Abstract:
As engineering continually pushes the boundaries of high-performance design, carbon fibre
reinforced plastic is continually increasing in the aerospace industry due to its lightweight and
superior mechanical properties. One of the most promising joining methods for composite
materials is secondary adhesive bonding. The parameters within the bonding process have been
widely studied. However, literature shows limited study on the effect of variation within the
control measures and how they can influence the bond characteristic in practice. The aim of
this investigation is to identify some of the key variances and impacts through different test to
failure methods.
A test plan containing 24 types of tests is generated to accommodate all the different parameters.
These parameters include different types of surface preparation, curing during different environmental
conditions (low and high humidity), and oil contamination before bonding. All joints
were manufactured under the same process and adhesive with the expectation of the mentioned
variables. Single lap shear testing and T-peel testing are the two test methods used to conduct
the testing.
The measured failure load from the lap shear testing and average peel load from the T-peel
testing are compared across all variables. The coefficient of variation for each individual input
and output are calculated. These results showed good consistency and reliability, except the
bondline thickness of each joint. The correlation coefficient is also used between the measured
strength and the geometric parameters. No specific relationship was found.
A significant load difference between the lap shear joints and T-peel joint is observed. The result
analysis shows a negative correlation between the increase of humidity during bonding and the
reduction in bond strength. Different surface preparation can also produce distinct variations
in terms of bond strength and bond quality. The influence of oil-contaminated bonded joint is
also studied. The investigation shows promising results on the variation and effectiveness of
contamination removal with different treatment methods.