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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Cetyltrimethyl Ammonium Bromide Modified Kaolin as a Reinforcing Filler for Natural Rubber

Cure characteristics, Mooney viscosity and physico-mechanical properties of natural rubber (NR) containing CTAB modified kaolin have been studied. NR mix containing 6 phr (parts per hundred part rubber) of CTAB modified kaolin showed significant increases in cure rate and state of cure as compared to gum NR compound and a mix containing the same amount of unmodified kaolin. Lower Mooney viscosity of the NR mix containing CTAB modified kaolin suggested improved processability. Reinforcing effect of CTAB modified kaolin in NR was evident from higher chemical crosslink density index, tensile modulus, hardness, tensile strength and tear strength. Besides, the NR vulcanizate containing 6 phr of CTAB modified kaolin showed lower abrasion loss and heat build-up which could be beneficial for applications such as tire treads.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Sustainable Use of Coffee Husks For Reinforcing Polyethylene Composites

The utilization of the coffee husk fiber (CHF) from the coffee industry as a reinforcing filler in the preparation of a cost-effective thermoplastic based composite was explored in this study. The chemical composition and thermal properties of the CHF were investigated and compared with those of wood fiber (WF). CHF proved to be mainly composed of cellulose, hemicellulose and lignin, and exhibited similar thermal behavior to WF. High density polyethylene (HDPE) composites with CHF loadings of from 40 to 70% were prepared using melt processing and extrusion. The processing properties, mechanical behavior, water absorption and thermal performance of these composites were investigated. The effect of maleated polyethylene (MAPE) used as a coupling agent on the composite was explored. The experimental results showed that increasing the CHF loading in the HDPE matrix resulted in an increase in the modulus and thermal properties of the composites, but resulted in poor water resistance. The addition of a 4% MAPE significantly improved the interfacial behavior of the hydrophilic lignocellulosic fiber and the hydrophobic polymer matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Performance of Cow Dung Reinforced Biodegradable Poly(Lactic Acid) Biocomposites for Structural Applications

In this work, performance of cow dung (CD) reinforced poly(lactic acid) (PLA) biocomposites was investigated for the potential use in load bearing application. CD of average 4 mm size was blended with PLA at different CD ratios (0–50 wt%) and their effects on the biocomposite properties were studied. The results showed an improvement in the flexural properties, while the tensile and impact strength dropped by 20 and 28% with the addition of 50% CD. The decline in the tensile and impact strength was due to micro-cracking and voids formation at higher CD content. Also, the incorporation of CD slightly decreased the thermal stability of the biocomposite. However, dynamic mechanical properties of the biocomposites generally improved. SEM analysis of tensile and impact fractured surfaces indicated that the CD had a reasonable adhesion with matrix. Moreover, the SEM micrographs of soil burial studies showed an accelerated degradation of higher CD wt% biocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Organically Modified Nanoclay and Aluminum Hydroxide Incorporated Bionanocomposites towards Enhancement of Physico-mechanical and Thermal Properties of Lignocellulosic Structural Reinforcement

A range of bio-nanocomposites were prepared by incorporation of organo modified montmorillonite nanoclay (OMMT) with or without use of aluminum hydroxide (Al(OH){sub 3}) within polylactic acid (PLA) solution. Furthermore, the solution was employed for modification of ligno-cellulosic (jute) fabric structural reinforcements. The successful incorporation of nanofillers within the host polymer, polylactic acid (PLA) was confirmed by Fourier-transform infrared spectroscopy (FT-IR). Water uptake and swelling behaviour studies revealed that the water uptake and swelling ratio of bio-composites reduced significantly as compared to pristine jute fabric, whereas upon incorporation of OMMT and Al(OH){sub 3}, the water barrier properties reduced even further in the developed bio-nanocomposites. The flexural strength of the bio-nanocomposites also showed improved mechanical and dimensional stability. Synergistic effects of OMMT and Al(OH){sub 3} were observed in enhancing the aforementioned physico-mechanical properties. Scanning electron microscopy (SEM) studies revealed microstructural details of developed samples. Similarly, the thermo-gravimetric analysis and linear burning rate studies of Al(OH){sub 3 }treated bio-nanocomposite materials revealed enhanced thermal resistance and reduced flammability respectively compared to both pristine woven jute fabric and fabrics treated with PLA alone or those without Al(OH){sub 3}. From the above results it can safely be said that the bio-nanocomposite material can be a prospective candidate for development of flame retardant biopackaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Reinforcement of Soy Protein-Based Bioplastics Through Addition of Lignocellulose and Injection Molding Processing Conditions

Bioplastics have gained great interest in recent years as a potential alternative to conventional plastics, since they are renewable and biodegradable materials. However, their mechanical properties are not able to match those of conventional plastics yet. In this context, the incorporation of additives to improve those properties of bioplastics is an interesting line of research. The aim of this work was to develop soy protein-based bioplastics with lignocellulosic fiber (additive) by injection molding. Mechanical and absorption properties of bioplastics reinforced with lignocellulose (0.1, 1.0, 5.0 wt%) have been studied, as well as their microstructure. Furthermore, a study of the effect produced by changing the mold temperature (70, 90, 110, 130 °C) was carried out. The results obtained confirm an improvement of the mechanical properties of these bioplastics, depending on the amount of fiber incorporated. In any case, these findings support the role of cellulosic compounds as additives in protein bioplastics.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Nano Graphene-Reinforced Bio-nanocomposites Based on NR/PLA: The Morphological, Thermal and Rheological Perspective

Bio-based graphene-reinforced thermoplastic elastomers (TPE) based on natural rubber (NR), and poly lactic acid (PLA) were successfully prepared via melt blending. The effect of graphene nanosheets (GNS) content and coupling agent were investigated on morphological, thermal and rheological properties of the PLA/NR/GNS bio-nanocomposites. More stable morphology of uniformly dispersed NR phase in the continuous PLA matrix with a relatively narrower diameter-size distribution was achieved in the presence of a compatibilizer. Moreover, transmission electron micrographs showed more improved dispersion of GNS with predominantly exfoliated morphology in the case of ENR-compatibilized PLA/NR/GNS bio-nanocomposites. Crystallization/melting studies revealed that, as the GNS content increased, the cold-crystallization peak, melting peak and glass-to-rubber transition temperature values shifted to higher temperatures and the crystallinities of blends slightly decreased (about 7%) which might be attributed to the reduction of polymeric segments mobility by the restricting effect of GNS. Dynamical mechanical investigation showed that the storage modulus (E′) increased about 25% by the introduction of GNS due to the inherent stiffness of GNS and the occurrence of compatibility in the PLA/NR blend in the presence of ENR. The presence of ENR shifted the T{sub g} of the NR phase and the PLA matrix towards each other which is a characteristic of higher miscibility and compatibility. The thermogravimetry (TGA) and derivative thermogravimetry (DTG) curves revealed higher thermal stability of the compatibilized-PLA/NR blends due to the enhanced interfacial adhesion and the homogenous dispersion of GNSs as direct effects of the presence of ENR. Rheological studies indicated that the formation of the effective GNS-polymer networks by the presence of ENR increased the storage modulus (G′) and complex viscosity (η*) value due to the effectiveness of the GNS in taking loads and restricted molecular motion, respectively. Graphical Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2019

A Simple Approach for the Synthesis of Cellulose Nanofiber Reinforced Chitosan/PVP Bio Nanocomposite Film for Packaging

The development of chitosan-based food packaging film has been increasing due to its wider availability, biodegradability, low-cost, and renewability. The purpose of this study was to develop cellulose nanofibers (CNFs) reinforced Chitosan/PVP(CHP) green bio nanocomposite film by solvent casting method with enhanced barrier and mechanical property. CNFs of dimension 9–11 nm and 100–200 nm were extracted from jute fibers by directly treating it with HNO{sub 3}–NaNO{sub 2} mixture. Bio nanocomposite films were synthesized with various concentrations of CNFs and evaluated using SEM, TGA/DTG and XRD to analyze the morphology, thermal behavior and crystallinity of bio nanocomposite films. SEM analysis revealed the uniform dispersion of CNFs in CHP matrix. Thermal stability of prepared bio nanocomposite films was improved with the loading of 5 wt% of cellulose nanofibers. ATR(FT-IR) spectra shows physical interaction between all the components of bio nanocomposite film. The bio nanocomposite films were also characterized for physical property like thickness, mechanical testing and barrier properties. The addition of CNFs significantly enhanced the mechanical property of bio nanocomposite films. Furthermore, water and oxygen transmission rate of bio nanocomposite film decreased with the increase in CNFs concentration. Overall the performed studies confirmed, the use of CNFs in polymer matrix makes it possible to produce a flexible, transparent, thermally stable bio nanocomposite film with enhanced mechanical and barrier properties for food packaging applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Experimental Validation of an Additively Manufactured Stiffness-Optimized Short-Fiber Reinforced Composite Clevis Joint

This effort describes experiments for the validation of the response of an additively manufactured stiffness-optimized short-fiber reinforced composite. A Direct Ink Write (DIW) method is used to additively manufacture a clevis joint plate which was designed such that its compliance would be minimized (i.e., stiffness maximized) for far-field axial loading. A unique aspect of the optimization scheme is that it accounts for manufacturing constraints, such as tool turn radius and tool path spacing. Along with the optimized clevis joint plate, additively manufactured 0°–90° and ± 45° composite plates of the same number of layers, as well as a control 0°–90° sample of resin only, were also studied. In addition to far-field load-displacement, near-field strain was monitored using digital image correlation (DIC). The results showed that the optimized plate did indeed exhibit the largest stiffness, based on far-field measurements. DIC-measured strains showed that locally the axial strain component, which is the largest, was also minimized for the optimized specimen, although the other strain components followed different trends. Furthermore, in the experiments it was seen that the optimized design exhibited a nonlinear/hysteretic behavior which is believed to be a consequence of its internal gap/cell structure. This internal structure, which results by optimized placement of material, although explicitly not accounted for in the optimization, may affect global response. Lastly, although not a part of the optimization study itself, the failure load for the optimized joint plate was also seen to be the largest of all the cases studied.

42 ENGINEERING↗
DOE OSTI2018

Mechanical and Tribological Behavior of Multiwalled Carbon Nanotubes-Reinforced AA7075 Composites Prepared by Powder Metallurgy and Hot Extrusion

Carbon nanotubes (CNT) are synthesized using arc discharge method in an open air. Various amounts of carbon nanotubes-reinforced AA7075 composites are prepared by powder metallurgy route and then hot extrusion at 450 °C. Hot-extruded composites are characterized, and mechanical properties are measured. Dry sliding wear properties of hot-extruded samples were evaluated using a pin-on-disk method for various loads (5-20 N) at room temperature and for various temperatures (100-400 °C) at the applied load 10 N as a function of CNT amount. Grain size of the composites is decreased compared with Al alloy matrix. Transmission electron microscopy of the composites revealed that the CNT are uniformly distributed in the composites. Mechanical properties of the hot-extruded composites are enhanced with an increase in CNT content. The wear performance is improved with an increased CNT amount, but decreases with an increase in the applied load and temperature as well. The wear damage is mild at lower applied loads and temperatures, whereas the damage is severe at 400 °C. The wear mechanism was plowing in the initial stages which is transformed to severe sliding and chipping with increasing load and temperature. The enhanced wear behavior of composites is attributed to self-lubricating nature of carbon nanotubes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

In Situ Quality Monitoring in AM Using Acoustic Emission: A Reinforcement Learning Approach

Additive manufacturing (AM) has attracted considerable attention in recent years. This technology overcomes the geometrical limits of workpieces produced with the traditional subtractive methods and so gives the opportunity to manufacture highly complex shapes. Unfortunately, the repeatability of the manufacturing process and the monitoring of quality are not reliable enough to be utilized in mass production. The quality monitoring of AM processes in commercial equipment has been largely based on temperature measurements of the process zone or high-resolution imaging of the layers. However, both techniques lack information about the physical phenomena taking place in the depth of the materials medium and this limits their reliability in real-life applications. To overcome those restrictions, we propose to combine acoustic emission and reinforcement learning. The former captures the information about the subsurface dynamics of the process. The latter is a branch of machine learning that allows interpreting the received data in terms of quality. The combination of both is an original method for in situ and real-time quality monitoring. Acoustic data were collected during a real process using a commercial AM machine. The process parameters were selected to achieve three levels of quality in terms of porosity concentration while manufacturing a stainless steel 316L cuboid shape. Using our method, we demonstrated that each level of quality produced unique acoustic signatures during the build that were recognized by the classifier. The classification accuracy reached in this work proves that the proposed method has high potential to be used as in situ and real-time monitoring of AM quality.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Micro-crack Pinning and Interfacial Fracture in Mixed Metal Oxide Reinforced Epoxy Nanocomposite

The effects of mixed metal oxides (Ce{sub x}Zr{sub 1−x}O{sub 2}) nanoparticle dispersion on the mechanical properties and fracture mechanisms of epoxy polymer matrix and its composite with glass fiber system are reported in this paper. Ce{sub x}Zr{sub 1−x}O{sub 2} nanoparticles are synthesized using sol–gel method, and its crystallinity is optimized. Epoxy nanocomposites are synthesized by a dispersion technique, and the compressive properties are optimized. The glass transition temperature has been improved. Epoxy with 5 wt.% of Ce{sub 0.75}Zr{sub 0.25}O{sub 2} shows optimal results with an increase of 17.4% in compressive modulus, and an increase of 23.4% in compressive strength with respect to those of neat epoxy. This improvement attributes to higher strength of shearing of polymer during the fracture of the nanoparticle interface. Micro-crack kinks at the interfaces can further delay fracture under compression. E-glass fabric-reinforced 5 wt.% Ce{sub 0.75}Zr{sub 0.25}O{sub 2}–epoxy nanocomposite also shows improvement in the mechanical properties via nanoscale interface with fibers. This type of ceramic nanocomposites has useful applications in thermal/electrical insulations besides improving the compressive/buckling properties.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Graphene-Reinforced Aluminum Hybrid Foam: Response to High Strain Rate Deformation

The compressive deformation behavior of 0.5 wt.% graphene-reinforced aluminum-SiC hybrid composite foam under dynamic loading over strain rates of 500-2760 s{sup −1} was studied using a split-Hopkinson pressure bar unit. It was found that under the dynamic loading, the plateau stress and energy absorption of aluminum hybrid foam increased with strain rate. On the other hand, the densification strain did vary only marginally with strain rate. Further, it was noted that the foam with lower relative density was more sensitive to strain rate. The lighter foams exhibited higher plateau stress and energy absorption as compared to the heavier ones. The plateau stress and energy absorption were enhanced marginally with relative density. Present results showed that the plateau stress is sensitive to strain rate and less sensitive to relative density. The coefficient, in scaling relation to predict compressive plateau stress, was in the range of 0.2-0.5 for strain rates 500-2760 s{sup −1}.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Elastic Modulus Estimation for Copper Syntactic Foams Reinforced with Iron Hollow Spheres of Different Wall Thicknesses

The present study estimates the effect on Young’s modulus of the percentage and thickness of iron hollow spheres reinforcing copper syntactic foams. The resulting materials were modeled by inserting hollow spheres in a random arrangement, using a combination of Discrete Element Method (DEM) for generating the sphere location coordinates and Finite Element Analysis (FEA). Estimations for syntactic foams were compared to those obtained for conventional copper foams with the same porosity. Results showed that the elastic modulus of both syntactic and conventional foams drops significantly as the percentage of spheres or porosity increases. Furthermore, the increase in the wall thickness of the iron hollow spheres leads to significant rises in the Young’s modulus. Depending on the desired mechanical properties, the outcomes presented in this work could be used for selecting the kind of foam (syntactic or conventional) and predesign some characteristics such as porosity or thickness of the spheres or pores.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Synthesis and Characterization of Aluminum Matrix Composites Reinforced with (Ni,Cu){sub 3}Al Intermetallic Particles via Mechanical Milling Technique

This study investigates the dispersion of (Ni,Cu){sub 3}Al intermetallic particles in an aluminum matrix via low-energy mechanical milling as an alternative to conventional stir casting. The precursor powders consisted in (Ni,Cu){sub 3}Al and reactive-grade Al particles with an average size of 15 and 3 microns, respectively. The concentrations used were 3, 5, 8 and 10 wt.% of the intermetallic powders. After 4 h of milling, the obtained powders were compacted in a unidirectional press with a pressure of 930 MPa and the obtained green compacts were sintered at 500 °C in a controlled atmosphere oven for 2 h. Result showed that the bulk composites displayed an increase in the Vickers microhardness as well as an increase in compressive strength and stiffness as the percentage of dispersed particles increased. The Al-8 wt.%(Ni,Cu){sub 3}Al sample achieved the best performance and is related to the findings in SEM micrographs that showed that higher reinforcement concentration increased the formation of microporosities that reduce the decohesion of the bulk sample and impact heavily on the mechanical performance of the material.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Carbon Fiber Surface Modification on the Mechanical Properties of Carbon-Fiber-Reinforced Ultrahigh-Molecular-Weight Polyethylene Composite

In this paper, the surface properties and morphologies of the concentrated nitric acid (HNO{sub 3})-modified carbon fiber (CF) were characterized by XPS, SEM, and contact angle goniometer, respectively. The results showed that both the oxygen-containing functional groups content and the surface roughness of concentrated HNO{sub 3}-modified CF significantly increased. The contact angle of concentrated HNO{sub 3}-modified CF was obviously lower than that of unmodified CF. Studies on the mechanical properties of carbon-fiber-reinforced ultrahigh-molecular-weight polyethylene (CF/UHMWPE) composite revealed that the stress–strain behavior gradually changed from nonlinear to linear relationship with the rise of CF content in UHMWPE matrix. Both the tensile strength and modulus increased with the rise of CF content. Conversely, as the CF content in UHMWPE matrix is increasing, the flexural strength and modulus increased first and then decreased. The flexural strength and modulus of CF/UHMWPE composite with 30 wt.% CF content reached the maximum value of 157.61 MPa and 9.82 GPa, respectively. Moreover, the CF surface modification and CF content have a synergistic effect on the tensile and flexural mechanical properties of the CF/UHMWPE composite. The influence of CF modification on the tensile and flexural mechanical properties of the composite became more and more obvious with the rise of CF content.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigation on Equal-Channel Angular Pressing-Induced Grain Refinement in an Aluminum Matrix Composite Reinforced with Al-Cu-Ti Metallic Glass Particles

In the present study, a homogeneous ultrafine grain structure composite consisting of metallic glass particles reinforcements was developed by equal-channel angular pressing (ECAP) process. The microstructure of composite was characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques. The uniaxial compression test was used to determine the mechanical properties. The mechanisms of grain refinement during ECAP process were discussed based on the microstructural evolutions. A composite was successfully produced after four passes of ECAP, having an average grain size of 610 nm and compressive yield strength of 242 MPa. Also, the yield strength of composite after each pass was quantitatively estimated by considering all the effective strengthening mechanism. The findings showed that the dislocations strengthening mechanism with contribution of more than 50% plays a major role in strengthening the composite. There was a negligible gap between the experimental and theoretical values of yield strength for all ECAP pass numbers.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Impact Damage Investigation on Glass Fiber-Reinforced Plate Laminates at Room and Lower Temperatures through Ultrasound Testing and Electronic Speckle Pattern Interferometry

In this work, the evaluation of damage area due to low-velocity impact tests at different impact energy values and different temperatures on glass fiber-reinforced plate laminates was investigated by two nondestructive evaluation (NDE) techniques, electronic speckle pattern interferometry (ESPI) and ultrasound testing (UT). Composites are characterized by several interacting failure modes such as matrix breakage, fiber failure and delaminations, which can be simultaneously induced by low-velocity impacts and can be different depending on the temperature. It can be complicated to detect by visual inspections of the structures for such phenomena. This paper aims to investigate the dependence of the damaged area with respect to temperature variation on glass fiber composite laminates. GF composite laminates were impacted with three energy levels (5, 10, 20 J) and at different temperatures (room temperature, − 25, − 50 °C) by a drop weight impact machine. The results show that at decreasing temperature, a decrease in the damage extension was observed, which is more evident at increasing impact energy. Moreover, as expected, the results confirm UT and ESPI techniques are able to identify the barely visible low-velocity impact damage. However, some limitations for detection were found in ESPI. Nonetheless, the ESPI technique can be considered as one of the useful NDE methods if the calibration and the post-processing methods are improved.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure Evolution and Improved Creep Behavior of Mg-Al-Si Alloy Matrix Composite Reinforced with SiC Nanoparticles

The Mg-9Al-1Si matrix composite reinforced with SiC nanoparticles is fabricated by semisolid stirring-assisted ultrasonic vibration, which contains finer grains and a more uniform microstructure compared to that of the Mg-9Al-1Si alloys. The sizes of the Mg{sub 17}Al{sub 12} and Mg{sub 2}Si phases decreased continuously as the volume fraction of n-SiCp increased from 0 to 1% and then increased apparently when the volume fraction of n-SiCp increased to 1.5%. The steady-creep rates of the 1 vol.% n-SiCp/Mg-9Al-1Si are approximately two times lower than those of the Mg-9Al-1Si matrix alloy at 200 °C under applied stress of 70 MPa due to the strengthening effect of the nanosized SiCp. The reason for the improved creep properties is mainly attributed to the obvious grain boundary strengthening, the Orowan strengthening mechanism, the load transfer effect, and the pinning effect of the n-SiCp and the refined Mg{sub 17}Al{sub 12} and Mg{sub 2}Si phases.

36 MATERIALS SCIENCE↗