Using Glass Mat Thermoplastic as Automotive Bumper’s Material to Enhance Pedestrian Safety

Abstract

The usage of softer systems in automotive bumper is a growing trend currently especially to serve the pedestrians safety function. The term softer here does refer to the bumper system’s dynamic behavior rather than its material’s flexure or tension modules. However, the usage of such softer systems would raise issues of structural integrity of the bumper during crash. There is a strong drive currently to adopt materials such as glass mat thermoplastic (GMT), high-strength sheet molding compound (SMC) for the bumper material and plastic polypropylene (PEP) for the bumper holders [1, 2, 3] in this regard. While both the GMT and SMC do enhance the pedestrian safety condition, they both show plastic deformation at crash, even in low-speed scenarios [2, 3]. The PEP holders react only as shock absorbers and act like mechanical fuses to be destroyed in car crash, preventing the main bumper from being damaged [4]. In this paper, we propose a remedy for this problem by changing the common system that the GMT and SMC materials are usually fitted at. We propose coating the bumper beam with a Rubber padding layer that eliminates the plastic strain at low-speed crash. We also examine the behavior of the PEP during such crash scenarios. We present here the results of a low-speed head-on automotive-pedestrian crash simulation scenario for these material models, using the explicit dynamics finite element code LS-DYNA within ANSYS integration setting. A simplified parameterized finite element model of the Ford Crown Victoria car’s bumper form is used in several crash simulations that are carried out to test the validity of this modified bumper system. Based on the results of these tests, we show that, applying the Rubber coating material for the GMT and SMC bumper beams eliminates the plastic stains at low-speed crash.