Browsing by Author "Ponnusami, Sathiskumar A."

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    Coupon scale Z-pinned IM7/8552 delamination tests under dynamic loading
    (Elsevier, 2019-08-01) Cui, Hao; Mahadik, Yusuf; Hallett, Stephen R.; Partridge, Ivana K.; Allegri, Giuliano; Ponnusami, Sathiskumar A.; Petrinic, Nik
    Dynamic impact onto laminated composite structures can lead to large-scale delamination. This can be mitigated by the introduction of through-thickness reinforcement, such as z-pins. Here, mode I & II and mixed-mode delamination tests have been designed and conducted at high loading rate, for both unpinned and Z-pinned coupons to study the effect of rate of loading. It was found that the Z-pins were not effective in delaying the dynamic crack initiation or resisting the dynamic propagation of delaminations shorter than 5 mm. However, the further growth of cracks was substantially delayed by Z-pinning, especially for the pure mode I and mode I dominated failure modes. On the other hand, the effectiveness of Z-pins in shear tests was relatively modest. The mode I dominated delamination resistance of Z-pinned laminates was found to be sensitive to the loading rate.
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    A wedge-DCB test methodology to characterise high rate mode-I interlaminar fracture properties of fibre composites
    (EDP Sciences, 2018-09-07) Ponnusami, Sathiskumar A.; Cui, Hao; Erice, Borja; Pathan, Mehtab; Petrinic, Nik
    A combined numerical-experimental methodology is presented to measure dynamic Mode-I fracture properties of fiber reinforced composites. A modified wedge-DCB test using a Split-Hopkinson Bar technique along with cohesive zone modelling is utilised for this purpose. Three different comparison metrics, namely, strain-displacement response, crack propagation history and crack opening history are employed in order to extract unique values for the cohesive fracture properties of the delaminating interface. More importantly, the complexity of dealing with the frictional effects between the wedge and the DCB specimen is effectively circumvented by utilising right acquisition techniques combined with an inverse numerical modelling procedure. The proposed methodology is applied to extract the high rate interlaminar fracture properties of carbon fiber reinforced epoxy composites and it is further shown that a high level of confidence in the calibrated data can be established by adopting the proposed methodology.