About the influence of a thermal aggression on the tensile behaviour of hybrid PEEK thermoplastic laminates

This study aims to investigate the influence of different thermal aggressions (resulting in the decomposition of the thermoplastic matrix) on thermal degradation and residual tensile mechanical behavior of hybrid carbon/ glass fibers reinforced PolyEther Ether Ketone (PEEK) laminates. The specimens are exposed to isothermal (from melting temperature to decomposition temperature by means of a furnace) and anisothermal conditions (116 kW/m2 and 1150 celcius kerosene flame by means of a burner bench) respectively. The mechanical tests are further conducted to evaluate the residual tensile properties at Room Temperature (RT). When the laminates are exposed to flame, the microscopic observation reveals the heterogeneous thermally induced damages, compared with the isothermal case. A significant reduction in the axial stiffness (-35 %) and axial strength (-90 %) occurs after a 900 s flame exposure, as the structural integrity of laminate is significantly affected, compared with virgin specimens. By means of a three-region modeling, the importance of different damage regions for a post-fire laminate under mechanical loading is quantified and it is possible to further predict the residual mechanical properties with different flame exposure time.