Probabilistic bending behaviour of a symmetric multi-directional composite laminate subjected to moisture induced material property asymmetry

In practical applications, moisture diffusion in a composite laminate occurs one dimensional, which results in moisture content asymmetry through-the-thickness of the laminate. The effect of such moisture content asymmetry on the bending behaviour of the laminate is investigated in this study. The bending response of the laminate is numerically simulated by following the first-order shear deformation theory and is experimentally validated. The probabilistic simulation was conducted by developing a surrogate model for the laminate bending response using the Polynomial Chaos Expansion method, and concurrently applying the Monte Carlo simulation. The necessity for a probabilistic simulation is also discussed in detail. The moisture diffusion through the thickness of the laminate is predicted using the Fick diffusion model, and the extent of moisture asymmetry is established for different ageing periods. The moisture asymmetry in the laminate resulted in the unwanted bending-extension coupling, which diminished as the laminate approached moisture equilibrium. Further, the moisture asymmetry introduced a material property asymmetry in the laminate, which affected the ply stresses. The study concludes that the ply stresses are dependent on the moisture content, position of the ply in the laminate, and the moisture induced stress redistribution.