Recycling Aerospace Carbon Fiber Composites as Functional Filler into Polymer Composites

Katherine Michelle Mody Rasmussen

The increasing demand for lightweight, durable, and high-performance materials—particularly in aerospace, transportation, and other industrial sectors, has led to widespread use of thermoset carbon fiber composites (CFCs). However, the energy-intensive production and limited recyclability CFCs, achieved through thermal and chemical pathways, present significant environmental challenges. This thesis investigates a sustainable strategy to address these issues by integrating mechanically processed thermoset recycled carbon fiber composites (rCFCs) to produce injection-moldable composite pellets. The rCFCs, recovered from aerospace-grade waste and ground to a pass 60 mesh fraction (≤250 µm), were evaluated as functional fillers in polyolefin matrices. For benchmarking, traditional mineral fillers such as talc and calcium carbonate (CaCO₃) were also incorporated into plastic matrices for direct comparison.The compounded materials were assessed through a combination of mechanical, thermal, and rheological testing to evaluate their performance and processability. Mechanically, rCFC-filled composites demonstrated increased flexural strength and stiffness compared to talc- and CaCO₃-filled counterparts, particularly at lower filler loadings (10–20 wt.%). Particle size analysis revealed that smaller rCFC particles (pass 60) provided higher mechanical reinforcement than coarser fractions. Thermogravimetric analysis (TGA) revealed that rCFC composites retained over 85% of their mass at 500 °C in certain formulations, demonstrating superior thermal stability compared to mineral-filled and unfilled plastics. Differential scanning calorimetry (DSC) indicated only minor shifts in melting and crystallization temperatures, confirming matrix compatibility. Rheological testing via parallel plate rheometry revealed increased complex viscosity and storage modulus (G') for rCFC composites, suggesting enhanced structural integrity during processing while maintaining processability within typical extrusion and injection molding conditions. By leveraging thermal resilience and mechanical reinforcement provided by recycled carbon fibers, this work demonstrates that rCFCs can serve as a high-performance, environmentally responsible alternative to conventional fillers. The compounded pellets produced in this study have strong potential as feedstock for high-value thermoplastic applications in transportation, infrastructure, and other durable goods sectors, providing both environmental and engineering benefits through the reuse of advanced composite waste.

Recycling Aerospace Carbon Fiber Composites as Functional Filler into Polymer Composites

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