Multiscale Modeling for the Long-Term Behavior of Laminated Composite Structures

Abstract

A multiscale modeling framework for the long-term behavior of fiber-reinforced-polymeric (FRP) laminated composite materials and structures is presented. Each unidirectional layer is idealized as a doubly periodic array of rectangular fibers. The authors' previously developed unit cell with four fiber and matrix subcells is used. The constitutive models for the elastic linear fiber and nonlinear viscoelastic matrix constituents are performed at the lowest level of the micromodel. This nonlinear micromodel is integrated with both three-dimensional and shell-based finite elements. A plane-stress constraint is added to the three-dimensional micromodel in the case where shell elements are used. Long-term experimental creep data from the literature for graphite/epoxy are used in order to characterize the material properties. The effect of material nonlinearity on the long-term behavior of FRP composites is also investigated. Applications are presented for long-term creep responses of a notched composite panel under surface pressure and a single lap joint under tensile load. This modeling approach is general and can include temperature, moisture, and physical aging effects.