To improve fuel economy, the automotive industry seeks to replace metal components with lightweight polymer composites. For non-structural or semi-structural components, short-fiber reinforced polymers are a low-cost solution for weight reduction. Conversely, when addressing structural components exposed to extreme in-service loads, high-performance continuous fiber composites offer solutions for elevated static loading and crash performance. However, the conventional manufacturing techniques for continuous fiber composites entail labor-intensive processes, resulting in high material costs, production times, and operator involvement.

 

To address these challenges, this work introduces a new manufacturing method aimed at mitigating the high costs and cycle times associated with continuous fiber polymer composites. This approach involves the production of a linear thermoplastic composite preform rod, referred to as M-TOW (Multi-tow), that can be formed into complex shapes to serve as tailored structural reinforcement in hybrid-molded parts. The research encompasses the processing of M-TOW, integration of functional components, and its application in real-world scenarios.

 

A comprehensive explanation of the M-TOW manufacturing process is provided, including the development of an optimal processing window for full compaction and consolidation that considers factors such as temperature, line speed, and overbraid pressure. A consolidation model based on Darcy’s law was developed to characterize resin "squeeze-out" during processing, while optical analysis was utilized to quantify springback during forming.

 

M-TOW’s segmented manufacturing line offers opportunities for integrating functional components to make multi-functional hybrid-molded structures. In this work, two functionalities were explored. First, metal wire was integrated via overbraiding to create

 

electrical and thermal conductivity pathways, achieving electrical conductivities up to 5.5×105 S/cm and thermal conductivities up to 21 W/mK across the composite. Second, optical fibers were introduced into the center of the M-TOW preforms. Experimentally, the attenuation of the fiber was examined under load and an ideal model was developed to predict this attenuation.

 

The reinforcing performance of M-TOW was evaluated through the production and testing of hybrid-molded demonstrator parts. Metal additively manufactured hardpoints were employed to enhance load transfer from the continuous fiber reinforcement. The results demonstrate significant improvements in part strength, elongation to break, and bonding between the overmolding polymer and the additively manufactured hardpoints.

 

These advancements in high-rate continuous fiber manufacturing demonstrate the versatility and potential of M-TOW in the development of multi-functional hybrid molded structures. These findings contribute to the expansion of applications where M-TOW can be confidently and effectively implemented, further solidifying its position as an innovative and high-performance composite manufacturing approach.