Analysis Of Mechanical Behaviors Of Hygro-thermo Loading On Composite Plates

Laminated composite structures are usually exposed in hygrothermal environment as they are manufactured and applied in engineering. As a result, hygrothermal internal stresses are generated with the change of environment. These stresses generally induce large deformation and even contribute to the failure of the structure. Thus, hygrothermal behaviors of composites have to be considered in design of composite structures. However, following problems have been encountered with development of theoretical models for hygrothermal analysis of laminated composites. For hygrothermal problems, the continuity conditions of interlaminar stresses are usually neglected, so that it is difficult to obtain accurately the interlaminate stresses of laminated composites under hygrothermal environment. In addition, in the recent studies on hygrothermal problems, thermal expansion coefficients are assumed to be independent of angle of each layer, which will result in misdirection.In this paper, a higher-order global-local theory(HGLM) satisfying the continuity conditions of interlaminar stresses is developed. Based on the proposed model, a refined nonconforming triangular element is constructed, and C0 continuity condition and C1 weak-continuity condition can be satisfied simultaneously in this element. Accuracy of the model developed in this paper is verified by thermal bending problem of laminated composites at first. Effects of hygrothermal expansion coefficients on hygrothermal behaviors are also studied. Moreover, mechanical behaviors of laminated composites under hygro-thermo-mechanical loading are analyzed.Numerical results show that the theory developed in this paper can be used to analyze hygrothermal behaviors of composites. The variation of hygrothermal expansion coefficients caused by ply stacking angle should be taken into account in hygrothermal problems of composites.