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Hat sections, single and double, made of steel are frequently encountered in automotive body structural components such as front rails, B-Pillar, and rockers of unitized-body cars. These thin-walled components can play a significant role in terms of crashworthiness and impact energy absorption, through a nonlinear phenomenon called as progressive dynamic buckling. As modern vehicle safety design relies heavily on computer-aided engineering, there is a great need for analysis-based predictions to yield close correlation with test results. Although hat sections subjected to axial loading have been studied widely in the past, there is scanty information in published literature on modeling procedures that can lead to robust prediction of test responses. In the current study, both single-hat and double-hat components made of mild steel are studied extensively experimentally and numerically to quantify statistical variations in test responses such as peak load, mean load and energy absorption, and formulate modeling conditions for capturing elasto-plastic material behavior, strain rate sensitivity, spot-welds, etc. that can lead to robust predictions of force-time and force-displacement histories as well as failure modes. In addition, keeping initial stages of vehicle design in mind, the effectiveness of soft computing techniques based on polynomial regression analysis, radial basis functions and artificial neural networks for quick assessment of the behaviors of steel hat sections has been demonstrated. The study is extended to double-hat sections subjected to eccentric impact loading which has not been previously reported. A lightweight enhancement of load carrying capacity of steel hat section components has been investigated with PU (polyurethane) foam-filled single and double hat sections, and subjecting the same to quasi-static and axial impact loading. Good predictions of load-displacement responses are again obtained and shortening of fold lengths vis-à-vis hollow sections is observed. Finally, the performance of hat sections made of glass fiber-reinforced composites is studied as a potential lightweight substitute to steel hat section components. The challenging task of numerical prediction of the behaviors of the composite hat sections has been undertaken using a consistent modeling and analysis procedure described earlier and by choosing an appropriate constitutive behavior available in the popular explicit contact-impact analysis solver, LS-DYNA.

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