Shahnor Basri

High Velocity Impact Damage Analysis for Glass Epoxy-Laminated Plates

The ultimate objective of the current work is to examine the effect of thickness on fiberglass reinforced epoxy matrix subjected to high velocity impact loading. The composite material chosen for this research was from type C-glass/epoxy 200 g/m2 and type C-glass/epoxy 600 g/m2. This material is used as a composite reinforcement in high performance applications since it provides certain advantages of specific high strength and stiffness as compared to metallic materials. This study investigates the mechanical properties, damage characterisation and impact resistance of both composite structures, subjected to the changes of impact velocity and thickness. For mechanical properties testing, the Universal Testing Machine (UTM) was used while for the high velocity impact, a compressed gas gun equipped with a velocity measurement system was used. From the results, it is found that the mechanical properties, damage characterisation and impact resistance of type C-glass/Epoxy 600 g/m2 posses better toughness, modulus and penetration compared to type C-glass/Epoxy 200 g/m2. A general trend was observed on the overall ballistic test results which indicated that as the plate specimen thickness continues to increase, the damage at the lower skin decreases and could not be seen. Moreover, it is also found that, as the plate thickness increases, the maximum impact load and impact energy increases relatively. Impact damage was found to be in the form of perforation, fibre breakage and matrix cracking. Results from this research can be used as a reference in designing structural and body armour applications in developing a better understanding of test methods used to characterise impact behaviour.

Velocity Measurements Using High-Speed Imaging System for Impact Test

This paper presents the velocity measurements for an impact test on a laminated fibre-glass composite plate. The free flight kinematic properties of a blunt-nosed cylindrical projectile on the upstream and downstream of a test coupon were measured using a high-speed camera imaging system. A visual geometric detection technique is discussed and it is shown that the uncertainties of velocity measurements are associated with an imposed constraint on the camera viewing area and shutter speed.

The Effect of Layers and Bullet Type on Impact Properties of Glass Fibre Reinforced Polymer (GFRP) Using a Single Stage Gas Gun (SSGG)

The purpose of this work is to study the best number of layer with the higher impact energy using Glass Fibre Reinforced Polymer (GFRP). The number of layers used in this study was 25, 33, 41, and 49. The impact test was performed using Single Stage Gas Gun (SSGG) for each layers given above with different bullets such as blunt, hemispherical and conical bullets. The gas gun pressure was set to 5, 10, 15 and 20 bar. All of the signals captured from the impact test were recorded using a ballistic data acquisition system. The correlation between the impact energy in terms of number of layer and type of bullet from this test are presented and discussed. It can be summarise that as the number of layer increases, impact energy also increases. In addition, from the results, it was observed that by using different types of bullets (blunt, hemispherical, conical), there is only a slight difference in values of energy absorbed by the specimen.

Elastohydrodynamic lubrication study of hard rolling contact using boundary element method

Presents a study on the application of boundary element method (BEM) to the solution of elastohydrodynamic lubricated hard rolling contacts in comparison with a solution using finite difference method (FDM). The developed program for the solution of Reynolds equation and the elasticity equation give results of pressure distribution and the lubricant film thickness for steady state, isothermal Newtonian lubricant behavior. Compares the BEM results and the computer effort with the solution using FDM. Uses an iterative Newton‐Raphson method to solve the non‐linearity of the problem. Discusses the effects of Hertzian pressure and rolling speeds on film thickness and pressure distribution. The numerical scheme of BEM has proved to have the advantage of being very effective and optimum in terms of accuracy, less computational effort and good constancy compared to other applied numerical techniques.

CAE Applications in a Thermoforming Mould Design

Preparation of honeycomb layer is a critical step for successful fabrications of thermoformed based sandwiched structures. This paper deals with an initial investigation on the rapid manufacturing process of corrugated sheet with 120° dihedral angles. Time history of local displacements and thickness, assuming viscous dominated material model for a 1mm thick thermoformable material, was computed by using ANSYS® Polyflow solver. The quality of formed surfaces was evaluated for selection of mould geometry and assessment of two common variants of thermoforming process. Inadequate mesh refinement of a membrane elements produces satisfactorily detailing and incomplete forming. A perfectly uniform material distribution was predicted using drape forming process. However, the geometrical properties of vacuum formed part are poorly distributed and difficult to control with increasing inflation volumes. Details of the discrepancies and the contributions of the CAE tool to complement traditional trial and error methodology in the process and design development are discussed.

High Velocity Impact Test on Glass Fibre Reinforced Polymer (GFRP) Using a Single Stage Gas Gun (SSGG) - An Experimental Based Approach

The aim of this work is to study the effect of thickness and type of bullet in impact test on structures made from a composite material. The composite material used in this study was Glass Fibre Reinforced Polymer (GFRP). This material was fabricated to produce laminated plate specimens with dimension of 100 mm × 100 mm and 6, 8, 10, and 12 mm thickness. The impact test was performed using a Single Stage Gas Gun (SSGG) with blunt, hemispherical, and conical types of bullets. The gas gun pressure was set to 5, 10, 15 and 20 bar. In the tests, gas gun pressure, bullet type and specimen thickness were varied to ascertain the influence of these parameters on the materials response. The relation between impact force with gas pressure, type of bullets and specimens thickness are presented and discussed. The best thickness for GFRP was identified according to the impact results. From the impact tests conducted, it was found that at the same amount of pressure, the higher the thickness, the bigger the impact force because as the specimen thickness increases, the amount of impact force absorbed by the specimen is higher.

Effect of Sintering Temperature on Functionally Graded Nickel/Alumina Plate

Functionally graded material that consists of gradually changed dual-phase compositions along the thickness direction of its structure has been introduced as an answer to sharp interfaces problems occur while the processing. In order to observe the morphological and shrinkage due to the sintering process, the Ni/Al2O3 FG samples were manufactured via powder metallurgy routes under argon atmosphere. This study reveals that the sintering temperature does affects the sintering behaviors including the microstructures and radial dimensions of the FG plates. The numerical simulation is found to be useful to predict the stress concentration area within the structures and consequently improve the design of the FG plates.

Assessment on Effects of Under-Relaxation Factors on 2D Incompressible Laminar Flow over a Backward-Facing Step (BFS)

In this paper, the effects of changing under-relaxation factors for different variables on the numerical solution of 2D incompressible laminar flow over a backward-facing step (BFS) are studied using PHOENICS commercial Computational Fluid Dynamics (CFD) software. This is conducted by changing under-relaxation factors for velocities and pressure during the 2D simulation. Ten different batches of under-relaxation factor for pressure ranging from 0.1 to 1.0 were used while the values of under-relaxation factor for velocities were manipulated between 0.1 and 1.0. For each batch of the computation, the error percentage of pressure and velocities were obtained. Based on this work, it is found that the recommended values of under-relaxation factor for pressure to achieve lower error percentage are between 0.6 and 0.8. Based on findings of the study, the appropriate values of under-relaxation factor for pressure and velocities can be selected to achieve the levels of error percentage permitted for computational studies.

OFEM: An Optimum Finite Element Algorithm for Heat Transfer Problem in Two-dimensional Insulated-tip Rectangular Fin

Among various available numerical solution techniques, finite element method (FEM) is one of the important methods of those. Usually elements are sub-divided uniformly in FEM which is known as conventional FEM (CFEM) to obtain temperature distribution behavior in a fin or plate for various aerospace and mechanical engineering applications. Hence, extra computational complexity is needed to obtain a fair solution with required accuracy. In this paper, an algorithm is proposed to generate non-uniform sub-elements and then implemented on FEM to obtain optimum FEM (OFEM) solution to reduce the computational complexity. This OFEM is applied for the solution of two-dimensional heat transfer problem in an insulated-tip thin rectangular fin. The obtained results are compared with CFEM. It is found that the OFEM exhibit around 65% more accurate results than CFEM showing its potentiality.