Reinforcement Interface Research Articles

Microstructure and mechanical behavior of magnesium rare earth alloy nanocomposite fabricated by hybrid casting method

The metal matrix nanocomposites (MMNC) were fabricated using matrix material - rare earth magnesium (ZE41) alloy and beta silicon carbide nanoparticles as reinforcements. It was successfully developed by using a hybrid casting method, which included a double stirring as well as ultrasonication process. The reinforcing material is 0.75 wt% of beta-silicon carbide nanoparticles (β-SiCp) with the particle size ranging from 45 to 60 nm, has achieved even spread throughout the matrix. The base and ZE41/0.75 wt% SiC MMNC were direct aged at T5 heat treatment condition. The samples were material characterized using an optical microscopy (OM) and a field emission scanning electron microscope (FESEM). The MMNC showed 23.93% improvement in ultimate tensile strength (UTS) values when compared with as-cast monolithic material and the MMNC heat treated by T5 condition showed 15.10% improvement in the UTS values when compared to the base ZE41 treated with T5 condition. The grain size reduction of composite was evident in the optical micrographs, which contributed in the increase in tensile strength. The SEM analysis on fractured surfaces revealed that the crack initiation was from the matrix reinforcement interface and the mode of failure in the composite was brittle. The effect of double stir ultrasonication for successfully fabricating the MMNC and comparing it with the base alloy was the main aim of this work.

Enhancing structural stability and physical properties of silver added iron-MWCNT composite prepared by high energy ball milling and spark plasma sintering

This paper reports the beneficial effect of silver addition (~0.1 wt%) on the structural stabilization of multiwalled carbon nanotube (MWCNT) reinforced in iron matrix by way of high energy ball milling (HEBM) and spark plasma sintering (SPS). Silver added Fe - x wt% MWCNT (x = 1, 2, 3 and 4) composites were prepared by HEBM followed by SPS. Structural characterization of silver bearing composite powder and its sintered mass was carried out by XRD. The structural damage of MWCNT after HEBM was assessed by Raman Spectroscopy. As a support, Fourier Transform Infrared (FTIR) spectroscopic study was used to look into the bonding characteristics. Detailed microstructural studies by optical, field emission scanning (FESEM) and high-resolution transmission electron microscopy were employed to further assess structural stabilization and evolution of micro constituents during processing. Finally, magnetic and electrical properties of the composites were determined.It was revealed that minor addition of silver aids in restoration of the structural integrity of MWCNT in iron matrix composite. Moreover, it was noted that silver added composite could achieve a contamination free matrix–reinforcement interface. It is propounded that silver atoms tether MWCNT surface and behave like coating over MWCNTs. Conductivity of silver doped iron-4 wt% MWCNT composites exhibited a conductivity value higher than that of electrical conductivity grade (EC grade) aluminum. Saturation magnetization of silver doped Fe-MWCNT composite was increased by 25% over pure iron at 3 wt% MWCNT. The observed improvement in properties of composite is ascribed to tethering of silver particles at MWCNT surface; this gave rise to better interfacial bonding and the physical properties.

Characterization, Prediction, and Optimization of Dry Sliding Wear Behaviour of Al6061/WC Composites

This investigation deals with an experimental analysis done on dry sliding wear behaviour of aluminium matrix composites reinforced with WC (tungsten carbide) particles. The composites were processed through powder metallurgy (P/M) technique with the addition of various fractions of WC particles. Results of scanning electron microscope (SEM) examinations and XRD analysis showed better dispersion of the reinforced particles and good matrix–reinforcement interface integrity. The results of dry sliding wear tests conducted on composite samples were analysed for varied conditions of WC volume fraction and sliding distance. The wear properties of composites were significantly affected by the variation of the WC volume percentage (5–25%). Smother wear tracks and closely spaced grooves on the composite pin worn surfaces were found for higher volume fraction WC particles. The postulated regression models for prediction of wear behaviour approximate their experimental values with an estimated error from 1.97 to 6.56%. The derived optimal wear properties to improve the sliding wear performance of the composites through a novel hybrid (GRA integrated TLBO) multi-response optimization approach are in a closer correlation with the experimentally measured values. Also, wear performance predicted values through hybrid multi-response optimization are closer to their validation experimental results compared with the predicted values through TLBO and GRA approaches. The derived optimal set of wear properties are 1.921 mm3/m wear rate and 0.292 coefficient of friction at 15 vol% of WC, 10 N applied load, 775 m sliding distance, and 1 m/s sliding velocity. The surfaces of the composite samples tested at the derived set of optimal wear behavioural parameters were also examined through SEM and analysed.

Vibration and Wear Characteristics of Aloevera/Flax/Hemp Woven Fiber Epoxy Composite Reinforced with Wire Mesh and BaSO4

ABSTRACT These articles presents an experimental investigation on mechanical, vibration, and wear behavior of (aloevera/flax/hemp/wire mesh/BaSO4) laminated composite. The mechanical characterization was performed with ASTM standard specimens. The free vibration performance was analyzed under two clamping conditions and boundary conditions (clamp-clamp & clamp-free). The wear test trails were accomplished using a pin on disc at different process parameters like sliding speed (3–5 m/s), sliding distance (1000 m) and applied load (10–30 N) under sliding dry environment at room temperature of 28 ± 5◦C. The scanning electron microscopy was used to examine the interaction between the matrix and reinforcement interface after the failure. The experimental results revealed that the addition of wire mesh and BaSO4 filler in the fabricated composite Aleovera+Hemp+Wiremesh+Flax+Aleovera+BaSO4 composite (C4) increased the tensile strength by 8.68% compared to Aleovera+Hemp+Wire mesh+Flax+ Aleovera (C3) composite and it also depicts that the addition of wire mesh and BaSO4 as reinforcement has improved 5.42% of flexural strength compare to Aleovera+Hemp+Flax+Aleovera+BaSO4 composite (C2). The addition of BaSO4 improved the hardness in both C2 and C4 composites. The 5% addition of BaSO4 enhanced the natural frequency of the composites. Among the composites, the C4 has shown the highest coefficient of friction during the experimental trials.

A Study on Particle Weight Fraction and Extrusion on the Mechanical Properties and Microstructural Evaluation of Al-Cu/Fly Ash Composite

Fly ash is the waste product coming out from thermal power plant is an increasingly urgent problem due to its storage and disposal. At the same time Metal Matrix composites (MMCs) reinforced with ceramic particles such as SiC, Al2O3 and B4C has their partial use in engineering application due to higher cost. The study focuses on the Al-Cu alloy reinforced fly ash particles produced by stir casting followed by hot extrusion. The composites produced by incorporation of fly ash reinforcements by varying 2%, 4%, 6%, 8% and 10wt% is hot extruded with an extrusion temperature of 400°C, extrusion rate of 5mm/s and extrusion ratio of 1.77:1. The extrusion composites have been evaluated based on the investigation of mechanical properties and microstructure. The results showed that, the amount of porosity increased with increasing the percentage of fly ash reinforcements in stir cast and the extruded composites is almost gratis from porosity. Hardness and tensile strength of composites increases with increases in percentage of reinforcement by stir and extruded composites. But extruded composites show better mechanical properties than stir cast composites. Wear test under different loads and for 45 minutes duration have been conducted on both cast and extruded composites. The worn surfaces have been observed under Scanning electron microscope (SEM) to understand the mechanism of wear. Extruded composites possess lower wear rates under all studied loads with constant sliding velocities when compared with cast composites. Microstructural study using SEM shows that the fly ash particulates in the molten matrix forms strong matrix reinforcement interface and their distribution might have led to the increase in mechanical properties of the composites due to fine grain structure during extrusion and dislocation density in the matrix.

Effect of Age Hardening Treatment on the Corrosion Resistance of AA6061, SiC and Fly ash Powder Metallurgy Composites

Identification of corrosion resistance through electrochemical methods for silicon carbide and fly ash reinforced metal matrix composites in automobiles is mandatory. In the present work, the composite developed through powder metallurgy process is studied for corrosion resistance. The effect of constant proportion of fly ash (10% wt.) and varying proportion of silicon carbide (5% wt., 10% wt., 15% wt.) on electrochemical corrosion resistance of aluminium alloy AA6061 base material is investigated. The sintered hybrid composites as well as age hardened composites particles were examined under Scanning Electron Microscope (SEM-EDS) to verify the elemental nature of the corroded material. The potentiodynamic polarization technique based corrosion rate measurements exhibited localized corrosion in the sintered hybrid composites. Severely corroded material closer to interface of reinforcements and matrix was observed in addition to attack on the matrix. Age hardening treatment improved the corrosion resistance of hybrid composites in which only general corrosion was observed.

Effect of short carbon fiber content on SCFs/AZ31 composite microstructure and mechanical properties

The magnesium matrix composites containing various content of short carbon fibers reinforcement (SCFs/AZ31) were fabricated by ball milling and solid state synthesis. Morphologies of composite, distribution of SCFs, and interface of matrix and reinforcement were analyzed. The effect of SCFs content on the mechanical properties of the composite was studied. When the content of SCFs is less than 3%, SCFs uniformly distribute in the composite and promote dynamic recrystallization, the refining effect of grain is obvious, and meanwhile SCFs can play the effect of load transfer to the matrix. With the increase of SCFs content, the degree of aggregation increases, the grain size of composite increases and mechanical properties decrease. For mechanical performance, the strengthen effects was firstly enhanced and then deteriorated with increasing SCFs content. The main strengthening mechanisms of composite are grain refinement strengthening, thermal residual stress strengthening, and load transfer strengthening.

Durability Test on the Bond Strength between SFRP Layer and Masonry Surface

The mechanical properties of masonry structural members strengthened by FRP (Fiber Reinforced Polymer) are affected by the bond strength of the reinforcement interface, in addition to the strength of the material FRP itself. This project is aimed at the new technology of Sprayed Fiber Reinforced Polymer Composites (SFRP), which is currently attracting attention. The bond strength between SFRP layer and masonry surface under high-humidity condition during strengthening construction and dry-wet cycle conditions after reinforcement were studied by experimental method. Different masonry substrates and different reinforcement methods were set as the test parameters. It is concluded that, compared with the currently used GFRP (Glass Fiber Reinforced Polymer) sheets reinforcement method, the SFRP reinforcement method has an significant improvement in the bond strength and the durability.

Assessing the quality of concrete – reinforcement interface in Self Compacting Concrete

Research has shown that even self-compacting concrete (SCC) mixtures can exhibit the so-called “top-bar effect” which impacts bond and anchorage. Several instances of conflicting results have nevertheless been published regarding interfacial bond between self-compacting concrete and steel reinforcement. The scope of this paper is to present an experimental methodology for assessing the quality of the interface between self-compacting concrete and ribbed reinforcement. For this purpose, seven different self-compacting and four normally vibrated concrete (NVC) mixtures with diverse rheological characteristics were examined. Digital Image Analysis of cut sections containing reinforcing bars at different cast-heights was used as a diagnostic tool. The study illustrates that the quality of the interface is strongly affected by the viscosity of the SCC mixtures and by the slump values in NVC. Self-compacting concrete mixtures show greater inherent robustness and cohesion at the steel–concrete interface compared to conventionally vibrated concretes.

Case study on the model test of staggered-jointed assembling shield tunnel structure reinforced by bonded steel plates under large deformation

Transverse large deformation is one of the main diseases of metro shield tunnels, gravely threatening the safe operation of tunnel structure. Reinforcing bonded steel plates is a primary means for repairing excessively deformed tunnels. Nevertheless, evaluations and analyses on the reinforcing effect of bonded steel plates are currently unclear. Therefore, destruction tests were performed on the tunnel without the reinforced structure and on the excessively deformed tunnel with the reinforced structure respectively with the similar model test method in this paper, so as to analyse deformation behaviours and failure modes of segment lining and compare the reinforcing effect. Test results show that the carrying capacity of the tunnel structure can still be improved through reinforcing the staggered-jointed assembling shield tunnel with bonded steel plates under large deformation; also, the reinforcement of bonded steel plates can effectively prevent the tunnel from deforming. The failure mode of the reinforced structure consists of the reinforcement interface debonding failure and steel plate bending failure. To be specific, the debonding failure being frequently detecting in seams is composed of slab staggering and expansive debonding. Research achievements in this paper may provide theoretical and data support for similar reinforcement projects.

Electrochemical impedance behavior of concrete containing natural zeolite and copper slag

The current study assesses the electrochemical impedance behavior of binary and ternary concrete mixtures containing natural zeolite and copper slag as supplementary cementitious materials (SCMs). To this aim, several mixtures were made by replacing up to 30% by weight of Portland cement with natural zeolite or a combination of natural zeolite and copper slag. A test setup was made and suitable equivalent circuits were used to measure the electrochemical behavior of reinforced concrete specimens. Strength and transport properties of these mixtures were also measured. The results of this study revealed considerable improvement in the polarization resistance of steel–concrete interface and corrosion rate of reinforcement by use of natural zeolite and copper slag. The corrosion rate was reduced by almost 65% when 30% of Portland cement was replaced with supplementary cementitious materials. Transport properties were also improved by inclusion of SCMs.

Predicting the response of continuous RC deep beams under varying levels of differential settlement

This paper investigates the effect of differential support settlement on shear strength and behavior of continuous reinforced concrete (RC) deep beams. A total of twenty three-dimensional nonlinear finite element models were developed taking into account various constitutive laws for concrete material in compression (crushing) and tension (cracking), steel plasticity (i.e., yielding and strain hardening), bond-slip at the concrete and steel reinforcement interface as well as unique behavior of spring-like support elements. These models are first validated by comparing numerical predictions in terms of load-deflection response, crack propagation, reaction distribution, and failure mode against that of measured experimental data reported in literature. Once the developed models were successfully validated, a parametric study was designed and performed. This parametric study examined number of critical parameters such as ratio and spacing of the longitudinal and vertical reinforcement, compressive and tensile strength of concrete, as well as degree (stiffness) and location of support stiffness to induce varying levels of differential settlement. This study also aims at presenting a numerical approach using finite element simulation, supplemented with coherent assumptions, such that engineers, practitioners, and researchers can carry out simple, but yet effective and realistic analysis of RC structural members undergoing differential settlements due to variety of load actions.

Consolidated Composites with Natural Textile Fabrics

The problems raised by the usage and manufacturing of composite materials are numerous, starting from the prediction of the properties of a new material and going to the determination of some procedures, methods or materials that will eliminate some disadvantages. Because there is a wide variety of the materials already used, with a great diversity of characteristics and properties in a wide range of combinations involving various effects (mechanical, physical, chemical and so on), there have also been a number of issues that need to be addressed differently. The general properties of the composites are decisively influenced by the nature and proportions of constituents, by the nature of the matrix–reinforcement interface, the volume fraction of reinforcement in the composite and its orientation, and the reinforcing component architecture. This paper addresses a major research area of great interest and relevant in the present context, the emphasis is increasingly on environmental protection, saving material resources by developing and creating new manufacturing and execution technologies to be used in composite materials. The paper presents the ways of producing composite materials reinforced with textile materials made of natural fibres, as matrix being used polyester resins. Considering the quantitative availability of these textile fabrics, the experiments take into consideration variants of the bast fibers (flax, hemp and/or jute) for the reinforcement component.

Effect of Maximum Aggregate Size on the Bond Strength of Reinforcements in Concrete

The bond between reinforcements and concrete is the only mechanism that transfers the tensile stresses from concrete to reinforcements. Several factors including chemical adhesion, roughness and reinforcement interface and bar bearing affect the bond strength of reinforcements with concrete. This work was carried out considering another varying factor which is maximum aggregate size. Four mixes of concrete with similar compressive strengths but different maximum aggregate sizes of 25.4mm, 19.05mm, 12.7mm and 9.53mm were used with the same bar size of 16mm. Compressive strength, splitting tensile strength and bond strength for each concrete mix were studied. Test results depict a slight increase in compressive and splitting tensile strength with decrease in maximum aggregate size. The bond strength remained at the same level with decrease in maximum aggregate size except at maximum aggregate size of 9.53mm when there was a drop in bond strength, despite better compressive and splitting tensile strengths. ACI-318 and FIB-2010 codes equation for bond strength calculation work well only when the maximum aggregate size is 12.7mm and above. Therefore, maximum aggregate size is critical for bond strength when smaller size aggregates are used.

Effect of patch repair and strengthening with EBR and NSM CFRP laminates for RC beams with low, medium and heavy corrosion

The experimental results on the effectiveness of patch repair and FRP bonded laminates to retrofit reinforced concrete beams with corrosion damage are discussed in this paper. The uncovering of the damaged concrete cover provides a more accurate assessment of the corrosion degree, as the actual mass loss of reinforcement can be better calibrated. The mass loss of the tensile reinforcement varied at approximately 7.5%–24%. The necessity of the removal of the cracked concrete substrate, treatment of corroded reinforcement and repair by patching with a polymer modified mortar is highlighted. Two different strengthening techniques are implemented, of externally bonded EBR or NSM Carbon FRP laminates, having equivalent axial rigidity. CFRP wraps were also applied for shear strengthening to replace corroded stirrups. The load-deflection curves showed that the effect of corrosion on load bearing capacity and bond between the concrete and steel was detrimental for high mass losses. A satisfactory force transfer through the old and patch repaired concrete and through repair mortar and CFRP reinforcement interface was noted. The shear strengthening not only prevented the debonding of the EB laminate at the end but also improved the bond performance between the laminate and concrete, especially for the high corroded beam.

Effect of high energy ball milling on the structure of iron — multiwall carbon nanotubes (MWCNT) composite

High energy ball milling is employed to produce iron matrix- multiwall carbon nanotube (MWCNT) reinforced composite. The damage caused to MWCNT due to harsh ball milling condition and its influence on interfacial bonding is studied. Different amount of MWCNT is used to find the optimal percentage of MWCNT for avoidance of the formation of chemical reaction product at the matrix - reinforcement interface. Effect of process control agent is assessed by the use of different materials for the purpose. It is observed that ethanol as a process control agent (PCA) causes degradation of MWCNT reinforcements after milling for two hours whereas solid stearic acid used as process control agent, allows satisfactory conservation of MWCNT structure. It is further noted that at a high MWCNT content (~ 2wt.%), high energy ball milling leads to reaction of iron and carbon and forms iron carbide (cementite) at the iron-MWCNT interface. At low percentage of MWCNT, dissolution of carbon in iron takes place and the amount of reinforcement in iron matrix composite becomes negligibly small. However, under the present ball milling condition (ball to metal ratio~ 6:1 and 200 rpm vial speed) iron-1wt.% MWCNT composite of good interfacial bonding can retain the tubular structure of reinforcing MWCNT.

Mechanical Properties of Coir/ G Lass Fiber Epoxy Resin Hybrid Composite

Sustainable development and environmental awareness directed researcher to focus on naturally occurring resources. Leading to this there is a growing trend for usage and experimenting on Natural fiber reinforced polymer composites. Fiber reinforced polymer composites shows many qualities which include low weight, easy manufacturability, biodegradability, high strength to weight ratio, low cost of production etc. Though natural fiber possesses good properties yet their affinity towards water and improper matrix interface bonding are major concern. Due to these challenge strength of composite is considerably affected. Uses of synthetic fibers do not impose any challenge as the natural fibers, but they are non-biodegradable and cost more than natural fiber. In present work properties of both synthetic and natural fibers are utilized in a way to improve the mechanical properties. For this purpose, naturally occurring coir fiber and synthetic glass fiber mats are used as reinforcement while thermosetting polymeric resin Epoxy is used as matrix material. To decrease moisture absorption behaviour of coir fiber, it is chemically treated with Sodium hydroxide. This chemical treatment reduces the affinity of fiber towards material and increases surface roughness thus results in better matrix reinforcement interface bonding. Short coir fiber /glass fiber mat hybrid composite is fabricated by hand-layup method. The study confirms that the mechanical properties of the composites are varies with volume fraction and fiber length of the fibers.

Lateral bearing capacity and failure mode of geosynthetic-reinforced soil barriers subject to lateral loadings

In addition to self-weight and vertical surcharge, geosynthetic-reinforced soil (GRS) structures have recently been used as barriers to resist lateral forces from natural disasters, such as floods, tsunamis, rockfalls, debris flows, and avalanches. The stability of such structures subject to lateral loading is often evaluated using conventional external stability analyses with the assumption that the reinforced soil mass is a rigid body. However, this assumption contradicts the flexible nature of reinforced soil. In this study, finite element (FE) models of back-to-back GRS walls were developed to investigate the performance of GRS barriers subject to lateral loading. The FE analysis results indicated that the failure mode and lateral bearing capacity of GRS barriers depend largely on the aspect ratio (L/H: ratio of wall width to wall height). When 0.5 < L/H < 1.0, the GRS barriers would fail internally because of internal sliding along the soil–reinforcement interface at the loading side and the active soil failure at the opposite side. When 1.0 < L/H < 3.0, bottom sliding failure would occur along the foundation–reinforcement interface. When L/H > 3.0, passive soil failure would occur within the GRS barriers at the side subject to the lateral force. The ultimate lateral bearing capacity of GRS barriers increased with an increase in L/H: the ultimate lateral capacity factor NL was 1.4–20.1 times Ka for L/H = 0.5–3.0. In addition to the effect of L/H, the numerical results indicated that the backfill friction angle ϕ, unit weight γ, and reinforcement vertical spacing Sv considerably affected the lateral bearing capacity of GRS barriers. A hypothetical case study of a GRS barrier against a tsunami force is provided, and a viable method using vertical preloaded soil anchors for improving wall lateral capacity is analyzed and discussed.

A Review on &lt;i&gt;In Situ&lt;/i&gt; Synthesis of Al/TiC and Al/SiC-Composites

The in-situ synthesis of ceramic particles in Al-matrix composites gives an uniform and homogeneous microstructure. The matrix reinforcement interface is compatible with the matrix, interface is clean and provides good interface bonding. The evenly distributed sub micron sized reinforcement particles in Al-matrix enhances the strength and toughness of the composite. The formation of particle clusters and agglomerations are minimized or eliminated by suitably choosing the in-situ process parameters. Large particles and agglomerate are easily fractured where as evenly distributed fine particles are resistant to crack propagation and improves the strength of the composites. The problem encountered with the formation of secondary intermetallic Al3Ti and Al4C3 phases are addressed.

Moisture Reduction Factors for Shear Strength of Unsaturated Reinforced Embankments

AbstractThis paper describes the construction and testing of six 1-m-high model embankments constructed at three different gravimetric water content (GWC) values to study their performance and to validate a set of moisture reduction factors (MRFs) introduced by the authors in their recent studies. The earlier MRF values were obtained from a series of pullout and interface shear tests on the same soil and reinforcement materials. The MRF in this study is defined as the ratio of soil-reinforcement interface shear strength at an increased GWC value [e.g., optimum moisture content (OMC) + 2%] to the shear strength at OMC − 2% representing construction conditions. Therefore, MRF values can be used to account for an anticipated reduction in the shear strength of the soil-geotextile reinforcement interface caused by wetting in the stability analysis and design of reinforced soil structures constructed with marginal soils. The embankment models were built using a lean clay (CL) at the GWC values ranging between O...