Base Matrix Material Research Articles

Design Exploration of Reliably Manufacturable Materials and Structures With Applications to Negative Stiffness Metamaterials and Microstereolithography1

One of the challenges in designing metamaterials for additive manufacturing (AM) is accounting for the differences between as-designed and as-built geometries and material properties. From a designer's perspective, these differences can lead to degradation of part and metamaterial performance, which is especially difficult to accommodate in small-lot or one-of-a-kind production. In this context, each part is unique, and therefore, extensive iteration is costly. Designers need a means of exploring the design space while simultaneously considering the reliability of additively manufacturing particular candidate designs. In this work, a design exploration approach, based on Bayesian network classifiers (BNC), is extended to incorporate manufacturing variation into the design exploration process and identify designs that reliably meet performance requirements when this variation is taken into account. The example application is the design of negative stiffness (NS) metamaterials, in which small volume fractions of NS inclusions are embedded within a host material. The resulting metamaterial or composite exhibits macroscopic mechanical stiffness and loss properties that exceed those of the base matrix material. The inclusions are fabricated with microstereolithography with features on the scale of tens of microns, but variability is observed in material properties and dimensions from specimen to specimen. This variability is measured and modeled via design, fabrication, and characterization of metrology parts. The quantified manufacturing variability is incorporated into the BNC approach as a manufacturability classifier to identify candidate designs that achieve performance targets reliably, even when manufacturing variability is taken into account.

Characterization & evaluation of Al7075 MMCs reinforced with ceramic particulates and influence of age hardening on their tensile behavior

Aluminium has a massive demand in the areas of automobile, aerospace and diverse engineering applications in order to furnish the requirement in those fields. But this technological evolution needs something more than aluminium. Materialogists are struggling hard to find out a material which owns sound mechanical and thermal properties and also superior than aluminium in each extent. Metal matrix composite (MMC) is a solution. Generally, metal matrix composites contain a low density material, i.e. aluminium or magnesium, reinforced with fibers or particulate of a ceramic material, i.e. silicon carbide or graphite. They show greater specific strength, high stiffness, elevated operating temperature, and superior wear resistance, along with the possibility to customize these properties for a specific use. In this study, Al 7075 is taken as a base matrix material, whereas ceramic materials like SiC, Al2O3, B4C and TiB2 are used as reinforcements. There are different methods available for fabricating metal matrix composite materials and in this work, stir casting technique, which is a liquid state process, is used. Four different MMC specimens were produced with 15 % SiC, 15 % Al2O3, 15 % B4C and 15 % TiB2. Mechanical properties i.e. tensile strength, hardness, and impact strength were studied for the prepared specimens. The results were charted and presented graphically to describe these materials characteristics.

3D printing processes for photocurable polymeric materials: technologies, materials, and future trends.

The aim of this review is a faithful report of the panorama of solutions adopted to fabricate a component using vat photopolymerization (VP) processes. A general overview on additive manufacturing and on the different technologies available for polymers is given. A comparison between stereolithography and digital light processing is also presented, with attention to different aspects and to the advantages and limitations of both technologies. Afterward, a quick overview of the process parameters is given, with an emphasis on the necessities and the issues associated with the VP process. The materials are then explored, starting from base matrix materials to composites and nanocomposites, with attention to examples of applications and explanations of the main factors involved.

Carbon nano fibers reinforced composites origami inspired mechanical metamaterials with passive and active properties

Core panels used for compression or impact damping are designed to dissipate energy and to reduce the transferred force and energy. They are designed to have high strain and deformation with low density. The geometrical configuration of such cores plays a significant role in redistributing the applied forces to dampen the compression and impact energy. Origami structures are renowned for affording large macroscopic deformation which can be employed for force redistribution and energy damping. The material selection for the fabrication of origami structures affects the core capacity to withstand compression and impact loads. Polymers are characterized by their high compression and impact resistance; the drawback of polymers is the low stiffness and elastic moduli compared with metallic materials. This work is focused on the study of the effect of Carbon Nano Fibers (CNF) on the global mechanical properties of the origami panel cores made of polymeric blends. The base matrix materials used were Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) blends, and the percentages of the PLA/TPU were 100/0, 20/80, 65/35, 50/50, 20/80, and 0/100 as a percentage of weight. The weight percentages of CNF added to the polymeric blends were 1%, 3%, and 5%. This paper deals with the fabrication process of the polymeric reinforced blends and the origami cores, in order to predict the best fabrication conditions. The dynamic scanning calorimetry and the dynamic mechanical analyzer were used to test the reinforced blended base material for thermomechanical and viscoelastic properties. The origami core samples were fabricated using per-molded geometrical features and then tested for compression and impact properties. The results of the study were compared with previous published results which showed that there is considerable enhancement in the mechanical properties of the origami cores compared with the pure blended polymeric origami cores. The active properties of the origami unit cell made of composite polymers containing a low percentage of CNF were also investigated in this study, in which the shape memory effect test conducted on the origami unit cell.

Study of Wear Characteristics of Hematite Reinforced Aluminum Metal Matrix Composites

Metal Matrix Composites (MMCs) are used in aerospace, transport, automotive, marine engineering due to their light weight with improved strength, stiffness and wear resistance. Wear is one of the reasons for the failure of the machine components. It is difficult to accurately predict the life of components due to wear, because, generally the wear rates are largely scattered. An attempt is made to study the Wear characteristics of Hematite (Fe2O3) reinforced Aluminum 6061 Metal Matrix Composites. The reinforcement is added in particulate form of 40-45 µm with an increment of 2% from 0% to 8% (by weight). Composites are fabricated by liquid metallurgy technique. The Microstructural study on as cast Al6061-Fe2O3 compositesreveals uniform distribution of reinforcement particles. The wear test was conducted on the specimens by varying speed from 200 – 400 rpm & load from 50 – 100 N. The wear rate was measured by the weight loss of the specimen. The results show that there is an increase in the wear resistance with increase in percentage of reinforcement. The wear factor has decreased 30 - 40% at 8% of reinforcement as compared to base matrix material.

Experimental Verification for Improving Dielectric Strength of Polymers by Using Clay Nanoparticles

Nanoparticles are a considerable attention due to very interesting properties have been accepted to base matrix materials during the nanostructure in- corporation. Therefore, this paper has been presented an experimental study for the dielectric strength of sev- eral new industrial polymer nanocomposites specimens. It has been studied the eects of clay nanoparticles in- corporation into polypropylene (PP), polyvinyl chloride (PVC), low density polyethylene (LDPE), and high density polyethylene (HDPE) on electric properties, dielectric properties, dielectric strength and voltage en- durance significantly for variant polymers by a simpli- fied breakdown model. Experimental results have been compared with respect to unfilled industrial materials under AC electric field (uniform and non-uniform) and variant thermal temperatures.

화장품 중 zinc pyrithione 분석방법 개발에 대한 연구

이 연구에서는 화장품 중 사용한도 성분으로 지정되어 있으나 아직 분석방법이 개발되지 않은 살균 보존 성분으로 사용되는 zinc pyrithione (ZnPT)에 대한 분석방법을 개발 확립하기 위한 목적으로 국 내외 자료 및 문헌을 조사하여 분석방법을 설정하였으며, 분석방법의 유효성 확인에 필요한 base matrix 시료의 선정을 위해 대상성분들의 사용량 및 사용제품들에 대한 자료를 조사하였다. Base matrix 시료를 선정·제조한 후 분석방법 유효성 확인 절차에 따라 각 대상성분들에 대한 분석방법의 유효성을 확인하였으며 실험실간 분석방법의 유효성 확인 수행을 통해 개발된 분석방법을 검증하여 확립하였다. 최종적으로 실제 시중 유통 화장품을 대상으로 개발된 분석방법을 적용하여 분석방법의 적합성을 검증하였다. 이 연구를 통해 개발된 분석방법을 '화장품 중 배합한도 성분 분석법 가이드라인'으로 제시함으로서 국내 시장 유통화장품의 검정에 활용되어 품질의 향상 및 국민 보건 안전성이 증진될 것이며 국내 화장품 산업의 국제 경쟁력 강화로 인해 수출 증대에 기여할 것으로 기대된다. This study aims to develop a new analytical method to detect zinc pyrithione, the ingredient of cosmetics appointed as restricted ingredients and used as preservatives.. The analytical method was based on data gathered from the relevant literature. Information about the amounts of these ingredients was researched in order to select the base-matrix materials used to validate the analytical method. After selecting and preparing the base-matrix materials, the analytical method was validated by method validation procedures. The analytical method was verified first by inter-laboratory validation and then through analyzing the cosmetics sold in the market. Based on the results of this study, guidelines are proposed for the analysis of restricted ingredients in cosmetics, which will provide a method to test the cosmetics circulating in the Korean market. The use of the proposed guidelines will increase the quality of the cosmetics as well as the safety of human health, which will enhance the competitiveness of the Korean cosmetics industry and lead to an increase in the exportation of cosmetics.

Wear Behavior of Magnesium Alloy AZ91 Hybrid Composite Materials

The influence of hybrid reinforcements including silicon carbide and graphite particles with a size 37–50 μm on the wear characteristics of AZ91 magnesium alloy was studied. The dry sliding wear test was conducted using a pin-on-disc wear testing machine in the load range of 20 to 80 N at different sliding velocities in the range of 1.047 to 2.618 m/s. The results show that the wear resistance of composites was much better than that of the base matrix material under the test conditions. At a speed of 1.047 m/s and load of 40 N, the wear rate (mm3/km) of the unreinforced alloy was 6.3, which reduced to 3.8 in the case of 3% reinforced composite. The antiwear ability of magnesium alloy composite was found to improve substantially with the increase in silicon carbide and graphite content from 1 to 3% by weight and the wear rate was found to decrease considerably. At a speed of 1.047 m/s and load of 80 N, the wear rate (mm3/km) reduced from 11.8 to 9.1 when the reinforcement content increased from 1 to 3%. However in both the unreinforced alloy and reinforced composite, the wear rate increased with the increase in load and sliding velocity. An increase in the applied load increases the wear severity by changing the wear mechanism from abrasion to particle cracking-induced delamination. The worn surface morphologies of the composite containing 3% reinforcement by weight for the sliding velocity of 1.047 m/s were examined using scanning electron microscopy. Different wear mechanisms, namely, abrasion, oxidation, and delamination, have been observed.

Formulation of a macroscale corrosion damage internal state variable model

A new consistent formulation coupling kinematics, thermodynamics, and kinetics with damage using an extended multiplicative decomposition of the deformation gradient that accounts for corrosion effects is proposed. The corrosion model, based upon internal state variable (ISV) theory, captures the effects of general corrosion, pit nucleation, pit growth, pit coalescence, and intergranular corrosion. The different geometrically-affected rate equations are given for each mechanism after the ISV formalism and have a thermodynamic force pair that acts as an internal stress. Pit nucleation is defined as the number density that changes as a function of time driven by the local galvanic electrochemical potential between base matrix material and second phase material. Pit growth is defined as pit surface area growth. Pit coalescence is the interaction of the pits as they grow together and is often characterized by transgranular corrosion and is mathematically constructed from Coulomb’s Law and the Maxwell stress. General corrosion is signified by thickness loss of the material and is characterized by a modified Faraday’s Law. The intergranular corrosion rate is related to the grain boundary effects so that it is characterized by the misorientation between grains. The total damage (void volume or area fraction) is the addition of the general, pitting, and intergranular corrosion. The ability of the model to predict aspects of the corrosion mechanisms and aging history effects of an engineering material are then illustrated by comparison with experimental data of an extruded AZ31 magnesium alloy.

Microcalorimetric study of the adsorption of native and mono-PEGylated bovine serum albumin on anion-exchangers

The adsorption of native bovine serum albumin (BSA) and 12kDa-PEG-BSA on 12 different commercially available strong and weak anion-exchange resins is studied at 25°C and pH 7. The resins differ in their base matrix material, their functional groups and the type of polymer modification. A combination of equilibrium measurements and microcalorimetric experiments is used to determine the specific enthalpy of adsorption of the proteins. From these data, the entropic contributions to the specific Gibbs energy of adsorption are determined. The results strongly differ for different resins. They also depend on the loadings. The adsorption of BSA on strong (Q) anion-exchangers is exothermic and enthalpy-driven. The adsorption of BSA on weak (DEAE) anion-exchangers is endothermic and entropy-driven. The adsorption of PEG-BSA on strong (Q) anion-exchangers is exothermic or endothermic, depending on the resin, while the adsorption of PEG-BSA on weak (DEAE) anion-exchangers is exothermic for all studied resins. The present study provides a large body of new experimental data that contribute to the understanding of the nature of protein adsorption on ion exchange resins and the influence of the resin properties and polymer modification of the proteins on this process.

Erosive wear properties of high V–Cr–Ni stainless spheroidal carbides cast iron at high temperature

To investigate the high temperature erosive wear properties of materials, a new testing machine was developed, and its performance was evaluated. In this machine, temperature of impact particles, air, and test pieces were all controlled independently from room temperature to 900 °C, respectively. And the test pieces were set in a chamber to avoid occurring oxidation at high temperature. Heated particles were accelerated by hot air of same temperature level to impact on test piece that was heated up to same temperature level, so testing temperature condition was remained constant. The impact angles of test piece stage can be easily adjusted from 0° to 90°. Some experiments were performed using this testing machine. Erosive wear resistances of S50C steel, SK3 and high V–Cr–Ni stainless spheroidal carbides cast iron (SCI-VCrNi) were evaluated. Surface morphology of each material was characterized with optical microscope and micro-hardness tester. Erosive wear resistance was related to both base matrix structure and material removal mechanism. The erosion rates of specimens increased with test temperature, among them, the erosion rate of SCI-VCrNi was the lowest. As a result, utilization of this erosion machine was confirmed to an effective way for the evaluation of high temperature erosion.

Catalytic nanocapillary condensation and epitaxial GaN nanorod growth

Intrinsic catalytic process by capillary condensation of Ga atoms into nanotrenches, formed among impinging islands during the wurzite-GaN thin film deposition, is shown to be an effective path to growing GaN nanorods without metal catalysts. The nanocapillary brings within it a huge imbalance in equilibrium partial pressure of Ga relative to the growth ambient. GaN nanorods thus always grow out of a holding nanotrench and conform to the boundaries of surrounding islands. The nanorods are epitaxially orientated with ${⟨0001⟩}_{\mathrm{Ga}\mathrm{N}}\ensuremath{\Vert}{⟨111⟩}_{\mathrm{Si}}$ and ${⟨2\underset{}{11}0⟩}_{\mathrm{Ga}\mathrm{N}}\ensuremath{\Vert}{⟨110⟩}_{\mathrm{Si}}$ similar to the matrix. Concaved geometry is essential and is a condition that limits the axial dimension of the nanorods protruding above the base (matrix) material region. Revelation of the growth mechanism in the current context suggests that fabrication of nanoquantum structures with controlled patterns is enabling for any attainable dimensions.

College of American Pathologists 2003 Fresh Frozen Serum Proficiency Testing Studies

College of American Pathologists 2003 Fresh Frozen Serum Proficiency Testing Studies

Surface chemical analysis of carbohydrate materials used for chromatography media by time-of-flight secondary ion mass spectrometry.

The surface chemical structure of two raw materials (agarose and dextran) and four base matrixes used in the manufacture of chromatography media were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The results show that the small differences in molecular structure between these materials result in significant differences in the TOF-SIMS spectra and that these differences can be identified and quantified using either of two different approaches. In a novel approach, fragment ion distributions were extracted from the TOF-SIMS spectra for each material, providing an immediate and systematic overview of the spectral features. Difference fragment distributions were used to highlight spectral differences between the materials. The results of the fragment ion distribution analysis, in terms of identification and quantification of spectral variations between different materials, were found to be in agreement with the results from a principal component analysis using the same set of data. Both methods were found capable of (i) distinguishing between agarose and dextran and (ii) detecting and quantifying the degree of cross-linking present in the four base matrix materials. In addition, using a deuterated chemical cross-linker, it was possible to identify spectral features specifically connected to the cross-link molecular structure.

Genetic design of solids possessing a random-particulate microstructure.

There exists a variety of difficulties in the computational design of macroscopic solid material properties formed by doping a homogeneous base matrix material with randomly distributed particles having different properties. Three primary problems are (1) the wide array of free microdesign variables, such as particle topology, property phase contrasts and volume fraction, which render the associated objective functions to be highly non-convex; (2) that the associated objective functions are not differentiable with respect to design variables, primarily due to prescribed constraints, such as prespecified restrictions on the microscale stress-field behaviour; and (3) the effective responses of various finite-sized samples, of equal volume but of different random particle distributions, exhibit mutual fluctuations, leading to amplified noise in optimization strategies where objective function sensitivities or comparisons are needed. The focus of this paper is the development of a statistical genetic algorithm which can handle difficulties due to non-convexity, lack of regularity and size effects. Theoretical properties of the overall approach are investigated. Semi-analytical and large-scale numerical examples, involving finite-element type discretizations, are given to illustrate its practical application.

Low Dielectric Nanoporous Poly(methylsilsesquioxane) (PMSSQ) Films via Inorganic/Organic Hybrids

Two types of methylsilsesquioxanes (MSSQ) were used as base matrix materials for nanoporous films. The hydrophilicity of MSSQ was controlled by copolymerization for the improved miscibility between MSSQs and star-shaped poly(caprolactone) (PCL) as a porogen. Linear relationship holds between porosity/refractive index and vol% of porogen upto 30%. Dielectric constant of porous MSSQ film could be reduced to 2.2 at the porosity of 30 vol%. Dielectric constant was very sensitive to the content of hydroxyl group of MSSQ and the the latter was reduced by treating surface silanols with hexamethyldisilazane.

Surface analysis of diamond and iron base matrix materials : Y-K. Wu, Y. Qing (Chongquing Non-Ferrous Metals Industry Corp, China)

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Erosion of a Silicon Carbide Whisker Reinforced Silicon Nitride

ABSTRACTThe steady-state solid particle erosion behavior of hot-pressed Si3N4 reinforced with 0, 10, and 20 weight percent SiC whiskers has been investigated at room temperature using angular alumina particles (63 to 270 μm diameter) as the erodent. The impact angle was varied from 30 to 90 ° and particle velocities were varied from 80 to 140 m/s. These materials were found to be very erosion resistant. However, there was little effect of the SiC whisker reinforcement on either the absolute erosion rate or on the velocity or particle-size exponents for the rates.The lack of a fiber reinforcement effect occurs even though the fiber additions provide an increase in the fracture toughness at high fiber contents. Results on differently processed Si3Na4 .base materials showed that microstructural variations due to processing history have very significant influence on the erosion resistance of the base (matrix) material. The results substantiate the idea that microstructure plays an important, but not fully understood role in the erosion processes for brittle materials.

An experimental study of hybrid fabric laminates of glass and graphite fibers

Abstract An experimental study of the mechanical properties of graphite/glass/graphite interply hybrid composite laminates subjected to pure tension and pure flexure is reported. The investigation includes single‐graphite, single‐glass and hybrid composite laminates. Straight side test coupons with dimensions of 200 mm × 14 mm and various numbers of layers were fabricated by hand lay‐up molding method. Epoxy resin served as the base matrix material. The types of layup of fabric warp directions include: 0°, 45°, 90°, [0°3/45°/0°3] and [0°3/45°/45°3]. Emphasis is given to the studying of the strength‐deformation behavior and the associated crack patterns of hybrid composite laminates, for monotonically‐increasing logitudinal elongation and angular deflection. Stress‐strain characteristics and crack patterns distinctive to each type of the specimen tested are presented. Mechanical strength data for hybrid composite laminates indicate the improvement in material characteristics over the single‐graphite fabric laminates.