JEC COMPOSITES MAGAZINE - Issue #78 - January/February 2013 - 34

natural fibre

Can flax replace E-glass
in small wind turbine blades?

Darshil U. Shah*, PhD Student,
Peter J. Schubel, Senior Research
Fellow, Division of Materials, Mechanics
and Structures, Faculty of Engineering,
The University of Nottingham
*Corresponding author

atural fibres for composite applications have become a topic of growing
interest. The low density, low cost
of raw material, high specific properties
and positive ecological profile of plant
fibres have portrayed them as prospective
substitutes for traditional reinforcements,
specifically E-glass [1, 3]. While the use of
plant-fibre composites (PFCs) has tripled
to 45,000 tonnes over the last decade [4],
today they make up only some 1.9% of the
2.4 million tonne EU FRP market (Fig. 1)
[4]. By commercial application, over 95% of
PFCs are used for non-structural automotive interior components [4].
Over the past few years, the Wind Energy

This article details a novel comparative case study on the physical and mechanical properties of 3.5-metre rotor blades manufactured using flax/polyester and E-glass/polyester. This study
shows that under current market conditions, flax can be considered as a sustainable and structural, but not low-cost, alternative
to E-glass.

Materials Group at The University of
Nottingham has been involved with the
design and manufacture of wind turbines.
Recently, the Group has been investigating
the potential of sustainable plant fibres as
a replacement for conventional E-glass
reinforcements in the manufacture of small
wind turbine (SWT) blades (Fig. 2).
The blades are a critical and costly component of a wind turbine system. Having
a service life of 20–30 years, rotor blades
are designed against several structural
conditions including strength, stiffness
and tip deflection during operational
and severe loading, as well as very high
numbers (> 109) of fatigue cycles during
service. Naturally, for certification, the
structural integrity of the blades needs to

Fig. 2: Plant fibres vs. E-glass

be demonstrated by analysis and full-scale
mechanical tests.
Recently, the Group analytically demonstrated that an 11-kW hemp/polyester SWT
blade can survive design fatigue loads for
the required 20-year service life [5]. A comparative case study on the manufacture and
mechanical testing of 11-kW composite
rotor blades built from flax/polyester and
E-glass/polyester is described in this paper.
Firstly, the mass, cost and manufacturing
properties of the two blades are compared
and, secondly, their mechanical properties,
through static flap-bending testing.

Design and manufacture of blades
Fig. 1: PFCs, primarily used in automotive components, account for 1.9% of the 2.4 MT EU FRP market [4]

34 jec composites magazine / No78 January - February 2013

Blade design summary
The aerodynamically optimised study

JEC COMPOSITES MAGAZINE - Issue #78 - January/February 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #78 - January/February 2013