2 research outputs found
Enhancement of impact damage resistance and tolerance in CFRP laminates using a single embedded polyurethane film
The aim of this study is to develop composite structures of high impact
resistance abilities. The PhD study involves the design, the manufacturing and the
testing of unidirectional carbon fibre reinforced polymer (CFRP) composites with a
single embedded polyurethane (PU) interleave to enhance the damage resistance to
low velocity impact (LVI) and damage tolerance to quasi static indentation (QSI). The
study involves three lay-up cases.
The objectives of this study include the understanding of the dynamics and the
overall behaviour of the manufactured laminates to low velocity impact damage. It
is essential to understand how the damage develops and how the failure modes
occurr in specific lay-up cases. Another objective is to draw a conclusion on how the
use of a single PU interleave would affect the damage path, the failure modes and
the overall behaviour of the laminates both under dynamic or static indentation.
There is an increased interest in impact resistant laminates to LVI due to the
increasing use of CFRP laminates in primary structures. Due to the nature of the
study, it is crucial to deploy laminates with the least manufacturing void content, as
voids can be a source of damage initiation that disguise the effect of impact-derived
damage. For the manufacturing of the examined laminates, out-of-autoclave process
was used. Compression moulding is a manufacturing process that leads to superior
laminate quality compared to other manufacturing processes such as vacuum
bagging.
The study examines three laminate lay-up configurations: Case I, a cross-ply
lay-up, Case 2, a quasi-isotropic lay-up, and Case 3 a bio-inspired lay-up. In each case,
the inclusion of a single PU interleave caused significant improvements in damage
resistance and damage tolerance. The compatibility of the PU interleave with the
epoxy resin and the carbon fibres is crucial for the investigation of the interfacial
damage. Thus, adhesion of the epoxy-PU bond was initially investigated. The depth
position of the single PU interleave in the laminate on its impact response is the main
focus of this PhD study. Each possible sub-case, featuring a different depth position
of a single PU interleave, resulted in a different extent of damage area and different
delamination mechanisms. Thus, both the laminate ply configuration and the
position of the interleave resulted in particular damage patterns, which are discussed
and analysed.
The damage path is strongly dependant on the stacking sequence and the
depth position of the PU interleave. Overall, the PU interleave is a positive inclusion
in the laminate. It has enhanced the damage resistance of the structure under low
velocity impact and the damage tolerance under static loading conditions. Depending
on the application needs the energy absorbance can be altered by incorporating in
specific locations a single PU interleave