Interfacial micro-level stress transfer in macroscopic thermo-viscoelastic creep of unidirectional composites

Stress transfer across the fiber-matrix interface is studied numerically via the Finite Element Method and the asymptotic expansion homogenization (AEH) approach. The thermo-viscoelastic equations are solved accounting for thermal strains. The external loads in the problem are constant over time and are applied on the macro-level creep specimen. The subsequent micro-stresses are computed via a localization procedure, or reverse-homogenization. The micro-level stress transfer across the matrix/fiber interface is accounted for by a layer of thin elements along the boundary that separates the two phases. The material properties of the interface elements are assumed always less than or equal to the matrix properties. This makes the microstructure a three phase composite. Verifications for elastic properties and illustrative examples emphasizing interface stress transfer issues are presented.