Key Engineering Materials Vols. 471-472

Abstract: Response of aging treatment on aluminum alloy towards its hardness has been investigated. Alloy used on this research was develop base on a US patent 4121951 that is use to produce aluminum cable with excellent strength and conductivity [1]. Solutioninzing treatment was carried out to the alloy at 520 °C for 2 hours. Alloy then were artificial aged at 180 °C, 200 °C and 220 °C for various periods up to 10 hours. Natural aging also has been carried out for 2 weeks right after solution quenching. By referring to the results, hardness increase as the aging time increase until it reaches the maximum peak and then decreases as the result of overaging. Hardness of artificial aged alloy then was compared with 99.99% pure aluminum, as-cast and naturally aged alloy. Alloy aged at 180 °C for 2 hours give the highest value of hardness which is 34.26 Hv followed by naturally aged alloy and pure aluminum with 30.92 Hv and 15.2 Hv. The effect of different time of artificial aging gives significant change in hardness in order to improve the strength of aluminum alloy. Minor addition of zirconium during the aluminum processing will probably cause by the precipitation of Zr particles towards the aluminum matrix [2], thus increase the strength even these particulate cannot be detected by XRD. These particles will retard the grain movement and also stable upon heating due the low solubility of zirconium in aluminum matrix.

Abstract: Poly(vinylidene fluoride)/Microcrystalline cellulose (MCC) nanocomposites were prepared by ultrasonic treatment and magnetic stir. Poly(vinylidene fluoride)-graft-maleic anhydride (PVDF-g-MAH) was added to promote matrix–filler compatibility. Transmission electron microscopy (TEM) results showed that the diameter of the MCC was decreased to several tens nanometers by the treatment of ultrasonic and magnetic stir. The results of differential scanning calorimetry (DSC) showed that the peak crystallisation temperatures (Tc) and the crystallisation enthalpy ΔHc increased with the addition of MCC, and the melting enthalpy ΔHm increased. With the addition of the compatibilizer (PVDF-g-MAH), peak crystallisation temperatures increased further, while without further increase of the ΔHc. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) showed that the addition of MCC induced β-phase PVDF, and the addition of PVDF-g-MAH can induce more β-phase PVDF. Mechanical properties of the nanocomposites were evaluated and the results showed that the addition of MCC did not increase the Young’s modulus, while the tensile strength and elongation at break decreased.

Abstract: This research concerns the effect of compression molding parameters on conducting polymer composite (CPC) properties such as electrical conductivity and flexural strength. In the present work on CPC, focus is given to graphite (G) as filler and polypropylene (PP) was use as the binder. The Taguchi’s L9 orthogonal array has been used as design of experiment (DOE) while the electrical conductivity and flexural strength were assumed to be quality characteristic (responses). The electrical conductivity was measured using four point probes and flexural strength was measured using three point tests according to ASTM D638. Classical analysis of variance (ANOVA) was used to investigate the significant of each compression molding parameters and finally propose the optimum compression molding parameters. But for several responses, the optimum condition for one response is not very likely to the optimum condition for other response.

Abstract: This paper presents an elastoplastic impact model for a spherical object impacting a supported composite layer or a half-space. The model utilizes a contact law that has been developed based on elastic-plastic and fully plastic indentation theories. For an impact event, the model parameters can easily be obtained analytically, computationally using Finite Elements (FE), and from experiments, by assuming transversely isotropic material behavior. Simulations are compared to those from a nonlinear FE model developed in ABAQUS, and to limited experimental data, with excellent results.

Abstract: This paper describes the preparation and characterization of proton conducting nanocomposite polymer electrolytes based a polyvinylidene fluoride-co-hexapropylene (PVDF-HFP) for protonic electrochemical cells. The electrolytes were characterized by Differential Scanning Calorimetry (DSC) and Impedance Spectroscopy (IS). It is observed that the crystallinity of the PVDF-HFP-NH4CF3SO3 system slightly increase upon addition of SiO2 nanofiller. The PVDF-HFP-NH4CF3SO3-SiO2 electrolytes reveals the existence of two conductivity maxima at 1 and 4 wt% of SiO2 concentration attributed to two percolation thresholds in the nanocomposite polymer electrolyte. The optimum value of conductivity of 1.07 × 10-3 S cm-1 is achieved for the nanocomposite polymer electrolyte film with 1 wt% SiO2. Protonic electrochemical cells was fabricated with a configuration Zn + ZnSO4.7H2O + PTFE (anode) | PVDF-HFP:NH4CF3SO3+SiO2 (electrolyte) | MnO2 + PTFE (cathode). The maximum open circuit voltage (OCV) is ~1.50 V and discharge characteristics of the cell were studied at different loads of resistances.

Abstract: Composite solid electrolytes in the system (1-x)Li2CO3-xAl2O3, where x = 0.1–0.7 were prepared by sol gel method using lithium carbonate and aluminum oxide precursors in ethanol. The gels obtained due to the addition of citric acid were calcined at 80 and 100 oC. Their structural, thermodynamic and electrical properties were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. The results indicated that interface phases of crystalline and amorphous exist in this composite system of (1-x)Li2CO3-xAl2O3. The presence of the interface phases are due to the chemical and physical interactions between both crystalline Li2CO3 and Al2O3. The Arrhenius plot of the composite system showed non-linear curves and reached maximum values of ∼10−4 - 10−5 S cm-1 at 150 -180 °C. Based on the results of this study, it can be concluded that the sol gel method used in the preparation of the composite system, has an important role to crystal morphology changes that results in high ionic conductivity.

Abstract: Strain rate sensitivity and dynamic mechanical properties of polymeric materials are affected to a certain extent especially by the rate of loading. However, there is limited number of works reported on that particular issue. Therefore, the paper presents on static and dynamic mechanical properties of various polymeric materials across strain rate from 10-2 to 10-3 s-1. The specimen were tested using universal testing machine (UTM) for static loading and a conventional split Hopkinson pressure bar (SHPB) apparatus for dynamic loading. From the results, the compression modulus and compressive strength of all tested specimen increased significantly with increasing strain rates. In addition, positive increment in terms of strain rate sensitivity was recorded for all tested polymers over a wide range of strain rate investigated. Meanwhile, the thermal activation volume has decreased as increasing strain rate. Of the three polymers, polypropylene shows the highest strain rate sensitivity at static region. On the other hand, at dynamic region, polycarbonate shows the highest strain rate sensitivity than that of polypropylene and polyethylene.

Abstract: In this work, sandwich composite properties were investigated by addition of coconut coir (CC). Fibres in the polyurethane foam cores ranges from 0 to 20 wt.%. Glass fibre reinforced epoxy panels were used as a skin and polyurethane foam as a core, these materials adhesively bonded to keep the whole structure attached with each other. Sandwich composite skins and core-skin bonding were attained via adhesive bonding technique. While polyurethane foam reinforced by coconut coir fibres were manufactured by using one shot process and polyurethane moulding method. Sandwich composite panels with different coir fibres compositions were subjected to the density test, weight per area test and flexural testing in order to investigate their physical and mechanical properties. From the experimental results and analysis, it was found that the sandwich composites with 10 wt.% of coir fibres offer higher mechanical properties.

Abstract: The motivation of this work is to lessen the dependence on non-degradable plastic packaging which can lead to waste disposal problems. In this paper, the alternative biodegradable material developed by using local available sago starch in the present of biodegradable glycerol as plasticizer, as well as a set of composition added with citric acid as co-plasticizer is reported. Starch was added with 15-30 w/w% of glycerol to prepare workable bioplastics. The samples were characterized by Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) and tested for mechanical properties. The results reveale that, the tensile strength of the bioplastic is increasing with the increasing of glycerol until the optimum amount of 30 w/w%. The similar trend is also observed upon the addition of the citric acid. The decrease of the strength after the optimum point, however is obvious in the specimens with the addition of citric acid which is about 50% lower than the specimen without citric acid.

Abstract: The attention in natural fiber reinforced biopolymer composite materials has been rapidly growing both in terms of industrial applications and basic research. This study investigated on the effect of aging time on mechanical properties and morphological structure of thermoset protein-based composites from egg albumen reinforced by natural cotton fibres. The cotton/albumen composites (CAC) were fabricated by hands lay-up technique with 10 w/w % of fiber content. The samples were cured and aged at room temperature for different aging time from 7 to 32 days. The cotton fibres have contributed in a significant improvement in mechanical strength and toughness of the composites. Tensile strength of the composites achieved the optimum strength of 9 MPa after 21 days of aging time and constant till 32 days. As the aging time increased, impact strength of the composites also improved to some value of 20 kJ/m2. Thereby after 21 days observation, the composites show an equilibrium moisture content of 6-9 wt%, and the strength remains stable at room condition with 50-60% relative humidity (RH). Morphology studied using SEM justify that the moisture content after aging time influenced mechanical properties of the composites.