Fire behavior and post-fire residual tensile strength prediction of carbon fiber/phthalonitrile composite laminates

Carbon fiber/phthalonitrile (Cf/PN) composite has a high potential for applications in the aerospace sector because of the outstanding heat and flame resistance of phthalonitrile resin. Here we aim to evaluate the fire behavior of Cf/PN laminate under localized one-sided flame heating as well as the residual tensile performance. The residual tensile strength after quasi-isothermal pyrolysis in an inert environment decreases linearly with the increase in the pyrolysis degree. The temperature response and pyrolysis behavior are analyzed through a combination of experiments and finite element simulations, and the damage mode of the laminate structure is concluded through morphological observation after flame exposure and the surface axial strain field using digital image correlation. Eventually, the residual tensile strength of laminates with different thicknesses after different times of flame exposure was effectively predicted based on the numerical simulated pyrolysis degree distribution. This research supplies fundamental test data on the mechanical properties of Cf/PN laminates and is expected to provide guidelines for the engineering application of Cf/PN composites in thermal protection/load-bearing all-in-one structures.