Mechanical properties of flax fiber-reinforced composites at different relative humidities: Experimental, geometric, and displacement potential function approaches

Due to the good mechanical properties, flax fiber-reinforced epoxy composites are being widely used as a green alternative to glass fiber composites. However, plant fibers absorb moisture from the environment, being in a higher moisture uptake as the relative humidity (RH) increases. This absorbed moisture deteriorates the mechanical properties of the composites. In this study, geometric and displacement potential function (DPF) approaches are used to predict the mechanical properties of flax fiber-reinforced epoxy composites under environmental conditions, in particular, different RH values. The tensile properties that were measured experimentally strongly agreed with the analytical findings. Almost similar results were found for the tensile strain those were measured experimentally and the one predicted by the geometric function. However, the predicted strain values were 38% and 42% less than the experimental ones for 0% and 95% RH conditioned composites, respectively, when DPF was used. Good conformity between the experimental, analytical, and DPF formulation for predicting mechanical properties ensures the practical applicability of this study. The formulations established in this work could, therefore, be utilized to analytically solve laminated composites under specific boundary conditions in structural applications.