Determination of macroscopic viscoelastic properties as well as macroscopic thermal deformation and cure-shrinkage properties of fiber reinforced plastics in consideration of cure process

Abstract

This study presents a method of determining the macroscopic viscoelastic properties as well as the macroscopic coefficients of thermal expansion and cure-shrinkage of fiber-reinforced plastics (FRP) in consideration of the dependence of the viscoelastic properties of the resin used in the matrix phase on the degree of cure (DOC). The DOC-dependent viscoelastic material behavior of the resin is represented by the generalized Maxwell model and is accompanied with nonmechanical strains such as thermal strain and cure shrinkage. Within the framework of computational homogenization, a series of numerical material tests (NMTs) are conducted on a representative volume element (microstructure) with different DOCs to discretely evaluate the macroscopic viscoelastic properties. On the assumption that the macroscopic material behavior can be represented by the anisotropic version of the generalized Maxwell model, we originally propose a method to determine the macroscopic viscoelastic properties and the macroscopic coefficients of thermal expansion and cure-induced shrinkage, both of which are functions of DOC. After numerical examples to determine these properties for a specific unit cell of FRP are presented, a simple numerical verification is carried out to demonstrate that the proposed method is capable of determining the DOC-dependent macroscopic viscoelastic properties associated with mechanical and non-mechanical strains.