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Glass fibres are by far the most extensively used fibre reinforcement in thermosetting composites because of their excellent cost-performance ratio. However, glass fibres have some disadvantages such as non- renewability and problems with ultimate disposal at the end of a materials lifetime since they cannot be completely thermally incinerated. The possibility of replacing E-glass fibres with hemp fibres as reinforcement in sheet moulding compounds (SMC) is examined in this thesis. The composites are manufactured with existing SMC processing techniques and similar resin formulation as used in the commercial industry. An attempt is made to enhance/optimise the mechanical properties of hemp/polyester composites. For this the fibre-matrix interface is modified via chemical modifications with alkaline and silane treatments. Influence of hemp fibre volume fraction, calcium carbonate (CaCO3)filler content and fibre-matrix interface modification on the mechanical properties of hemp fibre-mat-reinforced sheet moulding compounds (H-SMC) is studied. The results of H-SMC composites are compared to E-glass fibre-reinforced sheet moulding compounds (G-SMC). In order to get a better insight in the importance of these different parameters for the optimisation of composite performance, the experimental results are compared with theoretical predictions made using modified micromechanical models such as Cox-Krenchel and Kelly- Tyson for random short-fibre-reinforced composites. These models are supplemented with parameters of composite porosity to improve the prediction of natural fibre composite tensile properties. The influence of impact damage on the residual exural strength of the H-SMC composites is investigated to improve the understanding of impact response of natural fibre reinforced composites. The result of penetration and absorbed energies during non-penetrating impact of H-SMC composites are investigated and compared to values for G-SMC. A simple mechanistic model has been developed for H-SMC composites and is used to get an insight into the impact behaviour of these composite as well as to provide a guideline to compare the experimental results with theoretically calculated data. The fracture toughness properties in terms of the critical-stress-intensity factor KIc, and critical strain energy release rate, GIc, of H-SMC and G-SMC composites are studied using the compact tension (CT) method. It was shown that fracture toughness of H-SMC composites is significantly lower than that of glass fibre reinforced composites (G- SMC). However, results show that with an optimum combination of fibre volume fraction, (CaCO3) filler and surface treatment of the hemp fibres can result in H-SMC composites that have fracture toughness properties that can be exploited for low to medium range engineering applications. It is recommended that to further improve the fracture toughness properties of these natural fibre reinforced composites more research needs to be devoted to the optimization of the fibre-matrix interface properties and ways of reducing porosity content in these composites. Finally, environmental impact of H-SMC composite with conventional G-SMC composite for automotive and non-automotive applications was compared. The composites were assumed to be made in a traditional SMC manufacturing method. Two different types of performance requirements; i.e. stiffness and strength were investigated for both the non-automotive and automotive parts. Two different disposal scenarios: landfill and incineration of the SMC product at the end of life was considered. The LCA results demonstrate that the environmental impact of H-SMC composites is lower than the reference G-SMC composites. G-SMC composites have a significantly higher environmental impact on climate change, acidification and fossil fuels than H-SMC composites. Where as H-SMC composites have a much higher impact on land use and ecotoxicity than G-SMC composites.

Experiments have been performed in a rectangular duct for aspect ratios, B/H, varying between 0.1 and 10, and in a compound duct comprising of one rectangular main channel and two symmetrically disposed flood plains, for 0.057 < (H-h)/H < 0.491, B/b = 5.2 and b/h = 0.934, in order to obtain boundary shear stress distributions and primary flow isovels. follows page 41. The symbols are defined in Fig.(3.1) which In the smooth rectangular duct, perturbations were noticed in the bed shear stress distributions and were related to the secondary flow cells, which in turn depend upon the aspect ratio. An empirical equation is presented giving the number of these secondary flow cells for a given aspect ratio, for B/H < 3.0. Equations are also presented giving the percentage of the total shear force carried by the walls, the mean boundary shear stresses, the maximum boundary shear stress and the bed centreline shear stress, in terms of the aspect ratio. Experiments in the rectangular duct were also performed with rough and differentially roughened surfaces. The results are compared with the open channel results at comparable aspect ratios and small differences are shown to exist. In the compound duct, the boundary shear force results are used to calculate the apparent shear force on vertical, horizontal and inclined interfaces. Their variation with depth is studied to explore the lateral and vertical transfer of momentum. The effect of introducing roughness on the flood plains is also examined. The three-dimensional nature of the flow in the compound duct is demonstrated by the lateral variation of the depth mean velocities, the primary flow isovels and the variation of subsection mean velocities on the flood plains and in the main channel. Various sub division methods for discharge predictionlre examined and the methods with horizontal and inclined interfaces are shown to give the best discharge results. The results are also compared with the open channel results and are found to generally accord with them.