Temperature Effect on Mechanical Properties of Carbon, Glass and Hybrid Polymer Composite Specimens

Abstract

This paper presents the results of an experimental program to study the mechanical properties of currently available composite materials for the construction of wind turbine blade. The materials identified for this purpose include unidirectional glass fibre/epoxy (GFRP), carbon fibre/epoxy (CFRP) and hybrid combinations of these two materials to be used in a laminated design and at elevated temperatures. The tests conducted in the present programme includes short beam shear test and dynamic mechanical analysis tests after the specimens are exposed to temperatures ranging from 25 to 140°C. The results indicate that the inter-laminar shear failure strength and stiffness of GFRP, CFRP and hybrid specimens degrade with increasing temperature. However, the degradation is observed to be higher in single material specimens in comparison to hybrid specimens. In particular, stiffness of CFRP specimens decreased linearly as the temperature approached 40°C and increased up to the glass transition temperature of epoxy. Experimental results indicated that damping properties of Glass-Carbon-Glass/epoxy specimens improved at elevated temperatures which is important for noise and vibration control. In the present study, empirical models are proposed based on the test data to predict the variation of inter-laminar shear failure stress and stiffness as a function of temperature. The experimental results and proposed model can be used as input parameters to design and construct composite wind turbine blades to be used in tropical wind farms.