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

Abstract

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.

Mechanical evaluation of repair resins for fiber-glass wind turbine blades

“…Multiple approaches for calculating the overall strain energy release rate, G, and the mode I and mode II components, G I and G II , exist. [8][9][10][11][12] For example, the method of Hutchinson and Suo 12 requires that the applied loading on the specimen be separated into several component moments. This requires either a modification to the experimental setup to measure additional loads or the use of complimentary numerical calculations.…”