Bench-scale thermomechanical assessment of carbon fibre reinforced polymer C-channels

This study investigates the thermomechanical response of carbon fibre reinforced polymer (CFRP) C-channels using a bench-scale apparatus that combines mechanical loading and radiant thermal exposure. The study aims to assess the behaviour of pre-loaded CFRP C-channels, representative of aircraft sub-structures when subjected to fire conditions. Woven prepreg CFRP C-channels were tested under cantilever point load deflection while exposed to varying heat fluxes. Key aspects examined during the study include failure times, displacement, temperature distribution, and failure modes. The findings reveal that heated, pre-loaded C-channels experience distinct phases of physico-chemical decomposition and mechanical degradation. The mechanical degradation includes upward shear buckling of the horizontal flanges and vertical web, along with outward buckling of the vertical web towards the heat source. The study shows that thermal decomposition and mechanical degradation occur simultaneously, influenced by heat flux intensity. Higher heat fluxes accelerate decomposition and reduce load-bearing capacity, while lower fluxes slow degradation. Displacement data indicates that heat flux intensity significantly affects structural response. Temperature measurements show higher fluxes lead to elevated temperatures and steeper gradients, impacting failure times and modes. Increased temperatures correlate with shorter failure times, and variability in failure times decreases as heat flux rises. These insights are significant for understanding the thermomechanical response of C-channels in aircraft sub-structures. The knowledge obtained can contribute to developing more robust and safer aircraft designs, particularly for components exposed to fire conditions, enabling engineers to establish more precise safety margins for CFRP structures, potentially preventing catastrophic failures and thereby enhancing overall aircraft safety.