Analysis for creep behavior and collapse of thick-section composite structures

A nonlinear viscoelastic and multi-scale modeling framework is used for the analysis of creep behavior and collapse of thick-section and layered composite structures. Previously developed nonlinear viscoelastic micromodels by the authors [Haj-Ali RM, Muliana AH. Micromechanical constitutive framework for the nonlinear viscoelastic behavior of pultruded composite materials. Int J Solids Struct 2003;40(5):1037–57; Haj-Ali RM, Muliana AH. A multi-scale constitutive formulation for the nonlinear viscoelastic analysis of laminated composite materials and structures. Int J Solids Struct 2004;41(13):3461–90], are used in order to generate the effective viscoelastic response of both unidirectional and random layered media. These micromodels are integrated with a displacement-based finite element (FE) model to perform structural analysis. In this study, we investigate the nonlinear creep behavior and critical time for structural collapse of composite structures. To that end, long-term behavior of composite materials is calibrated for the proposed material models. Both 3D and shell based structural models are employed in this study. Numerical applications of the proposed multi-scale viscoelastic analysis are presented for creep analyses of axially compressed I-shaped thick-section composite columns and a laminated cylinder under surface pressure. It is shown that the compressive loading ratio, along with the residual stiffness of the structure after buckling, can affect the creep behavior and the magnitude of the critical time for initiation of unstable response. The proposed models are general and can be used to examine the serviceability life of these structures.