This paper is a review on the tensile properties of natural fibre reinforced polymer composites. Natural fibres have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for fibre reinforced polymer (FRP) composites. Due to their low cost, fairly good mechanical properties, high specific strength, non-abrasive, eco-friendly and bio-degradability characteristics, they are exploited as a replacement for the conventional fibre, such as glass, aramid and carbon. The tensile properties of natural fibre reinforce polymers (both thermoplastics and thermosets) are mainly influenced by the interfacial adhesion between the matrix and the fibres. Several chemical modifications are employed to improve the interfacial matrix-fibre bonding resulting in the enhacement of tensile properties of the composites. In general, the tensile strengths of the natural fibre reinforced polymer composites increase with fibre content, up to a maximum or optimum value, the value will then drop. However, the Young's modulus of the natural fibre reinforced polymer composites increase with increasing fibre loading.Khoathane et al. [1] found that the tensile strength and Young's modulus of composites reinforced with bleached hemp fibers increased incredibly with increasing fiber loading. Mathematical modelling was also mentioned. It was discovered that the rule of mixture (ROM) predicted and experimental tensile strength of different natural fibres reinforced HDPE composites were very close to each other. Halpin-Tsai equation was found to be the most effective equation in predicting the Young's modulus of composites containing different types of natural fibers.

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A commercial phenol formaldehyde based resole thermosetting resin supplied by Borden Chemical Australia Pty. was reinforced with ceramic-based fillers (SLG) to increase its fracture toughness. This is the second study of the same series. By testing fracture toughness and viscosity at a range of filler addition levels, the optimal addition of SLG was determined in terms of workability, cost and performance. The composites obtained were post-cured in conventional oven as in the previous study. The original contributions of this paper include lowering the cost of the composite (35% w/t of SLG) by 50 % but at the same time its the fracture toughness was reduced only by 20 % (compared to the neat resin), and increasing the fire resistance of the resins tremendously. It was also found that the values of fracture toughness of the samples in this study were higher than those obtained in the previous study when the percentage by weight of SLG varies from 0 to 35%. The shapes of the plots of fracture toughness against percentage by weight of SLG were also different. The possible reasons for the differences were explained.

Abstract. The fracture toughness of SLG filled phenolic composites have been determined by short bar tests. It is expensive to prepare the samples for the tests. Therefore, it is necessary to develop a mathematical model that will predict the fracture toughness of particulate filled phenolic composites. Mathematical models for tensile strength, Young's modulus are available but not for impact strength and fracture toughness. There is no sign that it can be built up from simple mathematical model; polynomial interpolation using Lagrange's method was therefore employed to generate the fracture toughness model using the data obtained from experiments. From experiments, it was found that the trend of the fracture toughness of the samples cured conventionally was similar to that cured in microwaves; it is therefore possible to predict the fracture toughness of the samples cured in microwaves from shifting the mathematical model generated for fracture toughness of samples post-cured in conventional oven. The shifted model represented the fracture toughness of the samples cured in microwaves vey well.