Materials Selection Charts Research Articles

Effective Mechanical Properties of Periodic Cellular Solids with Generic Bravais Lattice Symmetry via Asymptotic Homogenization.

In this paper, the scope of discrete asymptotic homogenization employing voxel (cartesian) mesh discretization is expanded to estimate high fidelity effective properties of any periodic heterogeneous media with arbitrary Bravais's lattice symmetry, including those with non-orthogonal periodic bases. A framework was developed in Python with a proposed fast-nearest neighbour algorithm to accurately estimate the periodic boundary conditions of the discretized representative volume element of the lattice unit cell. Convergence studies are performed, and numerical errors caused by both voxel meshing and periodic boundary condition approximation processes are discussed in detail. It is found that the numerical error in periodicity approximation is cyclically dependent on the number of divisions performed during the meshing process and, thus, is minimized with a refined voxel mesh. Validation studies are performed by comparing the elastic properties of 2D hexagon lattices with orthogonal and non-orthogonal bases. The developed methodology was also applied to derive the effective properties of several lattice topologies, and variation of their anisotropic macroscopic properties with relative densities is presented as material selection charts.

Implementation Of A Systematic Materials Selection Method In The Preliminary Design Of Propeller Shafts

The materials selection charts also known as “Ashby” charts are a versatile tool in engineering design. The use of such material property charts is due to technical difficulties in specifying properties during the design of a complex and major component as in the case of a propeller shaft. In addition, the tool combines innovation, minimizes design failures and practicality to technology. The aim of the research is to present the methodology for selecting the most convenient material for a given shaft and its performance. Using a propeller shaft as showcase, the method is based on the analysis of the materials selection charts and of the material performance index of EDUPACK from GRANTA Design. The required properties may be: tensile strength, yield strength, fatigue strength, impact strength and resistance to corrosion, where not all of them are necessarily explicitly expressed. The Ashby charts, with their consistent results seem to be the proper tool for the eventual future proposal for the extension the UR M68 formula for the propeller shaft diameter to stainless steels.

Engineered bi-material lattices with thermo-mechanical programmability

Lightweight meta-structures can reveal combinations of properties that do not occur in conventional structures. In this paper, a 2D bi-material unit cell is proposed based on a re-entrant architecture. Two 3D unit cells, so-called star and cubic architectures, are then constructed using the proposed 2D unit cell. Finally, lattice-based unit cells are periodically arranged to develop a meta-structure. The thermo-mechanical functionalities of the developed meta-lattices can be programmed by tailoring either architectural parameters (i.e., strut length, diameter, shape, and orientation) or the material combination of struts. The influence of the architectural parameters and material combinations on the effective elastic stiffness, Poisson’s ratio (PR), and coefficient of thermal expansion (CTE) is systematically investigated. A finite element (FE) model is established to perform a goal-driven multi-objective optimization and to attain an uncommon combination of PR and CTE (e.g. negative PR up to −1.8 or near-zero CTE) with uncompromised stiffness. Despite the complicated design (many struts are diagonal with respect to the printing bed), the low-cost additive manufacturing process (i.e., fused filament fabrication) parameters are optimized to fabricate a selected number of bi-material meta-lattices with a reasonable time and quality. By employing the FE model, the optimized architectural parameters are determined for a series of applied engineering applications such as structurally robust aerospace structures, energy absorbable structural elements, and shape transforming structures. The developed lightweight meta-lattices with tunable thermo-mechanical properties can offer the material selection charts with more economical material options for engineering applications such as antennas and precision instruments.

Computer-aided gear product realization using enhanced decision-making in material selection and reliability assessment

Unmatched in its diversity of applications, gears continue to be one of the most successful components used to transfer energy throughout a mechanical system. Certain project settings can require gears to meet more than one criterion to achieve optimal performance. In this paper, we proposed the simulation-based design synthesis using virtual simulations and material selection charts. For this, a computer-generated two gear mechanism is made to create a gear material selection chart, similar to an Ashby chart, that compares the desired conditions of angular velocity and torque. By utilizing computer software to personalize specifications, a gear design material selection chart can be constructed to expedite the material selection process for project environments and needs. Using this approach, gear designers and manufactures can promote design efficiency in the early stage of product development by flexibly determining possible material choices for their gear design based on the desired performance specifications.

Rapid manufacturing of automotive polymer series parts: A systematic review of processes, materials and challenges

Additive manufacturing (AM) is moving towards series manufacturing applications across a variety of industries. However, take-up for series production in the automotive industry is still slow and limited to very few materials. Therefore, this review assesses compatibility of polymer AM processes and materials and provides a method to check their formal applicability for automotive series part production. The proposed material and process selection method applies basic automotive requirements derived from the VDA 232-201 industry standard and an interior part case study. Materials and processes in AM are put into context via material selection charts and a process compatibility index. This graphical analysis enables first judgement about applicability and subsequent pre-selection of materials and processes. Insights may help users, equipment manufacturers and material developers in the fields of AM to match automotive requirements and reduce barriers for adoption of AM in series part manufacturing.

Alternative materials for grey cast iron corn-mill plates by computer-aided selection and weighted property methods: the case of Ghana

Most locally-manufactured corn-mill plates in tropical countries are made of grey cast iron due to its relatively low cost, good wear resistance, good hardness and other mechanical properties in general. However, these corn-mill plates are prone to corrosion and abrasive wear resulting to contamination of milled corn which is consumed by humans. This work focuses on the use of computer-aided selection and weighted property methods to identify alternative materials for grey cast iron corn-mill plates. Requirements such as non-toxicity, good corrosion resistance, good wear resistance, low friction coefficient, high thermal conductivity, low specific gravity, high compressive strength and low cost were used in the initial material selection stages. The derivation of material performance index in addition to Ashby’s materials selection chart are used to find suitable materials to replace grey cast iron. The decision method showed that white cast iron with high-chromium alloy had the highest weighted performance index (93.75%), while nodular graphite cast iron had the least weighted performance index (65.55%). High-chromium alloyed white cast iron was therefore considered as substitute for the grey cast iron corn-mill plates.

Shape-changing airfoil and actuated elevons for miniature-aerial vehicle: UniMorph

The material selection and designing for a shape-changing airfoil and actuated elevon mechanism to improve endurance, payload, flight trajectories, and mechanical-failure is presented. The selection of the active, expands on heating, and passive layer, resilient to expand on heating, was performed by investigating material selection chart, representing various material types. An analytical model was developed to calculate UniMorph (UM) surface area subject to the output force required. The developed mathematical model was validated with the experimental results obtained from the rectangular UM fabricated using a simple and rapid fabrication method demonstrated in this study. It was noted that the proposed analytical methodology helped to develop optimised structural sections of the UM, which was applied to generate shape-changing airfoil and actuated elevons for a miniature-aerial vehicle (MAV). A total payload improvement of 45 g with 4 min endurance improvement was noted for the MAV, whereas servo mechanism failure was eliminated. This study concentrates on the material and structural characteristics and not on the aerodynamic aspects of the MAV.

Bi-Material Re-Entrant Triangle Cellular Structures Incorporating Tailorable Thermal Expansion and Tunable Poisson's Ratio1

Abstract Based on the bi-material triangle lattice cell, a new cellular structure, bi-material re-entrant triangle (BRT) cellular structure, is devised to incorporate tailorable coefficient of thermal expansion (CTE) and tunable Poisson's ratio (PR) properties by replacing the straight base of a triangle with two hypotenuse members. A general thermoelasticity equation to systematically build the relationship among the external force, the temperature load, and the deformation for planar lattice structures with bounded joints is derived and then embedded into a theoretical model for the devised BRT structure. Using assembled thermoelasticity equation, effective PR, Young's modulus, as well as CTE are computed. In order to guide designers to construct initial concepts, the design domain for coupling negative CTE and negative PR properties is plotted. The material-property-combination region that can be achieved by this cellular structure is determined within an Ashby material selection chart of CTE versus PR. Nine available combinations of CTE and PR properties are extracted and demonstrated with abaqus simulation.

Can the maximum volume fraction ensure optimum reinforcement in short‐fiber composites?

ABSTRACTShort sisal fiber composites (SSFCs) based on a pectin matrix were prepared and characterized mechanical and optically. Different concentrations (1–30 wt %) of fibers were used to evaluate the packing effect on the reinforcement of a polymer matrix. Theoretical models were used to obtain the maximum packing or volume fraction (ϕmax) of randomly oriented short fibers and its relationship with the mechanical parameters. A higher elastic modulus and tensile strength were observed when the fiber content was increased in the composite at a fixed aspect ratio (length/diameter = 2.8). Material selection charts showed that SSFCs with a fiber concentration of 20 wt % had a higher reinforcement effect at ϕmax, as was predicted through theoretical models. Nevertheless, SSFCs with a fiber concentration of 7 wt % presented optimum reinforcement because it resulted in the strongest and lightest composite material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47821.

Design and additive manufacturing of electro-mechanical metamaterials with designed anisotropy and self-sensing

In this talk, I will present our research on design, additive manufacturing, and performances of new classes of multi-functional materials that transcend the common electro-mechanical coupling limitations. These materials are as light as carbon aerogels, but with orders of magnitude higher stiffness and strength, they possess multi-functionalities. They are composed of interconnected 3D hierarchical micro-structures as designed “atoms” and “molecules” as in natural materials to reach uncharted white space in the material selection charts. Attention is focused on our development of a suite of novel additive manufacturing and processing techniques to synthesis traditionally unprocessable inorganic/organic highly responsive building blocks and architect them into scalable form factors with precisely defined active three-dimensional micro- and nano-scale features. We will discuss the possiblities of coupling and decoupling of the piezoelectric coefficients, density stiffness scaling, and selective electro-mechanical amplifications through our metamaterial design and printing approach. These insights shed light on a next generation of metamaterials, with designed-in structural and smart functionalities, including self-sensing and actuation, vector sensing and detection as well as simultaneous impact wave absorptions and self-monitoring with only a fraction of solid, as opposed to relying on multiple components.

The effect of Zr and Sn additions on the microstructure of Ti-Nb-Fe gum metals with high elastic admissible strain

An open challenge on structural biomaterials is to obtain low-cost Ti-alloys with high elastic admissible strength (the ratio of yield strength to modulus). To reach this goal, we designed and characterized three quaternary alloys from the Ti-Nb-Fe system with additions of Zr and Sn. The samples were solution-treated and tested under two conditions: water-quenched and aged at 450 °C. Microstructures were analyzed with aid of scanning and transmission electron microscopy. Tensile tests performed at room-temperature confirmed a remarkable yield strength of 1271 MPa with an elastic modulus close to 90 GPa among aged Ti-19Nb-2.5Fe-6Sn (wt%) samples. Solution-treated Ti-19Nb-2.5Fe-10Zr samples presented a good combination of yield-strength and elastic modulus (1027 MPa and 69 GPa, respectively), displaying an elastic admissible strength close to 1.5. Although Zr and Sn are equally distributed between matrix and precipitates, the diffusion of Nb and Fe seem to be inhibited by the presence of Sn. As a result, Sn allows higher yield-strengths and more refined secondary α-phase, while Zr has a stronger effect on reducing the elastic modulus. In the end, a materials selection chart is presented to help designers to select materials for orthopedic implants considering the elastic admissible strain and cost as major guidelines.

Accessing small craft‘s boatbuilding sustainability: A materials selection chart‘s approach

AbstractMaterials properties charts are proposed to compare available materials for small fishing craft artisanal boatbuilding. Mechanical flexural performance parameters were selected for the boats’ seakeeping and service life. Price, CO2 footprint, and embodied energy were the parameters used for economic and environmental sustainability evaluation. Combined parameters showed a competitive performance for wood. Results indicate that adopting laminate composite construction as a substitute for wood in the fishing craft fleet can be less sustainable from both economical and environmental perspectives. Efforts could be more effective if directed to increase existing artisanal boatyards’ sustainability through enhancing wood durability, optimizing its scantlings, adopting alternative native wood, reforested wood or wood cored sandwich composites.

Material selection methodology for radio frequency (RF) microelectromechanical (MEMS) capacitive shunt switch

This paper describes the process of selecting the most optimum Radio Frequency Micro- electro- mechanical-systems (RF-MEMS) switch design using Ashby’s methodology. The switches are compared on the basis of parameters like actuation voltage, insertion loss, isolation and switching time using material selection charts. The chart shows that a low-voltage metal-to-metal contact shunt capacitive RF-MEMS having a bridge structure with Si-GaAs substrate, electroplated gold contacts and silicon nitride dielectric layer, is the most optimum of all the switches considered.

Cu Nanospring Films for Advanced Nanothermal Interfaces

An advanced thermal interface material comprised of dense and orderly arrays of 10‐µm high Cu nanosprings with tunable normal and shear compliance, lateral stability due to spring intertwining, and thermal resistance below 1 mm2KW−1 is presented. The Cu nanospring films possess the compliance of soft polymers but up to 100 times higher thermal conductivity than materials with similar elastic modulus. This unique combination of mechanical and thermal properties makes it possible for the first time to populate the large empty space in the materials selection chart of thermal conductivity versus elastic modulus.

An investigation of dielectric material selection of RF-MEMS switches using Ashby’s methodology for RF applications

This paper presents a dielectric material selection methodology for RF-MEMS switch used for radio frequency applications. Here Ashby's material selection approach is used to optimize the performance indices of RF-MEMS switch such as dielectric charging, stability, hold down voltage and RF performance. In this work, dielectric constant (źr), electrical resistivity (ź), thermal conductivity (ź), thermal expansion coefficient (ź), Young's Modulus (E) are chosen as material indices of dielectric layer in RF-MEMS switch to evaluate the various performance indices. The Ashby's material selection charts shows that Al2O3 and SiN are the best suitable material for dielectric layer in RF-MEMS switches to exhibit improved performance for radio frequency applications.

Material selection shape factors for compliant arrays in bending

Similar to the general class of metamaterials, compliant arrays (CAs) are engineered from an array of subelements that combine to produce a response that is typically not available from a flat panel made of a single material. As such, analysis and design of CA systems requires the integration of both the material and geometrical properties of the array. This paper proposes a convenient and efficient method of combining these essential elements using analytically derived shape factors for bending modes. The approach is validated experimentally, and used to demonstrate large regions of previously inaccessible property combinations in material selection charts that become attainable using carefully design CAs.

Structural, Nanomechanical, and Computational Characterization of d,l-Cyclic Peptide Assemblies

The rigid geometry and tunable chemistry of D,L-cyclic peptides makes them an intriguing building-block for the rational design of nano- and microscale hierarchically structured materials. Herein, we utilize a combination of electron microscopy, nanomechanical characterization including depth sensing-based bending experiments, and molecular modeling methods to obtain the structural and mechanical characteristics of cyclo-[(Gln-D-Leu)4] (QL4) assemblies. QL4 monomers assemble to form large, rod-like structures with diameters up to 2 μm and lengths of tens to hundreds of micrometers. Image analysis suggests that large assemblies are hierarchically organized from individual tubes that undergo bundling to form larger structures. With an elastic modulus of 11.3 ± 3.3 GPa, hardness of 387 ± 136 MPa and strength (bending) of 98 ± 19 MPa the peptide crystals are among the most robust known proteinaceous micro- and nanofibers. The measured bending modulus of micron-scale fibrils (10.5 ± 0.9 GPa) is in the same range as the Young's modulus measured by nanoindentation indicating that the robust nanoscale network from which the assembly derives its properties is preserved at larger length-scales. Materials selection charts are used to demonstrate the particularly robust properties of QL4 including its specific flexural modulus in which it outperforms a number of biological proteinaceous and nonproteinaceous materials including collagen and enamel. The facile synthesis, high modulus, and low density of QL4 fibers indicate that they may find utility as a filler material in a variety of high efficiency, biocompatible composite materials.

Natural fibre composites: Comprehensive Ashby-type materials selection charts

To aid design engineers in closing the existing gap between current scientific knowledge and actual market applications of plant fibre reinforced plastics (PFRPs), this article provides comprehensive Ashby-type materials selection charts for PFRPs to facilitate product design and development. General tensile mechanical property profiles are presented for a variety of PFRPs to enable the design for (i) optimal stiffness and strength, (ii) minimal weight (i.e. optimal specific properties), (iii) minimal cost, and (iv) minimal eco-impact. A large database is used to capture the range in properties of different (i) reinforcements forms (short fibres: pellets and nonwovens; long fibres: multiaxials and unidirectionals), (ii) polymer matrices (thermoplastic and thermosetting), and (iii) manufacturing techniques (injection moulding, compression moulding, hand lay-up, vacuum infusion, resin transfer moulding and prepregging). As PFRPs are often viewed as alternatives to glass fibre composites (GFRPs), for demonstrative purposes the tensile properties of the various PFRPs are compared with similar GFRPs. Moreover, highlighting that other mechanical parameters may be critical performance indices for specific products and applications, a materials property chart for a fatigue-limited design is also produced.

Developing plant fibre composites for structural applications by optimising composite parameters: a critical review

Plant fibres, perceived as environmentally sustainable substitutes to E-glass, are increasingly being employed as reinforcements in polymer matrix composites. However, despite the promising technical properties of cellulose-based fibres and the historic use of plant fibre reinforced plastics (PFRPs) in load-bearing components, the industrial uptake of PFRPs in structural applications has been limited. Through an up-to-date critical review of the literature, this manuscript presents an overview on key aspects that need consideration when developing PFRPs for structural applications, including the selection of (I) the fibre type, fibre extraction process and fibre surface modification technique, (II) fibre volume fraction, (III) reinforcement geometry and interfacial properties, (IV) reinforcement packing arrangement and orientation and (V) matrix type and composite manufacturing technique. A comprehensive materials selection chart (Ashby plot) is also produced to facilitate the design of a PFRP component, based on the (absolute and specific) tensile properties.

Wear and abrasion resistance selection maps of biological materials

The mechanical design of biological materials has generated widespread interest in recent years, providing many insights into their intriguing structure–property relationships. A critical characteristic of load-bearing materials, which is central to the survival of many species, is their wear and abrasion tolerance. In order to be fully functional, protective armors, dentitious structures and dynamic appendages must be able to tolerate repetitive contact loads without significant loss of materials or internal damage. However, very little is known about this tribological performance. Using a contact mechanics framework, we have constructed materials selection charts that provide general predictions about the wear performance of biological materials as a function of their fundamental mechanical properties. One key assumption in constructing these selection charts is that abrasion tolerance is governed by the first irreversible damage at the contact point. The maps were generated using comprehensive data from the literature and encompass a wide range of materials, from heavily mineralized to fully organic materials. Our analysis shows that the tolerance of biological materials against abrasion depends on contact geometry, which is ultimately correlated to environmental and selective pressures. Comparisons with experimental data from nanoindentation experiments are also drawn in order to verify our predictions. With the increasing amount of data available for biological materials also comes the challenge of selecting relevant model systems for bioinspired materials engineering. We suggest that these maps will be able to guide this selection by providing an overview of biological materials that are predicted to exhibit the best abrasion tolerance, which is of fundamental interest for a wide range of applications, for instance in restorative implants and protective devices.