Improving the Stiffness Performance of Glass Mat Thermoplastic Composite Bumper Beams Using BI- and Uni-Directional Thermoplastic Composites

The stiffness of randomly oriented, glass-mat thermoplastic (GMT) composites with a polypropylene matrix can be increased in a 3-point loading test through the selective use of a co-mingled E-glass and polypropylene filament thermoplastic prepreg. Bumper beams for a typical midsize vehicle made from combinations of these 2 materials were molded and tested using a static bumper test setup, with load being measured as a function of deflection. A design of experiments investigation based on the Taguchi methods [1, 2] was used to compare the effects of 4 glass-mat orientation variables on the measured static load response of the molded bumper beams. This led to follow-up tests of materials and design strategies for selectively increasing the stiffness of the GMT composites at select locations in the bumper beam. The details of the investigation and results will be discussed in this paper.