JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 46

delamination

Despite this additional investigation, matrix cracks could still
not be observed. The only damage seen in the material was fibre
breakage, and some very limited transverse matrix cracking in
the specimen loaded to final failure at 1.8% strain.

Numerical modelling
2D finite-element models were developed by Xu [2] to investigate and simulate the material's response under tensile and
compressive loading. The purpose of this study was to investigate
the influence of various geometric parameters on the stiffness
and strength (failure initiation) of laminates based on TeXtreme®
fabrics. The parameters of interest include the tow inclination
angle α, the fabric stacking sequence and the effect of multiple
layers on stiffness and strength.
A representative volume element (RVE) model was defined
from the characteristic geometry of the studied TeXtreme®
fabric at the meso level. The RVE was modelled in the plane
parallel to the 0°-fibre tow and perpendicular to the 90°-tapes.
Damage initiation in the fibre tows and tapes was then analysed
separately. Appropriate failure criteria were used to compare
element stresses to the allowable values for each material. The
strength of each material was calculated by increasing the strains
incrementally and evaluating the failure criteria for all elements
at each strain increment, until the failure index reached 1 for
any element. Using the measured mechanical properties (Table
1) and geometrical features measured from micrographs of the
plain weave laminates, Xu [2] concluded that for the TeXtreme®
fabric loaded in tension, matrix failure in the fibre bundle was
predicted to occur well before fibre fraction in the fibre tow
(however, this was not directly supported by the experimental
investigation, where no cracks were detectable at strain levels of
1.1-1.3%).
In compression, the predicted failure mode is fibre kinking in the
0°-fibre tow. The failure initiation site is located either inside or
very near the fibre tow inclination zone and the predicted values
correspond rather well with the experimental results. However,
since this method predicts damage initiation rather than ultimate
strength, which was determined by mechanical testing, the correct failure initiation sites are difficult to verify by visual inspection after conducting the test.

Impact response and damage
Impact is a prime concern in all current composite structures, as
impact damage has been found to considerably reduce stability
and strength, particularly in compression. Issues involve impact
resistance, i.e. the severity of damage after a given impact, and
impact damage tolerance, i.e. the effect of a given impact damage
on structural performance.
The present study conducted by Hellström [3], focused on the
impact resistance of laminates made of plain-weave spread tow

46 jec composites magazine / No84 October 2013

Fig. 4: Definition of impact locations X and C in the weave pattern

TeXtreme® material and established qualitative comparisons
with previous experience of similar cross-ply laminates made
of conventional carbon/epoxy UD prepreg. The differences in
impact response, damage mechanisms and damage morphology
were of prime interest. Impact tests were performed according
to ASTM D7136 using 4.04x101x151 mm laminates placed over
a rigid support with a 75x125 mm window, using rubber corner
clamps to provide simply supported boundary conditions.
Impact was performed at 20 or 30 J using a 1.5-kg instrumented
impactor with a 12.5-mm tip radius and a high-speed laser displacement sensor to measure back face deflection.
To examine the influence of impact location in the weave pattern, the laminates were made with the weave pattern equally
positioned in all plies. Specimens were manufactured to have the
centre (impact point) either at the crossing point of four weave
tapes (X-specimens) or at the centre of a weave tape square (Cspecimens), see Figure 4. Impact damage was characterized by
ultrasonic C-scan of all specimens followed by thermal deplying
to examine fibre fracture in all plies or microscopy of crosssections to examine the distribution of matrix cracks and fibre
fracture in the selected sections.
Figures 5a and 5b show superimposed delaminations and fibre
fracture in all plies after a 20-J impact in the weave crossing
point (X) and weave tape centre (C). Red (solid) lines represent the upper tape of each weave ply, while blue (dashed) lines
represent the lower tape of the plies. No significant differences
are seen in the overall delamination and fibre damage, although
there are slight differences in the distribution of fibre fractures.
Figure 5c shows an equally scaled damage in a conventional
quasi-isotropic prepreg laminate, impacted at 14 J [4]. Fibre
damage is much more severe in the thin ply laminate, while
delamination damage is smaller (considering differences in
impact energy). Thus, the thin plies constrain matrix cracking
and the associated delamination growth, which implies that
more impact energy is consumed when generating fibre damage.
The damage zone is strongly reduced along the minor axis of



JEC COMPOSITES MAGAZINE - Issue #84 - October 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #84 - October 2013

Cover
Edito
Point of view: global player
Contents
Agenda of Events
COMPANY & BUSINESS In Brief
APPLICATIONS
Industrial
Security
Automotive
MARKET
Trends
Bio-based
Basalt
FEATURE MARINE
Simulation
High-performance
TPT
Natural fibre
Core materials
Hybrid composite
China
RESEARCH & DEVELOPMENT
Curing agent
Delamination
TECHNOLOGY & INNOVATIONS
P.U.
Services
VARTM
Metrology
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Cover
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 2
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Edito
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Point of view: global player
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 5
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Contents
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 7
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 9
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Ad1
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Ad2
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - COMPANY & BUSINESS In Brief
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 11
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Industrial
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 13
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Security
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 15
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Automotive
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 17
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Trends
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 19
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Bio-based
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 21
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Basalt
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Simulation
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 24
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 25
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - High-performance
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 27
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 28
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 29
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - TPT
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 31
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 32
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Natural fibre
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 34
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 35
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Core materials
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 37
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Hybrid composite
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 39
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - China
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Curing agent
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 42
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 43
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Delamination
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 45
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 46
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 47
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - P.U.
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 49
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 50
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Services
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 52
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 53
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - VARTM
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 55
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Metrology
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - Index
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - In the world
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 59
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 60
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