Research engineer, Mechanics of Materials Branch, NASA Langley Research Center, Hampton, VA
Compressive loads can cause local buckling in composite laminates that have a near-surface delamination. This local buckling causes load redistribution, which in turn causes interlaminar stresses and delamination growth. In this study, a three-dimensional, geometrically nonlinear finite-element analysis (NONLIN3D) was used to calculate strain-energy release rate distributions for several laminates that exhibited this instability related delamination growth. Two stacking sequences ([0/90/90/0]6 and [90/0/0/90]6) were considered. The specimens were fabricated with a double layer of 0.013-mm Kapton film located between the fourth and fifth plies, thereby simulating a delamination. Initial delamination sizes were 30, 40, or 60 mm in diameter. The static strain corresponding to delamination growth was determined experimentally. Comparison of the analytical and experimental results indicated that delamination growth was governed by the magnitude of GI.
Paper ID: CTR10158J