The use of kenaf fibres has grown unexpectedly in the world as they help to establish green materials in automobile, sports and food packaging industries. Over the past few decades, unidirectional fiber-reinforced composites have been extensively used in industry due to their high specific strength characteristics. During manufacturing process, several defects especially fiber misalignment might exist in the unidirectional composite structure. This kind of deviation from its optimal parallel packing in a unidirectional fibre reinforced composite would influence its overall load-bearing efficiency. Performance data of kenaf composite due to this imperfection, however, is very limited in the literature. In this regard, the effects of fibre misalignments on the unidirectional kenaf composite compressive reaction have been studied. For this reason, pultruded kenaf composite specimens with different fibre alignment from 00 to 20 at 2.1 and 8.4 mm/s strain rates were subjected to a range of compression measures. The findings revealed that, the failure strain seems to be almost constant at value of 0.05 and 0.063 while the failure stress decreases from 140Mpa until 120MP when the fibre alignment increases when loaded within a range of 2.1~8.4s-1. Additionally, under increased fiber misalignment and strain rate, fibre plastic microbuckling, fibre breakage, fibre splitting and fibre matrix debonding was progressively formed on the specimen.

NiTi arch wires are commonly used at the initial stage of orthodontic treatment, due to their superelastic and biocompatibility properties. Numerous bending models have been considered to anticipate the mechanical responses of the superelastic NiTi wire in the oral environment. It is known that the magnitude of bending force exerted by the NiTi wire is relatively influenced by the magnitude of friction generated at the wire-support interfaces. These data on the variability of friction magnitude for various bending models, however, are very limited in the literature. This study investigated the magnitude of frictional force generated in different bending models through the numerical method. The frictional force in a three-point and a three-bracket model was quantified from the force difference, measured when the wire was deflected in friction and frictionless conditions. Overall, the frictional force magnitude gradually increased as the wire further pressing the support surface at higher deflection. The highest frictional force was recorded when the bracket support was considered, with values of 2.01 N during loading and 1.61 N during unloading. These loading and unloading frictional forces were significantly reduced to 0.25 N as soon as the point support was considered. The high frictional force generated in the bracket model transformed the constant force-deflection trend of superelastic NiTi wire into a gradient force.