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Several types of continuous fibre
reinforcements are available for advanced
textile reinforced composite materials,
including woven, stitched and braided
fabrics. Textile industries are constantly
enhancing weaving and stitching
technologies for such reinforcements in
order to reduce material cost and compete
against other materials for structural
applications, such as metals and ceramics.
However, a barrier to wider application of
textile reinforced composites is their
secondary manufacturing processes, which
tend to be relatively slow and labour
intensive compared with equivalent
processes for more traditional materials.
Slower manufacturing means higher
product cost and often limits application of
textile composites to expensive aerospace
and military components. To reduce
manufacturing time, automated
manufacturing methods such as press
forming are being adapted to suit textile
composites. This technique is particularly
suited to thermoplastic matrix textile
composites which can be heated, formed
and cooled within a short processing
window.
A common practice in the past was to
determine optimum forming conditions for
a given material by trial and error, where
various combinations of process
parameters were evaluated experimentally.
Rapid advances in numerical technology
and computational capability have seen
the rise of ‘virtual manufacturing’ as an
essential tool in optimising the press
forming of more traditional materials such
as metals and plastics where computational
techniques such as finite element analysis
are used to simulate the press forming
process. In order to apply similar virtual
manufacturing CAE tools to textile
composites, constitutive models that can
predict the large deformation behaviour of
textile composites during forming are
required. Development of such models is
one of the main research interests of Dr
Philip Harrison working within the Materials
Engineering Group at the University of
Glasgow. A fundamental aim of this work
has been to predict this forming behaviour
from the fabric’s meso-scale structure, such
as the fabric’s weave style and, for noncrimp
fabrics, from the fabric’s stitching
pattern. To do this, multi-scale modelling
methods are used which lend themselves
well to analysing the repeat structure of
typical fabric architectures.
The weave style of a fabric affects it’s forming
behaviour during manufacture.
Once these constitutive models are
implemented in the finite element code,
forming predictions have to be verified
against experimental results. This involves
comparing both force and strain
predictions, where the latter can be
measured conveniently using full-field
optical imaging techniques such as stereo
photogrammetry
Forming prediction of a textile composite over
hemispherical geometry.
This research is part of a wider
collaboration involving several UK and
international research groups. Phil Harrison
Forming of Textile Composites
Lines drawn on the material before forming (top)
help in determining the full-field strain map
(bottom) across the surface of the doubly curved
part (a helicopter pilot helmet). The fibre shear
angle is indicated using a colour map.
is an active member of the Composite
Forming International Benchmarking
Initiative, designed to compare and
evaluate the various modelling approaches
adopted by different research groups
working in this field.
Contact: Dr Phil Harrison,
p.harrison@mech.gla.ac.uk
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Dimensions • February 2009 • 7
John Edwards, Executive Officer -
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