Durable and reliable joining of composite blade elements remains a pivotal challenge faced bythe wind generation industry. Current industry practice uses joint designs which allow forunstable crack propagation within the thick adhesive layer between the shear web and the sparcap, which becomes the most fracture susceptible region of the blade structure. One designimprovement that will arrest an initiated crack involves integral 3D woven Pi-joint elements. Inthis work, the benefits of the novel Pi-joint versus current practice joints were first verifiedtheoretically, by performing the 3D stress/strain and failure analyses by means of the 3DMOSAIC code. Then, utilizing both the current and new joining approaches, a series of 3 mlong, complex cross section, cantilever I-beams were manufactured and exposed to a quasi-staticcantilever flexure loading. Experimental data showed excellent agreement with the theoreticalpredictions in terms of the deflection-load curves, the sites of initial failure, and the paths ofmajor crack propagation. They also confirmed significant advantage in the load-bearing capacityof the new joint. Records kept during the manufacture of the cantilever beams indicate that theuse of integral 3D woven Pi preforms also leads to significant savings in labor and materials.
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