Azizul Mohamad

General Lifetime Damage Model for Glass Fibre Reinforced Epoxy (GRE) Composite Pipes under Multiaxial Loading

This paper presents the modelling of a general lifetime performance for glass fibre reinforced epoxy (GRE) composite pipes similar to the well-known Tsai-Hill interactive failure criterion. Tsai Hill criterion is based on the Von Misses distortional energy criterion which was modified to satisfy the orthotropic nature of GRE composite pipes. The effects of stress developed in each ply from ultimate elastic wall stress (UEWS) test were expressed in a single quadratic term of axial and hoop stress through laminate theory. The term then solved to produce limits with respect to axial and hoop stress, which represented in a graphical form of failure envelope. The modelled envelop shows a good agreement with experimental data from the multiaxial UEWS test of ±55° GRE composite pipes. This indicates that such model can be used to predict the long-term performance of GRE pipes under combine loadings.

A Review of Experiments on Cold Start of PEM Fuel Cells

This paper evaluate previous experimental studies on sub-freezing start up of proton exchange membrane (PEM) fuel cell system, and identify issues for further investigation. In a successful cold start, product water from electrochemical reaction in the cathode must be removed from the cell before it turns into ice and causing voltage drop and shutdown also leads to permanent damage to fuel cell components. Successful single PEM fuel cell start up was achieved from temperature as low as-30°C. Some researchers found that cold start of a 30 W stack from-20°C was possible only with aid of external energy. Successful self-start up a 2 kW stack from temperature-5°C was reported but the time taken was unacceptably long and attempts to start up the stack at lower temperatures were failed. Based on the current state of research, further research is necessary to fully understand the operation and mechanism of PEM fuel cell cold start.

Experimental Investigation of PCM Spheres in Thermal Energy Storage System

This paper presents the experimental result of a small scale packed bed of random spheres with encapsulated PCM being charged and discharged. A vapor compression refrigerator and heated room with fan heater were used to supply constant heat transfer fluid at a minimum temperature of -28°C for charging and 16°C for discharging. Even though the temperature differences were not fixed in the experiments, the performance of the thermal energy storage is depicted in the form of effectiveness values. Different results were obtained for charging and discharging the thermal storage unit. The differences are expected to come from natural convection and super cooling. The super cooling during the charging process was as high as 6°C.

Effect of Nano-Clay and their Dispersion Techniques on Compressive Properties of Unsaturated Polyester Resin

This paper aims to understand the relationship between processing parameters and compressive properties of nanoclay filled polyester resin (dispersion method and wt% of nanoclay particles). Unsaturated polyester resin with 0-5 wt% nanoclay content was prepared by hand mixing and through shears mixing of water bath shaker. Static uniaxial compression tests were conducted to investigate how the unsaturated polyester resins with nanoclay contents and processing will effect on the compressive stress-strain behaviour and compression properties. The experimental results show that the compressive strength and elastic modulus of nanomodified resin are significantly affected by type of mixing methods to prepare the specimens and the ratio of nanoparticles content during mixing. It was found out that the compressive strength and compressive modulus increase with the nanoclay content. The findings also indicate the dispersion of nanoclay by hand-mixed method yield higher compressive strength compared to that dispersed by water shaker bath.

Effects of Elevated Temperatures on the Compression Strength of Nanoclay Filled Unsaturated Polyester Resin

The paper describes the effects of the montmorillonite (MMT) fillers commonly known as nanoclay, on the compression properties of unsaturated polyester resins at different weight percentage of nanoclay. Modified resin specimens with 1, 3 and 5 wt. % of nanoclay contents were prepared and subjected to compressive tests according to ASTM D695. The static uniaxial compression testing were conducted at various temperatures ranging from room temperature (RT) to the temperature closer to its glass transition temperature Tg to study the effect of nanoclay fillers on the compressive stress-strain behaviour at high temperatures (room temperature, 35, 45, and 75°C). The mechanical properties of the nanomodified resin including the elastic modulus, maximum stress and failure strain were determined. The experimental results imply that adding these nanoclay fillers has enhanced the elastic modulus, compressive strength, and toughness without sacrificing the strain to failure and thermal stability of the unsaturated polyester. However it was found that generally, all specimens showed degradation in compressive strength with increases in temperatures.

Mathematical Modeling on Thermal Energy Storage Systems

Mathematical representations of the encapsulated phase change material (PCM) within thermal energy storage (TES) models are investigated. Applying the Effectiveness - Number of Transfer Unit (ɛ-NTU) method, the performances of these TES are presented in terms of the effectiveness considering the impact of different variable parameters. The mathematical formulations summarized can be used for future research work with the suggestion to maximize the heat transfer within the storage. Thus the optimisation on the configuration of the encapsulation can be done through a parametric analysis.

Experimental Studies of a Ranque-Hilsch Vortex Tube

Vortex tube is a device that separates a compressed flow of gas into two streams simultaneously, one giving kinetic energy to the other, resulting one hotter than the inlet temperature and one lower, without having any moving part. This research focuses on investigating the effects of various physical parameters on the performance of the vortex tube, namely cold nozzle diameter, length of the tube, and air mass flow rate at the hot end of the tube. In general, there are two major design features associated with the vortex tube, namely (a) maximum temperature differentials in vortex tube to produce small amount of air with very low and very high temperatures, and (b) maximum cooling/heating effect by producing large quantity of air with moderate temperatures. By considering the experimental results, an optimized set of parameters that contribute to the most efficient vortex tube design would be proposed depending on the desired design features.

Effects of temperatures on the compressive strength of Napier grass filler-filled unsaturated polyester resin

This paper describes the effect of weight contents of fillers on the compression properties of the Napier grass filler-filled polyester resin. Unsaturated polyester resins with 0, 1, 3, 5 wt% Napier fibre based fillers were prepared through manually mixing process in accordance with ASTM D695 for compressive test. The static unaxial compressive tests were conducted using a Shimadzu Universal Testing Machine with a thermostatic chamber at temperatures ranging from room temperature (RT) to the temperature close to its glass transition temperature Tg (RT, 35, 55, 75 °C). The result shows that the elastic modulus and compressive strength of the modified resin were significantly affected by Napier fibre based filler contents and temperatures. It was found that the specimens showed reductions in compressive strength with increases in temperatures.

Finite Element Modeling of Intermetallic Compound (IMC) Solder Joints Fracture: Part B

Solder joints are exposed to drop impact, vibration loading, bending, and twisting of PCBs. Study on this matter will lead to prediction of fracture load, prevalent fracture mode, exact joint interconnect size and life of joints under brittle and fatigue failure. This paper presents a finite element modeling of intermetallic compounds solder joints failure based on displacement extrapolation method. Based on conceptual FE model of intermetallic IMC solder joints, this paper present the full model of IMC model for intermetallic Mode I and Mode II fracture prediction.

Review of Analysis on Vertical and Horizontal Axis Wind Turbines

Wind turbine is a device used to convert kinetic energy into electrical energy. Generally, wind turbine could be classified as horizontal axis and vertical axis wind turbine, depending on its axis of rotation. Two major factors affecting wind turbine performance are wind speed and aerodynamic design. While wind speed is depending on the location and weather, aerodynamic design of the wind turbine could be improved and optimized to enhance the wind turbine efficiency. This paper summarized few such design with particular attention on output power analysis as well as analysis tools development, for both type of wind turbine.