Influence of material nonlinearity on thermal distortion of polymer matrix composite panels

This paper discusses the influence of material nonlinearity on thermal distortion of polymer matrix composite panels. The load is transverse temperature gradient introduced by one-sided heat exposure, e.g., fire. For such low thermal conductivity materials, when there are no external mechanical loads, the transverse thermal gradient induces non-uniform thermal expansion along the thickness that results in transverse deformation field, known as thermal distortion. The power form stress–strain relation and the Ramberg–Osgood form stress–strain relation are discussed to include the temperature dependent behavior of polymer matrix composites. The degradation of polymer matrix composites at elevated temperature, thermal softening, is discussed. The variations of the reference stress and the reference strain with temperature are specified to describe the temperature dependent constitutive relationships. Semi-analytical simulation and finite element simulation are carried out for panels with roller end support condition. Results suggest that, while the material nonlinearity has insignificant influence on the transverse displacement of the panel, it has strong influence on local stress and strain. The stress and strain can go beyond the yield stress and the yield strain into plastic stage in certain circumstances.