JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 41

Self-healing cross-ply
laminates - encouraging
test results
Understanding and increasing the lifespan of composite materials
is vital for wider adoption. Fatigue-induced microcracks can cause
failures and are hard to detect and repair. Testing has demonstrated early promise for self-healing composites able to recover
properties such as interlaminar fracture toughness.

Transverse matrix damage

By
Rafael luteRbacheR, PhD ReseaRch stuDent,
DR tim cooPe, ReseaRch associate,
DR RichaRD tRask, ReaDeR,
PRofessoR ian bonD, heaD of school,
aDvanceD comPosites centRe foR
innovation anD science (accis),
univeRsity of bRistol Paul WateRfall,
imetRum limiteD

t present, a rapid uptake of composite materials is being observed
in industry, including many fatiguelimited applications such as aerospace
components, wind turbine blades and
automotive parts. The use of advanced
fibre-reinforced polymers to exploit their
high strength and stiffness with lowweight penalties also improves buckling
stability and resistance to bending. Their
high strength-to-weight ratio and resistance to corrosion are further key factors
behind this uptake, combined with an
appreciation of lifetime cost savings. However, there are still question marks around
material longevity and the ability to assess
damage in composite structures.

Intralaminar damage - or transverse
matrix damage - is one of the first damage
mechanisms to occur in fibre-reinforced
polymers. Even though the effect on
mechanical properties is limited, it acts as
an initiation point for subsequent internal
damage propagation. This interlaminar
damage in fibre-reinforced composites is
particularly difficult to detect, meaning
that more serious damage can develop
before a problem is detected. At present,
this is mitigated by using conservative
safety factors in design, leading to higher
cost and weight than would otherwise
be necessary. One way to eliminate this
problem is to produce materials with an
internal self-healing/repair or damage
control mechanism. In concept, self-healing materials have the ability to repair
structural damage caused by mechanical
usage. A material that can mitigate damage
will lead to safer composite structures, and
will also provide lower maintenance costs
for composite material-related industries,
both in terms of inspection and repair.
This has the potential to boost confidence
in fibre-reinforced composite materials,
and increase their rate of adoption across
the industry.

- Self-healing cross-ply
laminates - encouraging
test results ................ p41
- Automated path planning
and thermographic monitoring for automated fibre
placement ................... p44
- Susceptors improve
microwave curing technology for thermosetting
resins ......................... p47

Research & development

self-healing

Researchers from the Advanced
Composites Centre for Innovation and
Science (ACCIS) at the University of
Bristol have been looking at materials
No104 April - May 2016 /

jec composites magazine 41

http://www.experience-composites.com

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