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Most of the recent researches on sodium hydroxide (NaOH) treatment discusses on only the improvement in the properties of natural fibre composites. However, there is a potential in studying the effects of sodium hydroxide treatment even further by identifying the optimum NaOH concentration in order to achieve maximum improvement in the properties of the natural fibre composites. This work reports the development of a composite material derived from both renewable resource and biodegradable material with the emphasis to identify the optimum NaOH treatment condition to achieve maximum improvement in the flexural strength of poly-lactic acid (PLA) reinforced with rice straw (RS) fibres. The RS fibres were treated with different NaOH concentrations (1.25, 2.5, 3.75, 5 and 6.25 mol/L) and the optimum NaOH concentration was 5 mol/L of NaOH where the flexural strength of the PLA/RS fibres were improved by 185%. Thus, it can be concluded that with the optimum NaOH concentration, a strong adhesion between the PLA matrix and the RS fibre which resulted in the improvement in the flexural strength.

In this paper, the effects of stacking sequence and ply orientation on the mechanical properties of pineapple leaf fibre (PALF)/carbon hybrid laminate composites were investigated. The hybrid laminates were fabricated using a vacuum infusion technique in which the stacking sequences and ply orientations were varied, which were divided into the categories of cross-ply symmetric, angle-ply symmetric, and symmetric quasi-isotropic. The results of tensile and flexural tests showed that the laminate with interior carbon plies and ply orientation [0°, 90°] exhibited the highest tensile strength (187.67 MPa) and modulus (5.23 GPa). However, the highest flexural strength (289.46 MPa) and modulus (4.82 GPa) were recorded for the laminate with exterior carbon plies and the same ply orientation. The fracture behaviour of the laminates was determined by using scanning electron microscopy, and the results showed that failure usually initiated at the weakest PALF layer. The failure modes included fibre pull-out, fibre breaking, matrix crack, debonding, and delamination.

Compared to the common selective laser sintering (SLS) manufacturing method, fused deposition modeling (FDM) seems to be an economical and efficient three-dimensional (3D) printing method for high temperature polymer materials in medical applications. In this work, a customized FDM system was developed for polyether-ether-ketone (PEEK) materials printing. The effects of printing speed, layer thickness, printing temperature and filling ratio on tensile properties were analyzed by the orthogonal test of four factors and three levels. Optimal tensile properties of the PEEK specimens were observed at a printing speed of 60 mm/s, layer thickness of 0.2 mm, temperature of 370 °C and filling ratio of 40%. Furthermore, the impact and bending tests were conducted under optimized conditions and the results demonstrated that the printed PEEK specimens have appropriate mechanical properties.

Employment of natural fiber for the filament of fused deposition modeling (FDM) can be found in numerous studies from different areas. However, the presence of fiber such as kenaf in polymer filament could cause mechanical properties degradation with regard to the fiber loading owing to low compatibility between natural fiber and polymer matrix. Therefore, this study aims to study the mechanical properties of three-dimensional (3D)-printed structures of composites specimens with varying volume percentages of kenaf fiber. From the tensile and flexural testings, the findings revealed decrements in the tensile strength and modulus of kenaf fiber-reinforced ABS (KRABS) composites from 0 to 5% contents of kenaf fiber which were 23.20 to 11.48 MPa and 328.17 to 184.48 MPa, respectively. The raising amount of kenaf fiber at 5 to 10% raised the tensile strength and modulus from 11.48 to 18.59 MPa and 184.48 to 275.58 MPa, respectively. Flexural strength and modulus of KRABS composites were decreased at to 5% from 40.56 to 26.48 MPa and 113.05 to 60 MPa, respectively. With further kenaf fiber addition from 5 to 10%, the flexural strength and modulus were increased from 26.48 to 32.64 MPa and 60 to 88.46 MPa, respectively. These results were supported by the finding from the morphological analysis, where the presence of porosity and fiber pull out implied the poor interfacial bonding between kenaf fiber and ABS matrix. This study has successfully demonstrated the tensile and flexural performances of different volume percentages of KRABS composites filament for FDM through experimental research.

Fused deposition modeling possesses great advantages in fabricating high performance composites with controllable structural designs. As such, it has attracted attention from medical, automatic, and aerospace fields. In this paper, the influence of short carbon fibers (SCFs) and the orthogonal building orientation on the flexural properties of printed polyether ether ketone (PEEK) composites are systematically studied. The results show that the addition of SCFs raises the uniform nucleation process of PEEK during 3D printing, decreases the layer-to-layer bonding strength, and greatly changes the fracture mode. The flexural strength of vertically printed PEEK and its CF-reinforced composites show strengths that are as high as molded composites. X-ray micro-computed tomography reveals the microstructure of the printed composites and the transformation of pores during bending tests, which provides evidence for the good mechanical properties of the vertically printed composites. The effect of multi-scale factors on the mechanical properties of the composites, such as crystallization in different positions, layer-by-layer bonding, and porosity, provide a successful interpretation of their fracture modes. This work provides a promising and cost-effective method to fabricate 3D printed composites with tailored, orientation-dependent properties.

This paper aims to analyse the mechanical properties response of polylactic acid (PLA) parts manufactured through fused filament fabrication. The influence of six manufacturing factors (layer height, filament width, fill density, layer orientation, printing velocity, and infill pattern) on the flexural resistance of PLA specimens is studied through an L27 Taguchi experimental array. Different geometries were tested on a four-point bending machine and on a rotating bending machine. From the first experimental phase, an optimal set of parameters deriving in the highest flexural resistance was determined. The results show that layer orientation is the most influential parameter, followed by layer height, filament width, and printing velocity, whereas the fill density and infill pattern show no significant influence. Finally, the fatigue fracture behaviour is evaluated and compared with that of previous studies’ results, in order to present a comprehensive study of the mechanical properties of the material under different kind of solicitations.

Purpose 3D printing of composites has a high degree of design freedom, which allows for the manufacture of complex shapes that cannot be achieved with conventional manufacturing processes. This paper aims to assess the design variables that might affect the mechanical properties of 3D-printed fibre-reinforced composites. Design/methodology/approach Markforged Mark-Two printers were used to manufacture samples using nylon 6 and carbon fibres. The effect of fibre volume fraction, fibre layer location and fibre orientation has been studied using three-point flexural testing. Findings The flexural strength and stiffness of the 3D-printed composites increased with increasing the fibre volume fraction. The flexural properties were altered by the position of the fibre layers. The highest strength and stiffness were observed with the reinforcement evenly distributed about the neutral axis of the sample. Moreover, unidirectional fibres provided the best flexural performance compared to the other orientations. 3D printed composites also showed various failure modes under bending loads. Originality/value Despite multiple studies available on 3D-printed composites, there does not seem to be a clear understanding and consensus on how the location of the fibre layers can affect the mechanical properties and printing versatility. Therefore, this study covered this design parameter and evaluated different locations in terms of mechanical properties and printing characteristics. This is to draw final conclusions on how 3D printing may be used to manufacture cost-effective, high-quality parts with excellent mechanical performance.

The properties of single shear specimens connected by wooden nail frictional welding and twist nails were studied. The single shear properties of the specimens connected by wooden nail welding were lower than that of the twist nail specimens. The single shear capacity of the wooden nail welding specimen was determined by calculating the method of design value of the bearing capacity of the pin connection. Furthermore, the flexural properties of the wooden nail welding laminated timber were analyzed. Due to the larger diameter of the wooden nails compared with the twist nails, the wooden nail welding laminated timber in the elastic phase had higher stiffness. The elastic modulus of the wooden nail welding laminated timber exceeded the average elastic modulus of the constituent lumber pieces by 9.46%. The number of wood lumbers in wooden nail welding laminated timber had little effect on the elastic modulus of laminated timber, but the nail spacing had a certain effect. Therefore, in future research, it is recommended to use the construction method of twist nail connection to design the wooden nail welding laminated timber. In addition, the nail spacing should refer to the GB 50005 (2003) standard and the wood structure design manual.

This study evaluates the four-point flexural behavior of polyoxymethylene (POM) specimens exposed to different environmental conditions. Ten specimens were tested, for each of which five different mediums were studied: ambient environment, distilled water, cooling oil, UV-C radiation, and saline solution. The main objective was to find the influence of these environments on maximum bending stress and compare the values obtained for all four aggressive mediums to the value for the ambient environment. The results showed that exposure to the three liquid media-distilled water, cooling oil, and salt solution-leads to a reduction in bending stress, underscoring the potential weakening effects of these media. In contrast, samples exposed to UV-C showed an increase in bending stress, suggesting an increase in material stiffness under these conditions. This study provides guidelines for the optimal use of POM in various applications and provides clear information on its mechanical performance in various industrial and environmental environments.