A novel top surface analysis method for mode I interface characterisation using digital image correlation

The Double Cantilever Beam (DCB) test is the most widely used measurement technique for Mode I interlaminar fracture toughness of composite structures. However, the traditional testing methodology is based on the optical tracking of hand-marked scales on the specimen edge, which reduces its accuracy and makes it particularly dependent on human skills. Here, we present a novel Top Surface Analysis (TSA) method which overcomes these difficulties by analysing the top surface of DCB test samples via Digital Image Correlation. The automated measuring and data analysis procedure minimise the influence of human errors. This approach is able to simultaneously measure crack length and crack tip opening displacement. In order to verify the accuracy of the method, a comparison between TSA and conventional side-view evaluation methods was carried out on carbon and glass fibre reinforced composite laminates. The proposed method proves to be a promising tool to automate crack length measurements in arbitrary laminated structures and to provide more accurate fracture toughness properties for the prediction of damage tolerance in composite structures