High-strength Lightweight Materials Research Articles

Low-velocity impact behavior and damage mechanisms of honeycomb sandwich structures with elastomeric interlayers in CFRP skins

Elastomers help improve the toughness of lightweight high-strength materials, offering significant potential for enhancing the mechanical properties. However, introducing elastomers into CFRP interlayers as skin for composite sandwich structures has not yet been explored regarding the impact responses of such novel structures. This paper, for the first time in literature studies the low-velocity impact behavior and damage mechanisms of this novel sandwich structure using a combined experimental and numerical approach. The experimental results of sandwich structures with and without elastomer layers under different impact energies are presented. Finite element models of the two sandwich structures are built and impact behaviors were compared. The differences in internal damage and energy distribution during the impact are investigated to explain the reasons for the differing impact responses of the two sandwich structures. The results reveal that elastomeric interlayers have a significant advantage in enhancing the damage resistance of composite sandwich structures, especially under high impact energy conditions. The key contributions of this paper include the experimental characterization of the impact behavior of composite sandwich structures with elastomeric interlayers, and the explanation of the reasons for the changes in impact responses caused by the elastomers from the perspectives of damage mechanisms and energy distribution.

Research progress, application and development of high performance 6000 series aluminum alloys for new energy vehicles

For the development of new energy automobile industry and the trend of automobile lightweight have put forward a huge demand for high-strength lightweight materials, so developing high strength aluminum alloys is particularly momentous. As the most widely used aluminum alloy, 6000 series aluminum alloys (Al–Mg–Si alloys) have the advantages such as better mechanical properties, outstanding welding properties, excellent formability and fine processing capability, and therefore have obtained great attention as the structural materials. In addition, the Al–Mg–Si alloys with low density and corrosion resistance not only reduce the total weight of the car, but also extend the service life when subjected to chemical corrosion, which effectively achieve energy saving and emission reduction. This paper summarizes the research progress of 6000 series aluminum alloys, in particular, and reviews the methods of microalloying and particle strengthening, and their effects on the microstructure and properties of the alloy, thus providing a reference for the subsequent development of high-performance aluminum alloys in automobile and aerospace industries.

Validation of a ray-tracing-based guided Lamb wave propagation methodology in aerostructures

Validation of a ray-tracing-based guided Lamb wave propagation methodology in aerostructures

Design and assembly of chain-oriented-crystalline multilayered composite with largely improved mechanical strength

Design and assembly of organic/inorganic multilayered composite consisting of alternatively stacking of stiff inorganic platelets and soft organic polymers have great potential for developing next-generation lightweight high-strength materials. Beyond previous designs about the improvement of inorganic nanoplatelet alignment and inter-platelet bonding, a new design concept of control over the physical aggregation state of organic polymer chains within the multilayered structure for mechanical reinforcement is proposed. Based on a typical assembly system of nanoclay platelets and poly (vinyl alcohol) (PVA), a facile three-step process of gelation, uniaxial pre-stretching and evaporation is developed to construct chain-oriented-crystalline multilayered composite, in which the aggregation state of PVA including chain orientation (from 0.020 to 0.897), crystallinity (from 42.8 to 45.9%) and crystallite orientation (from 0.007 to 0.937%) is regulated successfully. These structural changes bring a 4.1-fold increase in the tensile strength of the multilayered composite because of substantial improvement in the strength of PVA layer that enlarges stress transfer from PVA to nanoclay platelets and leads to a failure mode change from the pull-out of nanoclay1 platelets to their fracture. These findings open an avenue for fabricating lightweight high-strength nanocomposites based on inorganic nanoplatelets and crystalline polymers.

Effect of tool pin profiles on the properties of foamable precursor developed by friction stir processing

The high-strength lightweight materials are commonly used in automotive industries. Foam is one such material that has a porous structure which makes it light but at the same time provides good absorbent of impact load. In recent years, friction stir processing (FSP) is commonly used for the development of foam. However, the quality of the foam developed mostly depends on the FSP parameters that control the distribution of foamable particles. Thus in this study, the impact of tool pin profiles and numbers of passes on the distribution of a foamable mixture of AA7075/TiH2 in the substrate has been investigated. The three different tool pin profiles, i.e. straight threaded cylindrical (STC), triangular (TR), and square (SQ) pins are used with 2, 4, and 6 number of FSP passes. It is observed that dispersion of TiH2/AA7075 particles in specimens produced with STC tool pin profiles is more uniform than that of TR and SQ pins, resulting in superior material stirring and flow. A significant reduction in particle clustering and improved mixture distribution has been observed in the STC pin profile. Vickers hardness test shows the SQ and TR pin profiles show higher hardness in the processed zone due to lower exposure of temperature. Microwave heating is used to heat the precursor for the development of foam. It is found that the foam developed by STC pin has superior compressive properties due to uniformly distributed small pores.

Selection of Optimum Hybrid Composite Material for Structural Applications Through TOPSIS Technique

Currently Aluminum alloys and polymer based fibre composites are being used for various structural applications. It is always an advantageous to have light weight high strength materials. In this context, hybrid nanocomposites are fabricated and tested for their mechanical properties to meet various applications. Due to the conflicting nature of the mechanical properties, a multi criteria decision model employing AHP (Analytic Hierarchy Process), Entropy, and TOPSIS techniques were developed with the goal of selecting an appropriate material to meet the objective out of various material combinations. A framework has been developed to assist composite structure designers in selecting the best fibre types for a given application. The purpose of this paper is to first investigate the impact of weighting methods in multiple criteria decision making (MCDM), and then to develop a systematic framework for optimum fibre selection among all fibre reinforced polymer (FRP) composites.

Dionysian Hard Sphere Packings Are Mechanically Stable at Vanishingly Low Densities.

High strength-to-weight ratio materials can be constructed by either maximizing strength or minimizing weight. Tensegrity structures and aerogels take very different paths to achieving high strength-to-weight ratios but both rely on internal tensile forces. In the absence of tensile forces, removing material eventually destabilizes a structure. Attempts to maximize the strength-to-weight ratio with purely repulsive spheres have proceeded by removing spheres from already stable crystalline structures. This results in a modestly low density and a strength-to-weight ratio much worse than can be achieved with tensile materials. Here, we demonstrate the existence of a packing of hard spheres that has asymptotically zero density and yet maintains finite strength, thus achieving an unbounded strength-to-weight ratio. This construction, which we term Dionysian, is the diametric opposite to the Apollonian sphere packing which completely and stably fills space. We create tools to evaluate the stability and strength of compressive sphere packings. Using these we find that our structures have asymptotically finite bulk and shear moduli and are linearly resistant to every applied deformation, both internal and external. By demonstrating that there is no lower bound on the density of stable structures, this work allows for the construction of arbitrarily lightweight high-strength materials.

A Brief Introduction on the Development of Ti-Based Metallic Glasses

Ti-based metallic glasses (MGs) possess high specific strength, low elastic modulus, high elasticity, high wear and corrosion resistance, and excellent biocompatibility, which make them highly attractive as lightweight high-strength materials as well as biomaterials. However, the glass forming ability (GFA) of Ti-based MGs, particularly those bearing no toxic, noble, or heavy metals, that is, Be, Pd, or Cu alike, largely sets back their wide applications for the restricted critical glass forming size of these Ti-based MGs. In this review, the outlines in developing Ti-based MGs are delineated in order to provide an overall view on the efforts ever made to fabricate bulk size Ti-based MGs. The state of the art in the knowledge on the GFA of Ti-based MGs is briefly introduced, and possible directions for fabricating bulk size toxic and noble element free Ti-based MGs are discussed.

Between-the-Holes Cryogenic Cooling of the Tool in Hole-Making of Ti-6Al-4V and CFRP.

Lightweight materials are finding plentiful applications in various engineering sectors due to their high strength-to-weight ratios. Hole-making is an inevitable requirement for their structural applications, which is often marred by thermal damages of the drill causing unacceptable shortening of tool life. Efficient cooling of the tool is a prime requirement for enhancing the process viability. The current work presents a novel technique of cooling only the twist drill between drilling of holes with no effect of the applied cryogenic coolant transferred to the work material. The technique is applied in the drilling of two commonly used high-strength lightweight materials: carbon fibers reinforced polymer (CFRP) and an alloy of titanium (Ti-6Al-4V). The efficacy of the cooling approach is compared with those of conventionally applied continuous cryogenic cooling and no-cooling. The effectiveness is quantified in terms of tool wear, thrust force, hole quality, specific cutting energy, productivity, and consumption of the cryogenic fluid. The experimental work leads to a finding that between-the-holes cryogenic cooling possesses a rich potential in curbing tool wear, reducing thrust force and specific energy consumption, and improving hole quality in drilling of CFRP. Regarding the titanium alloy, it yields a much better surface finish and lesser consumption of specific cutting energy.

Green and Intelligent Forming Technology and Its Applications for High Strength Lightweight Materials

Green and Intelligent Forming Technology and Its Applications for High Strength Lightweight Materials

Properties of Tool Steels and Their Importance When Used in a Coated System

The introduction of new light-weight high-strength materials, which are difficult to form, increases demands on tool properties, including load-carrying capacity and wear resistance. Tool properties can be improved by the deposition of hard coatings but proper combination and optimization of the substrate properties are required to prepare the tool for coating application. The aim of this paper is to elaborate on tool steel substrate properties correlations, including hardness, fracture toughness, strength and surface quality and how these substrate properties influence on the coating performance. Results show that hardness of the steel substrate is the most influential parameter for abrasive wear resistance and load-carrying capacity, which is true for different types of hard coatings. However, high hardness should also be accompanied by sufficient fracture toughness, especially when it comes to very hard and brittle coatings, thus providing a combination of high load-carrying capacity, good fatigue properties and superior resistance against impact wear. Duplex treatment and formation of a compound layer during nitriding can be used as an additional support interlayer, but its brittleness may result in accelerated coating cracking and spallation if not supported by sufficient core hardness. In terms of galling resistance, even for coated surfaces substrate roughness and topography have major influence when it comes to hard ceramic coatings, with reduced substrate roughness and coating post-polishing providing up to two times better galling resistance.

Tensile properties of α-titanium alloys at elevated temperatures

Hot-deep drawing is an innovative processing technology to produce complex shaped sheet metal components with constant wall thickness from high-strength lightweight materials. For some aerospace and automotive applications oxidation resistance at medium to high temperatures is an important aspect. In terms of this titanium α-alloys are often used due to their balanced relation of strength and oxidation resistance. In the presented study the stress-strain characteristics of several α-titanium alloys were determined at ambient and elevated temperatures by means of hot tensile tests. Besides the commercially pure Titanium alloy ASTM-Grade 4, two novel α-titanium alloys were investigated. Regarding the hot forming properties a comparison with α-β Ti-6Al-4V alloy was conducted. The hot tensile tests were carried out by means of a particular forming dilatometer type “Gleeble 3500” at 400, 500, 600, 650, 700 and 800 °C. The test showed favorable peak plasticity for all α-alloys at the temperature range between 600 and 650 °C in contrast to lower or higher temperatures. All samples were metallographically characterized.Key words: titanium α-alloys, hot tensile properties, elevated temperatures, Gleeble 3500.

Synthesis and Characterisation of B4C reinforced Al6061 Friction Stir Processed Surface Composites

Current industrial trends show increased usage of lightweight high strength materials such as Aluminium, Titanium, Magnesium, etc., in their products and components. To achieve an improved service life, particulates reinforced metal matrix composites are being favored over the monolithic alloys. Researchers have reported undesirable defects and interfacial reactions while trying to fabricate such composites using conventional methodologies. This motivates the present work to use friction stir processing, an allied process of friction stir welding, to fabricate metal matrix composites. Structurally stable and most commonly used AA6061 alloy was taken for the experiment. B4C particles were used as reinforcements. Experiments were carried out using different process parameters like tool revolution and tool traverse speed or processing speed along with a constant axial force. The B4C particles were packed into a 1.5 mm groove on the Al6061 plate and friction processing was carried out. The SEM investigations on the composites showed a defect-free microstructure with a homogeneous distribution of reinforcement particles. It was found that the reinforcements increased the tensile strength of the composite by 50%. The hardness and wear-resistant properties of the composites had also improved considerably.

Assessment of human-structure interaction on a lively lightweight GFRP footbridge

Human activities and occupancy can induce excessive structural vibrations. Human-structure interaction (HSI) can significantly affect responses. However, this phenomenon is not accounted for in many design guidelines due to lack of experimental studies. Concurrently, there is increasing application of lightweight high-strength materials such as glass fibre reinforced polymer (GFRP). The vibration sensitivity of such structures is not yet well known, despite the expectation that it could be important due to high human-to-structure mass ratio. This paper examines the effect of HSI on the vibration response prediction of a lively lightweight GFRP footbridge, and it compares the results to those from a heavy concrete-composite footbridge. An extensive ensemble of test trials was conducted, accompanied by a survey on vibration perception by the walkers. The influence of HSI on the lightweight bridge vibration response is quantified. It is found that the non-interacting moving force models produce poor predictions, especially for the GFRP bridge. It is also found that vibration of the bridge had a strong influence on walking force, and to a lesser extent on the dynamics of the human-structure system. Finally, it is found that a response factor of about 2 is appropriate for determining the vibration tolerance level by walkers.

Accumulative Roll Bonding—A Review

Different manufacturing processes can be utilized to fabricate light-weight high-strength materials for their applications in a wide spectrum of industries such as aerospace, automotive and biomedical sectors among which accumulative roll bonding (ARB) is a promising severe plastic deformation (SPD) method capable of creating ultrafine grains (UFG) in the final microstructure. The present review discusses recent advancements in the ARB process starting with the ARB basics, intricacies of the underlying mechanisms and physics, different materials, surface and rolling parameters, and finally its key effects on different properties such as strength, ductility, fatigue, toughness, superplasticity, tribology and thermal characteristics. Moreover, results of recent computational investigations have also been briefed towards the end. It is believed that ARB processing is an emerging area with tremendous opportunities in the industrial sector and ample potential in tailoring microstructures for high-performance materials.

Comparative Analysis of Different Surface Modification Processes on AA 7075 T651

Modern industries turn into light weight high strength materials. Aluminum alloys are having such a great property, in which, AA 7075 T651 provides good strength than other alloys. Hence, hardness of aluminum alloys are poor there by improvement of surface hardness of aluminum alloy is necessitate. Shot peening, severe surface mechanical treatment (SSMT) and laser shock peening (LSP) are the surface property enhancement processes, which are used to improve the surface hardness of AA 7075 T651. This article deals with study the effect of shot peening, Severe surface modification process and laser shock peening on AA 7075 T 651. Among these two processes, LSP reveals better improvement in surface hardness. The Vickers micro hardness test is contacted on the specimens. 15%, 18% and 29% of harness improvements are obtain than unpeened specimen in shot peened specimen, SSMT specimen and Laser shock peened specimen respectively. The deformed layer thickness is 500 µm found in the laser shock peened specimen and 300 µm in the shot peened and SSMT treated specimens.

Characteristics of the Narrow Fractions of Fly Ash Microspheres as the Basis of Light-Weight High-Strength Materials

The narrow fractions of microspheres with a size of −0.4 + 0.2 mm with a low bulk density in the range of 0.34–0.64 g/cm3 were separated from cenosphere concentrates of fly ashes and fly ash from local selection obtained from pulverized coal combustion. The main components of the chemical composition in obtained narrow fractions are SiO2 – 55–66 and Al2O3 – 21–40 wt. %. The part of amorphous glass phase are 63–93, the mullite phase are 1–34, the quartz phase are 2–8 and the calcite phase are 0–1 wt. %. It is found that microspheres, characterized by maximum values of bulk density 0.64 g/cm3 and apparent thickness of the shell 20 μm, has the best strength properties. The successive twofold compressive loading the particles by increased strength were selected, for which the values of bulk density and apparent shell thickness increased to 0.86 g/cm3 and 29 μm, respectively. It is shown that the spheres with the single-ring structure are primarily subjected to destruction; the particles with network and solid structure provide improved strength characteristics of narrow fractions of microspheres

Selective Laser Melting of Mechanically Alloyed Metastable Al5Fe2 Powders

Aluminum alloys, which are high-strength lightweight materials, were processed by selective laser melting (SLM) with high-energy consumption and poor finish due to quick heat dissipation. Previous investigations reported that SLM with 300 W laser power and 500 mm/s scanning speed can process the aluminum alloys, such as Al-Si12 and AlSi10Mg. This work aims to process the powders to alter their properties and to reduce the laser intensity required in the process, and it also reports that the SLM-processed Al–Fe alloys utilize the metastable alloy by mechanical alloying (MA). The elemental Al and Fe powders were first alloyed in a ball mill in a relative short time period (∼15 h) employing high milling intensities, high ball-to-powder ratio (≥20:1), and high milling velocities (≥400 rpm), which produced fine metastable Al–Fe powders, and these powders were processed later by the SLM. The optimum laser power, the scanning speed, hatch distance, and substrate temperature were investigated by a series of experiments. Experimental results indicated that decreasing the laser energy density while increasing the laser scanning speed can benefit for smoother laser hatch lines, and the metastable Al5Fe2 alloy powders can be processed and stabilized under a 200-W laser energy density and a scanning speed of 1000 mm/s. It is expected that the combination of pre-excited materials in a metastable phase will open a new window to optimize the SLM process for aluminum alloys and other metallic alloys.

Mechanical response of nanoporous metals: A story of size, surface stress, and severed struts

Abstract

Development and Application of Lightweight High-strength Metal Materials

This article reviews the performance, alloy composition and the development of advanced lightweight high-strength materials such as high-strength steels, high-strength aluminum alloys, high-strength magnesium alloys, and titanium alloys.