  The static and time-dependent behaviours of adhesively bonded polyethylene
Double-Strap (DS) joints were investigated to assess the viability of this
joint configuration relative to the Single-Lap (SL) joints. Both experiments
and finite element simulations are conducted. First, we individually
characterise the tensile and creep behaviour of the adhesive and adherent
materials; an epoxy-based adhesive and polyethylene, respectively. This
information is used to develop suitable constitutive models that are then
implemented in the commercial finite element package ABAQUS by means of user
material subroutines, UMATs. The numerical models are used to design the creep
tests on the adhesive joints. Afterwards, an extensive experimental campaign is
conducted where we characterise the static and creep behaviour of two joint
configurations, SL and DS joints, and three selected values of the overlap
length. In regard to the static case, results reveal an increase in the failure
load with increasing overlap length, of up to 10% for an overlap length of 39
mm. Also, slightly better performance is observed for the SL joint
configuration. For the creep experiments, we show that the DS adhesive joint
configuration leads to much shorter elongations, relative to the SL joints.
These differences diminish with increasing overlap length but remain
substantial in all cases. In both joint configurations, the elongation
increases with decreasing overlap length. For instance, increasing the overlap
length to 39 mm led to a 50% and a 30% reduction in elongation for SL and DS
joints, respectively. Moreover, the numerical predictions show a good agreement
with the experiments. The stress redistribution is investigated and it is found
that the shear stress is highly sensitive to the testing time, with differences
being more noticeable for the DS joint system.
