Effect of elastic properties dependence of the stress state in composite materials

Abstract

Buckling problem is quite important for the engineering practice, mostly in cases of lightweight structures. The use of composites reduces the weight of the structure but gives problems in choice of reliable methods to model buckling and postbuckling behavior of details, especially if they contain thin-walled components. One of the problems is the choice of correct elastic properties of composite material for analysis. Elastic characteristics of composite material depend on the type of loading and uniaxial tension/compression test results in some cases demonstrate an essential difference. The buckling analysis usually assumes compression of the structure and the choice of elastic constants obtained in compression tests leads to more accurate results, but does not guarantee a good correlation with experiments in case of postbuckling analysis due to ignoring some regions with tension stress state. A possible way of material stress-state sensitivity consideration is usage of material models that take into account stiffness susceptibility to different types of loading. Further development of nonlinear elastic model in problems related to buckling and postbuckling analysis for composite materials up to failure is the introduction of material progressive degradation model to consider material properties reduction due to damage in conjunction with nonlinear elasticity.