Three-dimensional hygromechanical analysis of fibre polymer composites: Effect of boundary conditions

Moisture diffusion through a unidirectional fibre reinforced polymer matrix composite is studied. The stresses due to the expansion of the matrix caused by moisture diffusion are evaluated. A three-dimensional (3D) micromechanical model is developed to study diffusion both across and along the fibre. The well-known 2D plane strain condition is modelled and validated as a special case of the 3D model. The utility of 3D modelling is further demonstrated to analyse the stress along the fibre length. It is demonstrated that the variation of boundary conditions along the fibre length has a dramatic effect on the stresses. The stresses along fibre length computed through finite element analysis (FEA) are compared against an analytical solution obtained from axi-symmetric concentric cylinder assemblage (CCA) model. This paper demonstrates the importance of 3D diffusion kinetics in unidirectional reinforced polymer composites.