Damage behaviour of fibre reinforced materials induced by high temperature oxidation for optimisation of thermal recycling routes

This study summarizes different characterisation methods performed with new carbon fibres(vCF - virgin carbon fibres) for structural applications as carbon fiber reinforced plastic (CFRP)as well as fiber samples which have been treated under different conditions. These parameters consistof combinations of temperature (400-600 C) and dwell time (30 - 60 min) in an oxidising atmospherein order to provide a fundamental basis for the definition of possible recycling processes to regain thehigh value raw material, i.e. the carbon fibre, after the use-phase of the initial CFRP-structure. The investigationsthat were performed on vCF and secondary fibres (rCF - recycled CF) show in very goodagreement, that below 500 C almost no degradation of the fibre is visible, between 500 and 600 C arapid decrease in different physical and mechanical properties occurs and above 600 C a recovery ofthe fiber in terms of a secondary use in high performance structural context seems not to be feasible.The investigations that were performed consist of optical microscopy for the measurement of the fibrediameter, the deformation of the cross section and a statistical analysis. The second method appliedwas the characterization of the monofilament density, alongside to the breaking force and elongation,leading to the calculation of tensile strength and Youngs Modulus and further statistical analysis ofWeibull Modulus and its decrease over temperature.