Mixed-mode delamination growth of laminar composites by using three-dimensional finite element modeling

摘要

Delamination is one of the most frequent failure modes in laminated composites. Its importance is crucial, because a delamination can occur in the interior of a panel without any noticeable damage on the surface, drastically reducing its strength and stiffness. A study has to be made on critical dimensions of delaminations and their shape, through the calculation of the strain energy release rate (SERR), G . This study was performed numerically, for a given geometry, with varying loads and shapes of delamination, in pure and mixed-mode propagation. All numerical values were obtained with three-dimensional finite element (FE) analyses from a commercial package. The use of three-dimensional analyses in simple geometries helps establish the basis for the more complex ones, and the correspondence with the usual analytical or numerical bi-dimensional plane-strain analysis. The conclusions were (a) G is not constant along the crack tip, even for mode I propagation and straight crack tip; (b) the mean value of G obtained from a three-dimensional analysis equals the value obtained in bi-dimensional plane-strain analysis; (c) in mixed-mode propagation, the method exhibits a good correlation with experimental results and (d) the shape and mode partitioning of the SERR depend not only on the loading, but also on the shape of the crack front. [References: 30]