A new procedure for thermo-viscoelastic modelling of composites with general orthotropy and geometry

In this paper, a solution procedure is presented for thermo-viscoelastic analysis of composites in a general form which can be used for general orthotropic materials with simple flat to complicated geometries with thickness change and curvature. Small deformation problems in which the prediction of thermal stresses and/or deformations is of interest, are considered. The incremental solution already available in FE packages is extended to the orthotropic case using available formulations in the literature, making it more general in the sense of having different relaxations in each orthogonal direction. Only the viscoelastic response of the polymeric part of the material should be obtained as input and characterisation tests on the composite material are not needed. The linear orthotropic viscoelastic response of the composite layer is obtained using self-consistent micromechanics equations in the Laplace domain. The material model is implemented in the ANSYS subroutine to define the time-dependent thermo-viscoelastic response of the composite layer. Numerical results are presented which verify the accuracy and applicability of the modelling procedure. The proposed approach can be used later for the residual stress analysis of anisotropic materials including full composites and also complex fuselage panels made of hybrid Fibre Metal Laminates (FMLs).