Applied Mechanics and Materials Vols. 268-270

Abstract: The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

Abstract: The Rotating Extrusion Alloying (REA) is a process which combined friction stir welding process and extrusion technology. In the REA process, dissimilar metals are mixed, cracked, and subjected to high speed, severe pressing deformation, and therefore rapidly alloy at a low temperature. The Al-Ti alloy has been prepared by REA. The result shows that during REA process, the original materials and the products after synthesis present high energy ball mill and from sintering the compound are avoided, and the contamination to the compound due to the contact with the surrounding atmosphere and high energy balls disappear. REA technology can be alloyed Al-Ti material. Its phases are mainly composed of Al and Al3Ti, which are distributed more evenly in the aluminum. After heat treatment, its phases’ types and pole figures have no significant change, but there is a trend of transition to the non-equilibrium stable phase. Small-angle grain boundaries decrease or even disappear.

Abstract: A novel composite humidity control material was prepared, in which konjac glucomannan grafted on sodium polyacrylate with halloysite loading, adopting aluminum chloride/sodium bicarbonate system to foam, and twice foaming to form porous structure in the composites by heating at 150 °C. The resultant composites were utilized as substrates and applied in a composite humidity control paper making. Humidity performances including hygroscopicity, moisture capacity, moisture absorption and desorption rate were tested. It was found that the composite paper presents good humidity control performances even in amplified experiments.

Abstract: The post mechanical behavior of Ti/APC-2 hybrid nanocomposite laminates after low velocity impact was investigated. The three layered Ti/APC-2/Ti cross-ply nanocomposite laminates were fabricated according to the modified the diaphragm curing process. Each sample, L×W×t=240mm×25mm×1.55mm, was first subjected to free drop of a rigid steel sphere (diameter=12.7mm) of 1m and 2m high. Then, the samples were due to static tensile tests at room temperature to measure their residual ultimate strength and longitudinal stiffness as the base-line data for constant stress amplitude tension-tension cyclic tests. The corresponding S-N curve, fatigue strength and life were obtained. Also, the failuremechanisms were observed.The mechanical properties do not reduce significantly due to low-velocity impact. Similarly, the fatigue resistance of impacted samples does not lose much. The enhancement by nanoparticles and superior bonding capability of matrix PEEK with Ti sheets take the responsibility of improvement of mechanical responses.

Abstract: Current energy resources derived from fossil fuels thinning, and the issue global warning make the relevant parties that concern about the environment has been trying to find alternative renewable energy. Among the renewable energy options, the fuel cell is one of the many alternatives studied by the researchers in the world. One type of fuel cell that is currently being investigated is the proton exchange membrane fuel cell cel. The utilization of graphite and carbon black waste product is expected to result in light-weight and cost-effective bipolar plates.by using recycle materials. In this paper, we used graphite EAF as reinforcement together with carbon black that comes from the coconut husk pyrolysis process and epoxy resin as a binder. We examined the effects of carbon black loading at 5 %wt and 10 %wt, which influenced by differential pressure applied on compression molding process on density, porosity, flexural strength and electrical conductivity of the resulting polymer carbon composite bipolar plate. Pressure was applied from 30 MPa - 60 MPa in increments of 5 MPa while maintaining constant temperature operation at 70oC for 4 hours. Maximum value of bipolar plate was achieved by 5 %wt CB at application 55 MPa, density of 1.69 g/cm3, the flexural strength was measured to be 48 MPa with the porosity of 0.7%, and electrical conductivity of 1.03 S/cm.We demonstrated that waste product such as graphite EAF and carbon black are a good candidate for manufacturing of polymer carbon composite bipolar plates.

Abstract: A series of fluorocarbon films were deposited on glass substrates by Pulsed Plasma Thruster. The effects of deposited angle on chemical structure and surface morphology of these films were investigated using X-ray photoelectron spectroscopy (XPS) and scanning probe microscope (SPM). XPS data imply various carbon-related chemical components present on the surface of the deposited films are strongly impacted by the deposited angle. AFM measurements show that the increase in deposited angle can smoothen the surface morphology and decrease the RMS roughness. Changes in density of the neutral particle and flux of ions that reach the surface affect the formation of fluorocarbon clusters in the films and reduce surface roughness.

Abstract: Blends of recycled LDPE and LLDPE were prepared by the twin-screw extruder at different ratios. Recycled LDPE was used as matrix in this work, LLDPE was used to improve the properties of RLDPE. Virgin LDPE was used in this study as a contrast. Rheological properties of the blends were carefully evaluated by a Haake rheometer and compared with pure LDPE. Rheological analysis shows that virgin LLDPE will promote the normal flow of RLDPE in the a large content and hinder the mobility of chain segments when in a small content of LLDPE. Consequently, the blends show potential applications in high-value products.

Abstract: In this paper, the multi-layered gradient materials consisting of polarized polymers and small molecules were prepared and the damping properties were studied by DMA. The predicted and experimental results showed that, it was possible to obtain damping material with broad efficient damping range by two-layered hybrid materials, the value in the middle of two peaks could be improved by increasing the number of layers of the multi-layered hybrids and there was a higher minimum value. On the other hand, with increased number of the layers of the multi-layered hybrid materials, the temperature dependence of could be improved. For five-layered gradient materials, it was almost rectangular transition range with values for the area under the linear curve. Thus, it would be feasible in theory and experiment to broaden the efficient damping range by multi-layered gradient materials based on organic hybrids, which provided a new approach and solid basis for developing high performance damping materials with a broad and high damping range.

Abstract: The PLA/tourmaline composites were prepared by co-extrusion of PLA chips and tourmaline fillers. Rheological behavior of PLA chips and PLA/tourmaline composites were analyzed using a capillary rheometer. Experimental results showed that the rheological curves complex viscosity of the PLA chips exhibited a non-Newtonian flow behaviour. Complex viscosity of the PLA chips decreased with the temperature increasing. A non-Newtonian flow behaviour was observed in all the PLA/tourmaline composites samples at lower shear rate. The complex viscosity of PLA blends increased with the input of tourmaline. The viscous flow activation energy of PLA/tourmaline blend melts decreased compared with that of neat PLA chips. Keyword: Rheological behavior; poly(lactic acid); tourmaline; meltblowing

Abstract: In order to improve the properties and the processability of kenaf fiber (KF) / polystyrene (PS) composites, the newly synthesized polymeric silane coupling agent (CA) was utilized and evaluated. KFs were reacted with CA in the melt system and in the solvent system. The composites reinforced by the modified KF showed enhanced mechanical properties compared with those reinforced by the unmodified KF. The effect was especially remarkable when the KF was modified with CA in the solvent system. As the CA content increases, the surface of KF recovered from the composites showed the higher Si / C ratio indicating the good reaction between KF and CA. The modified composites also showed a remarkable reduction in water uptake rate.