Composite Strips Research Articles

Application of powder metallurgy and hot rolling processes for manufacturing aluminum/alumina composite strips

In this study, aluminum matrix composites (AMC) with 2, 4, 6 and 10wt% alumina were produced using powder metallurgy (PM), mechanical milling (MM) and vacuum hot pressing (VHP) techniques; then, this was followed by the hot-rolling process. During hot rolling, AMCs with 6 and 10wt% Al2O3 were fractured whereas strip composites with 2 and 4wt% Al2O3 were produced successfully. Microstructure and mechanical properties of the samples were investigated by optical and scanning electron microscopes and tensile and hardness tests, respectively. Microscopic evaluations of the hot-rolled composites showed a uniform distribution of alumina particles in the aluminum matrix. It was found that with increasing alumina content in the matrix, tensile strength (TS) and hardness increased and the percentage of elongation also decreased. Scanning electron microscope (SEM) was used to investigate aluminum/alumina interfaces and fracture surfaces of the hot rolled specimens after tensile test. SEM observations demonstrated that the failure mode in the hot-rolled Al-2wt% Al2O3 composite strips is a typical ductile fracture, while the failure mode was shear ductile fracture with more flat surfaces in Al-4wt% Al2O3 strips.

Processing of nanostructured metallic matrix composites by a modified accumulative roll bonding method with structural and mechanical considerations

Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. Al/B4C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B4C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.

Continuous Production of Metal Matrix Composites from the Semisolid State

Continuous strip metal matrix composite (MMC) casting of 0.3 mm diameter hard-drawn stainless steel (316L) wire in a quasi-eutectic SnPb (64Sn36Pb) matrix was performed by a two-roll melt drag processing (TRMDping) method, with the wire being dragged through a semisolid puddle with a fibre contact time of approximately 0.2 s. A slag weir placed at the nozzle contained two wire guide holes: one located near the upper roll, and the other located between the rolls. A successful continuous composite strip casting with good fibre alignment was achieved by inserting and embedding the wire into the matrix using the guide hole between the rolls. Degeneration of eutectic/dendrite structures led to the formation of globular structures. The occurrence and formation mechanisms of cracks, de-lamination and voids in the matrix were discussed. TRMDping is economically viable and has significant benefits over other MMC fabrication methods.

Torsion of a layered composite strip

This paper examines the problem of the torsional loading of a composite strip composed of eleven layers of unidirectionally reinforced elements that are fully bonded. The shear moduli are obtained from the experimental torsional stiffnesses (T/ϕ) and data reduction techniques based on the orthotropic rectangular strip torsion model by Lekhnitskii. The stacking of laminae is also used to construct a computational model of the strip.

Unusual Reversible Photomechanical Actuation in Polymer/Nanotube Composites

An azobenzene-containing liquid crystalline polymer/carbon nanotube composite strip was synthesized that shows rapid and reversible deformation under UV irradiation. The aligned nanotubes also provide the composite with much higher mechanical strength than pure liquid crystalline polymers and a very high electrical conductivity.

Analytical beam theory for the in-plane deformation of a composite strip with in-plane curvature

The variational-asymptotic-method (VAM) provides a mathematically rigorous way to reduce a three-dimensional elasticity formulation to a one-dimensional beam theory without ad hoc assumptions. In this work, the VAM is employed to develop a beam theory to analyze the in-plane deformation of a laminated strip-beam with initial in-plane curvature. The cross-sectional stiffness constants and recovery relations for stress and strain are presented as analytical expressions. For the case of zero initial curvature, consistency of the expressions with those of plate theory is demonstrated. For strip-beams with initial curvature in the in-plane direction, results obtained show explicit dependence on the curvature. Results are verified by comparison with those obtained from VABS, the accuracy and consistency of which with three-dimensional finite elements has been reported in several published works. In addition to the internal consistency check this work provides and its utility in helping to validate VABS (which is based on the principles of VAM), it is hoped that the results obtained herein, since they are all analytical expressions, will help researchers and engineers validate the effect of initial curvature in their beam theories, whether existing or new.

Fabrication and characterization of HCl‐treated clinoptilolite filled ethylene vinyl acetate composite films

AbstractAs received and HCl treated Clinoptilolite (C)‐ethylene vinyl acetate (EVA) composites were prepared via the melt‐mixing technique, and extruded through a single‐screw extruder to obtain composite strips with an average thickness of 0.5 mm. The films were then characterized for their morphological, structural, thermal, and mechanical properties. Optical micrographs show that at higher C loading, the particles form large agglomerates, resulting in the formation of voids on the surface of the films. With increasing zeolite loading, the films become brittle, resulting in reduced Young's modulus. Acid treatment of the C tends to affect the crystal structure of the zeolite, resulting in poor tensile properties of the HCl‐treated zeolite‐filled EVA films. Addition of the zeolite also increased the crystallinity of the structure, acting as a nucleating agent in the EVA crystallization. Modeling of the tensile yield data with Pukanszky model indicate that there is poor interfacial adhesion between the polymer matrix and the filler particles. Thermal characterization studies showed that addition of the zeolites retarded the onset degradation temperature of EVA. However, degradation temperatures including Tmax and the final decomposed temperature were increased, suggesting improved thermal stability due to reduced inter‐chain mobility in the composite materials as a result of increased zeolite loading. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Dynamics of FRP strengthened unidirectional masonry walls, II: Experiments and comparison

In this part of the paper, the dynamic out-of-plane behavior of a unidirectional strengthened masonry wall is studied experimentally. The experimental phase focuses on shake-table testing of a full-scale masonry wall strengthened with carbon fiber reinforced composite strips. The tested wall is subjected to different combinations of in-plane compression and out-of-plane excitation. The dynamic behavior of the wall is monitored with emphasis on the global out-of-plane displacements and accelerations as well as on the localized displacements and strains near the mortar joints. The experimental results are also used for the assessment of the finite element model developed in part I of the paper. The experimental results, the numerical analysis, and the comparison between the two throw light on the global and local aspects of the dynamic response. The numerical model allows for further study of local-scale results, which cannot be monitored experimentally. In particular, the dynamics of the shear and peeling stresses at the adhesive layers are examined. The comparison of the experimental results with ones obtained for the same wall before strengthening demonstrate the potential of the method and its impact on the dynamics of the masonry wall.

Delamination detection in composites using wave modulation spectroscopy with a novel active nonlinear acousto-ultrasonic piezoelectric sensor

A novel structural health monitoring (SHM) methodology, based on nonlinear wave modulation spectroscopy, is presented for the detection of delamination cracks in composites. The basic element is a novel active nonlinear acousto-ultrasonic piezoelectric sensor enabling low-cost and wide-frequency operational bandwidth. The active sensor configuration involves two piezoceramic wafer actuators, each one excited with a low- and high-frequency signal respectively, and a piezoceramic sensor, all permanently bonded on the tested structure. Experiments are conducted on two sets of composite strips containing delamination cracks of different sizes. Measured results illustrate first the efficiency of the nonlinear ultrasonics methodology to detect delamination cracks, as well as, the potential and benefits of the new active sensor. The sensitivity of the active sensor response to the crack size and the applied high-frequency carrier signals at the actuators, vary at various frequency and voltage levels indicating the appropriate testing setup. Additionally repeatability of proposed SHM methodology is studied.

Microstructure and mechanical properties of Al/Al2O3 MMC produced by anodising and cold roll bonding

In the present paper, Al–Al2O3 composite strips are produced by the cold roll bonding process of anodised aluminium strips. This technique has the flexibility to control the volume fraction of metal matrix composites by varying the oxide layer thickness on the anodised aluminium strip. Microhardness, tensile strength and elongation of composite strips are investigated as a function of quantity of alumina and the applied production method. It is found that higher quantities of alumina improve microhardness and tensile strength, while the elongation value decreases negligibly. Furthermore, prerolling annealing is found to be the best method of producing this composite via the cold roll bonding process. Finally, it is found that both monolithic aluminium and aluminium/alumina composite exhibited a ductile fracture, having dimples and shear zones.

Investigation of nanostructured Al/Al2O3 composite produced by accumulative roll bonding process

In this study, the accumulative roll bonding (ARB) process was used for manufacturing nanostructured aluminum/15vol.% alumina composites. Microstructural characterization by transmission electron microscopy (TEM) identified the severe shear deformation, however, the grain growth was restrained by particles of oxide film and recrystallization produced the nanograins with an average size <100nm after the 13th cycle of composite strip. The findings also indicated that the presence of large particles and deformation structure in the vicinity of the particles made the particle stimulated nucleation (PSN) of recrystallization possible. The Williamson–Hall method was used to calculate the grain size from the X-ray diffraction (XRD) patterns, which were 150nm for pure aluminum and 63nm for aluminum/alumina composite after 13 cycles of the ARB process. The findings also revealed that after the first cycle, hardness rapidly increased, then dwindled, and finally reached saturation as the number of ARB cycles increased.

Effect of Si Content of Al-Si Matrix on Roll Cast Wire Inserted Strip

Effect of Si content of Al-Si matrix on roll cast wire inserted strip was investigated in this paper. 99.5%Al, Al-4%Si , Al-12%Si and Al-18%Si were used as matrix. Slit depth of the nozzle, superheat of melt, wire-diameter and roll speed was chosen as the casting parameters, too. Addition of the Si was useful to prevent the reaction between the matrix and the wire. A downward melt drag twin roll caster could cast the wire inserted strip of the Al-Si matrix of which Si content was ranging up to18%. Composite strip, which matrix was hyper eutectic Al-18%Si, could be cast at the speeds up to 20m/min. The gap between the wire and matrix became thin when the superheat was high. When the slit depth of the nozzle was too shallow, the wire could not be inserted in the strip. The thickness of the wire inserted strip became thinner as the roll speed became higher.

The thermal problem of friction for a three-element tribosystem with composite strip

The distribution of a non-stationary temperature field in a three-element tribosystem has been studied. It is assumed that the heat is generated by friction during uniform sliding on the surface of contact of the homogeneous top semi-space and a composite strip deposited on a semi-infinite foundation. The thermal contact of a top semi-space and a composite strip is imperfect, i.e. the jump of the temperatures takes place on the contact surface. The analytical solution of a thermal problem of friction for such a tribosytem has been found by means of Laplace integral transform method. The influence of the geometrical sizes of components of a composite and their physical properties on temperature in tribosystem has been investigated.

Piezoelectric Fiber Composite Strip Transducer Design Considerations for Generating Lamb Waves

Lamb waves have great promise among the various active monitoring schemes being researched for Structural Health Monitoring. Planar Lamb wave excitation using surface-bonded piezoelectric strips to function as comb transducers is investigated numerically for both the fundamental symmetric S0 and the antisymmetric A0 wave modes. This comb-type transducer is comprised of multiple piezoelectric elements, which are piezoelectric fiber composites sandwiched between electrodes. These transducer strips reduce the wiring requirements, can conform to curved surfaces, and the properties can be tailored to suit the application. Transducer variables are many; here fiber orientation, volume fraction, poling directions, and electrode locations are investigated. Specifically, piezocomposite properties are estimated through micromechanical modeling for input to finite element analysis of Lamb wave generation and propagation. For this multiphysics problem, the finite element analysis employs co-simulation using ABAQUS Standard and ABAQUS Explicit to simulate transient wave propagation from a strip transducer on a plate. In the finite element results, the amplitude of the Lamb wave at a prescribed distance from the transducer is evaluated to characterize the effectiveness of the composite comb transducer. Furthermore, results show that there are a number of cases where composite actuators provide a large amplitude response. After considering piezoelectric fiber direction, poling direction, and electric field direction, it appears that fiber, polarization, and activation electric fields through the thickness of the transducer represent the optimal design.

A damping mechanics model and a beam finite element for the free-vibration of laminated composite strips under in-plane loading

A theoretical framework is presented for predicting the nonlinear damping and damped vibration of laminated composite strips due to large in-plane forces. Nonlinear Green–Lagrange axial strains are introduced in the governing equations of a viscoelastic composite and new nonlinear damping and stiffness matrices are formulated including initial stress effects. Building upon the nonlinear laminate mechanics, a damped beam finite element is developed. Finite element stiffness and damping matrices are synthesized and the static equilibrium is predicted using a Newton–Raphson solver. The corresponding linearized damped free-vibration response is predicted and modal frequencies and damping of the in-plane deflected strip are calculated. Numerical results quantify the nonlinear effect of in-plane loads on structural modal damping of various laminated composite strips. The modal loss-factors and natural frequencies of cross-ply Glass/Epoxy beams subject to in-plane loading are measured and correlated with numerical results.

Composite Strips with Various Anchor Systems for Retrofitting Concrete Beams

This paper presents the performance of anchor systems for reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) strips. Nine simply-supported beams are tested with various anchor systems such as steel hooks, steel plates with anchor bolts, CFRP anchor plates, and near-surface mounted (NSM) CFRP strip. The effects of these anchors on the behavior of the retrofitted beams are discussed, including load-carrying capacity, failure modes, and ductility characteristics. Test results indicate that end-anchorage is an important parameter when a CFRP-retrofit design is conducted. Mechanical bolts and NSM CRFP anchors are recommended.

Casting of Net Inserted Aluminum Alloy Composite Strip

The net-inserted metal matrix composite strip could be cast by a twin roll caster at only one process. The net could be inserted in the strip or lower surface of the aluminium alloy strip. The matrix was Al-12mass%Si, and inserted net was made from SUS304 stainless steel. The diameter of the wire of the net was 0.29mm, and distance between the wires was 0.98mm (#20). The roll speed was 30m/min. The net was not reacted with the matrix, and there was not gap between the matrix and the net. The mechanical property of the net-inserted composite strip was affected by the direction of the wire of the net. When the angle of the wire against the tensile direction was 45 degrees, elongation of the composite became better than that of the matrix from 14% up to 23%. This reason was improvement of the local contraction of the composite strip. The net-inserted composite strip could be cold rolled. The reduction of the net was smaller than that of the strip. The reduction of the wire at rolling direction was larger than that of the wire at lateral direction.

Fabrication of MMC Strip by CRB Process

In this study, Al/Al2O3 composite strips were produced by the cold roll bonding (CRB) process. Microhardness, tensile strength, and elongation of composite strips were investigated as a result of changes in thickness reduction, quantity of alumina particles, and the production method used. It was found that higher values of reduction and quantities of alumina improved microhardness and tensile strength but decreased elongation. Furthermore, as-received strips exhibited the highest values for microhardness and tensile strength but the lowest for elongation. In contrast, post-rolling annealed strips recorded the lowest values for microhardness and tensile strength but the highest for elongation. Finally, it was found that pre-rolling annealing was the best method for producing this composite via the CRB process.

Fabrication and characterization of Al/SiC p composites by CAR process

Metal matrix composite strips are conventionally produced by strip casting technology and ingot casting followed by secondary mechanical processes. These composites usually suffer from poor distribution of the reinforcement particles, presence of porosity, and unsuitable bonding between reinforcement and matrix, which result in low mechanical properties. In order to eliminate these problems, CAR (continual annealing and roll-bonding) process was used in this study as a very effective method for manufacturing Al/SiC p composite strip. The microstructure of the fabricated composite after fifteen CAR cycles showed an excellent distribution of SiC particles in the aluminum matrix without any noticeable porosity. The results also indicated that when the number of cycles increases, the tensile strength of the produced composites improves, but their ductility and formability index decreases at first and then increases. The tensile strength and formability index of the fifteen cycle CARed composite were 1.58 and 1.23 times higher than those of the initial alloy, respectively, while the elongation value decreased slightly.

Tribocorrosion Behavior of Aluminum/Alumina Composite Manufactured by Anodizing and ARB Processes

In the present work, tribocorrosion behavior of Al/Al2O3 composite strips manufactured by anodizing and accumulative roll bonding (ARB) processes was investigated. The alumina quantity was 0.48, 1.13, and 3.55 vol.% in the aluminum matrix. Tribocorrosion experiments were conducted using a ball-on-plate tribometer, where the sliding contact was fully immersed in 1 wt.% NaCl solution. The composite sample served as a working electrode and its open circuit potential (OCP) was monitored before, during, and after sliding. In order to characterize the electrochemical behavior of the surface before and after sliding electrochemical impedance spectroscopy (EIS) was used and wear was also measured. Furthermore, the influence of quantity and distribution of reinforcement particles in the matrix on OCP and EIS was evaluated. It was found that the quantity, shape, size, and dispersion of alumina particles in the aluminum matrix strongly affected the measured tribocorrosion characteristics. The results showed that inhomogeneous, lower quantity, fine, and acicular-shape alumina particles cause serious materials loss in tribocorrosion process.