Wind blade joints based on non-crimp 3D orthogonal woven Pi shaped preforms

Current industrial designs for joining composite wind blade elements allow unstable crack propagation in the thick adhesive layer within the joint. In this work, a novel integral 3D woven Pi-joint element is developed and implemented in an I-beam joint construction that corresponds to a wind blade’s shear web and spar cap. In a series of iterative design–analysis–fabrication–testing cycles, 2.9 m long I-beams that used the current practice joint and the novel proposed joint were designed, studied theoretically with the use of a 3D Mosaic analysis tool, then manufactured and loaded to failure in a cantilever flexure loading set up. Experimental data showed significant advantage in the load-bearing capacity of the joint structure with the use of novel Pi-joint element. Excellent agreement was observed between the theoretical predictions and experimental data.