Structural Integrity of Welded Structures XI
Advanced Materials Development & Performance
Nanoscience, Nanotechnology, and Nanoengineering: Fundamentals and Applications
Recent Advances in Solid State Science and Technology
SOLID STATE SCIENCE & TECHNOLOGY Towards an Immersive Breakthrough
Proceedings from 21st Czech Concrete Day 2014
Advanced Materials Research V
Materials for Modern Technologies
Micro- and Nanotechnologies for Sustainable Development
Metal, Ceramic and Composite Materials
Material Science and Engineering Technology III
Binders, Materials and Technologies in Modern Construction
Modeling and Optimization of Materials and Structures
Advanced Materials Research V
摘要: The performances of PP/MMT nanocomposite (70μm thick films), in terms of thermal and rheological properties were investigated. A twin-screw extruder was used to compound PP, MMT, compatibilizer, and extruded nanocomposite films were collected for test. All results were compared and the influence of MMT contents on the final properties were observed and reported. The thermal properties of PP had improved by increasing MMT content from 0-3 phr. However at 4 phr thermal stability of the nanocomposite had slightly dropped. In terms of rhelogical properties, the addition of MMT to the PP blend increased the complex viscosity of the nanocomposites, particularly at low frequency regions.
摘要: Due to limitations of Conventional metallic biomaterials an attempt is made to develop a new hybrid polymer matrix composite for load bearing applications of Hip joints in the human body. Ultra high molecular weight polyethylene matrix material was blended with 50 wt% of short E-glass fibres and TiO2 particles with varying percentage of reinforcement, using injection moulding machine. Fabricated composites specimens were subjected to tensile strength test, Fatigue test, SEM, Wear analysis test and In vivo Biocompatibility test to evaluate mechanical and tribological properties, required for bone joints load bearing applications. The maximum tensile strength of 41.5 MPa and young’s modulus of 7.5 GPa is obtained. The behavior of S-N curve obtained after the test is linear in nature, which leads to failure at 105 cycles for the fabricated composite specimen. Also it reveals that fracture is due to brittle failure. The wear mechanism of composite specimen is, because of abrasion. Density of composite specimens was increased after dipping in the simulated body fluid solution.
摘要: In this paper hydroxyapatite biomimetic deposition on Ti void metal composites (Ti-VMC) have been shown. The Ti-VMC were prepared using saccharose (sugar crystals) as a space holder material that forms voids around the Ti scaffold. The Ti (100 and 325 mesh) with sugar (about 0.7−0.9 mm) particles were mixed together with different Ti/sugar ratio and uniaxially pressed. Then the sugar particles were dissolved in water, leaving mechanically bonded Ti particles, forming a metal scaffold. The titanium scaffolds were sintered at 1300°C, which lead to formation the Ti-VMC with voids of diameter of up to 0.9 mm. Because different Ti/saccharose ratio was applied, the Ti-VMC have been made with 50, 60 and 70% porosity. On the as-prepared Ti-VMC the hydroxyapatite (HA) was deposited using mineralisation procedure in Kokubo SBF (simulated body fluid). The Ti-VMC were kept in SBF for time from 7 up to 28 days. Finally the scaffolds were covered by layer of HA showing good corrosion resistance. The mechanical tests show, that most optimal property for implant applications have samples of 50% porosity, made from 100 mesh Ti. The scaffold of 50% porosity states a good background for implant applications.
摘要: Since discovery of graphene, great attention had been paid to other two dimensional (2D) layered materials. As a graphene-like layered nanomaterial, molybdenum disulfide (MoS2) had gained enormous attention from the materials fields which had been widely used in many areas such as solid lubricants, lithium ion batteries, photocatalysts, sensors or as conductive fillers in polymer composites. In this work, MoS2 nanosheets were incorporated into polymer matrix as nanofillers by three typical preparation methods, including solvent blending, in situ polymerization and melt blending method. The MoS2 nanosheets were dispersed well in the polymer matrices which improved the thermal stability, mechanical properties and reduced fire hazards of the composites obviously. The improvements in the thermal properties, fire resistance properties and mechanical properties of polymer/MoS2 nanocomposites were mainly attributed to good dispersion of MoS2, physical barrier effects of MoS2 and catalytic char function of MoS2 nanosheets.
摘要: The hydraulic properties of granulated blast-furnace slags have been studied for nearly 200 years, and use of slag in mortars and concretes dates back more than a hundred years. The use of ground blast furnace slag, added as a replacement for a portion of the portland cement, has gained increasing acceptance in recent years. The effects of sulphur-oxidizing bacteria Acidithiobacillus thiooxidans on concrete mixture with addition of ground granulated blast furnace slag compared to mixture without any additives were investigated in laboratory over a period of 91 days. A laboratory study was conducted to comparison the performance of concrete samples in terms of a concrete deterioration influenced by the leaching of calcium compounds from the cement matrix. The changes in the elemental concentrations of calcium ions in leachates were measured by using X – ray fluorescence method. Experimental studies confirmed: bacteria Acidithiobacillus thiooxidans caused much intensive calcium release from the concrete matrices into the solution; the higher resistance of concrete mixture with 65 % wt. slag addition was not confirmed.
摘要: This article reports on the possibilities of using selected alternative materials like hemp fibres, MgO-cement, recycled concrete, fly ash and steel slag as binder or filler replacement in composite materials in civil engineering production. These binder or filler substitutes were mixed into composites and their compressive strength was tested. The paper is divided into four parts providing the results of experiments. In first part strength parameters of lightweight composites based on natural fibres (hemp hurds) and alternative binder (MgO-cement) are presented. Compressive strength values of concrete samples with partial replacement of cement with mechanochemically activated coal fly ash are given. The third and forth part is aimed to utilization of recycled concrete and steel slag as a natural aggregate replacement in concrete mixture for purpose of structural concrete and surface roads.
摘要: The designs of hip joint prostheses have an influence on both the quality of the metal–bone cement contact and the failure rate of the cement mantle. The designers of implant systems must confront biomaterial and biomechanical problems, including in vivo forces on implants, load transmission to the interface, and interfacial tissue response. Cement spacers are being increasingly used for revision arthroplasties. In this study, a three-dimensional finite elements method is used to analyse the mechanical behaviour of the reinforced spacer out of the bone cement (PMMA) by computing the maximum stress. One of the most important factors in the reinforce design is to reduce the stress on the bone cement and the femur. The static load analysis is based, by selecting the peak load during the normal walking activity. Results show that, Von Mises stress is significantly reduced in the cement bone of full-stem and rod reinforced spacers.
摘要: In this study, a finite element analysis of the crack repair with composite wrap of circumferential through cracks in pipes subjected to bending moment is presented. Also, the evaluation of the long-term performance of composite repair systems has been addressed. The stress intensity factor is utilized as a fracture criterion. Finally, an attempt was made to provide industry with an overview of the current state of the art in composite repair technology and how the integrity of pipeline systems is being restored using composite materials. The obtained results show that the presence of the bonded composite repair reduces significantly the stress intensity factor, which can improve the residual fatigue life of the pipe. However, the main disadvantage of the technique of bonded composite repair in pipe is the impossibility to bond double sided composite wrap in order to equilibrate the stress transfer between the internal and external crack tip
摘要: Polymer/clay nanocomposites have been explored extensively over the last two decades. Many studies report nanocomposite properties. However, studies on the effect of processing conditions are still limited. This study evaluates the effect of rotor type, rotor rotation (rpm) and mixing time on mechanical properties of polyethylene organoclay composites. Samples were fabricated using two different rotors; roller and Banbury, in an internal batch mixer at various mixing conditions. The analysis shows that the Banbury rotor improved mechanical properties more than the roller rotor. Shear and diffusion mechanism, as well as material degradation, were the controlling factors at different processing conditions.