Material Modeling Of Structural Foams In Finite Element Analysis Using Compressive Uniaxial And Triaxial Data

Automotive engineers have been working to improve vehicle safety ever since the first car rolleddown some pathway well over 100 years ago. Today, there are many new technologies being developedthat will improve the safety of future vehicles. Featuring the 69 best safety-related SAE technical papers of 2003, this book provides the most comprehensive information available on current and emerging developments in automotive safety. It gives readers a feel for the direction engineers are taking to reduce deaths and injuries of vehicle occupants as well as pedestrians. All of the papers selected for this book meet the criteria for inclusion in SAE Transactions--the definitive collection of the year's best technical research in automotive engineering technology.

This thesis is concerned with developing numerical models to predict the mechanical behaviour of closed-cell aluminium (AI) foams under uniaxial loading. Many of the existing models produce responses which are very stiff initially and fall sharply after an initial peak (Type-II response). In contrast, the real Al foams exhibit a reduced stiffness and give a flat-topped curve in the neighbourhood of peak-load (Type-l response). Thus, the weakness of the existing unit-cell models in relation to the two qualitatively different load displacement responses was identified. A link has been established between the stretching dominated mode of deformation to the Type-II response and the bending dominated to the Type-l response respectively. The absence of Type-l response in the current unit-cell models in the literature moved the present research in a direction to identify an improved new 3D unit-cell, which can be used by future researchers to represent closed-cell Al foam in loading scenarios with large deformations. The unit-cell identified has a right polyhedra structure. Furthermore, the deformation for this model is bending dominated thus giving Type-l response in three principal loading directions. Two sets of polyhedra unit-cell based finite element (FE) models for the crushing of closed-cell Al foam were presented. The first set was constructed by stacking up to 6-cells along principal material loading directions. Perpendicular to the loading direction, the mechanical behaviour for an infinite system was simulated by using periodic boundary conditions (PBC). In the second set, a finite domain sample containing up to 64 unit-cells was used to capture the compressive response behaviour. The crush features of this system were obtained using 3D array of many cells (MC). Additionally, the application of the second type of FE models was extended further to study the performance of Al foam containing imperfections under low-velocity impact by a rigid indenter. A simple imperfection in the form of reduced cell-wall thickness was introduced into the unit-cell Al foam and a set of two different populations of imperfections were considered. All these aforementioned FE foam model predictions were compared with experimental results. Finally, the new 3D unit-cell model results were compared with the contemporary stretching dominated (Type-II response giving) models in literature namely, the truncated-cube and cubic-spherical. A parametric study was conducted to quantify the mechanical properties of aforementioned unit-cell models alongside the model developed in this thesis. It was demonstrated that the plateau phase stress-strain response of the developed 3D unit-cell model was more representative of real closed-cell Al foams. Further, it was shown that the crushing resistance and energy absorption features of this new 3D unit-cell model were higher, compared to the truncated-cube and cubic-spherical models.

From crash helmets to packaging, this is the complete guide to understanding, selecting, processing and working with polymer foams.

This work contains invited chapters by internationally renowned researchers in dynamics and impact mechanics and covers a wide range of topics, including both experimental and theoretical studies. Many comparisons between computer results and experimental measurements are included and readers will find a wealth of up-to-date information on many different aspects and applications of impact mechanics.

Metallic foams have become widely available and have unique properties that make them attractive for use in a variety of engineering applications. Due to their complex structure, the behavior of foams under complex loading conditions is a subject of continued research. Digital volume correlation is a technique wherein full-field strains in three dimensions can be measured from high resolution x-ray CT image data. This technique was employed to measured strains in two commercially available aluminum foams, one each of open and closed-cell morphology, under two complex loading scenarios: rigid spherical indention, and uniaxial compression of a sample with a central hole. In addition to comparing the behavior of the two foams, results are also compared to strain fields analytically predicted by a third-party constitutive model implemented in finite element analysis. Under indention loading, the two examined foams showed a distinct difference in deformation and strain field, however the foams behaved similarly under uniaxial compression of rectangular samples with central holes. The constitutive model was found to be unsuitable for modeling the experimentally measured foams.

Complete guide for materials, engineering, modeling and processing of novel syntactic material Lightweight metal-type foams for aeronautical, recreational and electronic applications Focused on a new type of material, the book investigates the elements, synthesis and practical applications of metal matrix syntactic foams, which share properties of foams and metal matrix composites. The text reviews how syntactic foams are synthesized from different types of hollow particles and metal matrixes. Part one explains processing techniques such as solidification and powder metallurgy and discusses foams made from a variety of matrix metals. Part two compares different syntactic foams based on density and strain rate. Original experimental data and modeling information are provided that show how metal matrix syntactic foams can be used for lighter weight components in vehicles, as well as for sensors and biomaterials.