Finite Element Analysis of J-Integral for Surface Cracks in Round Bars under Combined Mode I Loading

This paper numerically discusses the role of J-integral along the surface crack front in cylindrical bar under combined mode I loading. It is also verified the analytical model derived from the first part of this paper by comparing the results obtained numerically using ANSYS finite element program. It is found that the proposed model capable to predict the J-integral successfully along the crack front but not for the area away from the deepest crack depth. This is probably due to the fact that the problem of singularity

Physicochemical and thermal properties of lignocellulosic fiber from sugar palm fibers: effect of treatment

Sugar palm fiber (SPF) is one of the prospective fibers used to reinforce polymer composites. The aim of this study is to evaluate the physicochemical, thermal, and morphological properties of SPF after alkali and sea water treatments. The chemical constituents group and thermal stability of the SPF were determined using scanning electronic microscopy (SEM) along with energy dispersive X-ray spectroscopy and thermogravimetric analysis (TGA). Fourier transform infrared spectroscopy was carried out to detect the presence of functional groups in untreated and treated SPF. The SEM images after both treatments showed that the external surface of the fiber became clean as a result. However, the sea water treatment affected the fiber properties physically, while the alkali treatment affected it both physically and chemically by dissolving the hemicellulose in the fiber. The TGA results showed that untreated fiber is significantly more stable than treated fiber. In conclusion, the results show that the fiber surface treatment significantly affected the characterization of the fiber

Kesan lilin ke atas sifat hidrofobik permukaan daun pisang

Pengekstrakan lilin dilakukan ke atas dua jenis daun pisang iaitu Musa parasidiaca L. (pisang berangan) dan Musa acuminata Colla (pisang lemak manis) dengan merendamkan daun pisang ke dalam larutan kloroform bertujuan untuk mengenal pasti sifat-sifat hidrofobik dan pembersihan kendiri. Larutan hasil dikeringkan dan diikuti dengan proses penghabluran. Mikroskop imbasan elektron pancaran medan (FESEM) digunakan untuk melihat profil morfologi kedua-dua jenis sampel lilin dan elemen kimia yang diperoleh adalah karbon dan silikon melalui serakan x-ray (EDX). Takat lebur lilin Musa parasidiaca L. dan Musa acuminata Colla adalah 80.2oC dan 82.9oC manakala sudut sentuhan air pada permukaan lilin Musa parasidiaca L. dan Musa acuminata Colla adalah 137.3o dan 132.8o. Sudut sentuhan bagi kedua-dua sampel lilin melebihi 90o menunjukkan daun pisang adalah bersifat hidrofobik yang mana Musa parasidiaca L. menunjukkan nilai sudut sentuhan yang lebih tinggi dan sesuai untuk aplikasi biomimetik. Pencirian yang terdapat pada lilin daun pisang boleh diaplikasikan di dalam industri salutan permukaan dan tekstil

Effect of pH of Suspension and Mechanical Treatment on Nanosized Zirconia Dispersion / Noor Faeizah Amat...[et al.]

Understanding zirconia 3YSZ powder dispersion is crucial in achieving colloidal stability in order to produce high-strength and translucent structures required for dental applications. In this work, pH adjustment (pH 1–11) and mechanical treatment (ball milling, ultrasonic treatment, and centrifugation) were employed to remove agglomeration. As-received zirconia 3YSZ powder was characterized by transmission electron microscopy, Brunauer–Emmett–Teller method, and laser light scattering technique to identify the primary particle size and to verify the presence of powder agglomeration. Particle dispersion of nanosized zirconia 3YSZ in aqueous suspension at various pH and different mechanical treatments were investigated by measuring the particle size distribution and zeta potential. The particle size of zirconia powder after adjustment to pH 2 was found to decrease (195 nm) compared with that of the as-received powder (388 nm), thus indicating the occurrence of powder de-agglomeration. A higher zeta potential value was also observed at pH 2. The isoelectric point of the suspension was at pH 10.7, where agglomeration was found to occur. This result is in good agreement with the average particle size result, in which larger particle sizes were observed at pH 10 to 11. In addition, ball milling was found to be an effective method to remove weak agglomeration given that small particle sizes measuring 164 nm were produced, whereas ultrasonic and centrifugation treatments worsened the powder dispersion. Zirconia suspension at pH 2 and prepared via ball milling was well-dispersed and suitable for further consolidation process

The Effect of Filler on Epoxidised Natural Rubber-Alumina Nanoparticles Composites

Epoxidised natural rubber (ENR)-alumina nanoparticles composites (ENRAN) were produced by melt compounding followed by sulphur curing. Alumina nanoparticles were introduced in 10, 20, 30, 40, 50 and 60 parts per hundred rubber (phr) in the compounding recipes to study the effect of filler loading to the cure characteristics and mechanical properties. The dispersion of the alumina nanoparticles was studied using scanning electron microscopy (SEM). The increase in alumina nanoparticles loading in ENR matrices were found to accelerate the curing process up to 40% compared to unfilled ENRs. The minimum torque (ML), maximum torque (MH) and torque difference (MH-ML) also increased due to the increasing crosslink density with the presence of alumina nanoparticles. The increase in alumina nanoparticles content in the ENR compound resulted in the decrease of the tensile strength, elongation at break (EB) and the impact strength but increase the hardness and tensile modulus compared to unfilled ENRs. The alumina particles were observed to be uniformly distributed in the matrices which contributed to the enhancement of MH, ML, tensile modulus and hardness of the ENRANs. When present in the matrix, the particles formed spheres of agglomerates thereby able to effect high filler-matrix interaction which also contribute to the increase in torque values

Influence of treatments on the mechanical and thermal properties of sugar palm fibre reinforced phenolic composites

Sugar palm fibre (SPF) was used to prepare composites with phenolic resin. The SPF underwent treatment with either sea water for 30 d or a 0.5% alkaline solution for 4 h. The composites contained 30% (vol.) SPF in a powdered form, and the composite samples were fabricated by a hot press machine. The effects of the fibre treatments on the mechanical (flexural, impact, and compressive), thermal, and morphological properties of the composites were analyzed. The SPF treatments considerably improved the mechanical properties of the composites compared with the untreated composite. The alkaline treatment resulted in the most improved flexural and impact strength of the composites. In contrast, the sea water treatment had the best results for improving the compressive strength. Morphological analyses indicated that the surface treatments improved the fibre-matrix bonding. The thermal degradation analysis showed that both the sea water and alkaline treatments of the SPF slightly affected the thermal stability of the composites. Consequently, SPF can be effectively used as an alternative natural fibre for reinforcing bio-composites

The effect of the rheocast process on the microstructure and mechanical properties of Al-5.7Si-2Cu-0.3Mg alloy

This study shows the results of an experimental investigation of semisolid rheocasting of Al-5.7Si-2Cu-0.3Mg alloy using a cooling slope (CS) casting technique. However, the challenge is to determine process parameters of the CS process to get a desirable microstructure in the semisolid feedstock material. cooling slope technique was employed to create feedstock material for thixoforming under an argon gas atmosphere, where on an inclined plate that was fixed at a 60° slope angle, molten alloy is poured at different temperatures of 640°C, 650°C and 660°C at lengths 300, 400 and 500 mm. Examination the microstructure with optical microscope observed that the microstructure of conventionally cast alloy presented coarse and dendritic primary α-Al phase, whereas rheocast alloy included fine and nondendritic primary α-Al phase with homogeneous distribution of eutectic phase. The best CS processing condition has been identified for optimum pouring temperature of 650°C and the slope length of 400 mm as average globular grain size of around 31.67 ± 3 μm and a shape factor of about 0.66 ± 0.09 were obtained. The mechanical properties of conventional cast alloy were enhanced by the CS casting process. The ultimate tensile strength, the yield strength and elongation of the rheocast alloy were increased by 10%, 12% and 22% respectively compared to the conventional cast alloy. due to a reduction in shrinkage and porosity of the microstructure of the CS alloy

Dynamic mechanical analysis of treated and untreated sugar palm fibre based phenolic composites

Phenolic-based sugar palm fibres (SPFs) were used as a filler for composites that were fabricated by hot pressing. The composites were prepared using various volume loadings of SPFs. Dynamic mechanical analysis (DMA) was carried out to evaluate the storage modulus (Eʹ), loss modulus (Eʺ), and tan delta as a function of temperature. The SPFs were treated by seawater for 30 days and a 0.5 alkaline solution for 4 days. The phenolic composites with 30% volume loading of SPFs were used to determine the effect of treatments on the DMA properties of the composites. The obtained results indicate that incorporating a SPF filler notably increased the Eʹ and Eʺ properties and decreased the damping factor of the phenolic composites. Both treatments affected the DMA results. However, the alkaline-treated composites showed higher DMA properties compared with the seawater-treated and untreated fibre composites