Papers by Author: H. Ku

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.

Abstract: Low cost composite materials are widely used in civil and structural engineering applications. This project uses EPON to plasticize a commonly used resin, epoxy resin to lower the cost of the composite and to find out the mechanical and thermal properties of the plasticized epoxy resin to see if it is suitable for the said applications. Three point bending tests were carried out to evaluate the flexural properties of the plasticized resins. Differential scanning calorimetry and dynamic mechanical thermal analysis are used to evaluate the thermal properties of the plasticized epoxy resin. The study with epoxy and EPON showed that the mechanical properties of the epoxy composite were lowered but its ability to dissipate energy increased because of its improved thermal properties. As EPON is much cheaper that epoxy resin, the composite produced is therefore cheaper and provided the service requirements were not so demanding, it can be used in the said applications.

Abstract: Composite components made from vinyl ester resins by Centre of Excellence in Engineered Fiber Composites (CEEFC), University of Southern Queensland (USQ) suffer considerable shrinkage during hardening. Currently, CEEFC solves the shrinkage problem by breaking a large composite component into smaller composite parts because smaller parts tend to have less shrinkage. These smaller parts are then joined together to form the overall structure. The shrinkage of vinyl ester particulate composites has been reduced by curing the resins under microwave conditions. The reduction in the shrinkage of the resins by microwaves will enable the manufacture of large vinyl ester composite items possible. This project investigates the difference in impact strength, tensile strength and Young’s modulus of 33 percent by weight of fly-ash particulate reinforced vinyl ester composite, VE/FLY-ASH (33%) cured under microwave and ambient conditions. Drop weight impact tests were used to find out the impact strength of the composite, while tensile tests were used to find out the tensile strength and Young’s modulus of the composite. The power levels of microwaves used were 180 and 360 W; the duration of exposure of the composite samples to microwave irradiation varied from 20 to 50 seconds. The difference in impact strength and Young’s modulus between microwave cured vinyl ester particulate composites and those cured under ambient conditions had been found to be minimal. However, the tensile strength of the composite samples cured under microwave conditions can be higher than those cured under ambient conditions.