Predicting Compression Failure of Fiber-reinforced Polymer Laminates during Fire

Abstract

A thermo-structural model was developed to predict the failure of compressively loaded fiber-reinforced polymer (FRP) laminates during fire. The thermal model was developed as a one-dimensional heat and mass transfer model to predict the thermal response of a decomposing material. The thermal properties were defined as functions of temperature and material decomposition state. The thermal response was used to calculate mechanical properties. The structural model was developed with thermally induced bending caused by one-sided heating. The structural model predicts out-of-plane deflections and compressive failure of laminates in fire conditions. Laminate failure was determined using a local failure criterion comparing the maximum combined compressive stress with the compressive strength.

Intermediate-scale one-sided heating tests were performed on compressively loaded FRP laminates. The tests were designed to investigate the effect of varying the applied stress, applied heat, and laminate dimensions on the structural response. Three failure modes were observed in testing: kinking, localized kinking, and forced-response deflection, and were dependent on the applied stress level and independent of applied heating. The times-to-failure of the laminates followed an inverse relationship with the applied stress and heating levels. The test results were used to develop a relationship which relates a non-dimensionalized applied stress with a non-dimensionalized slenderness ratio. This relationship relates the applied stress, slenderness ratio, and temperature of the laminate at failure and can be used to determine failure in design of FRP laminate structures. The intermediate-scale tests were also used to validate the thermo-structural model with good agreement.