Search Results

The stiffness of randomly oriented, thermoplastic bulk molding compound (TP-BMC) composites can be increased in a 3-point loading test through the use of commingled thermoplastic materials. Bumper beams for a typical midsize vehicle produced from combinations of these 2 materials were molded and tested using a static bumper test setup that measures the applied load and resulting deflection. A design of experiments investigation based on the Taguchi methods [1] were used to compare the effects of 4 material and processing variables on static load. The optimum levels for each variable were found to achieve maximum load at 25 mm deflection, which led to a manufacturing strategy for selectively increasing the stiffness of TP-BMC composites for bumper beams. This paper details the development work.

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.

This paper presents material and design requirements for future bumper applications to meet the challenges future styling changes will bring. Automotive composites applications have increased steadily over the past several years. Composite bumper beams are becoming more common due to the increased number of low volume vehicles and to the greater emphasis toward weight reduction. Typical bumper systems and impact bars are presented with advantages and disadvantages shown. The competing composite materials are compared with each other and to the current dominate bumper material, steel. Material, processing, and design developments are needed in composites to be competitive with current steel and future 'World Class' steel. Composite materials are needed with increased stiffness, strength, and thermal stability. A competitive piece cost target for composite bumper beams is two dollars per pound of material used.