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SUMMARYA concise constitutive law for cohesive interfaces is proposed in this paper. A new state variable is introduced to track the extent of damage accumulated at the interface. The constitutive equations not only account for mixed-mode delamination propagation in composite materials, but also satisfactorily deal with mode ratio change during the debonding process. The interface model is implemented in the LS-DYNA explicit finite element code. The model has been applied to scaled open hole tension tests on laminated composite material. Comparison between numerical results and experiments shows good correlation for failure modes and strengths for a range of different specimen sizes.

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The open hole tension strength is an important parameter for composite structures since it is can be a limiting factor in design. It is also difficult to characterise and predict through analytical or numerical methods since there exists a wide variation in experimental results depending on testing configuration. Here a range of such variations are presented and the behaviour explained in terms of the development of sub-critical damage in the form of intra-ply splits and inter-ply delaminations and their interaction with each other and also with fibre failure. A finite element based numerical analysis technique has been developed and applied to each case in turn, successfully predicting the failure modes, trends and strengths. This is sufficiently robust to form the basis for a virtual testing framework for the open hole tensile strength of composite materials.

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The mechanical resonance properties of a microelectromechanical oscillator with a gap of 1.25  μm was studied in superfluid ^{3}He-B at various pressures. The oscillator was driven in the linear damping regime where the damping coefficient is independent of the oscillator velocity. The quality factor of the oscillator remains low (Q≈80) down to 0.1T_{c}, 4 orders of magnitude less than the intrinsic quality factor measured in vacuum at 4 K. In addition to the Boltzmann temperature dependent contribution to the damping, a damping proportional to temperature was found to dominate at low temperatures. We propose a multiple scattering mechanism of the surface Andreev bound states to be a possible cause for the anomalous damping.

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