| An improved two-sublaminate model based on first-order shear deformation theory is implemented in a general-purpose finite element software (ANSYS) to study delaminated composite plates. Double cantilever beam and end-notched flexure models of unidirectional and multidirectional composite plates with mid-plane and offset delaminations are analyzed. The total strain energy release rate and the mode-I, mode-II and mode-III components are evaluated using a plate-theory-based crack-closure technique.;The effects of variation of material properties, ply thickness, fiber orientation, coefficient of friction between the crack surfaces, finite element mesh density and virtual crack-closure length and applied load on the mixed-mode strain energy release rates are studied using Monte Carlo simulations. The statistics and trends are analyzed and quantified using sensitivity plots and scatter plots. Anderson-Darling goodness-of-fit tests are performed on the results to fit them to a two-parameter Weibull, normal or log-normal distribution and the statistically-based design values are calculated. Three-dimensional contour plots are also generated to study the overall variation in the strain energy release rate distribution along the delamination front.;In the case of double cantilever beam specimens, the ply thickness has a significant influence on the total and average strain energy release rate. Fiber misalignment controls the amount of mode-II and mode-III components observed. The maximum and minimum values are also highly dependent on the virtual crack-closure length. For unidirectional end-notched flexure models, sliding friction effects are found to be negligible and occur only adjacent to the supports. For the symmetric and unsymmetric end-notched flexure models studied, the energy loss due to sliding friction controls the total strain energy release rate for friction coefficients greater than 0.16 and 0.24, respectively. |
