Low-velocity impact performance of glass fiber, kenaf fiber, and hybrid glass/kenaf fiber reinforced epoxy composite laminates

The goal to decrease global dependency on petroleum-based materials has created a demand for bio-based composites. Composites that are reinforced with natural fibers often display reduced strength compared with those using synthetic reinforcement, and hybridizing both types of reinforcement within a common matrix system offers a possibly useful compromise. This research investigated the low-velocity impact performance of glass, kenaf, and hybrid glass/kenaf reinforced epoxy composite plates. The aim of the study was to determine the low-velocity impact behavior of biocomposite material in assessing its potential for application in the radome structures of aircraft. Natural fibers possess low dielectric constants, which is a primary requirement for radome. However, the structural integrity of the material to impact damage is also a concern. Composite samples were prepared via a vacuum infusion method. A drop weight impact test was performed at energy levels of 3 J, 6 J, and 9 J. The Impact tests showed that the impact peak force and displacement increased with the energy level. Hybrid glass/kenaf composites displayed damage modes of circular and biaxial cracking. The former is analogous to the damage observed in glass-reinforced composite, while the latter is unique to woven kenaf reinforced composites. The severity of the damage increased with impact energy and was found to be significant at 3 J

Honeycomb composite structures of aluminum: aerospace applications

A honeycomb composite structure is usually composed of a lightweight hexagonal core sandwiched between two thin face sheets that are adhesively joined. Both the core and the face sheets can be combinations of many types of materials depending on the application. In this article, an overview of the design and manufacturing process of aluminum honeycomb composite structures particularly for aerospace application is presented. Aluminum honeycomb composite structures are lightweight constructions with high specific strength and stiffness that are applied mainly in the aerospace industry. An aluminum honeycomb panel is typically made up of the secondary structural components and interiors of an aircraft such as the wing skin, trailing edge, control surface, flooring, partitions, aircraft galleys, and overhead bins, to name a few. Other applications are in the spacecraft, helicopter, missile, and satellite. Owing to its honeycomb design peculiar to the hexagonal beehives, it can reach more than 30 times higher in stiffness and 10 times higher in flexural strength compared to its solid counterpart of the same weight. The mechanical properties of the honeycomb composite structure hinge on the materials of the core and face sheets, the core geometries, and the thickness of the face sheets. Designed for superior flexural and shear loading, the selection of the optimal honeycomb design will depend on the application requirements. The principal design criterion of a sandwich structure in aerospace applications is weight saving, and there is a trade-off between performance and cost. In terms of manufacturing of the honeycomb composite sandwich structure, the two main processes are the expansion process commonly used for low-density cores and the corrugation process for higher density cores

Translation and validation of Malay version 5-items brief illness perception questionnaire, BIP-Q5 towards COVID-19 among Malaysian nurses

Introduction: Currently, own individual perception is recognized as one of the important factors in the prevention of disease, including coronavirus disease, COVID-19. Given the massive impact of COVID-19 on all population’s life, including nurses as one of the main health services providers in the country, this study aims to translate and validate the Malay Version 5-Items Brief Illness Perception Questionnaire, BIP-Q5 towards COVID-19 among Malaysian nurses. Materials and Methods: Forward and backward translations and pretesting of the BIP-Q5 to Malay were conducted among nurses, subject matter experts, and language professionals. The validations process was elicited through an online cross-sectional study involving 56 nurses based on a ~10:1 subject-to-items ratio sample size estimations. Results: The principal component analysis (PCA) revealed one best component with eigenvalues more than one, confirming the questionnaire’s original version. There are five items within the single component, and all are with weightage of over 43%. The scree plot supported the findings, which showed that at least one factors are suitable to be retained. The overall Cronbach’s α coefficient was 0.7 and the intraclass correlation coefficient was 0.659. The Kaiser-Meyer-Olkin was 0.655, and Bartlett’s test of sphericity p-value was <0.001. Conclusion: This study showed that the translated Malay Version 5-Items Brief Illness Perception Questionnaire, BIP-Q5 has a good psychometric property, and is a valid and reliable tool to be used to measure illness perceptions towards COVID-19 among Malaysian nurses

Mould design and characterization of Kenaf fiber honeycomb core- reinforced epoxy composites for aerospace applications

Sandwich structures with honeycomb core are known to significantly improve stiffness at lower weight and possess high flexural rigidity. These structures are found wide applications in aerospace as part of the primary structures as well as the interior paneling and flooring. High performance aluminum and aramid are typical material used for the purpose of honeycomb core whereas in addition to other industries, other materials such as fiber glass, carbon fiber, Nomex, and also Kevlar reinforced with polymer are used. Recently, growing interest in developing composite structures with natural fiber reinforcement has also spurred research in natural fiber honeycomb material. The performances of honeycomb cores are dictated by cell size, wall thickness and core thickness. In term of research purposes, it has been reported that the honeycomb core are fabricated using single core mould however, the mould is not specifically for aerospace application. In this work, a single core mould for honeycomb core is designed and fabricated as per aerospace standard. In terms of fiber direction, the majority of the previous works have generally emphasized on the usage of random chopped fiber and few are reported on development of honeycomb structure using unidirectional fiber as the reinforcement. This is mainly due to its processing difficulties which usually involve several stages to account for the arrangement of fibers and curing. In this work, honeycomb cores of neat epoxy, random chopped strand kenaf/epoxy and unidirectional kenaf/epoxy are introduced and their mechanical properties are compared in term of tensile test, edgewise compression test, flatwise compression test, and flexural test. In order to compare the performances of honeycomb in term of fiber orientations, the density and volume fraction are ensured to be the same for all samples. From the result, the coupon specimen of unidirectional kenaf/epoxy has high tensile strength which is 43.18% more than random kenaf/epoxy. In comparing between honeycomb core biocomposites, the honeycomb core of random kenaf/epoxy is superior to unidirectional kenaf/fiber in term of edgewise compressive strength, flatwise compressive strength and flexural strength which is 21%, 17.7%, and 88.67% respectively. Failure modes analysis shows that unidirectional kenaf fiber suffer fiber breakage, fiber pulled out, obvious stress lines, matrix cracking, cohesion failure and fiber buckling. However, in random kenaf fiber the fracture modes are defined only by fiber breakage, fiber splitting, obvious stress lines, fiber pulled out and compaction

Mould design and manufacturing considerations of honeycomb biocomposites with transverse fibre direction for aerospace application

Sandwich structures with honeycomb core are known to significantly improve stiffness at lower weight and possess high flexural rigidity. They have found wide applications in aerospace as part of the primary structures, as well as the interior paneling and floors. High performance aluminum and aramid are the typical materials used for the purpose of honeycomb core whereas in other industries, materials such as fibre glass, carbon fibre, Nomex and also Kevlar reinforced with polymer are used. Recently, growing interest in developing composite structures with natural fibre reinforcement has also spurred research in natural fibre honeycomb material. The majority of the researches done, however, have generally emphasized on the usage of random chopped fibre and only a few are reported on development of honeycomb structure using unidirectional fibre as the reinforcement. This is mainly due to its processing difficulties, which often involve several stages to account for the arrangement of fibres and curing. Since the use of unidirectional fibre supports greater strength compared to random chopped fibre, a single-stage process in conjunction with vacuum infusion is suggested with a mould design that supports fibre arrangement in the direction of honeycomb loading