Analytical prediction of the local Young’s modulus in CFRP laminate with ply discontinuity: a variational approach

Carbon fibre reinforced plastics (CFRPs) with continuous fibres are strong and stiff. However, ply discontinuities can introduce stress concentrations, potentially damaging the material and adversely affecting its mechanical properties. Evaluating the impact of ply discontinuities on the mechanical properties of CFRP laminate is, therefore, crucial. Extending the applicability of a variational stress analysis based on Hashin’s original approach, this study presents a method to predict local Young’s moduli in unidirectional CFRP laminate with ply discontinuity. The complementary energy for the specific length of the laminate in the longitudinal direction was used to derive the local Young’s moduli. An experimental study and a finite element analysis (FEA) were conducted to validate the results. In the experimental study, strain gauges of various lengths were placed on the ply discontinuity area; the measured Young’s moduli varied with the gauge length. The numerically derived local effective Young’s moduli showed a relatively positive agreement with the experimental and FEA results, especially for lower values of applied stress. For more accurate predictions, future analyses should consider the impact of delamination on the Young’s moduli.