Modelling of reinforced polymer composites subject to thermo-mechanical loading

A coupled finite element model is developed to analyse the thermo-mechanical behaviour of a widely used polymer composite panel subject to high temperatures at service conditions. Thermo-chemical and thermo-mechanical models of previous researchers have been extended to study the thermo-chemical decomposition, internal heat and mass transfer, deformation and the stress state of the material. The phenomena of heat and mass transfer and thermo-mechanical deformation are simulated using three sets of governing equations, i.e. energy, gas mass diffusion and deformation equations. These equations are then assembled into a coupled matrix equation using the Bubnov–Galerkin finite element formulation and then solved simultaneously at each time interval. An experimentally tested 1.09 cm thick glassfibre woven-roving/polyester resin composite panel is analysed using the numerical model. Results are presented in the form of temperature, pore pressure, deformation, strain and stress profiles and discussed. The maximum normal stress failure criterion is used in order to establish the load-bearing capability of the composite panel. Significant pore gas pressure build-ups (to 0.8 MPa and higher) have been perceived at high thermo-chemical decomposition rates where the material experiences a complex expansion/contraction phenomenon. It is found that the composite panel experiences structural instability at elevated temperatures up to 300◦C but retains its integrity even under moderate external loading