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