Papers by Keyword: Reinforcement

Abstract: The different amount of hydrophilic hydroxyl group, including 3, 5, 7 and 10 wt.% copoly (styrene-co - divinyl benzene – co - 2-hydroxylethylenemethacrylate) (poly (St- co -DVB- co -HEMA) s) nanoparticles were synthesized via microemulsion polymerization in the present paper. The average size of the poly (St-co-DVB-co-HEMA) s was ca. 44 nm after zetasizer (DLS) measurement and SEM observation. The characteristic peaks at 3200 ~3600 cm^-1 in FTIR was assigned at hydroxyl group of HEMA unit. The NBR/poly (St-co-DVB-co-HEMA) s composites films with 250 μm thickness were prepared simply via latex mixing and followed by spinning coating. The mechanical properties of the poly (St-co-DVB-co-HEMA) s/rubber nanocomposites, including the tensile strength, modulus and elongation, were increased with that of increasing of poly (St-co-DVB-co-HEMA) s adding. In addition, as the poly (St-co-DVB-co-HEMA) s nanoparticles carried out with constant St/HEMA molar ratio of 97:3 and the DVB content in 10 wt.%, the elongation at break that up to more than 3500% and the ultimate stress increased from 0.2 MPa to 0.6 MPa. The poly (St-co-DVB-co-HEMA) s nanoparticles prepared by emulsion polymerization could be successfully enhanced the mechanical properties of rubber latex.

Abstract: The history of acrylic bone cement comprise a long period of time, Sir John Charnley being considered the founder of modern artificial joint replacement, as he started to develop the cementing in the late 1950s. Acrylic bone cements (ACB) are polymer-ceramic composites based on polymethyl metacrylate (PMMA), widely used in orthopaedics as suture materials and fixation devices. The main features of these materials are: 1) biocompatibility and ability to support new bone growth (osteoconductive) and 2) bioactivity (ability to form a calcium phosphate layer on its surface). The main function of the cement is to serve as interfacial phase between the high modulus metallic implant and the bone, thereby assisting to transfer and distribute loads. During years of follow up, cemented prosthesis with acrylic bone cements (ABC) demonstrated a good primary fixation and load distribution between implant and bone, along with the advantage of fast recovery of the patient. However, several problems are still persisting, as the orthopedic acrylic bone cements have to meet several medical requirements, such as low values of maximum cure temperature in order to avoid thermal necrosis of the bone tissue during the setting time, appropriate setting time (so that cement does not cure too fast or too slowly) and high values of compressive strength in order to withstand the compressive loads involved by normal daily activities. Generally, the improvement mechanical properties can be realized in three directions: 1) by searching alternative material to PMMA acrylic bone cements; 2) chemical modification of PMMA; and 3) the reinforcement of PMMA by adding different bioactive particles, antimicrobials, vitamins. The aim of this rewiew is to explore the development of bone cements in the last decade, to highlight the role of bone cement additives with respect to mechanical properties and limitations of polymethylmethacrylate in orthopaedic surgery. The behavior of antibiotic-loaded bone cement is discussed, compared with other alternative additives including nanofillers, together with areas of research that are now open to explore new insights and applications of this well known biomaterial.

Abstract: In this investigation, A357 (Al-7.5%Si-0.5%Mg) alloy/Al₂O₃ composites with various weight fractions (4%, 8%, 10%) were prepared by using permanent mould casting. In addition, A357 alloys were cast for comparison purposes. Microstructure, hardness and tensile properties of these composites were evaluated and compared with as-cast alloy. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus at a constant sliding velocity of 1m/s and pressure of 0.35 MPa. The microstructure of the composites shows homogenous distribution of Al₂O₃ plate-like particles in the Al matrix except in the A357/10%Al₂O₃ composite. The wear and mechanical properties of composites improve with increasing the weight percentage of Al₂O₃ upto 8% and then decreases. Particularly, mechanical properties of the A357/10%Al₂O₃ composite are lower than the alloy indicating that the critical weight fraction of Al₂O₃ reinforcement in the A357 alloy is 8%. Wear morphology studies show that higher wear rate in case of unreinforced specimen was associated with higher thickness of hardened layer and consequent delamination of wear debris from the surface which was confirmed by optical and scanning electron micrography.Whereas ductile and brittle mode of fracture is observed in Fractographic observation of composite. The present paper highlights the salient features of casting technique and characterization of aluminum alloy A357 and alumina metal matrix composite.

Abstract: The handbook "Determination of load-carrying capacity of railway bridges" [1] has grown up due to updating of old Slovak guideline [2] taking into account Eurocodes. In the case of railway bridges, there are about 2300 bridges in Slovakia and about 78 % of them are from concrete or masonry. About 28 % of bridge total number is older than 77 years and about 18 % of them are even older than 100 years. Therefore, there is need to make regular inspections, recalculate them – determine of load-carrying capacity and then to decide, which of them should be repaired or reconstructed [3,4]. The paper presents general concepts and basic assumptions for determining the load-carrying capacity of reinforced and prestressed concrete railway bridges. In contrast to design of a new bridge, additional data related to existing bridge condition and its behaviour like information from regular inspections and real state of degradation can be taken into account. Special recommendation and allowances for global analysis of existing concrete superstructures for the purpose of the load-carrying capacity estimation are discussed, as well.

Abstract: This study investigated the improvement of hardness and flexural properties of a commercial stereolithography (SLA) resin by reinforcement with silica-based fillers. Three types of fillers were studied: synthetic amorphous silica, milled fiberglass, and geothermal scale powder. Particle size and aspect ratio of fillers were estimated from scanning electron microscopy (SEM) images, while chemical structure was characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Fillers were added to SLA resin at 0, 10, and 20 vol%. Hardness and flexural properties of SLA composites are higher than unfilled resin. Moreover, both hardness and flexural properties of SLA composites are improved according to type (milled fiberglass > synthetic amorphous silica > geothermal scale powder) and loading (20 vol% > 10 vol%). The observed effect of filler type and loading on hardness and flexural properties of SLA composites is due to aspect ratio, intrinsic properties and dispersion of filler.

Abstract: Presented work is focused on the time depend wettability deterioration of plasma treated polymeric macro-fibers. The commercial fibers designed especially for reinforcement of concrete composites – Concrix ES (made from polyolefin) and BeneSteel (polyethylene and polypropylene mixture) were surface modified by oxygen cool low-pressure coupled plasma to attain their water wettability enhancement. The wettability development of thus treated fibers was observed through contact angle sizes between fiber surfaces and distilled water using a direct horizontal optical static method. Contac angle measurements were realized (i) immediately, after (ii) 1 day, (iii) 7 days and (iv) 30 days over the treatment execution, while fibers were stored on the air on standard laboratory condition in the meantime (temperature ~22 °C, moisture ~50 %). Both, the treated Concrix ES and BeneSteel fibers exhibited significant wettability increase. The enhanced wettability of modified fibers stayed approximately constant even after 30 days over the treatment execution in the case of BeneSteel, while in the case of Concrix ES the wettability decreased almost to the reference (no treated) samples, respectively.

Abstract: Short glass fiber reinforced polypropylene films with different fiber content were produced by film extrusion using a coat-hanger die. Despite the elongation flow in the coat hanger die, a highly aligned fiber orientation in processing direction was observed. The typical increase of the tensile modulus with increasing fiber content was obtained whereas the tensile strength dropped down by incorporating small amounts of fibers. With 50 wt% fiber content the level of neat polymer film is reached again. The absence of a packing and consolidation step in compare to molding processes leads to a relative high surface roughness which increases the appearance of cracks in case of a load. For further improvement an additional pressure-related calendaring step is useful.

Abstract: Muti-wall carbon nanotubes (MWCNTs) were functionalized by grafting polyimide (PI) on their surface via Friedel-Crafts acylation. The functionalized MWCNTs (f-MWCNTs) showd less damages than unfunctionalized ones. The partially imidized polyamide acid as-spun fibers containing f-MWCNTs were prepared by wet spinning, and the final PI/f-MWCNTs composite fibers were obtained by heat treatment. The tensile strength of the PI based composite fiber containing 1.0 wt% f-MWCNTs was 818.3 MPa and the Young’s modulus was 9.26 GPa, which were about 81% and 88% higher than those of pure PI fiber, respectively. Besides, the thermal stability of PI/f-MWCNTs composite fibers was obviously improved.

Abstract: Carbon black and silica have been used as the main reinforcing fillers that increase the usefulness of rubbers. In this work the effect of carbon black (high abrasion furnace)/silica hybrid fillers on the mechanical properties, crosslink density and morphological behaviour of ethylene vinyl acetate (EVA) was investigated. EVA reinforced with 0/50, 10/40, 20/30, 30/20, 40/10 and 50/0 phr of carbon black (CB)/silica hybrid filler. The total hybrid filler is kept constant at 50 phr (parts per hundred rubbers) and six different compounds were prepared. EVA, CB and silica followed by compounding on a two roll mill and molding at 180°C and 20 megapascal (MPa) pressure. The mechanical properties such as tensile & tear strength, elongation at break and 100% modulus have been measured at 23°C on universal testing machine. Abrasion resistance, hardness and rebound resilience are studied using DIN abrader, Shore A durometer and vertical rebound resilience respectively. The tensile strength, modulus, tear strength, abrasion resistance, hardness and crosslink density increased with the CB filler content in hybrid filler, reached the maximum value at 50 phr of high abrasion furnace carbon black. Morphological properties of composites were evaluated by scanning electron microscopy analysis.

Abstract: The potential of natural resources such as pumice and sisal fiber for simple housing structural components is investigated in this research. Behavior of sisal fiber reinforcement of lightweight concrete beam under flexural loading was examined. The purpose of this study is to identify the prospect of sisal fiber as a replacement of steel bar reinforcement for structural element. The variations of reinforcement ratios were considered in order to optimize the performance of sisal fiber reinforcement. Twelve beam specimens size 100 x 150 mm with clean span of 1.5 m were examined in this investigation. Four variations of beam reinforcement were explored consist of 3 sisal fiber variation and 1 steel reinforcement as a control; where every variation was presented with three samples. Enerpac hydraulics Jack with 50 ton capacity connected to the load cell was operated as a source of loading. LVDT was fitted in the mid-span to measure vertical deflections during the loading. Test results indicated that the crack moment experiments were higher than the crack moment calculations. The valued were 1.44, 1.52, and 2.72 higher for sisal fiber reinforcement of B-LF, B-MF and B-HF, respectively. Whilst for steel reinforcement of B-LS the valued were 3.32 higher. Observation results also indicated that the moment resistant capacities of the specimens were twice higher compare to the calculated moment capacity. However, The lowest sisal reinforcement (B-LF) has only about 10% different service moment compare to the steel reinforcement (B-LS) where they both have equal ρ = 1.206 %. This indicate that the use of sisal fiber have considered as insignificant different service moment capacity to the steel reinforcement.