Recycling of fibre reinforced polymer (FRP) composites: Recovery and realignment of fibre

Abstract

Carbon fibre reinforced polymer (CFRP) wastes in landfill cause environmental and energy challenges. Fibre recycling and realignment will close the loop in life cycle of CFRP composites, which can reduce pollution by decreasing waste disposal, maximise material use and save energy. Cost-benefit analysis (CBA) and life cycle analysis (LCA) were used to evaluate ten CFRP and glass fibre reinforced polymer (GFRP) waste treatment solutions to determine the ideal recycling procedure for the Australian and European markets. CBA and LCA assessments show that pyrolysis has great economic returns and low environmental impacts. To optimise CFRP composite recycling, energy consumption, kinetic behaviour and thermal degradation mechanism during pyrolysis were studied. Result revealed that with the proposed thermal recycling process 80.3% of strength of carbon fibre can be retained. Additional solvolysis procedure can increase retention of fibre’s mechanical properties by decreasing heat consumption during recycling. When proper pre-treatment was used prior to thermal deterioration, the strength of recycled fibres can be preserved at up to 90.5% of their virgin state. Reclaimed carbon fibres are usually randomly distributed and cannot be remanufactured efficiently without fibre alignment process. Composites with well-aligned fibres show far higher tensile modulus than those with randomly-distributed fibres. A hydrodynamic fibre alignment method was developed to effectively control orientation of fibres after recycling. The technical parameters were optimised using Computational Fluid Dynamics (CFD) analysis and experiments. Results showed developed equipment was able to successfully align 77% of the fibres within 15 degrees and 89% within 30 degrees. The application of this study is expected to reduce the amount of CFRP waste discarded in landfill, revitalise the economic value of carbon fibre in composite waste, and improve the market for green engineering materials.