Mechanical and low-velocity impact properties of sandwich Carbon/Alfa and Kevlar/Alfa fiber-reinforced epoxy for wind turbine blade

Abstract

In this study, the mechanical and low-velocity impact properties of two varieties of sandwich composites made of an epoxy resin matrix reinforced by a 40wt.% of Carbon/Alfa and or 40wt.% of Kevlar/Alfa satin cloth from long Alfa fibers for wind turbine blade manufacturing. An alkali and thermal treatments were realized to improve both of interfacial bonding between Alfa satin cloth and carbon or Kevlar skins with the matrix. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and chemical decomposition of treated and untreated fibers lead to prove the treatment efficiency. Chemical analyses performed on fibers provided the cellulose, hemicellulose, and lignin contents which were applied to establish that the rate of cellulose is more important for the treated fibers than for the untreated ones. The thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses showed better thermal stability. The Differential scanning calorimetry (DSC) showed an increasing in the heat amount as a function of increasing the volume fraction of Alfa fibers. FTIR, SEM and chemical decomposition of Alfa fibers analysis have shown the effectiveness of alkaline treatment with increases the cellulose and a good interfacial adhesion between the treated fibers and the matrix. The static and low-velocity impact tests of Carbon-Alfa/Epoxy and Kevlar-Alfa/Epoxy give 6.81 ± 0.65 GPa and 5.42 ± 0.59 GPa in tension; 4.64 ± 0.25 GPa and 3.42 ± 0.74 GPa in 3-points bending; 11.51 ± 0.39 GPa and 8.04 ± 0.01 GPa in compression and 33.96 J and 34.15 J in impact strength.