Paper number 221


Hiroshi Suemasu and Osamu Majima

Department of Mechanical Engineering, Faculty of Science and Technology,
Sophia University
7-1 Kioi-cho Chiyodaku, Tokyo 102, Japan

Summary Instability and propagation process of multiple penny-shape interlaminar delaminations in circular axi-symmetric nonlinear plates subjected to a quasi static transverse load, which is an idealized problem of damage accumulation in composite laminates due to low velocity impact loading, is numerically studied through a finite element analysis. A fracture element proposed to simulate the crack propagation is modified for elements with mid-node. The condition for crack propagation is also changed to make the convergence of the solution with element size more smooth. Both failures due to maximum stress and fracture mechanical instability are possible to be considered by using the present element. The element is applied to a problem of a penny shape crack propagation in an infinite body. The results converge smoothly to the theoretically predicted solution with a quite rough element division. Then, the element is used to simulate the propagation of multiple delaminations in a laminate, where nonlinearity due to finite deflection is considered. The early stages of the damage propagation depend on the initial delamination size. When the plate size used in CAI test standard is considered, the effect of the nonlinearity is not significant for ordinary composite laminates except plates of very high interlaminar toughness. The finite element results are consistent with the failure process inferred from the energy release rate distribution theoretically obtained in the precedent studies.
Keywords plate, delaminations, impact, energy release rate, finite element analysis, finite displacement.

Theme : Composite Structures ; Modelling

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