Comparative study on the evolution of process-induced residual stresses and deformations in thick and ultra-thick vacuum-infused laminates for wind turbine blades

The current research provides a thorough numerical investigation to shed light on the evolution of longitudinal and interlaminar normal residual stresses and induced deformations in thick and ultra-thick vacuum-infused laminates. The impact of resin curing during the mold-filling stage on residual stresses is also examined through a non-isothermal simulation of the mold filling with reactive resin for both thick and ultra-thick laminates. In addition, the effect of two resin-mixing types, both online and offline, is studied on the residual stresses and induced deformations. An in-house code namely VIsim is employed to conduct numerical simulations for the laminates, which involve non-isothermal mold filling with reactive resin, flushing, bleeding, and thermo-chemo-mechanical analysis during the curing stage. The study analyzes two E-glass/epoxy laminates with thicknesses of 50 mm and 100 mm each with a length of 1m. The results indicate that the distribution of longitudinal residual stresses in the thickness direction differs significantly between thick and ultra-thick laminates. However, the maximum interlaminar normal stress for the ultra-thick laminate is 143% greater than that of the thick laminate at the end of the process. The influence of resin mixing type is also found to be more significant on the residual stresses of ultra-thick laminates than thick laminates. Additionally, considering resin curing during the initial three stages of the Vacuum Infusion (VI) process through non-isothermal numerical simulation significantly affects the deformation of both thick and ultra-thick laminates.