Composite life under sustained compression and one sided simulated fire exposure: Characterization and prediction

Abstract

Polymer matrix composites (PMC's) perform well under many loading conditions and situations. Exposure of PMC's to fire is a concern due to their inherent material degradation at elevated temperatures. The elevated temperature response of PMC's to combined thermal and mechanical loads are especially of concern. Fiber reinforced composite materials exposed to fire conditions exhibit a loss in strength and stiffness due to the dependence of material properties on temperature and time. These effects are reversible if the maximum temperatures reached are below approximately 200 [°C], Above 200 [°C] composite materials experience permanent effects such as mass loss, delamination, charring, and matrix cracking. Little is well-known of the performance of composites exposed to fire and mechanical loads simultaneously. This work focuses on the reversible effects temperature has on laminated composites performance under combined thermal and mechanical loads. Mechanical and thermal testing was conducted on a glass vinyl ester composite in an effort to characterize the at temperature performance of the material. Dynamic Mechanical Analysis was used in an effort to characterize the off axis stiffness reduction as a function of temperature. Two analytical approaches using the temperature dependent off axis stiffness properties were conducted in an effort to predict the mechanical response of composite specimens exposed to a constant heat flux and constant compressive load. Times to failures of samples along with strain profiles were predicted and compared to experimental data. Predicted times to failure are in good agreement with collected data for the higher compressive load cases, while some deviation exists in the predictions at lower applied stress levels.