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  • Publication
    Modelling the Fracture Behaviour of Adhesively-Bonded Joints as a Function of Test Rate - A Rate Dependent CZM is Required to Predict the Full Range of Behaviour
    Adhesive bonding of lightweight, high-performance materials is regarded as a key enabling technology for the development of vehicles with increased crashworthiness, better fuel economy and reduced exhaust emissions. However, as automotive structures can be exposed to impact events during service, it is necessary to gain a sound understanding of the performance of adhesive joints under different rates of loading. Therefore, characterising the behaviour of adhesive joints as a function of loading rate is critical for assessing and predicting their performance and structural integrity over a wide range of conditions. The present work investigates the rate-dependent behaviour of adhesive joints under mode I loading conditions. A series of fracture tests were conducted using tapered double-cantilever beam (TDCB) specimens at various loading rates [1-2]. The experiments were analysed analytically and numerically. The full details of the analysis strategy employing analytical approaches for different types of fracture are presented in [1]. The numerical modelling of the TDCB experiments was performed using the finite-volume based package ‘OpenFOAM’ [3].
  • Publication
    Modelling the fracture behaviour of adhesively-bonded joints as a function of test rate
    Tapered-double cantilever-beam joints were manufactured from aluminium-alloy substrates bonded together using a single-part, rubber-toughened, epoxy adhesive. The mode I fracture behaviour of the joints was investigated as a function of loading rate by conducting a series of tests at crosshead speeds ranging from 3.33 × 10−6 m/s to 13.5 m/s. Unstable (i.e. stick–slip crack) growth behaviour was observed at test rates between 0.1 m/s and 6 m/s, whilst stable crack growth occurred at both lower and higher rates of loading. The adhesive fracture energy, GIc, was estimated analytically, and the experiments were simulated numerically employing an implicit finite-volume method together with a cohesive-zone model. Good agreement was achieved between the numerical predictions, analytical results and the experimental observations over the entire range of loading rates investigated. The numerical simulations were able very readily to predict the stable crack growth which was observed, at both the slowest and highest rates of loading. However, the unstable crack propagation that was observed could only be predicted accurately when a particular rate-dependent cohesive-zone model was used. This crack-velocity dependency of GIc was also supported by the predictions of an adiabatic thermal-heating model.
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