STUDY ON THE TENSILE FATIGUE DAMAGE OF QUASI-ISOTROPIC COMPOSITE LAMINATES
STUDY ON THE TENSILE FATIGUE DAMAGE OF QUASI—ISOTROPIC COMPOSITE LAMINATES

Quasi-isotropic laminates have isotropic elastic properties in all in-plane directions. Therefore, this kind of laminate is widely used for structural elements. The simplest stacking sequence of quasi-isotropic laminates is 0/-60/60]s. When the direction of applied axial load to 0/-60/60]S laminate is inclined at a 30-degree angle, we have the other quasi-isotropic laminate 30/-30/90]s under axial load. The failure mechanisms of these two laminates are, however, entirely different from each other because these two laminates have different distribution of the interlaminar stresses. It was confirmed by tensile fatigue tests that the 0/-60/60]s laminate does not show any visible fatigue damage, but the 30/-30/90]s laminate develops edge-delamination during cyclic loading. The analytical results were in good agreement with the experimental results.