Skin wrinkling of sandwich polymer matrix composite panels subjected to fire exposure

This paper presents an analytical solution of skin wrinkling for sandwich polymer matrix composite panels in a combined thermal–mechanical condition. The thermal gradient in the transverse direction is induced by one-sided fire exposure, and the mechanical load is the in-plane compression. Due to low thermal conductivities of polymer matrix composites, the thermal gradient exists for a long period of time. The material properties of polymer matrix composites are degraded as temperature rises. These behaviors induce mechanical propertiesʹ gradients along the transverse direction. The general solution for the wrinkling load in the thermal–mechanical loading condition is investigated. The solution is characterized in terms of two non-dimensional parameters that represent material properties and dimensional lengths of the skin and the core. The wrinkling load is presented for fairly complete ranges of the two non-dimensional parameters. The wrinkling load is also derived from Winkler model for non-homogeneous materials. An example of thermal-mechanical simulation to design the wrinkling load-bearing capacity of a panel exposed to fire is given.