Obtaining the J-integral and mode mixity of climbing drum peel test by finite element modelling

Abstract

Fibre composites are used for their high specific stiffness and strength and possibility for tailoring the properties in the different directions depending on the loads in a given application. Wind turbine blades are almost entirely made of fibre composites and sandwich structures to keep the weight low at a reasonable cost. As a result, a wind turbine blade contains many interfaces both between the individual layers in the composite and sandwich structures, and as adhesive bond lines between the different parts. Therefore, it is of great importance to have reliable methods to experimentally measure the interface strength in composites. A commonly used approach to measure the mode I (opening) fracture toughness (GIC) of a composite is the Double Cantilever Beam (DCB) test. Although the crack is assumed to progress as a straight crack, the loading configuration in the standard DCB test (e.g. ASTM D5528) results in a parabolic-like shape of the crack. In addition, it is necessary to either measure the crack length during the test or carry out a compliance calibration. As an alternative to the DCB test for measuring GIC, Daghia and Cluzel proposed the Climbing Drum Peel (CDP), which is also a standardised test (ASTM D1781)