Test on progressive damage of open-hole composite laminates under compression load

In order to study damage initiation, evolution ways and damage characteristic of carbon fiber reinforced resin matrix composites open-hole laminates under compression load, compressive tests of open-hole domestic CCF300/5228A laminates of three kinds of layup [45/0/-45/90]_4s, [45₂/0₂/-45₂/90₂]_2s, [45₄/0₄/-45₄/90₄]_s were investigated based on four methods: macro photography, ultrasonic C-scan together with multi-stage loading, X-scan and scanning electron microscope. The damage initiation and damage propagation of open-hole laminates under compression load were observed and compared. The fiber micro-buckling, fiber extrusion, cracks and delamination on hole edge during tests were analyzed and explained. The test results show that delamination occurs easily at positions between 45° and 90° layups of laminates under compression load. Phenomenon of progressive damage is obvious at the edge of the hole in laminates within positions between 45° and 90° layups. The relief of stress concentration and strain energy on the hole edge are caused by the early initiation and propagation of damage. The relief delays the final failure and increases compressive bearing capacity of the laminates. The results can provide a guidance for the damage tolerance design of composite structures.