Fibre structure preservation in composite recycling using thermolysis process

Abstract Recycling of thermoset carbon fibre reinforced polymer (TS-CFRP) composites using thermal processes result in recovered carbon fibres (rCF), being fluffy and losing their alignment and length, leading to a deteriorating impact on the remanufactured part mechanical properties. In this work, the thermolysis recycling process is used to preserve the fibre structure including fabric stacking sequence, fibre orientation, alignment and length from the waste TS-CFRP parts. Investigation on the rCF structures with varying fabric and stacking sequence has been conducted to understand fibre nesting, alignment disturbance and permeability characteristics for composites remanufacturing. The fibre nesting in the rCF structures affects the permeability and hence should be considered for optimising the remanufacturing process parameters. Mechanical characterisation – tensile and interlaminar shear strength – of TS-CFRP and TS-rCFRP parts has also been carried out and compared with the properties from the existing literature to understand the effect of multiple recycling on the performance of the remanufactured composite parts with preserved fibre structure. The results showed that the overall fibre structure from the waste TS-CFRP part can be preserved using the thermolysis process providing the potential to directly replace the long virgin fibres in the manufacture of products with structural value. The remanufactured composite parts retain 80~90% of the TS-CFRP modulus after multiple recycling. The reduction in tensile properties of the TS-rCFRP parts was recorded compared to TS-CFRP parts, mainly due to the removal of fibre sizing. However, after first recycling, minimal reduction in tensile properties was recorded in the subsequent recycling.