Key Engineering Materials Vols. 471-472

Abstract: Research on the production of composites from natural fibers has an enormous attention from researchers due to environmental awareness, which focusing to produce compostable bio-based composites and renewable raw materials that can be safely disposed after their use without polluting the environment. This paper reports the study on the effect of the ultraviolet (UV) to the cotton/albumen composites (CAC). The CAC were prepared by using hands lay-up technique with 10 w/w % of cotton content and cured at room temperature for 14 days. The cured samples were cut before exposing to UV light up to 20 days. The increase in tensile strength was observed up-to 10 days of exposure before it is decreasing to about 15% after 20 days of exposure to UV. The morphological study through SEM micrograph shows that fibers breakage and the biopolymer matrix loss is more with longer duration of UV exposure.

Abstract: The aim of this research is to develop glass ceramic produced from recycling glass. Waste glass (e.g. container and bottles) of soda lime silica (SLS) glasses is utilised as main raw materials for the formulation of glass ceramic batch composition with the addition of ball clay. The ball clay was added in order to favour shaping. The recycled glass powder are then mixed with the ball clay according to the ratio of SLSG to ball clay of 95:5 wt.%, 90:10 wt.% and 85:15 wt.%. Differential Thermal Analyses (DTA) was carried out in order to determine the thermal characteristic glass powder prior to the batch formulation. The glass was then crushed, milled and sieved to < 75µm and mixed with the ball clay before it was pressed to a pellet by pressure-less method. This pressure-less route is conducted as an approach to a simple fabrication route of the glass-ceramic samples. The green samples are then sintered at different temperature. The dense and strong glass ceramic samples were obtaining at 850oC, with holding time of one hour and morphological characterized with X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses. Results shown that glass ceramic samples produced at this optimized sintering profile had high density and microhardness value with low porosity and negligible water absorption. Overall results indicates that glass ceramic samples have good mechanical properties (e.g. microhardness exceeding 700Hv) and physical properties (e.g. water absorption, density, porosity making them attractive to the structural application. These results are also utilised as a comparison to a glass ceramic samples produced via Cold Isostatic Press (CIP) from the same batch composition formulation and sintering profiles for the purpose of optimizing the waste glass utilization.

Abstract: Fiber reinforced composite structures are widely used in the aerospace, aircraft, civil and automotive applications due to their high strength-to-weight and stiffness-to-weight ratios and these applications require joining composite either to composite or to metal. There are three main methods for joining composite structures namely, bonding, mechanically fastened or a combination of the two. Bolted joint are preferred in structures where the disassembly is required for the purpose of maintenance and repair. Due to the stress concentration around the holes, bolted joints often represents the weakest part in the structure, and therefore it is important to design them safely. A review on the study of bolted joints in fiber reinforced composite structure is presented. It was found that the behavior of bolted joints in composite structure is affected by many factors, such as geometry, joint material, clamping–load provided by the bolts, ply orientations, etc. Accordingly, various researches have been conducted on the analyses of stress distribution, failure prediction, and strength properties of bolted joint both experimentally and numerically. Accurate prediction of stresses in bolted joints is essential for reliable design of the whole structure; if it is not optimally designed, premature and unexpected failures may be occurred.

Abstract: The objective of this study was to prepare a basic contributed model in beam to examine this novel composition supposed to apply for acetabular cup. Injection molding process used to manufacture of the component whereas ultrasonic welding was utilized to joint two components. Molding and welding value parameters were carried out by trial and error process. Strength bonding of two components was evaluated by single cantilever beam (SCB) test. The Interfacial fracture energy attained by single cantilever beam (SCB) test was exceeded over 1800 after 70 mm crack propagation.

Abstract: This paper presents finite element analysis (FEA) of static and dynamic tests of thick filament wound glass/epoxy tubes. The first part involves the validation of elastic properties and identification of damage initiation and its development in dynamic tests. The results of FEA of the dynamic tests without damage appeared satisfactory. An impact model, including material property degradation, is used for damage prediction. The simulated damage is compared with that obtained experimentally. The sizes of projected and cumulated surfaces are of the same order of magnitude as in the experimental measurements.

Abstract: In this research, natural rubber (NR) with halloysite nanotubes(HNTs)/carbon black (CB) hybrid filler at various filler loading was investigated where the total filler loading used in each compound were 40 phr. The curing characteristics, fatigue life and morphological properties of HNTs/CB/NR nanocomposites were studied. Laboratory two-roll mill was used for mixing process. The results revealed that vulcanizates containing more HNTs in hybrid filler exhibit longer scorch time (ts2) and cure time (t90) for curing characteristics and higher in fatigue life compared to vulcanizates with 40 phr of CB. The images from scanning electron microscope (SEM) confirmed that replacement of carbon black with halloysite nanotubes improved the fatigue life by showing more tearing surface on vulcanizates.

Abstract: In this research, the influence of processing temperatures and fiber chemical treatments to mechanical properties of polypropylene (PP) waste – kenaf fiber composites was investigated. Results from experimental and theoretical calculation of composite tensile strength were compared. The composites were made of PP wastes and unidirectional kenaf fiber, and manufactured by hot press molding. The processing temperature variations were 175 oC, 185oC and 195 oC. The chemical treatment used were alkaline and permanganate treatment. Kenaf fiber – PP composites were successfully made with the void volume fraction less than 5%, maximum fiber volume fraction 48% and maximum longitudinal tensile strength 110 MPa or 238% higher than PP’s strength. For non- and alkali treated fiber composites, 185oC was the optimum processing temperature. Elevated processing temperature up to 195oC could decrease composite strength due to the degradation of fiber-matrix interface. The effect of permanganate treatment did not significantly affect the composites strength. However, the improvement of interfacial properties at elevated temperature was found by the use of permanganate treatment.

Abstract: This paper presents an experimental and numerical characterization of ductile damage evolution in steel subjected to large plastic deformations. The main objective of this research is to better understand damage initiation and evolution in structural steel throughout the deformation process at different strain rates. The proposed study relies on a continuum damage mechanics approach that involves characteristic parameters to describe the accumulation of plastic strain, the damage variable, and the strain rates. The work was divided into experimental, and simulation phases. The experimental phase involved testing under monotonic uniaxial tensile loading under varying strain rates. The obtained material parameters are then used as the basic data in the simulations that are performed afterwards. Finally, this model was implemented as a new user defined material in the finite element analysis software ABAQUS where damage was quantified. Initial results of this research showed that a simple model with substantial cost and time saving can be developed for damage assessment in steel. The rate of loading is a main sensitive parameter that affects both damage initiation and propagation, as they increased significantly with increasing loading rate. Beyond the ultimate load, the strain energy was sufficient to cause the damage to increase without any further applied load.

Abstract: Significant stiffness reduction of the plate spring due to delaminations around the interwoven cloths could be prevented by using CFRTP (carbon fiber cloth and Polyethylene Terephthalate (PET)) rather than that by using CFRP (carbon fiber cloth and epoxy), when ultra high cyclic loading was applied to the plate spring under high humidity condition. To explain the result, the prediction model of stiffness reduction was introduced considering time-dependent crack propagation accompanying with creep deformation around the crack tip. Stiffness reduction of CFRP under high humidity condition was not only determined by cyclic crack propagation but also by time-dependent crack propagation accompanying with creep deformation around the crack tip. It was found that CFRTP was effective material of the plate springs on vibration conveyer for the uses under high humidity condition to prevent significant stiffness reduction, where the crack propagation accompanying with creep deformation should be prevented around the crack tip.

Abstract: Glass fiber reinforced polymer (GFRP) is a common composite material used for wind turbine blades because of its good strength to weight ratio. This paper describes the design process of GFRP material for a low wind speed (LWS) turbine blade. The wind turbine analyzed in this study is a 3-blades horizontal axis wind turbine (HAWT) with NACA 4415 airfoil and rotor diameter of 5 m. Parameters for the blade are thickness of skin and spar, lamination angle, and stacking sequence of the laminae. The design approach uses Carpet Plot Method based on Tsai-Hill failure criteria. Materials analyzed in this study are unidirectional E-glass fiber/epoxy composite and plain weave woven roving WR200 E-glass fiber/epoxy composite. There are 15 material configurations analyzed using a finite element software. The result shows top five of the composites configuration consisting of minimum 3 plies of 0°/90 direction fiber for the skin and ±45° direction fiber for the spar. The optimum configuration is [(0/90)]3 for the skin and (±45) for the spar both using plain weave woven roving WR200 E-glass fiber/epoxy composite. This configuration has margin of safety of 1.42 based on maximum principal stress and maximum deflection of 346 mm which is 0.14 of the total blade length. The predicted overall weight of the blade is 1.52 kg.