Fatigue behavior and lifetime distribution of impact-damaged carbon fiber/toughened epoxy composites under compressive loading

摘要

This paper presents fatigue lifetime data of impact-damaged carbon fiber/toughened epoxy composites under compressive loading to elucidate the lifetime prediction methodology based on statistical approaches. Drop-weight impact damage was induced to a composite specimen with impact energy of 6.7 J/mm in accordance with ASTM D7136. Postimpact fatigue tests were conducted using a test fixture defined in ASTM D7137 under compres sion-compression loading (R =10) at room temperature. The maximum compressive stress (Smin) was 200, 210, 220, 230, and 240 MPa, and the total number of specimens was 31. The compression-after-impact strength and fatigue lifetime show considerable scattering. This result is apparently derived from the variation in impact damage size. A simple statis tical model based on the weakest link theory was proposed for predicting the lifetime of impact-damaged composite laminates. Results show that the experimentally obtained data were confirmed consistently using this model. The ratio between the endurance limit at 10~6 and 107 cycles and the initial static strength was estimated as 0.74 and 0.68 as B-basis allowable values.