Multilayered Composite Sheets Research Articles

Improved Chemical Resistance During Use of Fiber-Reinforced Multi-Layer Composite Sheets

Improved Chemical Resistance During Use of Fiber-Reinforced Multi-Layer Composite Sheets

The Effect of Asymmetry on Strain Distribution, Microstructure and Texture of Multilayer Aluminum Composites Formed by Roll-Bonding

AA1050/AA7050 multilayered composite sheets with a proportion of 1:1 were produced by Accumulative Roll Bonding (ARB) and Asymmetric Accumulative Roll-Bonding (AARB), using up to 8 cycles and intermediate annealing treatments at 500°C. The main purpose was to produce one composite sheet with high strength and moderate ductility, taking advantage of the mechanical properties of these aluminum alloys. Microstructural features were investigated in order to evaluate the potential to achieve a refined microstructure and the development of structural patterns. The strain distributions as a function of friction and asymmetry were simulated by finite element analysis. Texture was evaluated by X-ray diffraction and electron backscatter diffraction. A continuous layer pattern was obtained by ARB, up to 6 cycles but after 8 cycles shear bands fragmented the harder layers. In the early AARB cycles, the bending and necking of the AA7050 layers yielded a wavy-pattern. The shear strain in the AARB process has a strong influence on achieving a wavy-pattern, more than the flow stress differences of the alloys in the composite. Shear texture increased with the degree of the layers’ discontinuity. Different sources of shear contributed to the formation of microstructural patterns: the shear due to asymmetry, the frictional shear at roll-sheet interface and at the central layer interface and the shear at the layers’ interface. In addition, the ARB process achieved a better interfacial adhesion at the middle interface and higher strength and elongation than the AARB process.

Comparison between Explosive Welding and Roll-Bonding Processes of AA1050/Mg AZ31B Bilayer Composite Sheets Considering Microstructure and Mechanical Properties

In this article, the effect of the manufacturing process on the microstructure and mechanical properties of AA1050/Mg-AZ31B bilayer composite sheets has been studied experimentally. In multilayer composite sheets, the interface bond strength plays a significant role in the mechanical properties of the composite. The most important factor affecting the bond strength is the manufacturing process of these sheets. So, two processes of explosive welding and roll bonding have been used to manufacture the bilayer composite sheets. The results show that the atomic diffusion in the interface is 6.5 microns in the explosive welding and 6.7 microns in the roll bonding. No intermetallic compounds have been observed in the interface of the studied bonding methods. The wavy and straight interface morphologies have been observed for explosive welding and roll bonding, respectively. Also, recrystallization has been observed in the microstructure of both methods. In the magnesium microstructure of rolled sample, twinning and deformation bands have been seen, while adiabatic shear bands have been formed in the explosive-welded sample. The ultimate tensile strength, elongation, and work of fracture (WOF) of explosive-welded sheets have been increased by 145%, 31%, and 407% relative to the rolled sheets, respectively. Besides, considering the separation of layers in the tensile test of rolled sheets compared to explosive welded ones, it can be stated that the structural failure in explosive welding occurs simultaneously for all layers. However, for roll bonding, the layer failure is independent of the entire structure failure. In this case, first, necking and fracture of the magnesium layer occur, and then, after the separation of the interface, the fracture of the aluminum layer happens.

The role of shear strain during Accumulative Roll-Bonding of multilayered composite sheets: Pattern formation, microstructure and texture evolution

The present study was designed to determine the effect of shear strain on the macro- and microstructure and texture evolution in the AA1050/AA7050 Al multilayered composite sheets. The sheets were processed by Accumulative Roll-Bonding (ARB) and Asymmetric ARB (AARB) at 450 °C and 500 °C. The shear strain in the AARB process has a remarkable influence in achieving a macrostructural wavy-pattern, more than the flow behavior of the materials. For ARB, a flat-pattern with slight waviness was produced mainly due to flow incompatibility, as estimated by finite element simulation and observed by macrostructural analysis. In addition, friction at the surfaces and at the interfaces, and the strain distribution, together with the coarsening or dissolution of precipitates in the AA7050 layers have also influenced the shear banding and microstructure evolution in the sheets. A reduction in the texture intensity by AARB was observed. The grain refinement in the AA1050 layers was controlled by continuous dynamic recrystallization and static recovery during the thermo-mechanical cycles for both processing routes. The AA7050 layers presented a more complex grain refinement behavior that was influenced by dissolution of the η- and η′-phases, which was observed for both temperatures in the ARB. In contrast, the shear strain accelerated this dissolution kinetics and grain growth in the AA7050 layers of sheets processed by AARB.

Microstructure evolution of multilayered composite sheets of AA1050/AA7050 Al alloys produced by Asymmetric Accumulative Roll-Bonding

In this investigation, AA1050/AA7050 multilayered composite sheets were produced by Asymmetric Accumulative Roll-Bonding (AARB) in order to evaluate microstructure evolution and the interfacial zone. The asymmetric rolls introduced an extra component of shear strain, which provided conditions for necking and/or rupture in the AA7050 layers during processing at 500 °C yielding a wavy-pattern. On the other hand, at 450 °C the continuity of layers was maintained. Thus, AARB parameters can be controlled to produce wavy- or flat-pattern structures in multilayered composites. The hardening of the AA7050 layers after processing at 450 °C was caused by overaging and grain refinement, whereas at 500 °C it was due to the precipitation of η’ and η-phases. The hardening of the AA1050 layers was attributed to grain refinement achieved from continuous dynamic recrystallization. In addition, diffusion bonding has a significant role in the formation of AA1050/AA7050 interfaces by the AARB process, as observed in the interdiffusion zone. Taken together, these findings provide insights into structural pattern formation and microstructural control in Al-based multilayered composites using the AARB process.

Compositional and structural design of thermoplastic polyurethane/carbon based single and multi-layer composite sheets for high-performance X-band microwave absorbing applications

In this study, morphological features, dielectric properties, and microwave absorbing performances of thermoplastic polyurethane composite sheets prepared with solution mixing method by using different amounts and types of carbon fillers, carbon black (CB), graphite (G), carbon nanofiber (CNF), and multiwalled carbon nanotube (MWCNT) were investigated, in detail. Microstructural properties and microwave absorbing characteristics of composites were analyzed with scanning electron microscope and vector network analyzer by transmission line method, respectively. Reflection loss (RL) analyses of composites showed that CNF and CNT were more efficient than CB and G for improving the electromagnetic wave absorbing performances of sheets at low filler contents. It was found that the broadest effective absorption area (EAA) (10.03–12.96 GHz) was obtained with the sample having 3 phr of CNF. However, single layer TPU/carbon composite sheets were not effective “RADAR stealth” materials because their RL values were higher than −10 dB at X-band. Thus, multilayer (two, three, and four-layer) composite structures were designed to obtain higher microwave absorption performance within this frequency range via genetic algorithm approach. Multilayer design and modeling works showed that a four-layer composite with a total thickness of 4.8 mm yielded excellent microwave absorbing performance and broad EAA, 6.98–13.415 GHz, at X-band.

A review on effect of thinning, wrinkling and spring-back on deep drawing process

There are various processes practiced in a market for manufacturing axisymmetrical cup with significant forming depth among which deep drawing process is most prompt. The deep drawing process is a forming process with ongoing interest which will have a major impact on industries in coming years. This article focuses on the current status and potential of future development of technology in the deep drawing process. First, it describes various types of approaches and techniques used in the deep drawing of different materials. This is followed by brief reviews of advantages and limitations of these technologies with its application in industries. The details of these technologies are just referred rather than explaining in detail. The further part of this article focuses on advanced methods for predicting defects like thinning, wrinkling and spring-back in deep drawing process which are mostly responsible for rejection of the components. The opportunity in the development of flexibility in deep drawing process is covered with an observed barrier in the prediction of defects such as thinning, wrinkling and spring-back. The obtained evidence indicates that deep drawing process may not be applicable for all materials, but represents an excellent opportunity in the drawing of multilayer metal and composite material sheets to complex shapes.

铜-镍多层复合薄板激光弯曲成形工艺建模与优化

铜-镍多层复合薄板激光弯曲成形工艺建模与优化

Role of shear in interface formation of aluminium-steel multilayered composite sheets

Aluminium – Interstitial Free (IF) steel multilayered composite sheets with different volume fractions of aluminium were produced by accumulative roll bonding (ARB) and Asymmetric Accumulative Roll Bonding (AARB). The IF steel and Al alloy (AA1050) sheets were stacked in a sandwich like structure and roll-bonded by two passes with varying roll diameter ratios (dr) equal to 1 and 2 for ARB and AARB processes, respectively. This work focused on a study of the effect of shear strain mode on the formation of the interface zone. The interface zone thickness, which formed by intermixing and diffusion, was characterised by different techniques including STEM-EDS line scan, HRTEM and Atom Probe. Furthermore, finite element simulations of both processes were conducted to determine the level of shear strain at the interfaces. It was demonstrated that the width of the interface zone directly correlates with the magnitude of shear strain and architecture of the hybrid material.

Feature Size Effect on Formability of Multilayer Metal Composite Sheets under Microscale Laser Flexible Forming

Multilayer metal composite sheets possess superior properties to monolithic metal sheets, and formability is different from monolithic metal sheets. In this research, the feature size effect on formability of multilayer metal composite sheets under microscale laser flexible forming was studied by experiment. Two-layer copper/nickel composite sheets were selected as experimental materials. Five types of micro molds with different diameters were utilized. The formability of materials was evaluated by forming depth, thickness thinning, surface quality, and micro-hardness distribution. The research results showed that the formability of two-layer copper/nickel composite sheets was strongly influenced by feature size. With feature size increasing, the effect of layer stacking sequence on forming depth, thickness thinning ratio, and surface roughness became increasingly larger. However, the normalized forming depth, thickness thinning ratio, surface roughness, and micro-hardness of the formed components under the same layer stacking sequence first increased and then decreased with increasing feature size. The deformation behavior of copper/nickel composite sheets was determined by the external layer. The deformation extent was larger when the copper layer was set as the external layer.

Effect of Annealing Temperature and Time on Microstructure and Mechanical Properties of Multilayered Steel Composite Sheets

Multilayered composite steels consisting of alternating layers of martensitic phase and austenitic phase exhibit an excellent combination of strength and elongation compared with conventional advanced high-strength steels. The deformation processes underlying these properties are of considerable interest. In this article, microstructure, grain size, and phase are characterized by scanning electron microscopy (SEM) and electron backscattering diffraction. The hardness of each layer is analyzed by a microindentation hardness testing system. Finally, the deformation and failure processes in multilayered steel are investigated by in-situ SEM. The hardness results indicate that various hardening modes occur in the soft austenitic layer and the hard martensitic layer. In-situ SEM results combined with microstructure analysis and hardness results reveal that annealing temperature and annealing time have a significant impact on final microstructure, fracture behavior, strength, hardness, and ductility.

Strain and Cohesive Energy of TiN Deposit on Al(001) Surface: Density Functional Calculation

To apply the high hardness of TiN film to soft and hard multilayer composite sheets, we constructed a new type of composite structural material with ultra-high strength. The strain of crystal and cohesive energy between the atoms in the eight structures of N atom, Ti atom, 2N2Ti island and TiN rock salt deposited on the Al(001) surface were calculated with the first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory. The calculations of the cohesive energy showed that N atoms could be deposited in the face-centered-cubic vacancy position of the Al(001) surface and results in a cubic structure AlN surface. The TiN film could be deposited on the interface of [Formula: see text]-AlN. The calculations of the strains showed that the strain in the TiN film deposited on the Al(001) surface was less than that in the 2N2Ti island deposited on the Al(001) surface. The diffusion behavior of interface atom N was investigated by a nudged elastic band method. Diffusion energy calculation showed that the N atom hardly diffused to the substrate Al layer.

Deformation behavior and interface microstructure evolution of Al/Mg/Al multilayer composite sheets during deep drawing

Abstract The Al(5052)/Mg(AZ31)/Al(5052) multilayer composite sheets were fabricated via accumulative roll-bonding process at elevated temperatures. The present study aims to investigate the formability of the composite sheets by deep drawing test and orthogonal experimental design. The deep drawing parameters such as punch temperature, punch speed and die curvature radius have been optimized to maximize the limit drawing radio of the composite sheets at temperatures ranging from 150 °C to 230 °C. The limit drawing radio of the composite sheets obviously increased with the forming temperature, and the maximum drawing radio of 3.1 was obtained at 200 °C. After forming at 150 °C and 200 °C, the microstructure evolution of the intermetallic compound layers, consisting of Al 12 Mg 17 and Al 3 Mg 2 layers at the interface at different regions of the drawn cup in rolling direction (RD) and transverse direction (TD), was investigated. At the bottom region which was considered as less deformation, the microstructure of the intermetallic compound layers showed almost no changes both at 150 °C and 200 °C. However, the Al/Mg/Al multilayer composite sheets showed more satisfactory bonding properties when drawing at 200 °C with less cracks appearing at the wall region and corner region of the drawn cup than that at 150 °C.

Use of Direct Active Thermal Imaging Technique for Sub Surface Delamination Detection in Aviation Composites

Various non-destructive testing and evaluation (NDTE) techniques are in use by the aviation industry. Thermal imaging as an NDTE tool for composite material is becoming an effective methodology. In this research, a direct energy method approach to active thermal imaging is applied with test specimen placed between the heating source and the camera to take only one diagnostics snap per unit area of region of interest (ROI). Purpose of this study is to assess the utility of direct method as a reliable NDTE technique during aerospace inspections as a quick ‘Go / No Go’ tool for the detection of sub-surface delamination in multilayered composite sheets. The research presents a quantitative comparison of temperature profiles as well as qualitative analysis of 2D active infrared thermo graphic testing of glass fiber epoxy to detect sub-surface delamination. The experimental results are in close agreement with the actual locations of delamination in test samples. The technique may serve as a reliable tool to quickly categorize the component under inspection. However, the size of delamination could not be ascertained with acceptable accuracy in this study, possibly due to the spread of epoxy to the delaminated regions during preparation of defective samples.

Effect of a ductility layer on the tensile strength of TiAl-based multilayer composite sheets prepared by EB-PVD

TiAl/Nb and TiAl/NiCoCrAl laminate composite sheets with a thickness of 0.4–0.6mm and dimensions of 150mm×100mm were successfully fabricated by electron beam physical vapor deposition. The microstructures of the sheets were examined, and their mechanical properties were compared with those of TiAl monolithic sheet produced by electron beam physical vapor deposition. Tensile testing was performed at room temperature and 750°C, and the fracture surfaces were examined by scanning electron microscopy. Among the three microlaminate sheets, the TiAl/NiCoCrAl micro-laminate sheet had the best comprehensive properties at room temperature, and the TiAl/Nb micro-laminate sheet showed the ideal high-temperature strength and plasticity at 750°C. The result was discussed in terms of metal strengthening mechanism.

Damping behavior of Al/SiCP multilayer composite manufactured by roll bonding

High damping materials comprising good mechanical properties as structural materials and high damping capacity for vibration loading are the best solutions for vibration problem. In current study, functionally graded material from composite sheets with different percentages of reinforcement was manufactured by hot rolling process. The damping behavior of base alloy composite including different percentages of SiC particles and Al/SiCP multilayer composite sheets was studied at room temperature conditions. The Al/SiCP composites were found to exhibit higher damping capacity compared to Al alloy. The damping capacity increased by increase in the percentage of reinforcement. Furthermore, Al/SiCP multilayer composite sheet provided higher damping capacity in comparison to Al alloy. Therefore, damping capacity enhanced by increasing the number of layers. The main source for damping behavior in composite materials is dislocation damping whereas in stepwise multilayer composite sheets, it comes from boundary conditions between layers.

Role of the interphase in the flow stability of reactive coextruded multilayer polymers

AbstractCoextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities. Important theoretical and experimental advances regarding theses defects have, during the last decades, been made using a mechanical and numerical approach. This study deals with the influence of the physicochemical affinity between the neighboring layers on interfacial instabilities for functionalized incompatible polymers. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interface of nonzero thickness (corresponding to an interdiffusion/reaction zone interphase) instead of a purely geometrical interface between the two reactive layers. According to the rheological investigations, an experimental strategy was here formulated to investigate the parameters that controlled the stability of the reactive multilayer flows. The role of the viscosity ratio, elasticity ratio, and layer ratio of the stability of the interface was also investigated coupling to the reaction rate/compatibilization phenomenon. Hence, based on this analysis, guidelines for a stable coextrusion of reactive functionalized polymers can be provided coupling the classical parameters and the physicochemical affinity at the polymer/polymer interface. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Reactive Functionalized Multilayer Polymers in a Coextrusion Process: Experimental and Theoretical Investigations of Interfacial Instabilities

Coextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities during flow. Important theoretical and experimental advances regarding the stability of compatible and incompatible polymers have, during the last decades, been made using a mechanical approach. However, few research efforts have been dedicated to the physicochemical affinity between the neighboring layers. The present study deals with the influence of this affinity on interfacial instabilities for functionalized incompatible polymers. Polyamide (PA6)/polyethylene grafted with glycidyl methacrylate (PE-GMA) was used as a reactive system and PE/PA6 as a non reactive one. Two grades of polyamide (PA6) were used in order to change the viscosity and elasticity ratios between PE (or PE-GMA) and PA6. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interphase of non-zero thickness (corresponding to an interdiffusion/reaction zone) instead of a purely geometrical interface between the two reactive layers. According to rheological investigations from previous work, an experimental strategy was here formulated to optimize the process by listing the parameters that controlled the stability of the reactive multilayer flows. Plastic films with two layers were coextruded in symmetrical and asymmetrical configurations in which PA6 was the middle layer. Indeed, for reactive multilayered systems, the interfacial flow instability could be reduced or eliminated, for instance, by (i) increasing the residence time or temperature in the coextrusion bloc (for T above the reaction temperature T = 240°C), and (ii) reducing the total extrusion flow rate. The reaction rate/compatibilization played a major role that must be taken into account. Furthermore, the role of the viscosity ratio, elasticity ratio, and layer ratio of the stability of the interface were also investigated coupling to the physicochemical affinity. The results show that it is necessary to obtain links between the classic factors that are introduced in the evaluation of the theoretical, given by linear stability analysis/longwave asymptotic investigations, and its corresponding experimental stability charts. Hence, based on this analysis, guide-lines for a stable coextrusion of reactive functionalized polymers can be provided.

Improvement of the properties of multilayer coextruded films by control of the interphase characteristics

Coextrusion technologies are commonly used to produce multilayered composite sheets of films. Each layer of these composite materials provides a specific end-use characteristic, suc as optical, mechanical or barrier properties. Processing together polymers of different natures may have two consequences : on the one hand, the flow of two adjacent different liquids may give rise to interfacial instabilities which are detrimental to the quality of the final product. On the other hand, the difference of chemical natures of the polymers may lead to delamination of the multilayer film. In order to avoid the latter problem, polymers are compatibilized by introducing a binder between adjacent layers. As a consequence, a non-zero thickness interphase is created between the layers. In this paper, it is theoretically analysed how this interphase may influence the flow stability. As a matter of fact, it is experimentally known that flows of compatible polymers are more stable than those of incompatible systems. Next, a way to optimize the process is proposed.

Critical current density of superconducting NbTi/Nb/Cu multilayer composite sheets

The critical current density J c of NbTi/Nb/Cu multilayer composite sheets has been investigated at 4.2 K in static magnetic fields ranging from 0.5 to 8T. The composite sheets consist of 30 Nb-46.5wt%Ti alloy, 60 Nb and 31 oxygen-free copper layers. The Nb layer is interleaved as a diffusion barrier at each interface between the NbTi and Cu. The thickness of each NbTi and Cu layer is ≈9 μm, while the total thickness of the composite sheet is 0.75 mm. A best J c of 1580 A mm −2 at 4T was measured by a transport current method with the sample heat treated at 350 °C for 672 h.