ENERGY-RELEASE-RATE EVALUATION FOR DELAMINATION GROWTH PREDICTION IN A MULTI-PLATE MODEL OF A LAMINATE COMPOSITE

In this paper, numerical methods for the evaluation of the energy-rele ase-rate along a delamination periphery under conditions of local buck ling of the delaminate, as well as global buckling of the entire lamin ate, are presented. A multi-plate model, using independent Reissner-Mi ndlin plate models for each of the delaminated and undelaminated plies , with Reissner-Mindlin constraints for relating the degrees of freedo m of the delaminated plates to those of the undelaminated plate at the crack front, is used to model the laminate with embedded delamination s. Explicit expressions, in terms of finite element nodal or Gauss-poi nt variables, are derived for the pointwise energy release rate in ter ms of the J-integral and the Equivalent Domain Integral in the context of a typical multi-plate model for characterising the delamination gr owth. A finite element method with a 3-noded quasi-conforming shell el ement, and an automated post-buckling solution capability, is used for conducting the numerical analyses in this paper. Using these numerica l results, mechanisms of multiple buckling modes and their effect on t he propagation of embedded delaminations in plates, are studied.