Formability Of Composites Research Articles

Microstructural changes near the interface of eleven-layered AZ31/AA1050 composites fabricated by single-shot explosive welding

The evolution of the microstructure of reaction regions in as-welded and annealed states was thoroughly investigated by SEM and TEM in the eleven-layered AZ31/AA1050 composite plates fabricated via a single-shot explosive welding process. With the detonation velocities used, only the first and second interface is wavy, while the others are flat. Near all interfaces, local melting and rapid solidification processes lead to the formation of reaction regions composed of phases of different chemical compositions and structures. Even though 2 equilibrium phases of γ-Mg17Al12 and β-Mg3Al2 have been found a large part of the solidified melt region consists of non-equilibrium phases that exhibit an amorphous or ultrafine-grained structure. Further heat treatment of the multilayer composite resulted in rapid nucleation and growth of the γ-Mg17Al12 and β-Mg2Al3 phases in the form of hard layers. Within the pre-existing reaction regions, the systematic transformation of phases of different chemical compositions into one β-Mg2Al3 phase was observed. It was found that using a pressure of 3 MPa is very important in preventing delamination of the clad during heating, but it is not able to block the formation of the linear cracks in the β-Mg3Al2 phase, which crucially reduces the composite formability.

Microstructure-Based Two-Scale Simulation of Deformation and Fracture of SiCp/2009Al Composite

Accurately predicting the formability of composites is quite important for designing the materials and optimizing the processing parameters of such components. This paper presents a microstructure-based two-scale model to analyze the deformation behavior of the SiCp/2009Al composite during upsetting. The microstructure-based micro-scale model with a displacement boundary condition that was obtained from a macro-scale model can predict particle cracking, interface failure and matrix fracture by introducing the normal stress criterion, the maximum stress ratio criterion and the shear fracture model. The simulation results show that, during unidirectional upsetting, the crack initiates in the matrix, and then propagates in the matrix, the interface and the particle. Comparing with the unidirectional upsetting, the bidirectional upsetting results in a more uniform stain distribution and a smaller maximum strain, which prevent the initiation of the crack in the matrix. The simulation results compare well with the deformation and fracture patterns observed in experiment, indicating an effective way to optimise the plastic working and designing of composites.

Formability Experiments for Unidirectional Thermoplastic Composites

Reliable composite forming experiments are required to characterize composite formability, to aid material development, and to validate process simulations models. Due to practical reasons, however, typically a limited amount of forming configurations is studied. The objective of this study is, therefore, to develop a methodology for obtaining controlled forming results in a wide range of configurations. Press forming experiments using a dome geometry were used to explore the formability of two commercial unidirectional thermoplastic composite materials. A variety of forming configurations was employed by changing the blank dimensions and layup. The observation of wrinkling defects was simplified by leaving an additional 3 mm tool gap. Blank width and layup had the most influence on the wrinkling severity, followed by blank thickness and length. Quasi-isotropic layups were found to produce wrinkles in nearly all cases, confirming a difficulty in general to form double curved parts. The size and number of wrinkles in these layups were found to change with the stacking sequence. Cross-ply layups showed better formability, but significant wrinkles were still observed depending on the orientation of the blank relative to the layup. The formability experiments using a dome geometry provided a reliable methodology for controlled forming results in many configurations using a generic toolset. Additionally, a comprehensive comparison of formability for two commercial thermoplastic UD materials in a variety of scenarios was provided.

Fabrication and Formability of Continuous Carbon Fiber Reinforced Resin Matrix Composites Using Additive Manufacturing

In the current process for additive manufacturing of continuous carbon fiber reinforced resin matrix composites, the fiber and resin matrix are fed into the molten chamber, and then impregnated and compounded in the original position, and finally extruded and deposited on the substrate. It is difficult to control the ratio of fiber and resin, and to achieve good interface fusion, which results in an unsatisfactory enhancement effect. Therefore, an additive manufacturing process based on continuous carbon fiber reinforced polylactic acid composite prepreg filament was explored in this study. The effects of various process parameters on the formability of composites were studied through systematic process experiments. The results showed that the process parameters of additive manufacturing have a systematic influence on the forming quality, accuracy and efficiency, and on the mechanical properties of CFRP. Through the experimental optimization of various process parameters, a continuous and stable forming process was achieved when the nozzle aperture was 0.8 mm, the nozzle printing temperature was 240 °C, the substrate temperature was 60 °C, the wire feeding speed was 5 mm/s, the nozzle moving speed was 5 mm/s, the path bonding rate was 40%, and the printing layer thickness was 0.7 mm. Based on the optimized process parameters, direct additive manufacturing of a lightweight and high-strength composite cellular load-bearing structure could be realized. Its volume fraction of carbon fiber was approximately 7.7%, and the tensile strength was up to 224.3 MPa.

Effect of hybrid fillers of Mg–Al layered double hydroxide and nanoclay on the mechanical behavior and formability of glass laminate AA5052‐reinforced epoxy composites

AbstractThis research work investigates the influence of hybrid particulate fillers, Mg–Al layered double hydroxide (LDH), and nanoclay (NC), on the mechanical properties and formability of glass laminate AA5052 epoxy composites (GLARE). The composite laminates were prepared by varying the weight percentage (i.e., 3, 4, and 5 wt%) of the hybrid fillers in the epoxy resin. The conventional hand layup technique was utilized for the fabrication of the laminates. The tensile test samples were prepared in different orientations with respect to the rolling direction (i.e., 0°, 45°, and 90°) to address their anisotropic nature. The flexural, impact, lap shear, and formability tests were conducted as per ASTM and IS standards. The Erichsen cupping test was performed to study the formability of the composite laminates. For each test, the results were compared with that of the laminates containing individual LDH filler, NC filler, and no filler material. The results showed that the composite laminate with 5 wt% of LDH + NC hybrid filler exhibited enhanced tensile properties, impact energy, and lap shear strength while the laminate of 4 wt% LDH + NC filler possessed better flexural properties. The formability of the composite laminates with hybrid LDH + NC fillers was observed to be lower than that of the laminates with individual filler materials and laminate without any filler. The variation observed in the test results was justified by investigating the failure mechanism of the composite laminates using a scanning electron microscope.

Compressive response and microstructural evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite

The hot forming behavior, failure mechanism, and microstructure evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300–450 °C and strain rates of 0.001-1 s−1. The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate, and dimple rupture of the matrix at high temperature and low strain rate. Full dynamic recrystallization, which improves the composite formability, occurs under conditions of high temperature (450 °C) and low strain rate (0.001 s−1); the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite. Based on the flow stress curves, a constitutive model describing the relationship of the flow stress, true strain, strain rate and temperature was proposed. Furthermore, the processing maps based on both the dynamic material modeling (DMM) and modified DMM (MDMM) were established to analyze flow instability domain of the composite and optimize hot forming processing parameters. The optimum processing domain was determined at temperatures of 425-450 °C and strain rates of 0.001-0.01 s−1, in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.

Effects of fabric structure on the formability characteristics of thermoplastic composites under various process conditions

Thermoplastic composites are broadly utilized for structural and automotive applications due to their higher specific strength and modulus, higher strain to failure, recyclability, and unlimited shelf life. This study investigates the effects of fabric structure on the forming behaviour of glass fabric reinforced polypropylene composites during the sheet forming of a doubly curved shape. Stamp forming, a novel thermoforming technique, is mostly used for hemispherical forming of thermoplastic composites. The study also investigates the influence of process parameters such as die temperature, blank temperature, and blank holder force on sheet formability. Forming ratio, thickness distribution, material draw-in, and punch force were used for the evaluation of the formability of composites. Conventional and novel plain weave glass fabric reinforced polypropylene composite laminates were fabricated using the film stacking technique. Thermo-stamp forming experiments were conducted on the basis of the Taguchi’s L9 orthogonal array. Experimental results revealed better forming characteristics by the novel glass fabric reinforced composite than for the conventional glass fabric reinforced composite. Production of defect-free components under high die temperature, low blank holder force, and medium blank temperature process condition was observed.

High temperature formability of graphene nanoplatelets-AZ31 composites fabricated by stir-casting method

Abstract Outstanding mechanical properties of graphene nanoplatelets (GNPs) make them ideal reinforcement for mass production of composites. In this research, the composites were fabricated by stir-casting method. GNPs were added in 1.5 and 3.0 wt.% into Mg–3wt.% Al–1wt.% Zn (AZ31) magnesium alloy. As cast ingots were preheated for one hour and extruded at 350 °C with extrusion ratio of 5.2:1. As extruded AZ31-GNPs composites were micro-structurally characterized with X-ray diffraction, optical microscopy and scanning electron microscopy. Vickers micro-hardness of synthesized materials was investigated both in parallel and perpendicular to extrusion directions. Room temperature mechanical testing revealed that with increasing GNP's content, tensile fracture strain was remarkably increased without significant compromise in tensile strength. Furthermore, as extruded AZ31-3GNPs composites were subjected to tensile testing at temperatures ranging from 75 °C to 300 °C with initial strain rate of 2 × 10−3 s−1 to evaluate high temperature formability of composite. It was found that like CNTs, GNPs also have the potential to sustain tensile strength at high temperatures.

Designing Bulk Metallic Glass Composites with Enhanced Formability and Plasticity

To address the main stumbling-block of bulk metallic glasses (BMGs), i.e., room temperature brittleness, designing BMG matrix composites has been attracted extensive attention. Up to date, BMG composites in various alloy systems have been successfully developed by forming crystalline phases embedded in the amorphous matrix through either ex-situ or in-situ methods. In this paper, a brief review of our recent work in this topic will be presented and the novel approaches to improving composite formability and mechanical properties will also be highlighted. The main purpose of this manuscript is not to offer a comprehensive review of all the BMG composites, but instead focuses will be placed on illustrating recently developed advanced BMG composites including Fe-based BMG composite with no metalloids, Al-based BMG composite and BMG composites reinforced by the TRIP (transformation-induced plasticity) effects. The basic ideas and related mechanisms underlying the development of these novel BMG composites will be discussed.

Development of corrugated composites using newspaper and biodegradable or nonbiodegradable resins and their mechanical properties

In the present study advantage of composite formability was used in developing newspaper‐reinforced composites and corrugated boards using both biodegradable and nonbiodegradable resins. Tensile and bending properties were characterized. The corrugated board forming processes for water‐based biodegradable and nonbiodegradable resins have been described and their workability assessed. The paper forming process where the pulp fibers flow in preferred direction creates anisotropy of paper properties. This anisotropy is reflected in the composite properties as has been expected. The newspaper‐based composites and corrugated boards showed moderate tensile and flexural properties that are comparable to the conventional materials used. The properties obtained can be further improved by increasing the newspaper content and better resin penetration. POLYM. COMPOS., 34:1863–1869, 2013. © 2013 Society of Plastics Engineers

Formability of Fiber-Reinforced Thermoplastics in Hot Press Forming Process Based on Friction Properties

High performance composites are used in commercial applications in a steadily growing degree. This increase of advanced materials is accomponied with the development of fully automated fabrication processes. It aims to drive down the time and costs of the production while ensuring a high quality of the product. This can achieved by considering the process of hot press forming with continuous fiber reinforced thermoplastics. The development of the process is, however, accompanied with a few difficulties, which require more research. For example, composite materials with different architectures, lay-ups, and constituents, show large differences in formability. This research examines the effect of friction on the formability of thermoplastic composites. Both experiments and simulations were conducted. Demonstrator products have been press-formed from laminates with different materials and architectures (UD-carbon PEEK, UD-carbon-PEI, 8hs-glass PPS, 5hs-carbon PEEK and UD-glass PPS), to investigate their effects on formability. Creating a doubly curved shape from a flat laminate requires at least three deformation mechanisms, namely in-plane shear, bending and inter-ply slippage This paper focuses on the sliding mechanism and the corresponding friction. In order to quantify the amount of sliding in the press-formed product, a dot pattern has been applied to both surfaces of the laminate. The slip between the outer plies can be analyzed by means of photogrammetry. Besides, the friction coefficient of each material is measured in a special designed friction test set-up. It can be seen that the composite formability is directly linked to its friction properties. FE simulations of the press-form process will be performed based on the measured material properties, to demonstrate the influence of the materials friction coefficient.

Formation of interfacial microstructures of Mo‐coating modified SiCf/Mo/Ti‐6Al‐4V composites

This paper addresses the role of Mo coating to modify the interface of SiC fiber reinforced Ti‐6Al‐4V composite (SiCf/Mo/Ti‐6Al‐4V). The formation of microstructure as well as the diffusion of elements in the interface of as‐prepared and heat‐treated SiCf/Mo/Ti‐6Al‐4V composites was investigated. The results show that the phases formed at the interfacial zone are: Mo coating∣TiC∣Mo + β‐Ti∣β‐Ti∣β‐Ti + α‐Tistrip, ordering from fiber to matrix. Mo coating can effectively hinder the diffusion of elements between the matrix and fiber to some extent, thus it can inhibit fiber/matrix interfacial reaction and protect the fiber from damage. It is believed that the β‐Ti layer formed around the interface can improve the formability of composites. Furthermore, it indicates that Mo coating exhibits excellent thermal stability bellow 700 °C according to the heat treatment of the composites at 700 °C for up to 200 h. Copyright © 2012 John Wiley & Sons, Ltd.

Influence of extrusion temperature on deformation behavior of C sf/AZ91D composite during semi-solid extrusion

Deformation behavior and formability of C sf/AZ91D magnesium composite were investigated by semi-solid extrusion between 695 K and 728 K, including temperatures below and above the partial melting temperature. A method of constructing kinematically admissible velocity fields for axisymmetric extrusion based on the theory of flow function was proposed. Flow lines were analyzed in C sf/AZ91D composite after extrusion at elevated temperatures. Based on an analytic flow function, the deformation field was obtained. The results show that when the composite is extruded in a semi-solid state containing a small volume of liquid, the presence of the liquid reduces deformation resistance by relaxing the stress concentrations, and improves the formability of composites as lubricant. However, the gradient of velocity field is increased and deformation uniformity is aggravated at temperatures greater than partial melting point at 701.3 K. A more uniform deformation field was attained at the temperature close to or slightly below the partial melting temperature.

Process–microstructure–property relationships in AA3003 expanded metal periodic cellular truss cores

Despite their significant potential as ultra-lightweight composite materials, comparatively little attention has been given to the microstructure of deformation formed periodic cellular metals (PCMs). Because shape plays such a determining role in their performance, it is the spatial distribution of microstructure which controls both the useful range of cellular architectures and their resultant mechanical properties. The present study examines the effects of non-uniform recrystallization in expanded AA3003 sheet precursors on the PCM composite formability and mechanical performance. Because fabrication induced work-hardening and crack formation is localized to the hinge region, the pre-annealing temperature prior to fabrication provides a trade-off between the resultant compressive modulus and inelastic buckling strength of the PCM.

Thermo-ductile composites: new materials for 21st Century manufacturing — micro-perforated thermoplastic composites

Affordable lightweight structures will acquire increasing importance in the 21st Century as improved performance and energy saving become mandatory requirements for all manufacturers of products with moving parts. Highly aligned fibre reinforced composites are capable of providing adequate specific stiffness, but existing fabrication techniques are unsuitable and too costly for volume manufacturing. A central problem is the lack of composite ductility, which reduces their value as semi-finished materials. Previous material developments aimed at enhancing composite formability are reviewed and compared with new novel micro-perforated thermoplastic composites, which exhibit significant temperature-dependent ductility. The potential of these materials for cost-effective, volume manufacturing of lightweight structures is briefly outlined.

Optimization of the formability of knitted fabric composite sheet by means of combined deep drawing and stretch forming

The formability of sheet metals has been investigated widely in the last 5 decades. However, formability studies on polymer composite materials are very limited and relatively new. This paper describes the sheet formability of knitted Kevlar fiber reinforced polypropylene composite material. Previous studies have indicated that sheet formability is governed by the complex interplay between pure stretch forming and pure deep drawing. For this purpose, a new parameter, X , which describes the amount of stretching relative to drawing during forming has been introduced. The formability characteristics of knitted fabric composite are discussed with reference to X . The effects of forming conditions (such as blank-holding load, the blank size and the tool geometry) on the composite formability are also described.

Elasto-plastic Finite Element Modelling To Determine The Effect Of Type Of Polymeric Adhesive On The Formability Of Steel-polymeric Adhesive- Aluminium (SPA) Laminated Composites

In order to increase the formability of steel-polymeric adhesive-aluminium (SPA) laminated composites, most popular polymeric adhesives are used. Then deep drawing, stretching and tensile tests are performed for steel, aluminium, polymeric adhesive and laminated composite. The mechanical properties obtained from tests for steel, aluminium and polymeric adhesives are used in ANSYS program to simulate the formability testings of the compositesand determine the effect of the mechanical behaviour of the polymeric materials on the fornability of the laminated SPA composite. Experimental and numerical results showed that the mechanical behaviour of the polymeric adhesives is the most important factor during formability of the composite if the thickness of the polymer is equal or greater than the thickness of the metal laminates. However, when the thickness of the polymer is reduced by applying pressure during manufacturing of composite the formability of composite is increased. In addition to them, it is also observed that new commercially available adhesives show good mechanical behaviours during testings and are good at formability of composites. Therefore, the success of laminated composites depends on the develpoments of the polymeric adhesives.