JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 42

self-healing

Fig. 2: Vascular self-healing skin-stiffener debond specimen test set-up procedure with Imetrum's UVX Flexi system

Fig. 1: Top left: Self-healing agent "bleeding" from matrix cracks in a cross-ply
test specimen; Right: Fractured cross-ply test specimen showing matrix cracking
in 90° layers; Bottom left: Automated injection of a self-healing agent via the
embedded microvascular channel

that heal or repair in a quasi-autonomous way for about 15
years. The concept behind this work mimics blood vessels and
the haemostasis process in living creatures. Upon damage,
internal cavities (vascules) release a healing agent with the
ability to re-polymerise and thereby repair and re-bond
internal damage fracture sites. Two papers recently published
by the team [1], [2] explore intralaminar damage arising under
tensile loading in cross-ply laminates, both for static and fatigue loading. The method used involves automated injection
of a self-healing solution through small micron-sized channels
(vascules), contained within cross-ply laminates (figure 1)
and skin-stiffener debond specimens (figure 2), using epoxy
resin-based healing agents to activate the repair process.

Static and fatigue testing
The experimental investigations involved both static and fatigue
testing of the cross-ply laminate specimens to assess the restoration of material stiffness following the injection of a range of healing agents. The team found that Imetrum's UVX Flexi system,
powered by Video GaugeTM software, is a vital part of collecting
the data they need.
According to the ACCIS team, Video GaugeTM software can be
used to extract deformation and strain data from any test, irrespective of scale, so long as a stream of images can be obtained.
For low-speed testing on conventional test machines, this data
can be extracted in real time up to at least 300Hz. It can also
be used in conjunction with the high-speed camera post-test.
When coupled with a miniaturised test machine and a metallurgical microscope, this gives the capacity to carry out very
fine scale studies of the strains within loaded composites at the
meso and micro scales.

42 jec composites magazine / No104 April - May 2016

For this particular research, the static testing used Imetrum's
system (UVX Flexi) to determine the material properties. Specimens were loaded to 15kN (340MPa, corresponding to 75% of
the failure stress) and then unloaded under displacement control
at a rate of 2mm/min. The benefits of using this approach over
other measurement devices such as a clip-on extensometer or
strain gauge include:
- Avoiding problems of clip-on devices that can compromise
the result, such as knife edges slipping or causing damage to
the specimen.
- Eliminating the operational challenges of using strain gauges,
such as the high skill levels required to bond effectively, and
aligning the gauge precisely with fibre directions.
- Measuring through failure without risk of damage to the
equipment.
- Permitting full visual observation of the specimen during
test.
- Time and cost savings, with minimal sample preparation.
All of these factors are only of benefit if the video extensometer is able to measure at sufficient resolution for the low
strains involved when operating within the elastic region of
composites, which is no problem for the UVX Flexi, which
often passes through calibration with an accuracy better than 1
micron. The static test results from this study showed that the
self-healing polymer was initially able to recover between 67
and 75% of the initial stiffness, depending on the healing agent
formulation used.

Fatigue performance
To assess fatigue performance, specimens without vascules
were cycled for 100,000 cycles in total. The vascularised
specimens were tested for 50,000 cycles and then the healing
agent was injected. Specimens were re-tested following curing
of the healing resin. These first 50,000 cycles indicated that
no change in mechanical properties or damage formation
was observed when a single vascule (representing 0.5% of the
cross-sectional area) was included in the 0/90 interface. Under fatigue conditions post-healing, after around 2,500 cycles
almost all of the restored stiffness was lost. This was caused by



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016

Cover
Edito
Point of view: Thailand smiles at composites
Contents
COMPANY & BUSINESS
Agenda of Events
APPLICATIONS
Cycle
Multisectorial
Music
MARKET
Trend
Carbon
SPECIAL JEC AMERICAS 2016
Conferences
Awards
Oil & Gas
Redevelopment
Laboratory
RESEARCH & DEVELOPMENT
Self healing
Fibre placement
Microwave
TECHNOLOGY & INNOVATIONS
LFT
Intermediate products
Multimaterial
Manufacturing
Process
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Point of view: Thailand smiles at composites
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - COMPANY & BUSINESS
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 9
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Ad1
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Ad2
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 11
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Cycle
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 13
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Multisectorial
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 15
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Music
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 17
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Trend
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 19
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 21
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Carbon
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 23
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 24
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Conferences
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 27
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 28
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Awards
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 30
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 31
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 32
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 33
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Oil & Gas
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 35
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Redevelopment
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 37
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Laboratory
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 40
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Self healing
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 43
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Fibre placement
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 46
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Microwave
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 48
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 49
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 50
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - LFT
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 52
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Intermediate products
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Multimaterial
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 56
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 57
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 58
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Manufacturing
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 60
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Process
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 62
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 63
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 64
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - Index
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 67
JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 68
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