Thermoplastic composite connecting rods

Abstract

Engineering carbon fiber thermoplastics have been used in the development and optimization of composite connecting rod(s) with design requirement of bearing 14,000 N and 1 mm maximum deflection. The studies featured engineering thermoplastics- 30 wt percent carbon fiber poly ether ether ketone (C-PEEK) long fiber thermoplastics (LFT) injection over molded in conjunction with 70 wt percent carbon/polyphenylene sulfide (C-PPS) and carbon/poly ether imide (C-PEI) tapes. Over molding of thermoplastic tapes has been investigated in terms of number of tape winding around the small and big end, and different winding patterns within the connecting rod geometry. The design was progressively optimized for the geometry of the connecting rod, i.e., increasing the wall thickness of the small end and width of the center section. The effect of over molded metal bushing with C/PEEK LFT at the bearing surfaces was also investigated. The material and geometry optimization successfully met 14,000 N while several design iterations were necessary to meet the 1 mm deflection limit constraint. Finite element analysis (FEA) was adopted to optimize the increase of the width of the center section width and wall thickness of the small end. The optimized composite connecting rod was estimated to be 78% lighter than the steel incumbent.