Characterization of High Fiber Volume Fraction Glass Pultruded Plates for Wind Turbine Blades

Abstract

In recent years, the wind energy industry shows more and more interest in composite materials manufactured with a new process called pultrusion. The advantage of pultruded composite plates includes high fiber volume fraction, low price and simplified blade manufacturing. However, pultruded plates are fully cured and crosslinking is absent at interlaminar interface, which may lead to potential risks when being applied into the real structure. This project focuses on characterizing and evaluating this new type of material.

Microscopy and burn-off test were carried out to measure the actual fiber volume fraction in the material. Roughness of interlaminar surface was measured with microscope by focus variation. These parameters are essential to understand the material.

To characterize the mechanical behaviour of the material, multiple different types of mechanical tests were carried out. Mode-I and mode-II interlaminar fracture toughness were tested with Double Cantilever Beam(DCB) and End-Notched Flexure(ENF) specimens. A new test procedure was developed to measure the mode-I interlaminar fatigue toughness of the material. For in-plane tensile and compression test, Finite Elements Methods(FEM) was used to optimize the specimen geometry in order to obtain results closest to actual material behaviour. During the tensile test, acoustic emission was measured to monitor the damage in the specimens in these tests. Fatigue tests with stress ratio R=0.1 and R=-1 were carried out to understand the fatigue behaviour of the material.