No abstract

The present study reports on a systematic experimental test that evaluates the effect of drilling parameters on the open-hole tensile properties of flax fibre epoxy reinforced laminates. Additionally, three lay-up configurations of the flax fibre, namely, [0°/90°]6, [0°]6 and [±45°]6, were investigated and compared. The results demonstrated that the [0°]6 lay-up configuration was superior in terms of mechanical or tensile strength retention of the composites given an 8 mm hole. Conversely, damage due to delamination was not significant due to the changes in feed rate and cutting speed. This suggests that the drilling parameters were less sensitive towards the mechanical strength of the flax fibre composites with the drilled hole. The less severity of the delamination can be attributed to the high fracture toughness (high mode I critical strain energy release) of the flax fibre when compared with that of the synthetic fibre reinforced composite counterparts. The use of the step drill bit design also potentially contributes to the reduced severity of the delamination damage to the flax fibre composites.

Flax fibre reinforced composites have been very attractive in numerous applications such as wall and automotive panels. With chemical treatments and modifications, their mechanical competent can be at par with the existing synthetic fibre composites. The flax fibre composites are normally fabricated to near-net shape, but very often these composites require a secondary cutting process such as milling to attain final geometrical and dimensional tolerances. Due to the continuous contact of the milling tool on the composite material during cutting process, several undesirable damage such as delamination, matrix cracking, fibre pull-out; existed which may lead to deterioration of their mechanical strength. In this study, parametric effects of milling parameters, namely; feed rate, spindle speed, and number of end mill flutes on delamination damage and surface roughness, were investigated. Taguchi L18 orthogonal array was used to design the experimental plan. Signal to Noise (S/N) ratio and response tables were implemented to analyse the experimental data. It was found that spindle speed and feed rate had equal effects on delamination damage and surface roughness, whereas the number of end mill flute had a marginal influence on the aforementioned machining outputs.

Metal cutting fluids (MCFs) have played a principal role as coolants and lubricants in the machining industry. However, the wide use of mineral-based oil MCFs has contributed to an adverse effect on humans and the environment. Thus, to overcome the adverse effects of mineral-based oil MCFs, eco-friendly vegetable oil, which is non-edible oil, has been implemented to overcome the issues related to edible oil such as manufacturing costs and food shortages. This study investigated the performance of three different types of non-edible oil, namely castor, neem, and rice bran oils in drilling Inconel 718 using a coated titanium aluminum nitride (TiAlN) carbide drill towards tool life, tool wear, surface integrity, dimensional accuracy, and chip thickness. The MCFs were implemented under the minimum quantity lubrication (MQL) condition at a 50 mL/h flow rate using different cutting speeds (10, 20 m/min) and a constant feed (0.015 mm/rev). The results showed that castor oil minimizes the rapid growth of tool wear and prolongs the tool life by 50% at 10 m/min as compared to rice bran oil. At 20 m/min, castor oil obtained the lowest values of average surface roughness (1.455 µm) and chip thickness (0.220 mm). It was also found that different cutting speeds did not contribute to any significant trend towards hole diameter and roundness for all MCFs. The outstanding performance of castor oil proved that the oil is a potential alternative as an eco-friendly MCF for a cleaner machining environment. Castor oil was determined to be optimum in terms of tool life, tool wear, surface roughness, and chip thickness.

Nitinol, also known as nickel-titanium shape memory alloy, has a high potential in medical implantation due to its unique mechanical properties, shape memory effect, and low modulus of elasticity which close to bone’s modulus. However, high composition of nickel element in this alloy is harmful whenever the element is released into human body that can induce inflammation and allergic reactions. The objective of this study is to develop a deposition layer of titanium oxide on nitinol surface through the study of electrical discharge coatings (EDC) parameters effects. In particular, deionized water and pure titanium rod were as the dielectric fluids and electrodes, respectively, during the EDC process. Variation settings of polarity, gap voltage and erosion depth were employed in this study. Experimental results examined the coating thickness and surface roughness through full factorial design with ANOVA analysis. It was determined that the polarity gave the highest significant effect on the deposition thickness. Meanwhile, the interaction between polarity and gap voltage was exhibited significant effect to the surface roughness. In additional, reverse polarity and low gap voltage were preferred in EDC process to provide good surface roughness and higher uniformity of the material deposition.