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Author

Omar Bapokutty

Other affiliations: National University of Malaysia
Bio: Omar Bapokutty is an academic researcher from Universiti Teknikal Malaysia Melaka. The author has contributed to research in topics: Ultimate tensile strength & Glass fiber. The author has an hindex of 6, co-authored 14 publications receiving 76 citations. Previous affiliations of Omar Bapokutty include National University of Malaysia.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the effects of fiber stacking configurations on the tensile and quasi-static penetration of kenaf/glass hybrid fiber metal laminates (FMLs) were investigated.
Abstract: The hybridization of natural and synthetic fibers in composite materials has gained the attention in the research field due to environmental awareness. Therefore, this study focuses on the effects of fiber stacking configuration on the tensile and quasi-static penetration of kenaf/glass hybrid fiber metal laminates (FMLs). Kenaf/glass reinforced polypropylene FMLs with two different hybrid stacking configurations were prepared using hot compression process. Non-hybrid kenaf and glass fiber reinforced metal laminates were also prepared for comparison. The tensile test was conducted according to ASTM E8, while the quasi-static penetration test was carried out in accordance with ASTM D 6264 using 12.7 and 20 mm hemispherical indenters. The fractured surface of FMLs due to tensile loading was examined using scanning electron microscope, while optical micrograph was used to investigate the failure mechanism of quasi-statically penetrated laminates. From the results, FMLs with the glass plies at the outer layers of composite (H1) showed a positive hybrid effect as they displayed better tensile and penetration resistance, compared to the non-hybrid kenaf and glass reinforced FMLs. Furthermore, it could be seen that the overall performance of FMLs decreased as the kenaf content in the laminates further increases for hybrid FML.

39 citations

Journal ArticleDOI
TL;DR: In this article, the mechanical properties of composite materials with different types of natural fibre and various fibre compositions were investigated, and the results demonstrated that the tensile strength and flexural strength of pineapple leaf fibre (PALF)-based composites were 7.83% and 54.23% higher than kenaf-based composite materials at a fibre content of 30.
Abstract: The arising trend of using natural fibres in the composite materials has stimulated the continuous exploration of their mechanical properties. The positive environmental behaviours of natural fibres are the driving factor that allows them to gain their wide acceptance in industries. However, the mechanical behaviour of natural fibre-based composites is still not fully explored. In this research study, the mechanical properties of composite materials with different types of natural fibre and various fibre compositions were investigated. The polypropylene-based composite materials were fabricated through hot press compression moulding method using a hydraulic hot press machine. The composites were then subjected to mechanical tests to study the tensile, flexural and impact properties of such materials. The results demonstrated that the tensile strength and flexural strength of pineapple leaf fibre (PALF)-based composites were 7.83% and 54.23% higher than kenaf-based composites at a fibre content of 30 wt%. Moreover, the impact strength of PALF-reinforced composites was 3.08% and 5.56% higher than kenaf fibre-reinforced composites in the flatwise and edgewise impact orientations. Overall, composites with 30 wt% evidenced the top most mechanical properties irrespective of types of plant fibre.

32 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of fiber orientation on the fatigue strength of fibreglass reinforced composites (FGRCs) was investigated. And the results showed that the mechanical properties and fatigue behaviour were significantly affected by the fibre orientation of the FGRC.
Abstract: The material used in vehicle parts could significantly affect the vehicle efficiency. Fibreglass reinforced composites are among the materials that can be used to manufacture the components due to their excellent lightweight properties. Composite structures may undergo fatigue failure when subjected to a certain number of cyclic loading, which normally occurs below the ultimate strength of the material. However, studies on this material’s behaviour remain lacking, including on its integrity under fatigue loading. This paper aims to emphasize a study on the effect of fibre orientation on fatigue strength of fibreglass reinforced composites (FGRC), which are [±45°] and [0/90°]. The composite is fabricated from unidirectional glass fibre and epoxy resin using a hand lay-up technique. The experimental test is carried out at room temperature according to ASTM D3039 for tensile test at rate 5mm/min and ASTM D3479 for fatigue test at R=0.1 subjected to constant amplitude loadings. The results were presented in the form of S-N curves, showing that [0/90°] orientation has a higher fatigue strength as a function of fibre orientation. The results show that the mechanical properties and fatigue behaviour were significantly affected by the fibre orientation of the FGRC.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of geometric parameters on the failure load of bolted joint hybrid composite laminate was investigated and the results concluded geometric parameters significantly affect both failure load and failure mode of hybrid composites.
Abstract: Understanding of composite bolted joint behaviour is vital since it has been widely used in application involving mechanically fastened joints. The advent of advanced technology had led to the use of hybrid composite to reduce the usage of non-environment friendly material such as synthetic fibre. This current study aims to investigate the effect of geometric parameters on the failure load of bolted joint hybrid composite laminate. Composite laminates were fabricated using hot press moulding compression method and they were cut according to the appropriate dimension with the width/diameter (W/D) and edge-distance/diameter (E/D) ratio of 3, 4, 5 and 6. The hole diameter of each composite laminate was fixed at 6 mm. Bolted joint tests were conducted in accordance to ASTM D5961 using the Universal Testing Machine and several failure modes were identified. The results concluded geometric parameters significantly affect both failure load and failure mode of hybrid composites. The increase in W/D and E/D ratio increase the load carrying capability of the laminate.

12 citations

01 May 2017
TL;DR: In this paper, the tensile properties of FML with notch and different fiber orientation were investigated. And the results showed that FML with three layers of glass fibre exhibited higher tensile strength compared with hybrid FML.
Abstract: Efforts to reduce manufacturing cost and negative environmental impacts have seen the mixture of natural fibre with synthetic fibre in composite structures. However, there are limited studies on the notch effect and fibre orientation on mechanical properties of hybrid fibre metal laminate (FML). In this study, tensile properties of FML with notch and different fibre orientation were investigated. The hybrid FML incorporated with kenaf fibre at the middle layer was compared with FML with three layers of E-glass fibre. Kenaf fibre and E-glass fibre used were in plain woven form. The FML in 2/1 configuration was manufactured through hot press manufacturing method to bond layers of annealed aluminium 5052 to the composite. Tensile test was conducted in a quasi-static manner according to ASTM E8. The results showed FML with three layers of glass fibre exhibited higher tensile strength compared with hybrid FML. However, the introduction of kenaf fibre in hybrid FML reduces the notch and fibre orientation sensitivity compared with glass fibre reinforced FML.

9 citations


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Journal ArticleDOI
01 Sep 2021
TL;DR: In this article, the authors highlighted some of the important breakthroughs associated with the NFRPCs in terms of sustainability, eco-friendliness, and economic perspective, and elucidated the significance of using numerical models for NFRMCs.
Abstract: In the contemporary world, natural fibers reinforced polymer composite (NFRPC) materials are of great interest owing to their eco-friendly nature, lightweight, life-cycle superiority, biodegradability, low cost, noble mechanical properties. NFRPCs are widely applied in various engineering applications and this research field is continuously developing. However, the researchers are facing numerous challenges regarding the developments and applications of NFPRCs due to the inherent characteristics of natural fibers (NFs). These challenges include quality of the fiber, thermal stability, water absorption capacity, and incompatibility with the polymer matrices. Ecological and economic concerns are animating new research in the field of NFRPCs. Furthermore, considerable research is carried out to improve the performance of NFRPCs in recent years. This review highlights some of the important breakthroughs associated with the NFRPCs in terms of sustainability, eco-friendliness, and economic perspective. It also includes hybridization of NFs with synthetic fibers which is a highly effective way of improving the mechanical properties of NFRPCs along with some chemical treatment procedures. This review also elucidates the significance of using numerical models for NFRPCs. Finally, conclusions and recommendations are drawn to assist the researchers with future research directions.

121 citations

Journal ArticleDOI
TL;DR: A method for in-situ monitoring of residual strain/stress evolution during annealing treatments has been developed using a new induction heating setup designed for neutron strain-scanning instruments as discussed by the authors.

44 citations

Journal ArticleDOI
TL;DR: In this article, the authors performed model updating of a go-kart chassis structure in order to reduce the percentage of error between the experimental modal analysis (EMA) and finite element analysis (FEA).
Abstract: Model updating is concerned about the correction of finite element models by processing the record of dynamic response from test structures in order to have an accurate model for any simulated analysis. Finite element model updating had emerged years ago as an important subject in structural dynamics. It has been used frequently and has been successfully applied to many fields especially in detecting the dynamic stiffness of a structure. The purpose of this study is to perform model updating of a go-kart chassis structure in order to reduce the percentage of error between the experimental modal analysis (EMA) and finite element analysis (FEA). Modal properties (natural frequency, mode shapes, and damping ratio) of the go-kart chassis structure were determined using both EMA and FEA. Correlation of the modal parameters gathered in FEA and EMA was carried out before optimizing the data from finite element. By adjusting the selective parameters, incongruities between those two analyses are generally reduced. The sensitivity of selected parameters is also obtained. The significant reduction in percentageof error before and after model updating procedure was carried out in this study clearly shows that model updating technique is a reliable method in reducing the discrepancies between EMA and FEA. Therefore, in cases of high discrepancies between analytical and actual test data, model updating can be considered as an option in order to obtain better correlation between those two sets of data.

43 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of fiber stacking configurations on the tensile and quasi-static penetration of kenaf/glass hybrid fiber metal laminates (FMLs) were investigated.
Abstract: The hybridization of natural and synthetic fibers in composite materials has gained the attention in the research field due to environmental awareness. Therefore, this study focuses on the effects of fiber stacking configuration on the tensile and quasi-static penetration of kenaf/glass hybrid fiber metal laminates (FMLs). Kenaf/glass reinforced polypropylene FMLs with two different hybrid stacking configurations were prepared using hot compression process. Non-hybrid kenaf and glass fiber reinforced metal laminates were also prepared for comparison. The tensile test was conducted according to ASTM E8, while the quasi-static penetration test was carried out in accordance with ASTM D 6264 using 12.7 and 20 mm hemispherical indenters. The fractured surface of FMLs due to tensile loading was examined using scanning electron microscope, while optical micrograph was used to investigate the failure mechanism of quasi-statically penetrated laminates. From the results, FMLs with the glass plies at the outer layers of composite (H1) showed a positive hybrid effect as they displayed better tensile and penetration resistance, compared to the non-hybrid kenaf and glass reinforced FMLs. Furthermore, it could be seen that the overall performance of FMLs decreased as the kenaf content in the laminates further increases for hybrid FML.

39 citations

Journal ArticleDOI
TL;DR: In this article, the stress relaxation behavior and mechanisms of conventionally processed and additively manufactured Inconel 625 (CP-IN625) at 600 and 700°C were investigated via compression tests up to an engineering strain of 9% with in situ neutron diffraction characterization.
Abstract: The complex thermal histories in additive manufacturing (AM) of metals result in the presence of residual stresses in the fabricated components. The amount of residual stress accumulated during AM depends on the high temperature constitutive behavior of the material. The rapid solidification and repeated thermal cycles with each laser pass result in material contraction, and subject the surrounding, constrained material to both elevated temperatures and internal stresses, providing driving forces for stress relaxation. In this study, the stress relaxation behavior and mechanisms of conventionally processed and additively manufactured Inconel 625 (CP-IN625 and AM-IN625) at 600 °C and 700 °C were investigated via compression tests up to an engineering strain of 9% with in situ neutron diffraction characterization. The stress decayed to a plateau stress equivalent to 18% of the peak stress in CP-IN625 and 16% in AM-IN625 at 600 °C, and 39% in CP-IN625 and 44% in AM-IN625 at 700 °C. At the same temperature, the stress relaxation rate in AM-IN625 was twice as high as that in CP-IN625, and the magnitude of the plateau stress in AM-IN625 was slightly lower than that in CP-IN625, as the textured AM-IN625 had much larger grains than the texture-free CP-IN625. The stress relaxation in CP- and AM-IN625 was deduced to be controlled by dislocation glide and climb, where dislocations interact with grain boundaries, solute atoms, and secondary phases. The stress relaxation constitutive behavior reported here is a necessary input for the development of accurate thermomechanical models used to predict and minimize residual stresses and distortion in AM, as well as to predict the stress relaxation behavior of Inconel 625 in high temperature structural applications.

37 citations