INFLUENCE OF LOW-ENERGY IMPACT ON FATIGUE BEHAVIOR OF THE CARBON/EPOXY LAMINATE COMPOSITES

摘要

Impact toughness and fatigue behavior of carbon fiber reinforced epoxy composites with and without subjecting low energy impact have been investigated. The [0/45/90/-45]_(2S) and [0/45/90/-45]_(4S) T300/976 Carbon/Epoxylaminates were utilized in this study. The impact response of the laminates shows a linear force-deformation relationship in the initial stage of penetration impact test which imply an elastic behavior of the composites; the afterward zigzag peaks imply the fracture initiation and arrested. In [0/45/90/-45]_(2S) composites, the static tensile strength of the laminates and residual strength after low energy impact were measured. Furthermore, the fatigue behavior before and after low energy impacts are investigated. The fatigue tests were performed at various stress levels under tension-compression loadings with a fatigue frequency of 10 and stress ratio of-1. A linear S-N curve under the test condition is observed. Moreover, C-Scan and X-ray inspections are utilized to examine the damage zone of the specimen subjected to low energy impacts. According to the test results, it is found that both the spread and cycles of the fatigue life of the laminates are reduced after low energy impact. In [0/45/90/-45]_(5S) laminates, a strength degradation model is adopted to predict the residual strength of the composites subjected to a specific fatigue cycle and stress level.