Applied Mechanics and Materials Vol. 749

Abstract: The epoxy composites with high thermal conductivity for metal-core printed circuit board (MCPCB) can be prepared by varnish coating and a hot press method. Alumina filler of plate-like shape was used as primary micro-filler, while plate-like alumina filler, h-BN, a-BN and s-BN filler were used for blending into the plate-like alumina filler as the secondary filler. Results showed that the secondary fillers a-BN and s-BN loaded epoxy composites have higher thermal conductivity than alumina filler single-loaded composites. Also, BN filler has high thermal conductivity, but h-BN filled epoxy composite has lower thermal conductivity than alumina filled epoxy composite. The decrease of voids in epoxy composite are very important, and the filler shape and surface modification is also necessary to achieve high thermal conductivity in epoxy composite for MCPCB

Abstract: Kevlar fiber are artifical fibers that have been globally commonly used due to their attributes of a high modulus, a low elongation, an impact resistance, a chemical resistance, and thermostability. Therefore, this study proposes nonwoven geotextiles by corporating with recycled Kevlar unidirectoinal selvage with a low production cost, crimped polyester (PET) fibers, and low-melting-point PET (LPET) fibers. The content of LPET fiber is specified as 20 wt%, while the content of Kevlar fiber varies as 0 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%. The optimal tear strength of 195 N occurs with a content of Kevlar fiber being 20 wt%.

Abstract: Liquid crystalline epoxy, 4,4’-Diglycidyloxy-α-methylstilbene (DOMS) was synthesized and Aluminum Nitride reinforced DOMS composites were fabricated by melt blending with sulfanilamide (SAA) as a curing agent. Thermal degradation behavior was investigated by thermogravimetric analysis (TGA) under nitrogen atmosphere at the temperature range from 30 to 1000°C. Activation energies for decomposition (Ed) by TGA were determined as a function of conversion by weight loss process.

Abstract: The effects of the montmorillonite clay surface modified with 25-30 wt% octadecylamine (clay) on mechanical and morphological properties of poly (methyl methacrylate) (PMMA)/ ethylene-octene copolymer (EOC)/clay composites were investigated. The composites of blends of PMMA/EOC with clay were prepared by melt mixing in an internal mixer. The results showed that the Young’s modulus of the composites increased with increasing clay content. The ratio of PMMA and EOC was 80/20 by weight and the clay content was 3 and 5 phr. The results showed Young’s modulus of the composites increased with increasing clay content. While the impact strength, tensile strength and percent strain at break of the composites decreased with increasing clay content. Scanning electron microscopy analysis showed that the droplet of dispersed EOC phase in PMMA matrix was changed to the elongated structure after adding clay.

Abstract: Single layer of titanium dioxide (TiO₂) is common metal oxide in fabricating memristor device. In this study, two types of memristor with composite metal oxide thin films will be demonstrated. The two types of memristor are titanium dioxide (TiO₂) thin film coated on zinc oxide (ZnO) thin film and ZnO coated on TiO₂ thin film. Sol-gel spin coating method was to coat metal oxide thin film and sputtering method for depositing the metal contact. Platinum (Pt) was selected as the top electrode and indium tin oxide (ITO) as the bottom electrode. The electrical characteristics were defined by performing I-V measurement using two point probe equipment. I-V characteristics showed shape of pinched hysteresis loop for both samples. Sample with TiO₂ coated on ZnO has slightly higher R_off/R_on ratio than sample ZnO coated on TiO₂ which means it more memristive than another one. The cross-section of sample with TiO₂ coated on ZnO had been performed as well by using Field-Emission Scanning Electron Microscopy (FESEM).

Abstract: Hydroxyapatite (HA) / Multi-walled Carbon Nanotube (MWCNT) composites were sintered by Spark Plasma Sintering (SPS). The adhesion characteristics of the composite are measured with Atomic Force Microscopy (AFM) at the different volume percent of MWCNT and the temperature. Experimental results have shown that the addition of MWCNT has caused the meaningful change in the adhesive force.

Abstract: High strength steel (HSS) was used as raw material in the automotive industry, which required lightweight and high strength, such as chassis and etc. However, the strength and hardness of the steel are relatively high, leading to the low permeability and large spring-back occurring after forming operation. As a result, the work piece is not shaped desire. This research proposes neural network for predicts the spring back values, in U-bending process, that the materials were differences in mechanical properties, such as SPFH590 (JIS) and SPEC980Y (JIS). In the experiment, the input factors for predictable data consists as the punch radius (RP), die radius (Rd), clearance (Cl) and counter punch force (Fc). After that, the input data were analyzed relation with spring-back values by the Pearson Correlation of One-tailed. Next, It was selected by Leave-one-out and k-fold Cross validation (K-fold and LOOCV), to improve efficiency of the prediction process. Moreover, the result was a measurable performance with Root Mean Square Error (RMSE) technique, equal to 0.788 and 2.10 respectively. In the final analysis, the neural network is effective to predict the Spring-back values of SPFH590 (JIS) rather than SPEC 980Y (JIS) in U-bending process.

Abstract: The crack propagation behavior in a 2024 T351 Aluminum Alloy under constant amplitude loading has been studied. This study is analyzed in term of crack opening load measurements using a compliance technique. The results obtained under constant amplitude fatigue tests show that different crack propagation stages can be identified. Significant effects due to load ratio changes have been quantified.

Abstract: Structural lightweight aggregate concrete offers several benefits as compared to the normal weight concrete. Most common methods of producing structural lightweight concrete is by using artificial lightweight aggregates. However, the cost of the production of artificial lightweight aggregates is high due to energy and raw materials consumption. The use of waste and by-product materials as lightweight aggregate in concrete can provide a better solution to reducing the negative impact of the concrete industry. This paper reports an investigation to produce structural lightweight aggregate concrete by utilizing the locally available solid waste materials, namely oil palm shell (OPS) and oil-palm-boiler clinkers (OPBC) as coarse lightweight aggregates. Two different mix proportions were studied. In the first concrete mix, just OPS was used as coarse aggregate. However, 40% of OPS (by volume) of the first mix was replaced with OPBC in the second mix. The test results showed that by replacing OPS with OPBC, it directly affects the characteristics of the lightweight concrete. The 28-days compressive strength of the blended coarse lightweight aggregate concrete was significantly increased compared to OPS concrete.

Abstract: According to the recent community-based structures enlargement, specification, and diversification. It needs appropriate construction materials in terms of intensity and environmental aspects. Thus, in manufacturing the cement using micro limestone powder that is main material. It is also expected to save energies and reduces CO₂, by using the blast furnace slag and fly ash which are mitigated environmental load construction materials that emerged. In this research, the durability aspect tries to be grasped considering the chemical property according to the coherence of the hydration product. Consequently, the compressive strength was measured over 30Mpa on 3rd. In addition, according to the content of the limestone powder, the setting time is promoted. It has the feature expanded in the length change. And it is determined because the possibility of replacing the existing for construction material such as it is measured compared with the time to use the portland cement usually that flexural strength is high with the age 7 days ago, so it is sufficient.