Engineering Commons^™

Experimental Investigation Of Long-Term Performance Of Fiber-Reinforced Epoxy And Polyurethane Polymer Composites, Abdel Hamid I. Mourad, Amir Hussain Idrisi, Asima Zahoor, Muhammad M. Sherif, Beckry M. Abdel-Magid

Michigan Tech Publications, Part 2

The primary challenge encountered by polymers and their composites when exposed to saline water is their inadequate ability to withstand wear and tear over time. With a potential to replace conventional materials the long-term performance of FRP composites is still a novice area. This manuscript thus, reports an experimental investigation and prediction of the durability of fiber-reinforced polymer composites exposed to seawater at different temperatures. E-glass/epoxy and E-glass/polyurethane samples were exposed to 23 °C, 45 °C and 65 °C seawater for up to 2700 days (90 months). Tensile tests evaluated the mechanical performance of the composite as a function of …

Characterization Of Microstructural And Mechanical Properties Of 17-4 Ph Stainless Steel By Cold Rolled And Machining Vs. Dmls Additive Manufacturing, Pablo Moreno-Garibaldi, Melvyn Alvarez-Vera, Juan Alfonso Beltrán-Fernández, Rafael Carrera-Espinoza, Héctor Manuel Hdz-García, J. C. Díaz-Guillen, Rita Muñoz-Arroyo, Javier A. Ortega, Paul Molenda

Mechanical Engineering Faculty Publications and Presentations

The 17-4 PH stainless steel is widely used in the aerospace, petrochemical, chemical, food, and general metallurgical industries. The present study was conducted to analyze the mechanical properties of two types of 17-4 PH stainless steel—commercial cold-rolled and direct metal laser sintering (DMLS) manufactured. This study employed linear and nonlinear tensile FEM simulations, combined with various materials characterization techniques such as tensile testing and nanoindentation. Moreover, microstructural analysis was performed using metallographic techniques, optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results on the microstructure for 17-4 PH DMLS stainless steel reveal …

Analysis Of Bombyx Mori Silk And Polyimide Nanofibers, Sabrina Leseul

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis presents a study on the properties of Bombyx Mori silk nanofibers and polyimide (PI) nanofibers. Firstly, a Bombyx Mori silk solution has been created with degummed silkworm cocoons in order to separate the fibroin and the sericin, the two main proteins of the silk. The fibroin was then centrifuged to remove insoluble particles and stored and 4°C before mixing with hexafluoroisopropanol (HFIP). On the second part, a polyimide solution, made with shavings of polyimide and N,N-dimethylformamide (DMF). Both solutions are then electrospun. Electrospinning parameters are studied. In this way, a part of my thesis has been dedicated to …

Twin-Solute, Twin-Dislocation And Twin-Twin Interactions In Magnesium, Materials Yue, Jian Wang, Jian-Feng Nie

Department of Mechanical and Materials Engineering: Faculty Publications

Magnesium alloys have received considerable research interest due to their lightweight, high specific strength and excellent castability. However, their plastic deformation is more complicated compared to cubic materials, primarily because their low-symmetry hexagonal closepacked (hcp) crystal structure. Deformation twinning is a crucial plastic deformation mechanism in magnesium, and twins can affect the evolution of microstructure by interacting with other lattice defects, thereby affecting the mechanical properties. This paper provides a review of the interactions between deformation twins and lattice defects, such as solute atoms, dislocations and twins, in magnesium and its alloys. This review starts with interactions between twin boundaries …

Finite Element-Based Machine Learning Model For Predicting The Mechanical Properties Of Composite Hydrogels, Yasin Shokrollahi, Pengfei Dong, Peshala T. Gamage, Nashaita Patrawalla, Vipuil Kishore, Hozhabr Mozafari, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In this study, a finite element (FE)-based machine learning model was developed to predict the mechanical properties of bioglass (BG)-collagen (COL) composite hydrogels. Based on the experimental observation of BG-COL composite hydrogels with scanning electron microscope, 2000 microstructural images with randomly distributed BG particles were created. The BG particles have diameters ranging from 0.5 μm to 1.5 μm and a volume fraction from 17% to 59%. FE simulations of tensile testing were performed for calculating the Young’s modulus and Poisson’s ratio of 2000 microstructures. The microstructural images and the calculated Young’s modulus and Poisson’s ratio by FE simulation were used …

Evaluation Of Microstructural And Mechanical Behavior Of Ahss Cp780 Steel Welded By Gmaw-Pulsed And Gmaw-Pulsed-Brazing Processes, Alan Jadir Romero-Orozco, Jaime Taha-Tijerina, Rene De Luna-Alanis, Victor Hugo Lopez-Morelos, Maria Del Carmen Ramirez, Melchor Salazar-Martinez, Francisco Fernando Curiel-Lopez

Manufacturing & Industrial Engineering Faculty Publications and Presentations

Joints of complex phase 780 (CP-780) advanced high strength steel (AHSS) were carried out by using an ER-CuAl-A2 filler metal for the gas metal arc welding pulsed brazing (GMAW-P- brazing) process and the ER-80S-D2 for the GMAW-P process employing two levels of heat input. The phases in the weld bead and HAZ were analyzed, and the evaporation of zinc by means of scanning electron microscopy (SEM) was also monitored. The mechanical properties of the welded joints were evaluated by tension, microhardness and vertical impact tests. It was found that there was greater surface Zn evaporation in the joints welded with …

Elimination Of Extraordinarily High Cracking Susceptibility Of Aluminum Alloy Fabricated By Laser Powder Bed Fusion, Holden Hyer, Le Zhou, Sharon Park, Thinh Huynh, Abhishek Mehta, Saket Thapliyal, Rajiv S. Mishra, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

Using the calculation of phase diagrams approach and Scheil solidification modeling, the Al-2.5Mg-1.0Ni-0.4Sc-0.1Zr alloy was designed, intentionally with an extraordinarily high cracking susceptibility, making it prime for solidification cracking during laser powder bed fusion. This study demonstrates the ability to mitigate even the most extreme solidification cracking tendencies in aluminum alloys with only minor alloying additions of Sc and Zr, 0.5 wt.% max. Furthermore, by employing a simple direct ageing heat treatment, good tensile mechanical properties were observed with a yield strength of 308 MPa, an ultimate tensile strength of 390 MPa, and a total elongation of 11%.

Microfabricated Platforms To Investigate Cell Mechanical Properties, Amir M. Esfahani, Grayson Minnick, Jordan Rosenbohm, Haiwei Zhai, Xiaowei Jin, Bahareh Tajvidi Safa, Justin Brooks, Ruiguo Yang

Department of Mechanical and Materials Engineering: Faculty Publications

Mechanical stimulation has been imposed on living cells using several approaches. Most early investigations were conducted on groups of cells, utilizing techniques such as substrate deformation and flow-induced shear. To investigate the properties of cells individually, many conventional techniques were utilized, such as AFM, optical traps/optical tweezers, magnetic beads, and micropipette aspiration. In specific mechanical interrogations, microelectro- mechanical systems (MEMS) have been designed to probe single cells in different interrogation modes. To exert loads on the cells, these devices often comprise piezo-electric driven actuators that attach directly to the cell or move a structure on which cells are attached. Uniaxial …

High-Throughput Computation Of New Carbon Allotropes With Diverse Hybridization And Ultrahigh Hardness, Mohammed Al-Fahdi, Alejandro Rodriguez, Tao Ouyang, Ming Hu

Faculty Publications

The discovery of new carbon allotropes with different building blocks and crystal symmetries has long been of great interest to broad materials science fields. Herein, we report several hundred new carbon allotropes predicted by the state-of-the-art RG² code and first-principles calculations. The types of new carbon allotropes that were identified in this work span pure sp² , hybrid sp²/sp³ , and pure sp³ C–C bonding. All structures were globally optimized at the first-principles level. The thermodynamic stability of some selected carbon allotropes was further validated by computing their phonon dispersions. The predicted carbon allotropes …

The Effect Of Nanostructures In Aluminum Alloys Processed Using Additive Manufacturing On Microstructural Evolution And Mechanical Performance Behavior, Rachel Boillat, Sriram Praneeth Isanaka, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper reviews the status of nanoparticle technology as it relates to the additive manufacturing (AM) of aluminum-based alloys. A broad overview of common AM processes is given. Additive manufacturing is a promising field for the advancement of manufacturing due to its ability to yield near-net-shaped components that require minimal post-processing prior to end-use. AM also allows for the fabrication of prototypes as well as economical small batch production. Aluminum alloys processed via AM would be very beneficial to the manufacturing industry due to their high strength to weight ratio; however, many of the conventional alloy compositions have been shown …

Additive Manufacturing And Mechanical Properties Of The Dense And Crack Free Zr-Modified Aluminum Alloy 6061 Fabricated By The Laser-Powder Bed Fusion, Abhishek Mehta, Le Zhou, Thinh Huynh, Sharon Park, Holden Hyer, Shutao Song, Yunali Bai, D. Devin Imholte, Nicolas E. Woolstenhulme, Daniel M. Wachs, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

For additive manufacturing such as laser powder bed fusion (LPBF), commercial aluminum alloy (AA) 6061 is typically considered unsuitable due to formation of solidification cracking and/or excessive porosity. In this study, to improve buildability/printability of AA6061, 1 wt% of Zr was alloyed to produce Zr-modified AA6061 by LPBF. Powders of unmodified and Zr-modified AA6061 were produced by gas atomization, and utilized as a feed-stock for the LPBF to fabricate specimens for microstructural examination and mechanical testing. The as-built unmodified AA6061 exhibited poor printability due to formation of cracks and porosity in the microstructure regardless of LPBF parameters. However, the Zr-modified …

Impact Of Sintering Time And Temperature On Mechanical Properties In Projection Sintering Of Polyamide-12, Justin Nussbaum, Taranjot Kaur, Julie Harmon, Nathan B. Crane

Faculty Publications

In powder bed fusion additive manufacturing (AM), the fusing process is temperature and time dependent. However, little work has been done to understand how different processing temperatures and times might impact the mechanical properties at longer sintering times than are typical in laser sintering (LS) systems. Prior results with projection sintering have shown that heating for longer times (>1s) improves part toughness compared to laser sintering. In this work, Large Area Projection Sintering (LAPS) is used to sinter entire layers of material simultaneously over the course of a few seconds with spatial control of layer temperature. This work evaluates …

Effects Of Zirconia Doping On Additively Manufactured Alumina Ceramics By Laser Direct Deposition, John M. Pappas, Aditya R. Thakur, Xiangyang Dong

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The ability to additively manufacture functional alumina ceramics has the potential to lower manufacturing costs and development time for complex components. In this study, the doping effects of zirconia on laser direct deposited alumina ceramics were investigated. The microstructure of the printed samples was analyzed in terms of grain size and composition distribution. The addition of zirconia was found to accumulate along alumina grain boundaries and resulted in significant grain refinement. The zirconia doping largely reduced crack formation during processing compared to that of pure alumina samples. In the case of 10 wt% zirconia, cracking during deposition was nearly completely …

Boron Nitride Nanotube Based Lightweight Metal Matrix Composites: Microstructure Engineering And Stress-Transfer Mechanics, Pranjal Nautiyal

FIU Electronic Theses and Dissertations

Lightweight metals, such as Aluminum, Magnesium and Titanium, are receiving widespread attention for manufacturing agile structures. However, the mechanical strength of these metals and their alloys fall short of structural steels, curtailing their applicability in engineering applications where superior load-bearing ability is required. There is a need to effectively augment the deformation- and failure-resistance of these metals without compromising their density advantage.

This dissertation explores the mechanical reinforcement of the aforementioned lightweight metal matrices by utilizing Boron Nitride Nanotube (BNNT), a 1D nanomaterial with extraordinary mechanical properties. The nanotubes are found to resist thermo-oxidative transformations up to ~750°C, establishing their …

Hierarchical Mechanisms Of Lateral Interactions In High- Performance Fibers, Taylor A, Stockdale, Daniel P. Cole, Jeffrey M. Staniszewski, Michael R. Roenbeck, Dimitry Papkov, Steve R. Lustig, Youris A. Dzenis, Kenneth E. Strawhecker

Department of Mechanical and Materials Engineering: Faculty Publications

The processing conditions used in the production of advanced polymer fibers facilitate the formation of an oriented fibrillar network that consists of structures spanning multiple length scales. The irregular nature of fiber tensile fracture surfaces suggests that their structural integrity is defined by the degree of lateral (interfacial) interactions that exist within the fiber microstructure. To date, experimental studies have quantified interfacial adhesion between nanoscale fibrils measuring 10−50 nm in width, and the global fracture energy through applying peel loads to fiber halves. However, a more in-depth evaluation of tensile fracture indicates that fiber failure typically occurs at an intermediate …

Investigation Of Through Thickness Microstructure And Mechanical Properties In Friction Stir Welded 7n01 Aluminum Alloy Plate, Xingxin Zhao, Zhiyong Yang, Joseph P. Domblesky, Jianmin Han, Zhiqiang Li, Xiaolong Liu

Mechanical Engineering Faculty Research and Publications

An on-going problem in friction stir welded (FSW) joints used in the high-speed train sector is that the microstructure and mechanical properties can significantly vary in thick sections. Because inhomogeneous properties can reduce weld efficiency and degrade service performance, it is of some interest to understand how inhomogeneous properties can develop in FSW welds made from precipitation hardening alloys such as 7N01. In the current study, butt welds were made using 12 mm thick plates and then sectioned perpendicular to the weld line. Five 2.2 mm thick slices were cut from a section and used to measure tensile properties access …

Mechanical Characterizations Of 3d-Printed Plla/Steel Particle Composites, Hozhabr Mozafari, Pengfei Dong, Haitham Hadidi, Michael P. Sealy, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The objective of this study is to characterize the micromechanical properties of poly-L-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 μm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus of …

Mechanical Properties Of Zr-Based Bulk Metallic Glass Parts Fabricated By Laser-Foil-Printing Additive Manufacturing, Yingqi Li, Ming-Chuan Leu, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The application of bulk metallic glasses (BMGs) has been traditionally limited to parts with small dimensions and simple geometries, due to the requirement of fast cooling during the conventional process of casting. This research exemplifies a promising additive manufacturing method, i.e., laser-foil-printing (LFP), to fabricate high-quality BMG parts with large dimensions and complex geometries. In this study, Zr_52.5Ti₅Al₁₀Ni_14.6Cu_17.9 BMG parts were fabricated by LFP technology in which MG foils are laser welded layer-by- layer upon a substrate. The mechanical properties of the fabricated BMG parts were measured using micro-indentation, tensile test …

Functionalized Graphene Oxide As Reinforcement In Epoxy Based Nanocomposites, F. V. Ferreira, F. S. Brito, W. Franceschi, E. A. N. Simonetti, L. .S Cividanes, Mircea Chipara, Karen Lozano

Mechanical Engineering Faculty Publications and Presentations

The effects of amine-modified graphene oxide on dispersion and micro-hardness of epoxy based nanocomposites are reported. Graphene oxide was prepared by the modified Hummers method followed by hexamethylenediamine functionalization. Analysis conducted through Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy-based infrared spectroscopy show that the functionalization process effectively promoted a replacement of oxygen with amine groups while simultaneously creating defects in the graphitic structure. An increase in hardness was observed for the developed nanocomposites.

Mechanical Properties And Flame Retardancy Of Surface Modified Magnesium Oxysulfate (5mg(Oh)2·Mgso4·3h2o) Whisker For Polypropylene Composites, Eui-Su Kim, Ye Chan Kim, Jungwoo Park, Youngjun Kim, Sung-Hoon Kim, Kwang Jin Kim, Jonghwan Suhr, Youngkwan Lee, Seong Hoon Lee, Dae-Sik Kim, Soo-Hyun Kim, Ju-Ho Yun, In-Kyung Park, Jae-Do Nam

Mechanical Engineering Faculty Research

Magnesium oxysulfate (MOS) whisker is considered as a promising inorganic material recently attracting a great attention for being used as a reinforcing filler for polymer composites due to high aspect ratio and extremely-low bulk density. In this study, the MOS was treated with 3-methacryloyloxypropyl-trimethoxy silane (MPS) via sol-gel condensation reactions, which successfully allowed melt mixing with polypropylene (PP) up to 30 wt% of MOS. The tensile strength at yield and modulus of the MOS/PP composites were substantially increased by 50.8% and 362%, respectively, when compared with the pristine PP. As a novel finding, the flame retardancy of MOS was proved …

Impact Of Vapor Polishing On Surface Quality And Mechanical Properties Of Extruded Abs, Clayton Neff, Matthew Trapuzzano, Nathan B. Crane

Faculty Publications

Purpose — Additive manufacturing (AM) is readily capable of producing models and prototypes of complex geometry and is advancing in creating functional parts. However, AM processes typically underperform traditional manufacturing methods in mechanical properties, surface roughness, and hermeticity. Solvent vapor treatments (vapor polishing) are commonly used to improve surface quality in thermoplastic parts, but the results are poorly characterized.

Design/methodology/approach — This work quantifies the surface roughness change and also evaluates the effect on hermeticity and mechanical property impacts for “as-printed” and acetone vapor-polished ABS tensile specimens of 1, 2, and 4 mm thicknesses produced by material extrusion (FDM).

Findings …

Pulsed Laser Beam Welding Of Pd43Cu27Ni10P20 Bulk Metallic Glass, Ling Shao, Amit Datye, Jiankang Huang, Jittisa Ketkaew, Sung Woo Sohn, Shaofan Zhao, Sujun Wu, Yuming Zhang, Udo D. Schwarz, Jan Schroers

Electrical and Computer Engineering Faculty Publications

We used pulsed laser beam welding method to join Pd₄₃Cu₂₇Ni₁₀P₂₀ (at.%) bulk metallic glass and characterized the properties of the joint. Fusion zone and heat-affected zone in the weld joint can be maintained completely amorphous as confirmed by X-ray diffraction and differential scanning calorimetry. No visible defects were observed in the weld joint. Nanoindentation and bend tests were carried out to determine the mechanical properties of the weld joint. Fusion zone and heat-affected zone exhibit very similar elastic moduli and hardness when compared to the base material, and the weld joint shows high …

Mechanical Characterization Of Parts Produced By Ceramic On‐Demand Extrusion Process, Amir Ghazanfari, Wenbin Li, Ming Leu, Gregory Hilmas

Faculty Publications, Mechanical Engineering

Ceramic On‐Demand Extrusion (CODE) is an additive manufacturing process recently developed to produce dense three‐dimensional ceramic components. In this paper, the properties of parts produced using this freeform extrusion fabrication process are described. High solids loading (~60 vol%) alumina paste was prepared to fabricate parts and standard test methods were employed to examine their properties including the density, strength, Young's modulus, Weibull modulus, toughness, and hardness. Microstructural evaluation was also performed to measure the grain size and critical flaw size. The results indicate that the properties of parts surpass most other ceramic additive manufacturing processes and match conventional fabrication techniques.

Sputtering Power Effects On Growth And Mechanical Properties Of Cr2alc Max Phase Coatings, Muhammad Naveed, Aleksei Obrosov, Andrzej Zak, Wlodzimierz Dudzinski, Alex A. Volinsky, Sabine Weiß

Mechanical Engineering Faculty Publications

Coating growth and mechanical properties of nanolamellar Cr₂AlC coatings at various sputtering power were investigated in the present study. Cr₂AlC coating was deposited on the IN 718 superalloy and (100) Si wafers by DC magnetron sputtering at different sputtering powers. The structure and properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. It was found that coatings had columnar structure with nanocrystalline substructure. Deposition rate increased with the sputtering power. XRD results showed the presence of the Cr₂AlC MAX phase, intermetallic AlCr₂ and Cr_{7 …}

Effect Of Original Layer Thicknesses On The Interface Bonding And Mechanical Properties Of Ti-Al Laminate Composites, Minyu Fan, Joseph P. Domblesky, Kai Jin, Liang Qin, Shengqiang Cui, Xunzhong Guo, Naksoo Kim, Jie Tao

Mechanical Engineering Faculty Research and Publications

It is of great significance in high-temperature aeroengine applications for large-surface-area TiAl laminate composites to be fabricated into Ti-Al₃Ti parts by plastic forming and subsequent vacuum hot pressing. Then the original layer thicknesses have an important influence on the interface bonding and mechanical properties of TiAl laminate composites, but only few reports about it have been published so far. In the present study, vacuum hot pressing was employed to fabricate TiAl laminate composites using Ti and Al foils of different thickness. The resulting interface bond and mechanical properties of TiAl laminate composites were then studied to determine the …

Role Of Interphase In The Mechanical Behavior Of Silica/Epoxy Resin Nanocomposites, Yi Hua, Linxia Gu, Sundaralingam Premaraj, Xiaodong Zhang

Department of Mechanical and Materials Engineering: Faculty Publications

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had significant influence on the effective stiffness of nanocomposites, while its sensitivities with respect to both the thickness and the gradient property of the interphase was minimal. The stiffer interphase demonstrated a higher load-sharing capacity, which also increased the stress distribution uniformity within the resin nanocomposites. Under the condition of imperfect interfacial bonding, the effective stiffness of nanocomposites …

An Investigation Of The Effect Of Direct Metal Deposition Parameters On The Characteristics Of The Deposited Layers, Tarak A. Amine, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

Multilayer direct laser deposition (DLD) is a fabrication process through which parts are fabricated by creating a molten pool into which metal powder is injected as particles. During fabrication, complex thermal activity occurs in different regions of the build; for example, newly deposited layers will reheat previously deposited layers. The objective of this study was to provide insight into the thermal activity that occurs during the DLD process. This work focused on the effect of the laser parameters of newly deposited layers on the microstructure and mechanical properties of the previously deposited layers in order to characterize these effects to …

Effect Of Architecture And Porosity On Mechanical Properties Of Borate Glass Scaffolds Made By Selective Laser Sintering, Krishna C. R. Kolan, Ming-Chuan Leu, Greg Hilmas, Taylor Comte

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The porosity and architecture of bone scaffolds, intended for use in bone repair or replacement, are two of the most important parameters in the field of bone tissue engineering. The two parameters not only affect the mechanical properties of the scaffolds but also aid in determining the amount of bone regeneration after implantation. Scaffolds with five different architectures and four porosity levels were fabricated using borate bioactive glass (13-93B3) using the selective laser sintering (SLS) process. The pore size of the scaffolds varied from 400 to 1300 μm. The compressive strength of the scaffolds varied from 1.7 to 15.5 MPa …

Adding Autonomic Healing Capabilities To Polyethylene Oxide, Dorina M. Chipara, Maritza Flores, Alma Perez, Nancy Puente, Karen Lozano, Mircea Chipara

Mechanical Engineering Faculty Publications and Presentations

The addition of autonomic healing (frequently defined as self-healing) capabilities to a water-soluble polymer (polyethylene oxide, PEO) is for the first time reported. The self-healing system consists of urea-formaldehyde microcapsules filled with dicyclopentadiene and first-generation Grubbs catalyst, dispersed within polyethylene oxide. Raman spectroscopy, optical microscopy, electron microscopy, and thermogravimetric analysis were used to characterize this autonomic healing system. Self-healing capabilities were confirmed by mechanical testing (load–displacement, engineering stress–engineering strain, and true stress–true strain dependences) recorded at very slow elongation rates (0.01 mm/s). The testing fate was chosen to allow for the complete consumption of the monomer before fracture (the polymerization …

Freeze-Form Extrusion Fabrication Of Functionally Graded Material Composites Using Zirconium Carbide And Tungsten, Ang Li, Aaron S. Thornton, Bradley K. Deuser, Jeremy Lee Watts, Ming-Chuan Leu, Greg Hilmas, Robert G. Landers

Materials Science and Engineering Faculty Research & Creative Works

Ultra-high-temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as their oxidation resistance, at temperatures above 2000⁰C. However, their brittleness makes them susceptible to thermal shock failure. As graded composites, components fabricated as functionally-graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGM parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and W were developed …