JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 41

Fig. 4: Compression after impact (CAI) strength for composites with and without
4.5gsm Xantu.Layr™ nanofibre veils

bridge the micro-cracks that form in the interlayer during Mode
II fracture. Such bridging absorbs crack energy, and it is thought
that as long as the nanofibres are well bonded to the matrix resin,
a nanofibre veil with a relatively high tensile strength will provide
resin reinforcement and will better resist the opening of these
micro-cracks, resulting in a higher Mode II ILFT.

Compression after impact strength
Compression after impact (CAI) has become a key experiment
to gather damage performance data for the design or certification of composite materials. Damage tolerance in laminates is
usually evaluated by determining the effect of different impact
energies on their residual strengths. In this investigation, CAI
tests were performed on 16-ply QI laminates made from SE70/
VRC/200/400/35+/-3% UD prepreg interleaved with Xantu.
Layr™ nanofibre veils in accordance with ASTM D7136/
D7136M and ASTM D7137/D7137M.
As can be seen in Fig. 4, the compression after impact strength
of laminates interleaved with Xantu.Layr™ was greatly increased
over a range of impact energies. It can also be seen that a nanofibre-interleaved laminate impacted at 30J exhibited a similar CAI
strength to a non-interleaved laminate impacted at 10J, representing a significant increase in damage tolerance.
This increase in CAI strength is due to the toughening effect
of the nanofibre veils in the composite interlayers, resulting in
reduced delamination of the laminates after being impact damaged. The interleaving nanofibres deflect cracks in the matrix and
absorb crack energy during the impact and compression test, thus
increasing the amount of energy required for crack growth. Other
toughening mechanisms such as fibre bridging, debonding and
pull-out could also have increased the energy required for crack
propagation and reduced the overall degree of damage, resulting
in higher CAI strengths.

Fig. 5: Fatigue life of composites with and without 4.5gsm Xantu.Layr™
nanofibre veils

and interfacial debonding. In this investigation, tension-tension
fatigue tests were performed on 16-ply QI laminates made from
SE70/VRC/200/400/35+/-3% UD prepreg interleaved with
nanofibre veils in accordance with ASTM D3479/D3479M.
As can be seen in Fig. 5, the fatigue life of composites can be dramatically increased by interleaving the laminates with 4.5 g/m2
Xantu.Layr™ nanofibre veils. An improvement of 394% was seen
for interleaved laminates tested at a cyclic stress of 450MPa.
This observed improvement in fatigue life is most certainly due
to the toughening effect of the nanofibre veils in the resin-rich
interlayers of the composite, as described previously in this article. Since the interleaving veils delay the onset of matrix cracking
and delamination, the strength of the composite is maintained for
longer before the integrity of the material is compromised.
Fracture surfaces of non-interleaved and interleaved fatigue test
specimens can be seen in Figures 6 and 7. The non-interleaved
composite (Fig. 6), displays a smooth, shiny but jagged fracture
surface that is typical for brittle epoxy matrices. The Xantu.Layr™
interleaved composite (Fig. 7), on the other hand, shows a dull,
rough but less jagged fracture surface suggesting a more ductile
failure mode. It is likely that the fatigue cracks in the interleaved
resin were not able to join up to form a continuous and smooth
fracture surface, but were instead re-directed in many different
directions by the nanofibre veils to form a rough surface. It is also

Fatigue life
Fatigue is the main reason for failure of structural materials in service. Repetitive cyclic loadings of composite components eventually result in extensive damage throughout the material, leading
to failure from matrix cracking, delamination, fibre breakage

Fig. 6: Fracture surface of non-interleaved fatigue test specimen after 350,000
cycles (600x magnification)

No102 January - February 2016 /

jec composites magazine 41



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016

Cover
Edito
Point of view : additive manufacturing
Contents
COMPANY & BUSINESS
DSM Composite Resins to be renamed Aliancys
Aerion and Airbus announce expanded collaboration on supersonic AS2
Agenda of Events
APPLICATIONS
Defence
Sports & leisure
MARKET
Overview
FEATURE AUTOMOTIVE
CFRP
Natural fibres
Prepreg
Thermoplastic
PUR
Phenolic
Process
RESEARCH & DEVELOPMENT
Impact resistance
Trace
TECHNOLOGY & INNOVATIONS
Control
Quality
Automation
Thermoplastic
Nano
Compound
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Point of view : additive manufacturing
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - DSM Composite Resins to be renamed Aliancys
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Aerion and Airbus announce expanded collaboration on supersonic AS2
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 11
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - pub1
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - pub2
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Defence
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Sports & leisure
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 14
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Overview
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 16
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 17
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - CFRP
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 19
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 21
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 22
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Natural fibres
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 24
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 26
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Prepreg
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Thermoplastic
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 29
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 30
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - PUR
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Phenolic
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 33
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 34
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Impact resistance
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Process
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 37
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 38
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 40
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 41
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Trace
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 44
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Control
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 47
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 48
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Quality
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 50
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 51
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Automation
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Thermoplastic
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Nano
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Compound
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - Index
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 59
JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 60
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