Strain-Energy Release Rate Analysis of Cyclic Delamination Growth in Compressively Loaded Laminates

Delamination growth in compressively loaded composite laminates was studied analytically and experimentally. The configuration used in the study was a laminate with an across-the-width delamination. An approximate superposition stress analysis was developed to quantify the effects of various geometric, material, and load parameters on Mode I and Mode II strain-energy release rates G_I and G_II, respectively. Calculated values of G_I and G_II were then compared with measured cyclic delamination growth rates to determine the relative importance of G_I and G_II. High growth rates were observed only when G_I was large. However, slow growth was observed even when G_I was negligibly small. This growth apparently was due to a large value of G_II.