A Comparison of C-Shaped and I-Type Cross-Sections for Bumpers Using Compression Molded Thermoplastics

The C-section bumper design has developed through an evolutionary process and has come to be regarded as a reasonable geometry for frontal bumper impacts, especially for use with glass-filled sheet-stampable thermoplastic composite materials. C-section bumpers are now well proven and accepted in the automotive industry, performing satisfactorily in a variety of crash situations.

A new and more complicated cross-section geometry (I-type with multiple ribbing) has recently been proposed for glass-filled thermoplastic composites. While, in some specialized cases, these highly engineered bumper cross-sections can be useful, they may not perform adequately in all reasonable crash scenarios. Further, it is important to consider manufacturing limitations and the realities of material performance in such complex geometries.

Data will be presented to question the practical advantages of the use of ribbed bumper designs over the traditional C-section beam. It will also be shown that when the processing difficulties inherent with these designs are taken into account, the traditional C-section bumper design remains the most logical choice for mass-production vehicle use.