Performance evaluation of thin walled tube filled with nano based polyurethane rigid foam for increased roof strength of a vehicle
Automotive crash has garnered significant attention in the recent years with increasing fatality and safety concerns. Substantial effort and great amount of time and expertise has been directed towards the issues related to crashworthiness such as impact, rollover scenarios and restraint performance. Automotive rollover is one of those important concerns for the auto industry as the fatality rates and death causing conditions are vital compared to other crashes. In the past few decades, research has been focused towards developing efficient roof structure by implementing crashworthy structures, to protect or at least reduce the severity of the accident to the occupants of the vehicle during an event of a rollover. Studies have been carried in this area in developing efficient crashworthy structures. As the technology is evolving, researchers have found that thin walled tubes filled with foam materials possess high energy absorption properties compared to empty crashworthy structures. Further research in this has area led to the interference of nanotechnology, which implements emerging techniques in developing advanced materials for engineering applications. Scientists were able to develop low density, lightweight foams with high energy-absorption characteristics with these techniques. The purpose of this thesis is to analyze and evaluate the performance of low density carbon nanofoam (CNF) as an energy absorbing material in improving the roof strength of the vehicle. The LS- DYNA code, a non-linear dynamic finite element solver is utilized to accomplish this study. First, a three- point bending test simulation is carried as component level testing to analyze the behavior of foam materials. Then, the energy absorbing characteristics of a hollow tube is studied and the results are compared with regular polyurethane (PU) foam and carbon nanofoam inserts into the hollow tube, under similar conditions. Finally, PU foam and CNF is applied into the critical areas of roof supporting structures as two different conditions and static roof crush and dynamic inverted drop test simulations are conducted depicting an actual rollover scenario to study the crashworthy behavior of the vehicle roof with and without the foam. This study highlights that carbon nanofoam is found to be more effective compared to the regular polyurethane foam exhibiting better energy absorption characteristics.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering