure time, and automated mass production. The lack of fatigue data for the laser "stake" welds used to create the enclosed sandwich panel geometry raised concerns with respect to fatigue life. The primary focus of this study was to determine whether or not infinite fatigue life was possible. Two different laser welding technologies were investigated, Laser Beam Welding (LBW) and Hybrid-Laser Arc Welding (HLAW). Test specimens were fabricated and tested in order to examine fatigue resistance based on a localized load effect between adjacent core stiffeners. Finite element models were used to obtain the stress range for each individual test due to complex geometry and partially restrained boundary conditions. In order to assess the fatigue performance of the overall deck system, additional finite element models were created to study the local and global behavior of different sandwich panel configurations. As a whole the investigation yielded promising results. Infinite fatigue life is achievable due to outstanding fatigue performance. The HLAW stake welds demonstrated superior fatigue resistance in comparison to the LBW process. Localized load effects can be minimized through the modification of different panel parameters. Pushing forward, full scale testing is essential to the future employment of this innovative bridge deck system.

This work focuses on the compressive strength to weight ratio optimization of reinforced composite honeycomb materials for sandwich panel construction. Currently, metallic honeycomb has densities up to four times that of composite honeycomb, and compressive strengths up to ten times greater. The objective of this research is to eliminate the use of aluminum honeycomb in aircraft structures by replacing them with reinforced composite honeycomb with equivalent or better compressive strength. In order to evaluate reinforced composite alternatives, a finite element model was developed to analyze many reinforcement configurations. The analysis was extremely non-linear and required significant work to develop a model that would successfully converge to a solution for the many different reinforced configurations to be analyzed. A parametric study showed that the crushing resistance of the reinforcement governed the overall compressive strength to weight ratio of the reinforced composite honeycomb. It was found that the compressive strength to weight ratio of reinforced composite honeycomb can be 22% higher than that of aluminum honeycomb of comparable weight.