Papers by Author: Faizal Mustapha

Abstract: 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.

Abstract: The use of laminated composites in aircraft structures is not totally new. However, the idea of using woven fiber glass as reinforcement in primary structural members is not widely addressed as compared to unidirectional fibers. In an effort to characterize the dynamic behavior of a woven laminated composite subject to dynamic loads, modal testing is performed experimentally on a cantilevered laminated woven glass fiber/epoxy composite flat plate which resembles an aircraft wing with aspect ratio of 5. To that end, the effect of stacking sequence and fiber orientation of the laminated composite plate on the modal properties is assessed. 6-layer laminated composite configurations with various stacking sequence and fiber orientation are fabricated so as to generate variable stiffness plates. The modal test employs the single roving hammer technique to obtain the frequency response of the plate and the results of the first five modes against the fiber orientation and stacking sequence are analyzed.

Abstract: In this paper, manufacturing process of aircraft radome via closed mold with vacuum infusion process is presented. Closed mold is needed to get smooth inner and outer surface. The radome mold was formed from the original part of the aircraft Duke 60 Beachcraft. The closed mold is made from fiber glass/polyester composite via hand lay-up technique. Tooling grade vinyl ester gel coat is applied on the mold to produce fine smooth surface and protection. Later, the radome part is fabricated with vacuum infusion and the consistency of thickness is achieved.

Abstract: 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.

Abstract: The thin-web structure component is widely used in aviation and aerospace industries with the reason of light weight and high performance. However, the thin-web components are tending to deflect because of their poor rigidity and the effect of cutting force during cutting process. It is required to perform of high-speed machining that can remove the large number of material in a shorter time in order to allow machining of such structure. The performance of high-speed machining operation is restricted by the static and dynamic stiffness of the tool and part that can cause some problems such as regenerative chatter and ‘push-off’. The tool path plays an important function to avoid the problem occurs as it assists to reduce the workpiece vibration during machining. The optimization of tool path is done by determining the element removal sequences and the materials removal are implemented using milling cutter. The maximum deflection for each element removed is recorded in order to define the optimum solution of element removal sequences. The analysis shows that there are significant effects of workpiece stiffness with relation to the cutting parameters setting.

Abstract: At present, aircraft structural integrity is a concerned due to heavy usage of composite materials and cost saving on the operational. Structural health monitoring system is one of condition based monitoring introduced to supplement the current aircraft maintenance non destructive inspection. One approach is to embed or attach sensors such as lead zirconate titanate (PZT) to detect the anomalies either passively or actively. Due to the aircraft operational environment the defects and damage are likely to occur. Repair has to be carried out as per recommended and the requirement to replace back the sensors are important in order to monitor back the structure at post repair situation. The Lamb waves generated by using the PZT sensor can be used to monitor the surface structural integrity for damage or pristine condition. The effect of the lamb wave signals when surface condition of the aircraft component changes is concerned. One hundred data sets were recorded for the undamaged, damage and repair condition. An outlier analysis was used to analyze the situation by overlaying the isolated signal spectrum and the range of the voltage peak to peak (Vpp) mean values. Different signals were observed for different type of structural condition tested and more tests were required to make a conclusive solution.

Abstract: In this paper, a numerical simulation on a new fabrication miniature composite fuselage structure- a woven composite laminated with an adhesively bonded butt joint under the axial compression loading is presented. A FEA via Abaqus/Explicit was utilized to capture the complete compressive responses to predict the crushing behaviour and its mechanical strength from the initial compression loading till its final failure mode. A woven C-glass fiber/epoxy 200 g/m2 composite laminated [908] with the orthotropic elastic material properties is modeled as a continuum composite layup in the proposed numerical model. The adhesively bonded joint progression was modeled using the cohesive element technique. The proposed model was used to observe the crushing load and collapse modes under the axial compression impact. The finite element results showed a good agreement with the experimental results under the actual quasi-static tests. The validation code was extended to further undergo parametric studies in order to visualise the effect of angle orientations and special laminate cases as to attain the optimum design criteria for the proposed composite structure.

Abstract: Known as “coir”, the fibrous husk of the coconut fruit has potential for integration as a constituent in impact-resisting aerospace materials. As a preliminary study, kinetic energy absorption of this natural fiber is studied prior to further testing, for instance; a non-ballistic surface impacted at high velocity by a small mass is the equivalent mock-up to runway debris. The purpose of this study is to find the relationship between the thickness of the fiber with the kinetic energy absorption. Fabricated fiber panels measuring 10×10×t cm with various thickness are subjected to mild steel projectiles launched by a light gas gun at a constant pressure. The velocity of the projectiles is set to be consistent with the velocity range of typical transport-category aircraft. The impact response of the panels aids in predicting the required amendments where plies of coir sheets are increased to which perforation is impossible. The relationship established from the experimental results is then used to predict the amount of layers required for total translational kinetic energy absorption.

Abstract: An aircraft radome usually refer to radar transparent, dome-shape structures which protects radar antennas on aircraft from aerodynamic loading, weather as well as impacts from bird strikes. Materials that are used for small aircraft radome usually have low dielectric constant and high toughness. Current composite material using high strength fibers such as glass fiber, carbon and aramid are commonly used in aerospace structures. However, the need for biodegradable materials has prompted the usage of natural fibers. Natural fibers have comparable mechanical properties such as low weight, low cost, renewable and biodegradable. In this preliminary work, comprehensive reviews of biocomposites materials are discussed in term of their properties for the purpose of evaluation for aircraft radome application. The present review will cover five local natural fibers namely bamboo, banana, kenaf, oil palm and pineapple leaf fiber.

Abstract: Thermal buckling and thermal post-buckling behaviours of laminated composite plates are improved by embedding shape memory alloy wires within laminates of composite plates. The procedure is to use the recovery stress that is induced when the reverse transformation of the shape memory alloy from martensite to austenite phases is constrained. For aerospace applications where the source of the shape memory alloy heating is the high temperature environment itself, a study is conducted to see the effect of shape memory alloy in improving the thermal buckling and post-buckling of composite plates. Due to the temperature dependent nature of the composite matrix and the shape memory alloy, the finite element formulation developed here is in the incremental form. Solving this non-linear model using the developed in-house source code, critical loads are determined and the post-buckling paths of the shape memory alloy composite plates are traced. This study shows that by embedding the shape memory alloy within composite plates, the thermal buckling and post-buckling behaviours of composite plates can be improved substantially.