JEC COMPOSITES MAGAZINE - Issue #111 - March 2017 - Special JEC World - 114

TECHNOLOGY natural fibres

Flax fibre composite
for vibration damping design
Natural fibres, especially flax, are already known for their damping properties
due to their specific structure. ESTACA and the LAUM laboratory compared the
behaviour of flax and glass fibres embedded in a thermoplastic acrylic resin for
infusion moulding.
THUY-QUYNH.TRUONG-HOANG, Lecturer,
ZOUHAIER JENDLI, Associated Pr.,
ESTACA - Campus Ouest
Parc Universitaire Laval
ABDERAHIM EL MAHI,
Professor, Université du Maine
- LAUM Laboratory

l

n recent times, the transport industry has focused on lightweight
materials with good mechanical properties and lower environmental impact. Glass fibre-reinforced composites have good
mechanical properties and are widely used in many application areas. However, the manufacture of glass fibres and their end of life
disposal remain a major environmental problem. Natural fibres
have a lower environmental impact and offer high specific mechanical properties as well as sound absorption and vibration damping
properties. Vibration and damping issues have become increasingly
important over the past decades since vibrations are undesirable in
structures that need to combine performance, durability, and noise
reduction. One of the alternative solutions to reduce vibration disturbances is to use natural fibres for the reinforcement of composite
structures.
In the work described in this paper, flax fibre-reinforced thermoplastic composites were characterized in terms of vibration behaviour and compared with glass fibre-reinforced thermoplastic composites. The purpose was to characterize the damping properties of
these two composite materials in order to propose new solutions to
reduce structural vibrations.
Elium™ is an innovative liquid acrylic thermoplastic resin produced
by Arkema that can be processed with techniques conventionally
used for thermosetting resins. The flax and glass fibres used were
±45° bidirectional superimposed fabrics supplied by Terre de lin

and Saertex. Their average fibre weight was respectively 400g/m2
for the flax fibre fabric and 440g/m2 for the glass fibre fabric.

Experimental measurements
Composite processing
Vacuum-assisted resin transfer moulding was used to produce the
composite plates. This liquid composite moulding process has been
widely used to manufacture thermosetting composites. Before processing, the flax fibre preforms were dried in an oven at 110°C during 5 hours. Then, the preforms were sealed using a flexible vacuum
bag. The composite plates were made of two layers of flax or four
layers of glass in order to obtain an equivalent nominal thickness
value. After processing, the fibre volume fraction was determined
for both composites: 40% for the flax fibre composite and 44% in
the case of the glass fibre composite.
Damping measurements
The experimental equipment used is represented in Figure 1. A
fixed-geometry beam was clamped at the end of a fixed support.
A force hammer was used to impact the point close to the clamped
side. A laser Doppler vibrometer measured the velocity of the free
end of the beam. Then, the signals were processed by a laboratory software using the circle fitting method to determine damping
as a function of the vibration frequency. By definition, the modal
damping loss factor η relates to the damping ratio ζ by the relation
η=2.ζ. In order to compare the damping loss factor between different materials, the specific loss factor was defined by dividing the
damping loss factor by the composite density (dc).

Fig.1: Geometry
of the vibration beam
testing samples

114

jec composites magazine / No111 March 2017
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #111 - March 2017 - Special JEC World
