SAMPE Journal - January/February 2017 - 11

Feature Article
are used throughout (C3D8R
elements). Failure at the adherend
bondline is modelled using cohesive
surface interactions. In the case
of the perforated joints, cohesive
surface interaction is also used for
the bond surfaces of the resin in
the steel perforations. A Cohesive
Zone Model (CZM), as indicated in
Figure 9, defines the behaviour of the
cohesive surface. Unfortunately, a
literature search has not provided all
of the parameters that are required
for the CZM, so it has been necessary
to make an initial estimate of suitable
parameters and then to carry out a
parametric study with the aim of
calibrating the CZM model against
the physical test data. The required
parameters are:
snt, initiation stress in the normal
direction
* tsmax, ttmax, initiation stress in the
two orthogonal shear directions
* Knn= smax
n stiffness in the normal
o direction
un
stiffness in the shear
* Ktt=tmax
t
direction
uto
* GIC & GIIC, fracture energy in
the normal and shear directions
respectively
Data given by Zhou et al7 and CVC
Thermoset Specialities8 have been
used to determine an initial baseline
estimate of these parameters for
a GRP-to-resin CZM, see Table 2.
With regard to the bond between
the GRP plate and the resin that
fills the perforations in the steel
plate, it should be noted that we are
assuming that the behaviour of this
bond is matrix dominated, i.e. it is
dominated by the GRP resin rather
than the fibers. Thus we are assuming
that it is valid to use fracture data
derived from GRP specimens, i.e. a
GRP-to-GRP interface, for the GRPto-resin interface in our FE models.
The FE parametric study that has
been undertaken to adjust these
GRP-to-GRP parameters is described
in the following.
The FE models of the perforated
and non-perforated joints have been

Table 2. Baseline initial estimate of Cohesive Zone Model (CZM) parameters for a
GRP-to-GRP interface. Based on data from Zhou et al7 & CVC Thermoset Specialities8.

used to carry out a parametric study of the CZM and thus modify the
on the CZM for both the GRP-to-steel tensile failure load of the joint. A
bond and the GRP-to-resin bond. "similar triangles" approach was
The non-perforated joints only have used when factoring the parameters.
one pair of interface materials at the The same reduction factor was
bondline, i.e. GRP / steel, while the applied to both the peak stress and
perforated joints have two pairs of the fracture toughness parameter in
interface materials, i.e. GRP / steel order to define the adjusted CZM.
and GRP / resin. Therefore, the non- See Figure 9 which shows the effect
perforated joint model has only a of applying factors of 0.65 and 0.30 to
single set of CZM parameters that the CZM of Table 2.
are required to model the bondline 4. Repeat steps 1, 2 and 3 until a
interface; thus the non-perforated good match is achieved between the
joint model was the first type to be failure load of the model and the
used in the parametric study. The physical test failure load.
following iteration methodology
A very simplistic preparation
was used for the parametric study:
has been applied to the steel plate
1. Carry out a displacement controlled bond surface of the joint specimens,
explicit analysis in Abaqus using the just grit blasting and degreasing.
CZM parameters given in Table 2. As a result, we would expect that
Material stiffness
and
plasticity
parameters
were
determined from
physical
coupon
tests carried out at
ICL.
2. Determine the
tensile failure load
of the joint for this
CZM.
3. Apply a factor to
the peak stress and
fracture toughness
parameters of the
CZM in order to
Figure 9. Graphical representation of Cohesive Zone
modify the strength

SAMPE Journal, Volume 53, No. 1, January/February 2017

Models (CZM).

11



Table of Contents for the Digital Edition of SAMPE Journal - January/February 2017

Contents
SAMPE Journal - January/February 2017 - Cover1
SAMPE Journal - January/February 2017 - Cover2
SAMPE Journal - January/February 2017 - Contents
SAMPE Journal - January/February 2017 - 2
SAMPE Journal - January/February 2017 - 3
SAMPE Journal - January/February 2017 - 4
SAMPE Journal - January/February 2017 - 5
SAMPE Journal - January/February 2017 - 6
SAMPE Journal - January/February 2017 - 7
SAMPE Journal - January/February 2017 - 8
SAMPE Journal - January/February 2017 - 9
SAMPE Journal - January/February 2017 - 10
SAMPE Journal - January/February 2017 - 11
SAMPE Journal - January/February 2017 - 12
SAMPE Journal - January/February 2017 - 13
SAMPE Journal - January/February 2017 - 14
SAMPE Journal - January/February 2017 - 15
SAMPE Journal - January/February 2017 - 16
SAMPE Journal - January/February 2017 - 17
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