Modeling compressive skin failure of sandwich composites in fire

A thermal-mechanical model is presented for calculating the residual compressive strength of flammable sandwich composite materials in fire. The model can also estimate the time-to-failure of the laminate face skin to sandwich composites exposed to fire. The model involves a two-stage analysis: thermal modeling and mechanical modeling. The thermal component of the model predicts the temperature profile and amount of decomposition through sandwich composites exposed to one-sided heating by fire. The mechanical component of the model estimates the residual compressive strength of the sandwich composite and the onset of skin failure. The model is tested for sandwich composite materials with combustible glass/ vinyl ester skins and balsa core. Experimental fire tests are performed on the sandwich composites under combined compressive loading and one-sided heating at constant heat flux levels between 10kW/m(2) (T-max approximate to 250 degrees C) and 50 kW/m(2) (approximate to 600 degrees C). The model predicts that the time-to-failure increases with the skin thickness and decreases with an increase to the applied compressive stress or heat flux. The predictions are supported by experimental data from fire-under-load tests. It is envisaged that the model can be used to design sandwich composite materials with improved compressive load capacity in fire.