Augmented Cohesive Elements for Efficient Delamination Analyses of Composite Laminates

In this paper, a new type of cohesive element that employs multiple subdomain integra-tion (MSDI) for improved cohesive stress integration accuracy of bonded plate/shellelements has been formulated. Within each subdomain, stress integration is compatiblewith existing schemes such as Gaussian integration (GI), Newton–Cotes integration, orthe mixed Gaussian and subdomain integration (mixed GI&SDI). The numerical accu-racy, efficiency, and robustness of this element when employing three integration methodsfor MSD cohesive stress integration have been evaluated and compared through a bench-mark mode-I fracture problem of bonded double-cantilever plates. The MSDI offers atleast 50% improvement of numerical accuracy as compared to the best integrationmethod in literature and has the best numerical robustness. This significant improvementpushes the structural mesh size restriction from limiting size of 1/3–1/5 cohesive zonelength to 1.5–2 times the cohesive zone length. The formulation is very easy to be imple-mented into any finite element programs including commercial packages. Furthermore,this formulation enables the use of dual-mesh for delamination analyses of bonded struc-tural shells/plates, which is of practical importance because it greatly reduces the burdenof mesh generation for complicated composite structures. It has also been demonstratedthat using high-order shell/plate elements can improve the numerical accuracy in generalbecause the nonlinear deformation profile permitted by this type of elements can betterdescribe the nonlinear deformation in the crack-tip element (partially bonded elements).[DOI: 10.1115/1.4004694]Keywords: Cohesive element, delamination, fracture, laminates

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