Influence of carbon fibre orientation on the post-fire tensile behaviour of carbon fibre reinforced polymer (CFRP) laminates

The effect of carbon fibre orientation on the post-fire tensile behaviour of carbon fibre-reinforced polymer (CFRP) laminates is investigated in this study. CFRP specimens produced using unique carbon fibre orientations, unidirectional, bidirectional and multidirectional denoted S1, S2 and S3, respectively, are compared before and after exposure to thermal exposure. This study has practical usefulness as CFRP laminates containing these types of carbon fibre orientations are often utilised adjacent or close to fuel storage in aircraft that may present a fire hazard. The study's results showed that the S1 specimens exhibited the highest resistance to tensile failure before and after thermal exposure, whereas the S3 specimens exhibited the lowest resistance to tensile failure before and after thermal exposure. Furthermore, the data has shown that after thermal exposure, the tensile properties of the S1, S2 and S3 CFRP specimens reduced by 35%, 51% and 52%, respectively, compared to before thermal exposure. This loss in tensile properties can be attributed to the pyrolysis of the epoxy matrix and subsequent loss of interfacial bond strength, as the irradiance intensity used in the study was purposely chosen to represent the heat from a fire due to a small fuel leak in an aircraft resulting in temperatures lower than those required to oxidise the carbon fibres. Post-fire imagery has also shown that all the specimens in their undamaged state exhibit brittle failure; however, after thermal exposure, all CFRP specimens exhibit explosive delamination failure.