Materials Science Forum Vols. 675-677

Abstract: Stitched carbon fiber cloth reinforced zirconium carbide composite (C/ZrC) was prepared by polymer infiltration and pyrolysis (PIP) process. C/ZrC-SiC composite was obtained by further introduction of SiC with PIP process in order to improve anti-oxidation property. The results show that 1.9vol% SiC addition improves the mechanical and anti-oxidation properties of C/ZrC composite. The flexural strength of C/ZrC is 247.9MPa, while that of C/ZrC-SiC is 273.1MPa. After oxidation in a muffle furnace at 1200°C for 30 minutes, the mass loss rate was reduced from 30.6% (C/ZrC) to 20.1% (C/ZrC-SiC), and the flexural strength and elastic modulus of C/ZrC were 56.7MPa and 5.7GPa, respectively, while those of C/ZrC-SiC were 122.9MPa and 17.2GPa, respectively.

Abstract: Carbon nanotubes (CNTs) were incorporated into glass fiber/ vinyl ester resins composites to improve their mechanical and thermal properties, especially the interlaminar shear and longitudinal compressive strengths which are belong to the matrix-dominanted properties and much weaker than the fiber-dominated properties. In this study, a higher temperature initiator was added to improve the polymerization degree and raise the transition temperature (Tg). Mechanical testing indicated that by adding 0.4 wt% CNTs, the nano-filled composites attributed to 21%, 16%, 10%, and 8% improvement in interlaminar shear strength, compressive strength, tensile strength and flexural strength with respect to their counterparts without CNTs, respectively. Moreover, Thermogravimetric analysis (TGA) also exhibits approximately 14°C higher decomposition temperature than those of conventional composites.

Abstract: Waste Paper-Al-Plastic materials including Tetrapak beverage and milk boxes are used to extrude the WPC instead of normal wood fiber material in this research. As many WPC products are applied as exterior wallboard at present, the research on the durability and flame retardancy of Wood-Plastic Composites is important. In this paper, various durability influences and flame retardancy of WPC are analyzed in the laboratory conditions. Some experimental results are presented as follow: Water absorption of WPC is influenced by immersion time. After immersion of simulated acid rain solution and alkali environment, and accelerated ultraviolet radiation tests, WPC samples are observed with banding strength decrease. Nonetheless, the performances of WPC wallboard achieve the requirements of national code when it is properly provided with anticorrosion coating systems. Oxygen index of 27 indicates that WPC is inflammable material. Zinc borate (ZB) and ammonium polyphosphate (APP) are effective flame retardant for Paper-Al-Plastic WPC.

Abstract: In the past decade, natural fibre composites with thermoplastic matrices had attracted many composites manufactures for the superiority of lightweight and low-cost. A major challenge for natural fibre composites was to achieve high mechanical performance at a competitive price. Composites constructed from yarn and fabric structure preforms were better than composites made from random nonwoven mats. However, the twist structure of conventional ring spun yarns prevented the full utilization of fibre mechanical properties in the final composites. In this paper, the wrapped yarns were produced by wrap spun method with flax and polypropylene (PP), in which all flax fibres were twistless, then woven to be fabric preforms. The PP fibres served as a carrier for flax fibres during processing and became the polymer matrix in the final composites. The homogenous distribution of fibre and thermoplastic matrix in preforms could be achieved before hot pressing, so that not lead to impregnate difficultly, and prevented damage to the reinforced nature fibres during processing. Composites made from the wrapped yarn demonstrated significant tensile and peeling properties. The fabric structures (include plain, twill, and basket weave) and yarn tensile orientation (in 0°, 90°, 45°), had great influence on tensile strength and elongation of preforms. The cavity thickness of hot pressing mould had different influence on the tensile strength and peeling strength of thermoplastic composites, and the mechanical properties were superior when the thickness was 0.8-1.2 mm. The microstructure of thermoplastic composites showed uniform infiltration between layers, and had good bonding interface between flax fibre and PP matrix in composites.

Abstract: In order to evaluate the effect of natural fiber lumen size on the transverse thermal conductivity of the unidirectional natural fiber-polymer composite, a two-dimensional unit cell model of natural fiber-polymer composite was studied using finite element method (FEM). In this study, the FE cell model was kept in the steady state thermal condition. The results showed that the effective transverse thermal conductivity K has a relationship with the geometrical ratio (α, 0<α<1) of lumen radius (rl) to fiber radius (rf). When the lumen size ratio α is small, K increases with increasing fiber volume fraction Vf, while K decreases as the Vf increases when α is large. It indicates that the thermal property of composites changes with fiber’s lumen size. When a composite is designed for thermal insulation material, we should choose the natural fiber with large lumen, and to design thermal conductive composite, small lumen size should be used. The result from present method was compared with experimental data and shows a good agreement.

Abstract: Polymers have been proved to have attractive mechanical characteristics, which made it desirable to choose these materials over traditional materials for numerous types of applications. As the uses of polymers increase, a thorough understanding of the mechanical behavior of these materials becomes vital in order to perform innovative and economical designs of various components. The main objective of this paper is to develop an effective method with the use of the Laplace inverse transform to describe the time dependent mechanical response of viscoelastic polymers. This general methodology is based on differential constitutive relations for viscoelastic polymers, avoiding the use of relaxation integral functions. As its application, the creep and relaxation properties of the materials are exhibited in the numerical examples.

Abstract: Laminated materials and clad metals have received much attention in the industrial production due to the superior mechanical properties different from those in any of the constituent materials. Clad metal is a composite metal plate generally made by bonding a metal such as stainless steel plate to another metal such as carbon steel or low alloy steel plate. Clad metal not only has sufficient strength required of structural materials but provides other functions including resistance to heat and corrosion. As a result, the application of clad metals can significantly save precious alloying elements and reduce the cost. Therefore, clad metals have become an increasingly interesting topic in a variety of industrial fields. In this paper, fabrication technique and evaluation on mechanical properties of laminated metals have been briefly overviewed. In addition, the applications of laminated materials including clad metals are reviewed and the prospect of clad metals in the future is also described.

Abstract: Electret filter composed of permanently charged electret fibers is a good material for environmental protection. A novel kind of electret melt-blown nonwovens (EMNs) doped with nano-tourmaline was developed by corona charging in this paper. The structure of web, mechanical properties, surface charge density and filtration efficiency of samples were discussed. The results showed that the structure of EMNs became loose and the initial surface charge density was increased markedly. Furthermore, the EMNs exhibited higher filtration efficiency and lower pressure drop, especially the content of nano-tourmaline was about 6 wt. %.

Abstract: In order to investigate the effect of loading rate on the tensile performance, the uniaxial tensile experiments were conducted on universal testing machine under different loading rates (5 mm/min, 10mm/min, 50 mm/min, 100 mm/min and 150 mm/min), and a constant gage length equal to 200mm, resulting in loading strain rate of 4.17×10-4, 8.33×10-4/s, 4.17×10-3/s, 8.33×10-3/s,1.25×10-2/s, and the tensile stress-strain curves were obtained. The experimental results show that the tensile properties of the conveyor belt exhibit obvious rate-dependent behavior. In this paper, the rate sensitivity coefficient varied with loading rate, was calculated, and the nonlinear rate-dependent behavior was also investigated.

Abstract: Recently in electronic and automobile industry, polymer materials were selected to replace metals in many products because of miniaturization and weight reduction. So the weld between polymers and metals became very important. Currently, the ways were limited to adhesive joint or the mechanical weld which both had obvious defects. In this paper, the direct-welding methods were studied and the welds based on compress-molding were viable and useful. The welding strength enhanced because the reaction between polymers and modified metals were confirmed.