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Experimental Investigation and Parameter Optimization of Low Power CO2 Laser Cutting of a Carbon/Kevlar Fibre-reinforced Hybrid Composite
K. Moghadasi and K. F. Tamrin

To overcome the limitations of a singular fibre-reinforcement composite, a number of hybrid composites have been developed consisting of two or more different types of fibres in a common matrix. With the correct combination of dissimilar fibres, a variation of hybrid composite can be obtained possessing improved physical and thermal properties which is previously not possible with a single kind of reinforcement. The use of powerful lasers (several kW) in the cutting of composites is fairly widespread so as to overcome challenges regarding the anisotropic properties of these materials, but at the expense of a large heat affected zone (HAZ), kerf width, and fibre pull-out. The primary aim of this paper is to investigate low-power CO2 laser cutting of a carbon/Kevlar fibre-reinforced hybrid composite. Response surface methodology (RSM) along with Box-Behnken design (BBD) was employed to understand the interactions between the process parameters, such as laser power, cutting speed and standoff distance (SOD), and their effects on the cut quality characteristics including size of the HAZ and kerf characteristics. Following this, process parameter optimization was successfully carried out using ANOVA to minimize the HAZ and kerf width. Qualitative measurement using a scanning electron microscope (SEM) was performed to evaluate the effects of process parameters and fibre orientation on fibre pull-out, HAZ and material decomposition. Difference between the thermal properties of carbon fibres, Kevlar fibres and polymer matrix (epoxy) was found to influence HAZ and kerf width. High thermal conductivity of carbon fibres particularly led to large extent of matrix recession and burning of Kevlar fibres around the cut path.

Keywords: CO2 laser, carbon fibre, Kevlar, hybrid, synthetic, composite, laser cutting, processing parameters, response surface methodology (RSM), Box-Behnken design (BBD), optimization

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