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A lot of work on reinforcement deformation mechanisms during composites forming has been performed over the past decades. This paper demonstrates the relative importance of bending behaviour during composites forming, by showing algorithms to calculate bending and shear energies. Bending energy is estimated from a bending energy surface, a function of the displacement and rate, plotted using experimental measurements obtained by means of a large-displacement buckling test at a variety of displacement rates. Shear energy is predicted from a shear energy surface, a function of shear angle and rate, plotted using experimental measurements from a Picture Frame test. Conclusions provide a comprehensive understanding of forming mechanisms of viscous composites and suggest the need for development of a theoretical bending model. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Normalisation methods for both Picture Frame (PF) and Bias Extension (BE) tests on rate-independent compressible fabrics undergoing trellis shear are presented. Normalisation of PF test results is relatively straightforward and involves dividing the force results by a characteristic length. A normalisation procedure for BE test results has been developed based on an energy argument that uses a number of simple assumptions to account for the non-uniform shear strain field induced across the whole of the BE samples during testing. A discussion of the more usual method of monitoring a gauge section of the deforming sample during tensile testing highlights potential problems that can occur as a result of the highly anisotropic nature of textile composites, problems that may lead to misinterpretation of data. The derivation and application of the energy method is relatively complicated but permits normalisation of results from samples with any length / width ratio. Smaller length / width specimen ratios have proved to be preferable since these samples tend to maintain their integrity better during testing than specimens with higher length / width ratios; an issue particularly important for more fragile fabrics. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]