Impact of carbon fiber geometries on the compression strength of pultruded composites for wind turbine blades

Abstract

Modern wind turbines use carbon fiber pultruded composites in their blades to carry the large loads and limit the deflection. These pultruded profiles are either in tension or compression. Composites perform worse in compression than in tension, and this is thus the case pultruded composites are designed for. Some aspects of carbon fiber pultruded composites that can influence the compressive strength is the cross-sectional geometry and the matrix material.
The aim of this research is to investigate how different fiber cross-sections affect the change in compressive strength of the composite it is embedded in.
The effect of cross-sectional shape is investigated using physical tests on fibers with varying geometry, and simulation tools. The effect of the matrix material is investigated using simulation tools.
These tests and simulations resulted in showing that simulated Representative Volume Elements (RVE) with fibers obstructing a possible kink band path have higher compressive strengths. Additionally, fibers with higher area moments of inertia have higher simulated compressive strengths as well. Matrices with higher stiffnesses and, more importantly, higher yield stresses, also make carbon fiber pultruded composites perform better in compression.
This leads to the conclusion that fiber geometry and RVE packing type are the main factors on how cross-sectional geometry effects a pultruded composite performing in compression. The matrix stiffness and yield strength are also essential components of the compressive performance of the pultruded composite.