Papers by Author: Harry Ku

Abstract: Epoxy resin was filled with glass powder with a view to increasing strength of the composite for structural applications by a research Centre on composites, University of Southern Queensland (USQ). In order to reduce costs, the Centre wishes to fill as much glass powder as possible subject to maintaining sufficient strength of the composites in structural applications. This project varies the percentage by weight of the glass powder in the composites which are then subjected to flexural tests. The results show that composite with 25 % by weight of the glass powder produces the highest flexural strength and Young’s modulus combined with a reasonable fluidity for casting; the highest flexural strain was achieved when the percentage by weight of glass powder is 10 %.

Abstract: The flexural properties of SLG filled phenolic composites have been determined in previous study. It is time consuming to prepare the samples for the tests. In addition, it is even more time consuming to carry out the tests and analyze the results. It is therefore necessary to develop a mathematical model that will predict the flexural properties of particulate filled phenolic composites. Mathematical models for tensile strength, Young’s modulus are available but not for impact strength, flexural 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 flexural properties model using the data obtained from experiments. From experiments, it was found that the trend of the flexural properties of the samples post-cured conventionally was similar to that post-cured in microwaves; it is therefore possible to predict the flexural properties of the samples post-cured in microwaves from the mathematical model generated for flexural properties of samples post-cured in a conventional oven. The workload is therefore halved as the process of generating the mathematical was much faster and simpler.

Abstract: Among different sterilization methods, heat-treatment of bone is recognized as one of the simple and practical methods to lower the human immunodeficiency virus (HIV) infection and overcome the risks of rejection and disease transfer from allograft and xenograft during bone transplantation. In order to best characterize the micro-structural mechanical property of bone after heat treatment, the nanoindentation technique was applied in this study to measure the localized elastic modulus and hardness for interstitial lamellae and osteons lamellae of bovine cortical bones at temperature 23°C (room temperature-pristine specimen), 37°C, 90°C, 120°C and 160°C, respectively. The elastic modulus (E) and hardness (H) of interstitial lamellae obtained higher values as compared with osteons lamellae which show that interstitial lamellae are more stiff and mineralized than osteons. Moreover, as a specimen pre-heat treated at 90°C, the E and H values of interstitial lamellae and osteons were closed to a pristine specimen. For a specimen pre-heat treated at 120°C, both interstitial lamellae and osteons obtained an increase in E and H values. As a specimen pre-heat treated at 160°C, the interstitial lamellae and osteons obtained a slight decrease in E and H values. These findings are correlated to results reported by other researchers [1, 2] that calcified collagen molecules starts to degenerate at about 120°C and complete at 160°C. Interestingly, when a specimen was pre-heat treated at 37°C, both interstitial lamellae and osteons obtained significant decreases in E values of 57% and 40%, respectively as compared to the pristine specimen; while in H values, there was a decrease of 27.4% and 15%, respectively. Thus, this paper will investigate the mechanical properties of bovine cortical bones under various temperature ranges by nanoindentation technique.

Abstract: The mechanical and thermal properties of hollow glass powder reinforced epoxy resin composites have been measured and evaluated in earlier studies. This basic but critical and important data have caused interests in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the dielectric properties of the composites with a view to benefit the relevant industry. The relationship between the dielectric and thermal properties will also be studied and correlated. The original contributions of this paper are that samples post-cured in conventional ovens have higher electrical as well as mechanical loss tangent values than their counterparts cured in microwaves only. The storage modulus of all samples post-cured conventionally is higher than its counterpart. This is in line with the fact that they are softer material with lower glass transition temperatures. For all percentages by weight of glass powder, the glass transition temperature for the microwave cured sample was higher and the composite was stiffer; the opposite was true for the conventionally cured samples.

Abstract: Epoxy resin was filled with glass powder to optimize the strength and of the composite for structural applications by a research centre in the University of Southern Queensland (USQ). In order to reduce costs, the centre wishes to fill as much glass microspheres as possible subject to maintaining sufficient strength and fracture toughness of the composites in structural applications. This project varies the percentage by weight of the glass powder in the composites. After casting the composites to the moulds, they were cured at ambient conditions for 24 hours. They were then post-cured in a conventional oven and subjected to tensile tests. It was found that the best percentage of glass powder by weight that can be added to the epoxy resin to give an optimum yield and tensile strengths as well as Young modulus and cost was five percent. It was also found that the fractured surfaces examined under scanning electron microscope were correlated with the fracture toughness. The contribution of the study was that if tensile properties were the most important factors to be considered in the applications of the composites, glass powder is not a suitable filler. It is also hoped that the discussion and results in this work would not only contribute towards the development of glass powder reinforced epoxy composites with better material properties, but also useful for the investigations of tensile properties in other composites.

Abstract: Vinyl ester resin was filled with of glass powder with a view to increasing the flexural strength of the composites for civil and structural applications by a research Centre on composites, University of Southern Queensland (USQ). In order to reduce costs, the Centre wishes to fill as much glass powder as possible to the resin subject to maintaining sufficient strength of the composites in civil and structural applications. This project varies the percentage by weight of the glass powder in the composites, which are then subjected to flexural tests. The flexural strength and strain of the glass powder filled vinyl ester composites decreased with increasing filler content but the flexural modulus was highest at 20 w/t % of glass powder. Scanning Electron Microscope (SEM) was used to analyze the fractured samples and it was found that the fractured surfaces examined were correlated with the flexural properties.

Abstract: A commercial phenol formaldehyde based resole thermosetting resin supplied by Borden Chemical Australia Pty. was filled with ceramic-based fillers (Envirospheres or SLG) to increase its flexural strength. By performing flexural tests at a range of filler addition levels, the optimal addition level of SLG was able to be determined in terms of workability, cost and performance. The composites obtained were post-cured in conventional oven and in microwaves respectively. It was found that the maximum flexural strength of the microwave cured composites were only 5% lower than those cured in conventional oven when the percentage by weight of SLG was 24%. However, the time required for post-curing was also reduced from 10 hours (in conventional oven) to 40 minutes (in microwaves).