Materials Science Forum Vol. 894

Abstract: In order to meet demanding of non-magnetic, changing the reinforcement ratio, the degree of prestress and cross section form, four partially prestressed concrete beam (3 T shape section, 1 rectangle section) were made with CFRP as longitudinal reinforcement and stirrup. The results show that: the pure bending sections of the test beams conform the plane-section assumption; the beams with bigger rate of reinforcement or with stronger prestress tends to appear more cracks with smaller spacing and width, also their cracking load were higher with relatively lesser deflection. The cracking load and ultimate load of T-shape beam are slightly larger than the rectangular beam’s, but their deflections are similar nearly. Based on experimental research, nonlinear finite element analysis software ANSYS was utilized to establish the model, the results of numerical simulation and experiments showed good agreement.

Abstract: The stereomicroscope, microscopic metallograph and scanning electron microscope (SEM) were adopted to investigate the fracture mechanism of two-layer steel/aluminum composite plates impacted by spherical fragment. The composite plates with the same total thickness (5mm) were fabricated by the method of explosive welding. In ballistic experiment, the spherical fragments were launched by a 14.5mm slip chamber gun to penetrate the composite plate. The effect of the combination state of the interface on the fracture mechanism was analyzed based on the experimental results. The results show that the fracture mechanism of the steel front plate is shearing and plugging and that of aluminum rear plate is ductile prolonging deformation when the tied interface failed by tension (or shearing and plugging when the interface combination remained connected).A narrow adiabatic shear band was formed in the local yield plate damaged by shearing and plugging during the penetration process.

Abstract: The recent trend in bioceramics research is mainly concentrated on bioactive ceramics, i.e. hydroxyapatite, tricalcium phosphates and bioactive glasses, as they exhibit superior biological properties over other materials. Among these tricalcium phosphates have been found very important member due to their biocompatible and biodegradable properties that can help to promote new bone formation when implanted in a bone defect site. Therefore the aimed of the present work was to investigate the synthesis of tricalcium phosphate via simple microwave route at Ca/P molar ratios below, 1.67 and at pH of reaction environment equal 5. The detail characterizations of the prepared samples were carried out using Energy-dispersive X-ray spectroscopy (EDX), FT-IR spectroscopy (FTIR) and X-Ray Diffraction (XRD) analysis. From the analysis of EDX, FTIR and XRD patterns, the formation of β-TCP was confirmed.

Abstract: This research focusing on mechanical properties of rubber toughened polyester filled carbon black (RPCB) reinforced with untreated kenaf (RPCBUK) and treated kenaf (RPCBTK). The samples were fabricated via compression moulding technique in which 3 % of LNR was added as toughening agent in this composite. Percentages of carbon black (CB) is 4 % and kenaf used vary from 5,10,15,20 and 25wt %. The mechanical properties were evaluated by impact and fracture toughness testing. The result for each test was discussed to determine the most optimum loading of kenaf fibre used to produce the best properties of composite. Untreated hybrid composite showed improvement on impact strength as compared to RPCB composite. RPCBTK with 25% of kenaf and RPCBUK with 5% of kenaf loading give the highest impact strength among the hybrid composites, approaching the strength of neat polyester. Same trend shows by fracture toughness testing. The microstructures of the composites’ fracture surface images from scanning electron microscope (SEM) prove the mechanical properties of the hybrid composites.

Abstract: In the present work, aluminum AA6061 chip metals were extruded by hot extrusion and the effect of extrusion parameters on the mechanical properties and surface integrity were investigated. The objective of the present studies it to analyze the mechanical and structural properties of 6061 after plastic consolidation by hot extrusion. Tensile test results showed that material extruded using temperature 550°C exhibit higher ultimate tensile strength (UTS) compared with temperature of 400°C. Fracture surfaces shown that ductile fracture mode occurred at condition 500°C and 2 hours, and brittle fracture occurred at condition 400°C.

Abstract: Polyurethane has a wide range of chemical structures available led to the design of materials that easily can meet requirements to shape memory polyurethane (SMPU) due to its ability to retain its shape after deformation through giving a certain disturbance like magnetic field. Based on the previous study, polyurethanes synthesized by reacting 4,4’-methylenebis (cyclohexyl isocyanate) to poly(ethylene glycol) Mw: 6000 as polyurethane chain with 1,1,1-trimethylol propane as chain extender, is a potential candidate for shape memory polyurethane (SMPU). Furthermore this study was performed by adding Fe₃O₄ nanoparticles as a filler to provide magnetic behavior. In this study, The magnetic and mechanical properties of the SMPU after adding Fe₃O₄ nanoparticles were evaluated by observing compatibility between the filler and matrix, morphology, ability in retaining shape, and mechanical properties through measuring FTIR, FESEM, Vibrating Magnetometer and UTM, respectively. This study reported a good compatibility between Fe₃O₄ and the polyurethane, and lack agglomeration of Fe₃O₄ nanoparticles indicated FTIR and FESEM-EDAX, the fastest ability on retaining its shape obtained from materials with lowest Fe₃O₄ (3 wt%). Meanwhile the best mechanical and magnetic was resulted from adding 11 wt% of Fe₃O₄

Abstract: Polylactic acid (PLA) reinforced kenaf fibres composites were fabricated using melt compounding and compression moulding. Kenaf bast and core fibres had undergone chemi-mechanical treatment before use. The mechanical properties of kenaf bast composites (KBC) and kenaf core composites (KCC) were studied by performing flexural and impact testing. KBC and KCC treated with 1.0M acid treatment at 60 rpm speed shows highest flexural and impact properties. The fibre surface treatment had an efficient effect on the flexural strength at 1.0M concentration, with improvement of approximately 27% of strength.

Abstract: TiB₂p/Al-10Zn-1.7Mg-1.0Cu-0.12Zr composite was prepared by synthesis of in-situ Al-TiB₂ master alloy, high purity aluminum, pure zinc, pure magnesium, Al-50 wt% Cu and Al-4 wt% Zr master alloys. The mass fraction of TiB₂ particles was varied from 0% to 9.14%. SEM and TEM were applied to evaluate the microstructure and phase component. HB hardness test were carried out on hardness value of the matrix alloy and the composite. The results showed that TiB₂ particles uniformly distributed in the composite and well combined with the matrix alloy. The average grain size of the composites decreased from 110.35μm to 52.07μm when the TiB₂ particles is 4.47%, and the grain size changed slightly when TiB₂ content increased further. The hardness value of the composites which raised from 189HB to 206HB is superior to that of the matrix alloy. As the content of TiB₂ particles increased, HB hardness value also increased.

Abstract: The aim of this study is to enhance the interfacial bonding strength of carbon nanotubes (CNTs)/AZ91 composites by heat treatment (HT). Ternary carbides (Al₂MgC₂) were in situ formed and uniformly dispersed between CNTs and AZ91 matrix by 823K heat treatment of CNTs/AZ91 composites for 12 h. In situ synthesized Al₂MgC₂ can strengthen the interfacial bonding of CNTs/AZ91 composites, and guarantee an effective load transfer between matrix and CNTs. The HT-CNTs/AZ91 composites showed outstanding mechanical properties due to the excellent interface enhancing effect of Al₂MgC₂. Compared with pure AZ91 alloy, HT-CNTs/AZ91 composites exhibit improved ultimate tensile strength and 0.2% yield strength by 7% and 22% respectively.