Crashworthiness Analysis Using Advanced Material Models In Dyna3d

As part of an electric vehicle consortium, LLNL and Kaiser Aluminum are conducting experimental and numerical studies on crashworthy aluminum spaceframe designs. They have jointly explored the effect of heat treat on crush behavior and duplicated the experimental behavior with finite-element simulations. The major technical contributions to the state of the art in numerical simulation arise from the development and use of advanced material model descriptions for LLNL's DYNA3D code. Constitutive model enhancements in both flow and failure have been employed for conventional materials such as low-carbon steels, and also for lighter weight materials such as aluminum and fiber composites being considered for future vehicles. The constitutive model enhancements are developed as extensions from LLNL's work in anisotropic flow and multiaxial failure modeling. Analysis quality as a function of level of simplification of material behavior and mesh is explored, as well as the penalty in computation cost that must be paid for using more complex models and meshes. The lightweight material modeling technology is being used at the vehicle component level to explore the safety implications of small neighborhood electric vehicles manufactured almost exclusively from these materials.

Composite materials have excellent mechanical and thermal properties and are the materials of choice for many applications. Even though, the low inter-laminar mechanical properties and poor impact resistance of fiber reinforced composite materials has limited their use. The study of axial crushing behavior of metal and composite tubes has become an important aspect for the design of crashworthy structures in aircraft and automotive applications. This behavior can be studied using different crushing modes based on different failure criteria. Therefore it is important to have a tool that could simulate the crushing response of the composite tubes under crushing or impact load. This thesis is aimed at the validation of finite element simulation methods for composite tubes using different failure criteria. The crushing behavior and the effect of post-failure parameters on the composite tubes are studied using a finite element solver, LS-Dyna. Three different composite tubes have been chosen for the finite element analysis, which have been crushed under impact loading conditions. Composite material models, from Dyna library, are assigned for the tubes to analyze which material model correlates with the experimental results. The results indicate that the average crushing force for the numerical and experimental results are same except for the peak force, in load-displacement curves. Also, interface elements are modeled between the shell elements for the composite tubes and conducted analysis using cohesive material model. Besides, conducted simulations to determine the effect of geometric parameter like trigger and post-failure parameters like softening reduction factor, maximum effective strain, SLIM which is the factor to determine residual strength and maximum strain on the composite tubes.

The automotive industry faces many challenges, including increased global competition, the need for higher-performance vehicles, a reduction in costs and tighter environmental and safety requirements. The materials used in automotive engineering play key roles in overcoming these issues: ultimately lighter materials mean lighter vehicles and lower emissions. Composites are being used increasingly in the automotive industry due to their strength, quality and light weight. Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness provides a comprehensive explanation of how advanced composite materials, including FRPs, reinforced thermoplastics, carbon-based composites and many others, are designed, processed and utilized in vehicles. It includes technical explanations of composite materials in vehicle design and analysis and covers all phases of composite design, modelling, testing and failure analysis. It also sheds light on the performance of existing materials including carbon composites and future developments in automotive material technology which work towards reducing the weight of the vehicle structure. Key features: Chapters written by world-renowned authors and experts in their own fields Includes detailed case studies and examples covering all aspects of composite materials and their application in the automotive industries Unique topic integration between the impact, crash, failure, damage, analysis and modelling of composites Presents the state of the art in composite materials and their application in the automotive industry Integrates theory and practice in the fields of composite materials and automotive engineering Considers energy efficiency and environmental implications Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness is a comprehensive reference for those working with composite materials in both academia and industry, and is also a useful source of information for those considering using composites in automotive applications in the future.