The objective of this research is to optimize the alkaline treatment variables, including sodium hydroxide (NaOH) concentration, soaking, and drying time, that influence the mechanical behavior of bamboo fiber-reinforced epoxy composites. In this study, a Box-Behnken design (BBD) of the response surface methodology (RSM) was employed to design an experiment to investigate the mercerization effect of bamboo fiber-reinforced epoxy composites. The evaluation of predicted tensile strength as a variable parameter of bamboo fiber (Bambusa vulgaris) reinforced epoxy composite structures was determined using analysis of variance (ANOVA) of the quadratic model. In this study, a total of 17 experiment runs were measured and a significant regression for the coefficient between the variables was obtained. Further, the triangular and square core structures made of treated and untreated bamboo fiber-reinforced epoxy composites were tested under compressive loading. It was found that the optimum mercerization condition lies at 5.81 wt.% of the NaOH, after a soaking time of 3.99 h and a drying time of 72 h. This optimum alkaline treatment once again had a great effect on the structures whereby all the treated composite cores with square and triangular structures impressively outperformed the untreated bamboo structures. The treated triangular core of bamboo reinforced composites gave an outstanding performance compared to the treated and untreated square core composite structures for compressive loading and specific energy absorbing capability.
Present study, deals about isolation and characterization of cellulose nanofibers (CNFs) from the Northern Bleached Softwood Kraft (NBSK) pulp, fabrication by hand lay-up technique and characterization of fabricated epoxy nanocomposites at different filler loadings (0.5%, 0.75%, 1% by wt.). The effect of CNFs loading on mechanical (tensile, impact and flexural), morphological (scanning electron microscope and transmission electron microscope) and structural (XRD and FTIR) properties of epoxy composites were investigated. FTIR analysis confirms the introduction of CNFs into the epoxy matrix while no considerable change in the crystallinity and diffraction peaks of epoxy composites were observed by the XRD patterns. Additions of CNFs considerably enhance the mechanical properties of epoxy composites but a remarkable improvement is observed for 0.75% CNFs as compared to the rest epoxy nanocomposites. In addition, the electron micrographs revealed the perfect distribution and dispersion of CNFs in the epoxy matrix for the 0.75% CNFs/epoxy nanocomposites, while the existence of voids and agglomerations were observed beyond 0.75% CNFs filler loadings. Overall results analysis clearly revealed that the 0.75% CNFs filler loading is best and effective with respect to rest to enhance the mechanical and structural properties of the epoxy composites.
This paper presents the study of mechanical properties of short random oil palm fibre reinforced epoxy (OPF/epoxy) composites. Empty fruit bunch (EFB) was selected as the fibre and epoxy as the matrix. Composite plate with four different volume fractions of oil palm fibre was fabricated, (5 vol%, 10 vol%, 15 vol% and 20 vol%). The fabrication was made by hand-lay up techniques. The tensile and flexural properties showed a decreasing trend as the fibre loading was increased. The highest tensile properties was obtained for the composite with fibre loading of 5 vol% and there were no significant effect for addition of more than 5 vol% to the flexural properties. Interaction between fibre and matrix was observed from the scanning electron microscope (SEM) micrograph.
In this study, graphene oxide (Go) filled epoxy nanocomposites were prepared using hot pressed method. The GO was produced using modified Hummers' method. The produced GO at different compositions (0.1, 0.3 and 0.5 wt%) were mixed with epoxy before the addition of hardener using ultra-sonication. The produced epoxy nanocomposites were characterized in terms of mechanical and thermal properties. The mechanical properties of the nanocomposites were significantly enhanced by the addition of GO. About 50% of increment in the flexural strength of the composite sample filled with 03 wt% of GO as compared to the neat epoxy sample. However, only slight improvement in the impact strength of the composite were obtained by adding 0.1 wt% of GO.
Polymer blends is a well-established and suitable method to produced new polymeric materials as compared to synthesis of a new polymer. The combination of two different types of polymers will produce a new and unique material, which has the attribute of both polymers. The aim of this work is to analyze mechanical and morphological properties of bio-phenolic/epoxy polymer blends to find the best formulation for future study. Bio-phenolic/epoxy polymer blends were fabricated using the hand lay-up method at different loading of bio-phenolic (5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt%) in the epoxy matrix whereas neat bio-phenolic and epoxy samples were also fabricated for comparison. Results indicated that mechanical properties were improved for bio-phenolic/epoxy polymer blends compared to neat epoxy and phenolic. In addition, there is no sign of phase separation in polymer blends. The highest tensile, flexural, and impact strength was shown by P-20(biophenolic-20 wt% and Epoxy-80 wt%) whereas P-25 (biophenolic-25 wt% and Epoxy-75 wt%) has the highest tensile and flexural modulus. Based on the finding, it is concluded that P-20 shows better overall mechanical properties among the polymer blends. Based on this finding, the bio-phenolic/epoxy blend with 20 wt% will be used for further study on flax-reinforced bio-phenolic/epoxy polymer blends.
Fiber composites are known to have poor through-thickness mechanical properties due to the absence of a Z-direction binder. This issue is more critical with the use of natural fibers due to their low strength compared to synthetic fibers. Stitching is a through-thickness toughening method that is used to introduce fibers in the Z-direction, which will result in better through-thickness mechanical properties. This research was carried out to determine the mechanical properties of unstitched and silk fiber-stitched woven kenaf-reinforced epoxy composites. The woven kenaf mat was stitched with silk fiber using a commercial sewing machine. The specimens were fabricated using a hand lay-up method. Three specimens were fabricated, one unstitched and two silk-stitched with deferent stitching orientations. The results show that the stitched specimens have comparable in-plane mechanical properties to the unstitched specimens. For the tensile mechanical test, stitched specimens show similar and 17.1% higher tensile strength compared to the unstitched specimens. The flexural mechanical test results show around a 9% decrease in the flexural strength for the stitched specimens. On the other hand, the Izod impact mechanical test results show a significant improvement of 33% for the stitched specimens, which means that stitching has successfully improved the out-of-plane mechanical properties. The outcome of this research indicates that the stitched specimens have better mechanical performance compared to the unstitched specimens and that the decrease in the flexural strength is insignificant in contrast with the remarkable enhancement in the impact strength.
The application of natural fibers is rapidly growing in many sectors, such as construction, automobile, and furniture. Kenaf fiber (KF) is a natural fiber that is in demand owing to its eco-friendly and renewable nature. Nowadays, there are various new applications for kenaf, such as in absorbents and building materials. It also has commercial applications, such as in the automotive industry. Magnesium hydroxide (Mg(OH)2) is used as a fire retardant as it is low in cost and has good flame retardancy, while polyester yarn (PET) has high tensile strength. The aim of this study was to determine the horizontal burning rate, tensile strength, and surface morphology of kenaf fiber/PET yarn reinforced epoxy fire retardant composites. The composites were prepared by hybridized epoxy and Mg(OH)2 PET with different amounts of KF content (0%, 20%, 35%, and 50%) using the cold press method. The specimen with 35% KF (epoxy/PET/KF-35) displayed better flammability properties and had the lowest average burning rate of 14.55 mm/min, while epoxy/PET/KF-50 with 50% KF had the highest tensile strength of all the samples. This was due to fewer defects being detected on the surface morphology of epoxy/PET/KF-35 compared to the other samples, which influenced the mechanical properties of the composites.
To date, the mechanical performance of kenaf composites is still unsatisfied in term of its mechanical performance. Therefore, research focuses on kenaf composites fabrication through the selection of polymer resin, including epoxy, polypropylene, and polylactic acid. The incorporated kenaf fibre at 10 wt % to 40 wt % loadings was conducted using injection and a compression moulding process. The compressed materials indicated high tensile strength at 240 MPa compared to inject materials (60 MPa). Significant improvement on impact strength (9 kJ/m2) was due to the unpulled-out fibre that dispersed homogenously and hence minimize the microcrack acquire. Meanwhile, high flexural strength (180 MPa) obtained by kenaf/epoxy composites due to the fibre orientate perpendicular to the loading directions, which improve its mechanical properties. The findings indicate that the kenaf fibre reinforced thermoset materials exhibit better mechanical properties as a function to the battery tray applications.
This study aims to explore the mechanical properties of hybrid glass fiber (GF)/sisal fiber (SF)/chitosan (CTS) composite material for orthopedic long bone plate applications. The GF/SF/CTS hybrid composite possesses a unique sandwich structure and comprises GF/CTS/epoxy as the external layers and SF/CTS/epoxy as the inner layers. The composite plate resembles the human bone structure (spongy internal cancellous matrix and rigid external cortical). The mechanical properties of the prepared hybrid sandwich composites samples were evaluated using tensile, flexural, micro hardness, and compression tests. The scanning electron microscopic (SEM) images were studied to analyze the failure mechanism of these composite samples. Besides, contact angle (CA) and water absorption tests were conducted using the sessile drop method to examine the wettability properties of the SF/CTS/epoxy and GF/SF/CTS/epoxy composites. Additionally, the porosity of the GF/SF/CTS composite scaffold samples were determined by using the ethanol infiltration method. The mechanical test results show that the GF/SF/CTS hybrid composites exhibit the bending strength of 343 MPa, ultimate tensile strength of 146 MPa, and compressive strength of 380 MPa with higher Young's modulus in the bending tests (21.56 GPa) compared to the tensile (6646 MPa) and compressive modulus (2046 MPa). Wettability study results reveal that the GF/SF/CTS composite scaffolds were hydrophobic (CA = 92.41° ± 1.71°) with less water absorption of 3.436% compared to the SF/CTS composites (6.953%). The SF/CTS composites show a hydrophilic character (CA = 54.28° ± 3.06°). The experimental tests prove that the GF/SF/CTS hybrid composite can be used for orthopedic bone fracture plate applications in future.
This research investigates the strength of kenaf or epoxy composite filled with mesoporous silica and
studies the hybrid effects between mesoporous silica or kenaf in epoxy matrix. The volume of kenaf
woven mat is maintained constantly at 7.2vol%, whereas proportion of epoxy is varied with inclusion of
mesoporous silica and silicon, keeping constant the volume of the composite at 67.5cm3. The proportion
of mesoporous silica is altered from 0.5vol%, 1.0vol%, 3.0vol% and 5.0vol%, while silicon is kept
constant at 3.0vol%. A total of 11 specimens were produced, each with its distinctive composition and
mechanical strengths. Variation of fillers composition affects the mechanical strengths of the composite.
SEM analysis shows that epoxy bonds well with silicon, kenaf and mesoporous silica. Some de-bonding
among the components is observed within the composite although there is also some tearing of fibres and
impregnation of epoxy within fibre, proving that the components have good interaction and do not act
individually. Flexural test shows that mesoporous silica improves the flexural strength of the composite,
where the highest value is 35.14MPa, obtained at 5.0vol% Mesoporous Silica in Kenaf/Epoxy (SiaK/
Ep). It also improves the flexural modulus, where the highest value is 1569.48MPa, obtained at 3.0vol%
SiaK/Ep. DMA result reveals that adding mesoporous silica increases the Tg of the composite produced.
Highest Tg is obtained at 0.5vol% Mesoporous Silica in Kenaf/Epoxy modofied Silicon (SiaK/Ep-Si)
with the value of 87.54°C.
This work focuses on the fabrication of hybrid bio-composites using green epoxy as the matrix material, hemp (H) and sisal (S) fibre mats as the reinforcements. The hybrid composite with sisal/hemp fibres were fabricated by cost effective hand lay-up technique, followed by hot press with different stacking sequences. Static properties of the composites such as tensile, compressive, inter-laminar shear strengths (ILSS) and hardness were examined. The physical properties such as density, void content, water absorption and thickness swelling were also analyzed. The experimental results indicate that hybrid composites exhibited minor variation in tensile strength when the stacking sequence was altered. The hybrid composite with the intercalated arrangement (HSHS) exhibited the highest tensile modulus when compared with the other hybrid counterparts. Hybrid composites (SHHS and HSSH) offered 40% higher values of compressive strength than the other layering arrangements. HHHH sample exhibited the highest ILSS value of 4.08 MPa. Typical failure characteristics of the short beam test such as inter-laminar shear cracks in the transverse direction, micro-buckling and fibre rupture were also observed.
Natural fiber composites have been widely used for various applications such as automotive components, aircraft components and sports equipment. Among the natural fibers Typha spp have gained considerable attention to replace synthetic fibers due to their unique nature. The untreated and alkali-treated fibers treated in different durations were dried under the sun for 4 h prior to the fabrication of Typha fiber reinforced epoxy composites. The chemical structure and crystallinity index of composites were examined via FT-IR and XRD respectively. The tensile, flexural and impact tests were conducted to investigate the effect of the alkali treated Typha fibers on the epoxy composite. From the microscopy analysis, it was observed that the fracture mechanism of the composite was due to the fiber and matrix debonding, fiber pull out from the matrix, and fiber damage. The tensile, flexural and impact strength of the Typha fiber reinforced epoxy composite were increased after 5% alkaline immersion compared to untreated Typha fiber composite. From these results, it can be concluded that the alkali treatment on Typha fiber could improve the interfacial compatibility between epoxy resin and Typha fiber, which resulted in the better mechanical properties and made the composite more hydrophobic. So far there is no comprehensive report about Typha fiber reinforcing epoxy composite, investigating the effect of the alkali treatment duration on the interfacial compatibility, and their effect on chemical and mechanical of Typha fiber reinforced composite, which plays a vital role to provide the overall mechanical performance to the composite.
The use of the colloidal-gold technique in electron microscopy immunocytochemistry has provided important information on the in situ localisation of intracellular antigens. We have developed a post-embedding technique for prolactin localisation on resin-embedded human pituitary tissue sections by the use of the protein-A gold conjugate. Human pituitary tissue obtained at autopsy was processed for electron microscopical study without post-osmication and then embedded in Epon. The indirect immunoperoxidase method was used for light microscopical targetting of lactotroph cells for subsequent electron microscopical antigen localisation. Ultra-thin sections were labelled with human anti-human prolactin followed by protein-A gold conjugate. Specific labelling was observed over secretory granules with a density of 15-30 particles per granule, as determined by the Quantimet 570 image analysis system. This technique provides a means of studying the pathophysiology of hormonal secretion at ultrastructural level and can be a useful tool in diagnostic and research investigations.
The mold-making industry is currently facing several challenges, including new competitors in the market as well as the increasing demand for a low volume of precision moldings. The purpose of this research is to appraise a new formulation of Metal Epoxy Composite (MEC) materials as a mold insert. The fabrication of mold inserts using MEC provided commercial opportunities and an alternative rapid tooling method for injection molding application. It is hypothesized that the addition of filler particles such as brass and copper powders would be able to further increase mold performance such as compression strength and thermal properties, which are essential in the production of plastic parts for the new product development. This study involved four phases, which are epoxy matrix design, material properties characterization, mold design, and finally the fabrication of the mold insert. Epoxy resins filled with brass (EB) and copper (EC) powders were mixed separately into 10 wt% until 30 wt% of the mass composition ratio. Control factors such as degassing time, curing temperature, and mixing time to increase physical and mechanical properties were optimized using the Response Surface Method (RSM). The study provided optimum parameters for mixing epoxy resin with fillers, where the degassing time was found to be the critical factor with 35.91%, followed by curing temperature with 3.53% and mixing time with 2.08%. The mold inserts were fabricated for EB and EC at 30 wt% based on the optimization outcome from RSM and statistical ANOVA results. It was also revealed that the EC mold insert offers better cycle time compared to EB mold insert material.
The effects of hole size on open hole tensile properties of Kevlar-glass fibre hybrid composite laminates were thoroughly investigated in this work. Woven Kevlar/glass fibre epoxy composite laminates were fabricated using hand lay-up and vacuum bagging technique. Specimens of five different hole size (1 mm, 4 mm, 6 mm, 8 mm and 12 mm) were carefully prepared before the tensile test was performed according to ASTM D5766. Results indicated that hybridizing Kevlar to glass fibres improved tensile strength and failure strain of hybrid composite specimen. In addition, increasing the hole size reduced strength retention of the hybrid specimen from 96% for 1 mm hole size to 62% and 44% for 6 mm and 12 mm, respectively. Fractography analysis showed that several types of failure mechanisms were observed such as brittle failure, ductile failure, fibre breakage, delamination and fibre-matrix splitting. It is concluded that as hole size increased, failure behaviour changed from a matrix dominated failure mode to a fibre-dominated failure mode.
Hollow epoxy particles (HEP) serving as reinforcing fillers were prepared using the water-based emulsion method in this study. HEP was incorporated into the polyester matrix at various loading, ranging from 0 wt% to 9 wt%, to toughen the brittle polyester thermoset. The polyester composites were prepared using the casting technique. The fracture toughness and impact strength of the polyester composites increased with increasing the HEP loading up to 5 wt%, after which
there was a drop. The improvement in fracture toughness and impact strength is attributed to the good polymer-filler interaction. This finding was further supported by the scanning electron micrograph, in which it was shown that the polyester resin was interlocked into the pore regions of the HEP filler. The reduction in fracture toughness and impact strength of the polyester composite were believed to be attributed to the filler agglomeration. This filler-filler interaction would create stress concentration areas and eventually weakened the interfacial adhesion between the polymer matrix and the filler particles. Hence, lower fracture toughness and impact strength of the highly HEP-filled polyester composites (above 5 wt%) were detected.
The finite element method is gaining acceptance in predicting mechanical response of various loading configurations and material orientations for failure analysis of composite laminates. Both fabrication of laminate samples and experimental procedures are often expensive and time consuming, and hence impractical, especially during the initial design stage. Finite element analyses require minimal amounts of input data, and the resulting stress and strain distributions can be determined throughout each individual ply. Using ANSYSTM, a commercially available finite element package, failure loads were predicted by simulating a uniaxial tensile loading on HTS40/977-2 Carbon/Epoxy composite with [+/-4512s lamination scheme. Two built-in failure theories in ANSYSTM features, viz., Maximum Stress and Tsai-Wu were applied in the simulation. The stress-strain and load-extension curves for both actual testing and FEA were then compared and the results are in good agreement. This paper is intended for researchers who have used or are considering using ANSYSTM for the prediction of failure in composite materials.
The development of advanced composite materials has taken center stage because of its advantages over traditional materials. Recently, carbon-based advanced additives have shown promising results in the development of advanced polymer composites. The inter- and intra-laminar fracture toughness in modes I and II, along with the thermal and electrical conductivities, were investigated. The HMWCNTs/epoxy composite was prepared using a multi-dispersion method, followed by uniform coating at the mid-layers of the CF/E prepregs interface using the spray coating technique. Analysis methods, such as double cantilever beam (DCB) and end notched flexure (ENF) tests, were carried out to study the mode I and II fracture toughness. The surface morphology of the composite was analyzed using field emission scanning electron microscopy (FESEM). The DCB test showed that the fracture toughness of the 0.2 wt.% and 0.4 wt.% HMWCNT composite laminates was improved by 39.15% and 115.05%, respectively, compared with the control sample. Furthermore, the ENF test showed that the mode II interlaminar fracture toughness for the composite laminate increased by 50.88% and 190%, respectively. The FESEM morphology results confirmed the HMWCNTs bridging at the fracture zones of the CF/E composite and the improved interlaminar fracture toughness. The thermogravimetric analysis (TGA) results demonstrated a strong intermolecular bonding between the epoxy and HMWCNTs, resulting in an improved thermal stability. Moreover, the differential scanning calorimetry (DSC) results confirmed that the addition of HMWCNT shifted the Tg to a higher temperature. An electrical conductivity study demonstrated that a higher CNT concentration in the composite laminate resulted in a higher conductivity improvement. This study confirmed that the demonstrated dispersion technique could create composite laminates with a strong interfacial bond interaction between the epoxy and HMWCNT, and thus improve their properties.
Six impact energy values, ranging from 2.5 J to 10 J, were applied to study the impact properties of neat epoxy and bamboo composites, while six impact energy values, ranging from 10 J to 35 J, were applied on bamboo/glass hybrid composites. Woven glass fibre was embedded at the outermost top and bottom layer of bamboo powder-filled epoxy composites, producing sandwich structured hybrid composites through lay-up and molding techniques. A drop weight impact test was performed to study the impact properties. A peak force analysis showed that neat epoxy has the stiffest projectile for targeting interaction, while inconsistent peak force data was collected for the non-hybrid composites. The non-hybrid composites could withstand up to 10 J, while the hybrid composites showed a total failure at 35 J. It can be concluded that increasing the filler loading lessened the severity of damages in non-hybrid composites, while introducing the woven glass fibre could slow down the penetration of the impactor, thus lowering the chances of a total failure of the composites.
This research aimed to assess the stress distribution in lower premolars that were obturated with BioRoot RCS or AH Plus, with or without gutta percha (GP), and subjected to vertical and oblique forces. One 3D geometric model of a mandibular second premolar was created using SolidWorks software. Eight different scenarios representing different root canal filling techniques, single cone technique with GP and bulk technique with sealer only with occlusal load directions were simulated as follows: Model 1 (BioRoot RCS sealer and GP under vertical load [VL]), Model 2 (BioRoot RCS sealer and GP under oblique load [OL]), Model 3 (AH Plus sealer with GP under VL), Model 4 (AH Plus sealer with GP under OL), Model 5 (BioRoot RCS sealer in bulk under VL), Model 6 (BioRoot RCS in bulk under OL), Model 7 (AH Plus sealer in bulk under VL), and Model 8 (AH Plus sealer in bulk under OL). A static load of 200 N was applied at three occlusal contact points, with a 45° angle from lingual to buccal. The von Mises stresses in root dentin were higher in cases where AH Plus was used compared to BioRoot RCS. Furthermore, shifting the load to an oblique direction resulted in increased stress levels. Replacing GP with sealer material had no effect on the dentin maximum von Mises stress in BioRoot RCS cases. Presence of a core material resulted in lower stress in dentin for AH Plus cases, however, it did not affect the stress levels in dentin for cases filled with BioRoot RCS. Stress distribution in the dentin under oblique direction was higher regardless of sealer or technique used.