-Quasi-unidirectional glass fibre non crimp fabric composites are routinely used in wind energy applications. An important factor to consider in this type of application is the fatigue behaviour of the materials. The present paper gives an overview of the current approach to material fatigue testing and design in the wind energy industry, as well as a review of available material data for the fatigue of unidirectional glass fibre composites. Both "pure" unidirectional and quasi-unidirectional (NCF-based) materials are considered.

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This paper aims to identify the main parameters that influence the mechanical properties of long-glass-fibre-reinforced poly(ethylene terephtalate) parts in order to optimise the potential of these composites. A Taguchi design of experiments (DOE) was used for this purpose. The shape of the injection-moulded specimen was representative of the complexity of industrial parts (presence of sharp frontal and tangential steps). The mechanical properties (bending and Charpy impact tests) were measured at different locations in the part in order to highlight anisotropy. Variance analysis has shown that holding pressure, injection speed, and mould temperature are the most effective processing parameters. It has also shown that the optimised parameter sets that lead to the highest flexural strength on the one hand and the highest impact strength on the other hand are different, the polymer melt and mould temperatures being opposite. Finally, microstructure analysis has shown a fibre content gradient along the flow axis, which is greatly amplified by the presence of geometrical accidents (frontal and tangential steps) including the reorientation of fibres in the flow direction at the end of the parts.

This paper aims at highlighting the influence of different additives (carbon black and nucleating agents) on both the notched and unnotched Charpy impact properties of long glass fibre reinforced poly(ethylene terephtalate) injection mouldings. The relationship with the polymer matrix and composite microstructure modifications (variations of crystalline morphology and local fibre content) was investigated. Adding carbon black alone decreases the impact performances. This highly conductive additive actually increases the cooling rate, and therefore the fibre ‘frettage’ effect (higher internal stresses). It also acts as filler, which increases the material brittleness. The nucleating agents allow reducing the mould temperature, but their effect on the impact strength may be favourable or not depending on the processing temperatures. The addition of such additives induces perturbations of the polymer melt rheology in the mould cavity and of the cooling kinetics of the part, which both act on the fibre distribution during mould filling and on the degree of crystallinity of the composite parts

The paper aims to assess the fiber/matrix interface and adhesion quality in commingled GF/PP composites by means of complementary experimental methods. For this purpose, different interfacial qualities were obtained by a modification of the sizing of the fiber reinforcement (polypropylene specific sizing, non-specific sizing and no sizing), and of the matrix (with or without coupling agent). Transverse tensile stress-strain curves have been recorded while monitoring acoustic emissions. An analysis of acoustic emission data associated with fracture surface examinations has helped explain the differences observed in mechanical properties and damage mechanisms, emphasizing the importance of the interphase in the performance of these new composites. Thus it has been shown that the association of three experimental investigation methods (transverse tension, acoustic emission, and fracture surface analysis) makes it possible to characterize both the glass/silane bond (so-called fiber/matrix interface) and the global fiber/matrix adhesion (addition of several different zones and interfaces). Polym. Compos. 25:577-588, 2004.