Residual Stresses Generation in Ultra-Thick Components for Wind Turbine Blades

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The present paper investigates the generation of cure induced residual stresses during the cure stage of the Vacuum Assisted Resin Transfer Moulding (VARTM) process for the fabrication of ultra-thick components (i.e. 105 mm) for wind turbine blades manufacturing (i.e. root insert). The viscous-elastic material characterisation of the Airstone 780E epoxy resin mixed with the 785H Hardener has been undertaken and the corresponding coupled thermo-mechanical simulation has been implemented using a commercial FE solver. The finding points out that the level of residual stresses generated during the cure stage leads to a spring-in of about 1.3 cm when Manufacturer Recommended Cure Cycle is applied and that improvements in both spring-in and cure time can be obtained by applying different cure cycles.