Work

Quantifying the Impact of Multiple Twin-Screw Extrusion Cycles on Discontinuous Carbon Fiber Composites

Year: 2026

Type: article

Abstract: To enable re-use, recycled fiber filled thermoplastics may require intermediate processing, such as twin-screw compounding. These intermediate processes can introduce additional processing-induced degradation and performance variability. This study evaluated the recyclability of carbon fiber reinforced acrylonitrile butadiene styrene (CF-ABS) through ten consecutive pilot-scale extrusion cycles to determine the primary degradation mechanism as a function of lifetime and to quantify the impact on mechanical performance. Chemical analysis revealed that the ABS matrix remained chemically robust throughout repeated extrusion cycles, whereas optical microscopy showed that fiber breakage was significant. Fiber length exponentially decayed with repeated cycles, with the decay rate stabilizing between the 3rd and 5th cycle and resulting in fiber length reduction after the 10th cycle of 62%, using a weighted average. The reduction in fiber length was found to govern both the rheological and mechanical behavior of the composite material. Viscosity and storage modulus decreased with decreasing fiber length while tan(δ) and elongation at break increased, shifting toward values characteristic of neat ABS and indicating a transition from fiber-dominant to matrix-dominant behavior. A strong correlation between fiber-length decay and a reduction in tensile strength enabled the development of a simple analytical model, which predicted tensile strength more accurately than the Kelly-Tyson model and required fewer experimentally derived inputs. Overall, this study demonstrated that fiber breakage, rather than chemical degradation of the ABS matrix, dictates performance of recycled CF-ABS and provides an approach for predicting material properties prior to manufacturing for a range of thermoplastic composites.

Source: Polymers

DOI: 10.3390/polym18212634