Advanced Materials Research Vols. 311-313

Abstract: In this paper improved SEA method and Hybrid FE-SEA method were used to predict the underwater acoustic radiation. The prediction of underwater acoustic radiation results showed a larger error appeared in the shell structure of the first order "breathing mode", when improved SEA method be used. Using the hybrid FE-SEA method to analysis the rigid subsystem that the SEA approach can not handle. The results using hybrid FE-SEA method very accurate in interested frequence.

Abstract: Commercially pure aluminum and commercially pure titanium plates have been explosively welded and annealed at temperature of 630 °C for 5, 20, 50 and 100 hours. The investigation of intermetallic formed during explosion welding and heat treatment processes has been carried out. The metallographic studies showed variation in the intermetallic volume fraction according to the deformation degree of different interfaces. Moreover the relation between the intermetallic layer thickness and time of explosively welded “Al-Ti” composite annealing has been found. The X-ray analysis reviled that intermetallic layer formed during the heat treatment process consisted of Al₃Ti compound.

Abstract: This study is mainly about the drilling of carbon-epoxy laminates. Variation of cutting parameter such as feed rate (50,100 and 150 mm/min) and speed(400,800,1200 rpm) were tested in this study. 6 different laminates orientation (0°/0°/0°/0°, 45°/45°/45°/45°, 0°/45°/0°/45°, 45°/0°/45°/0°, 0°/0°/45°/45° and 45°/45°/0°/0°) were tested in order to see which one is the best. HSS twist drill with 4mm diameter was use in this study. The damage of the composites was seen under digital microscope. The aim of this study is to find the minimum force and the minimum damage mechanism i.e.: entry and exit delamination. The drilling process with different parameter of cutting and the orientation were carried out in order to see the influenced of this parameter to the force and the damage mechanism. The general factorial was used to randomise the number of experiment.

Abstract: A proton exchange membrane of poly (vinylidene fluoride) grafted onto poly (2-acrylamido-2-methylpropane sulfonic acid) (PVDF-g-PAMPS) was prepared as follows: acrylamido-2-methylpropane sulfonic acid (AMPS) was first added to a N-Methyl pyrrolidone (NMP) solution containing poly (vinylidene fluoride) (PVDF) that was modified with plain sodium silicate. Ammonium persulfate was then added as an evocating agent and PAMPS was directly grafted onto the PVDF that was modified with plain sodium silicate. The influences of AMPS contents on the proton conductivity and mechanical properties were studied. The results showed that AMPS is easily grafted into PVDF modified by Plain sodium silicate (Na4SiO4) and mechanical properties were improved, with increasing of the content of 2-acrylamido-2-methylpropane sulfonic acid, the proton conductivity of PVDF-g-PAMPS membranes was increased.

Abstract: In this paper, an eight-node solid hybrid-stabilized element for general piezoelectric laminate plate analysis is formulated based on the electromechanical Hellinger-Reissner functional. The independent field variables in the functional include the displacement, electric potential, stress and electric displacement. The non-constant electromechanical stress modes are contravariant in nature and chosen to be orthogonal with respect to the constant ones. The othogonality and the practice put forward in the admissible matrix formulation allow the electromechanical flexibility matrices to be block diagonal. As a result, the computational cost for inverting the electromechanical flexibility matrices can be greatly reduced. Numerical examples indicate that the proposed hybrid piezoelectric element is more accurate than their conventional counterpart.

Abstract: On the basis of the shear-lag theory, a layered shear-lag model was established to study the stress redistributions of cross-ply laminates with multiple transverse matrix cracks in the 90º ply under bending. The present results are in a good agreement with variational solutions and finite element results and show that approximate solutions of stress distributions for cross-ply laminates with transverse cracks under bending can be obtained by using a shear-lag method. The present paper therefore affords a new way or method for studying the stress redistributions and failure mechanism for cross-ply laminates with flaws under bending.

Abstract: Kenaf fibre is a natural fibre which is growing in popularity due environmental issues and its properties as filler. Unsaturated polyester was used in this investigation via add 1% MEKP concentration ratio as the catalyst. This matrix was combined with untreated kenaf fiber with various fiber sizes (1-6) mm and (10-30) mm, alkalized with 6% NaOH solution for treated kenaf fiber to form natural fiber for two different fiber lengths composites. Composites were prepared by adding various percentages of kenaf fiber in unsaturated polyester resin. A general trend was observed whereby alkalized fiber composites possessed superior flexural strength and modulus and the maximum strength and modulus was at the 20wt% weight fraction. The length of (10-30) mm gave higher tensile and flexural properties compared to (1-6) mm. The modulus of elasticity showed a regular trend of an increase with fiber weight percent until 30% for both fiber lengths and afterwards a decrease in modulus of elasticity for composites with greater fiber weight fraction. The experimental modulus of elasticity was compared with the theoretical predictions and was found to be in good agreement with Hirsch’s model while the results obtained from Cox – Krenchel underestimating the experimental data.

Abstract: Complex product design is a knowledge-intensive process that involves various aspects of technical knowledge and experience. This paper contends that the conventional Product Data Management (PDM) system has some inherent limitations due to its original intention to manage processes and results, not to manage and reuse knowledge. Therefore, to overcome the shortage that knowledge cannot be discovered and reused effectively in PDM systems, a “Domain Ontology - Index Knowledge – Data Resource” (OKD) three-layer mapping model is proposed to organize DK. The key idea behind our approach is a flexible ontology-based schema that domain ontology is used as semantic model and index knowledge as data indexing to enable the capture and reuse of problem-solving knowledge to improve PDM’s performance. Finally, conclusion is made.

Abstract: High-temperature mechanical properties, machinability, oxidation resistance and thermal shock resistance of different content of carbon particles modified silicon carbide composite ceramics (Cp/SiC) prepared by pressureless sintering techniques were studied. Adhesion of Cp/SiC to melted glass under 1000°C was also observed. The results showed that 15-Cp/SiC had the optimum machinability and it also did not adhere to melted glass at high temperature. And flexural strength, hardness, and fracture toughness of 15-Cp/SiC is 136.5MPa, 274.6kgf/mm2, 2.58MPa•m1/2 respectively. The good performance of Cp/SiC made it possible to be used as high temperature glass fixture, which means that Cp/SiC can not only improve the service life of fixture materials, but also broaden the application fields of SiC ceramics.

Abstract: The effect of different solution temperatures has been investigated on the tensile properties of Na-modified Al-Mg₂Si in situ composite specimens which were subjected to solutionizing at different temperatures of 480 °C, 500 °C and 520 °C for holding time of 4 h followed by quenching. Tensile test results indicated that elongation value gradually increases upon solution treatment whereas ultimate tensile strength (UTS) reduces. The results of solution treatment also showed that the highest quality index is achieved in 500 °C (354 MPa) and so it is revealed optimum solutionizing temperature level (500 °C) for improving tensile properties.