Abstract
Experimental approaches to free-edge delamination onset and growth are presented in combination with strain energy release rate calculations. Crossply and quasi-isotropic carbon-epoxy laminates are subjected to tension-tension and compression-compression fatigue loads and the interfaces at which delamination took place are compared with those recently predicted by the authors. The excellent correlations between analytical predictions and experimental results show the existence of loading direction effects and initial defects. Next, quasiisotropic carbon-epoxy laminates (45°/-45°/0°/90°)s with different thinckness have been tested under static tensile loads. The delamination onset strains of the laminates with and without detectable initial delaminations are measured and used to calculate the energy release rates as a function of the delamination length by a finite element method, and the length of undetectable initial defects is obtained. Finally, the static tensile test of carbon-epoxy laminates (±θ°/0°/90°)s and (0°/±θ°/90°)s where θ=25, 35, 45 with initial delaminations simulated by inserted thin films has been conducted to obtain the critical strain energy release rates. And the contribution of opening and shear mode energy release rates on the delamination onset are studied.
