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Results for “Interfacial bonding”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Interlaminar shear properties of graphite fiber, high-performance resin composites

Short beam testing was used to determine the shear properties of laminates consisting of T-300 and Celion 3000 and 6000 graphite fibers, in epoxy, hot melt and solvent bismaleimide, polyimide and polystyrylpyridine (PSP). Epoxy, composites showed the highest interlaminar shear strength, with values for all other resins being substantially lower. The dependence of interlaminar shear properties on the fiber-resin interfacial bond and on resin wetting characteristics and mechanical properties is investigated, and it is determined that the lower shear strength of the tested composites, by comparison with epoxy resin matrix composites, is due to their correspondingly lower interfacial bond strengths. An investigation of the effect of the wettability of carbon fiber tow on shear strength shows wetting variations among resins that are too small to account for the large shear strength property differences observed.

Needles, H. L.↗
NASA NTRS2018

Joint Strength Optimization and Damping Assessment of NiTi-Polymer Matrix Hybrid Composites

Approaches to optimize the adhesive joint strength between shape memory alloy ribbons and carbon fiber-reinforced epoxy composites were investigated for potential use as either an actuating structure or a dampening composite for structural applications. The interfacial bond strength between nickel-titanium (NiTi) and a polymer matrix composite (PMC) was measured by double lap shear testing as a function of NiTi surface treatment and adhesive material. The effect of NiTi surface treatment on damping was investigated using dynamic mechanical analysis. Lap shear data show that treating the surfaces of NiTi ribbons by light sandblasting and primer application increased the interfacial bond strength by 20 percent over the baseline composite structure. Lap shear data also reveal that out of three different film adhesives investigated, samples bonded with AF 191U and Hysol® 9696U display the highest adhesive joint strengths. Optical microscopy reveals that most samples failed by either cohesive failure within the adhesive or by adhesive failure at either the adhesive/PMC or NiTi/adhesive interface. Adhering NiTi to the PMC did not appear to negatively impact damping performance; however, a more thorough examination into NiTi's role on vibration damping should be investigated.

lap shear↗
NASA NTRS1990

Experimental observations and finite element analysis of the initiation of fiber microbuckling in notched composite laminates

A better understanding of the factors that affect the semi-circular edge-notched compressive strength is developed, and the associated failure mode(s) of thermoplastic composite laminates with multidirectional stacking sequences are identified. The primary variables in this investigation are the resin nonlinear shear constitutive behavior, stacking sequence (orientation of plies adjacent to the 0 degree plies), resin-rich regions between the 0 degree plies and the off-axis supporting plies, fiber/matrix interfacial bond strength, and initial fiber waviness. Two thermoplastic composite material systems are used in this investigation. The materials are the commercial APC-2 (AS4/PEEK) and a poor interface experimental material, AU4U/PEEK, designed for this investigation. Notched compression specimens are studied at 21, 77, and 132 C. Geometric and material nonlinear two-dimensional finite element analysis is used to model the initiation of fiber microbuckling of both the ideal straight fiber and the more realistic initially wavy fiber. The effects of free surface, fiber constitutive properties, matrix constitutive behavior, initial fiber curvature, and fiber/matrix interfacial bond strength on fiber microbuckling initiation strain levels are considered.

Guynn, E. Gail↗
DOE OSTI2025

Microstructure and bonding between calcium aluminate cement‐containing gahnite–alumina matrix and refractory aggregates

Calcium aluminate cement enhances the thermomechanical properties of refractory castables through the formation of acicular calcium hexaluminate (CaO·6Al 2 O 3 ), Ca 2 Mg 2 Al 28 O 46 (CAM-I), and CaMg 2 Al 16 O 27 (CAM-II) phases in MgO- or MgAl 2 O 4 -containing castables. The compatibility of CA 6 with gahnite (ZnAl 2 O 4 ), and acicular Ca 2 Zn 2 Al 28 O 46 (CAZ-I) and CaZn 2 Al 16 O 27 (CAZ-II) phases formation have been previously reported. Here, in this work, the interaction between a CAC binder containing ZnAl 2 O 4 -Al 2 O 3 matrix with commonly used refractory aggregates such as tabular alumina (TA), alumina-rich (AR90, AR78) and stoichiometric (SM72) MgAl 2 O 4 spinels, and fused and dead-burned magnesia (FM, DBM, respectively) were investigated at 1650°C for 5 h. Microstructural analysis, using digital microscopy, scanning electron microscopy, and energy dispersive spectroscopy, revealed the formation of acicular CaZn 0.18 Al 11.82 O 18.91 , CAZ-I and CAZ-II grains, and strong interfacial bonding between the matrix and TA and spinel aggregates. FM and DBM were found to debond from the matrix. Thick interface layers were observed between the matrix and all the aggregates but TA. Null hypothesis significance testing (NHST) shows that the difference in the number of acicular grains between the interface zone and the bulk matrix (Z) is statistically significant for AR90/Z, SM72/Z, FM/Z, and DBM/Z interfaces, but not significant for TA/Z and AR78/Z. The role of the aggregates’ chemistry on the interfacial bonding and microstructure evolution is discussed.

Ramteke, Rajat Durgesh [Univ. of Alabama, Birmingh↗
DOE OSTI2020

Structural Implications of Interfacial Hydrogen Bonding in Hydrated Wyoming-Montmorillonite Clay

Montmorillonite (MMT) clay - a layered porous nanomaterial used as seals in engineered waste containment barriers for spent nuclear fuel - adopts discrete hydration/swelling states depending upon surrounding water and ion activities and confining pressure. The structure of nanoconfined water and charge-balancing counterions in the clay mineral interlayers dictate the swelling and mechanical behavior of MMT, so a molecular model for this clay with high structural fidelity is required to accurately predict the reliability of long-term nuclear waste storage. Here, we present a molecular model for MMT that is based on high resolution transmission electron microscopy of Wyoming-MMT single crystals. Imaging data unambiguously show a cis-vacant arrangement of structural hydroxyl groups in the octahedral sheet, whereas existing molecular models assume a centrosymmetric trans-vacant configuration for MMT. Furthermore, using atomistic simulations, we find that the cis-vacant arrangement of structural hydroxyl groups significantly affects the structure of adsorbed water yielding a larger population of hydrogen bonds with bridging oxygens on the tetrahedral sheet and weak hydrogen bonding between the hydroxyl groups in the octahedral sheet and water in the clay mineral interlayers. As a result, water adsorbed in the interlayer is more "ice-like", with stronger ordering and lower density, although the diffusivity of the interlayer species is not significantly diminished. Our improved structural model for MMT provides insight into the energetics of water adsorption, which ultimately dictates its pore- to macro-scale swelling, transport, and fracture properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Plasma treatment on both adhesive tape and adherends for significantly enhanced CFRTP-related adhesive joints

Unlike existing literature that primarily concentrates on either the plasma treatment of adherends alone or solely on adhesive surfaces, this work leverages plasma modification of both adhesive in tape form and adherend surfaces to largely enhance the interfacial bonding between a thermoset-based adhesive tape and carbon-fiber-reinforced thermoplastic polymer (CFRTP) for structural bonding applications. Here, by conducting single lap shear tests on adhesively-bonded AA6061-CFRPPA (carbon-fiber-reinforced polyphthalamide) dissimilar joints, it is shown that the plasma treatment of adherends alone can increase the lap shear strength (LSS) of the joints by approximately 200% compared to non-treated counterparts. An additional plasma treatment of adhesive tape surfaces leads to even higher LSS improvement, reaching up to 315%, due to the formation of a denser crosslinked network of covalent bonds and a reduced area fraction of interfacial voids at the CFRPPA/adhesive interface. The highest plasma-enhanced LSS of the metal-CFRTP dissimilar joints rivals that of metal-metal joints, which is typically stronger than the joints associated with fiber-reinforced polymers. This study is important for achieving strong CFRTP-related structural components bonded using adhesive tape, providing better compatibility with plasma treatment and other joining methods like riveting compared to adhesive paste or liquid.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Measurement System Analysis of a Novel Phase-Based Ultrasonic NDE Technique for Bond Strength Measurement

Fiber reinforced polymer parts have shown tremendous benefits in aerospace structural applications, but their qualification and certification for use in safety critical areas are currently hindered by the lack of a capable non-destructive evaluation (NDE) method or technique for the inspection of these adhesively bonded parts. Conventional NDE methods and techniques typically detect gross bond defects in a qualitative (Pass/Fail) manner. These techniques struggle to detect weak or kissing bonds. Also, there are no widely adopted NDE methods or techniques for measuring interfacial bond strength or detecting kissing bonds. Bond strength is currently ensured by process control and semi-destructive testing. Results from recent research from other authors, including but not limited to mechanical testing, have shown an excellent correlation between interfacial stiffness of an adhesively bonded joint and the adhesive bond strength of that joint. In this paper, a measurement system analysis (MSA) of a novel phase-based ultrasonic NDE Technique, developed at NASA Langley Research Center, is presented for bond strength measurement to assess at an increased level the measurement process and identify components of variation in that measurement process.

Ultrasound↗
DOE OSTI2021

Understanding geopolymer binder-aggregate interfacial characteristics at molecular level

The interfacial characteristics of geopolymer binder to aggregate composites are poorly understood, especially at molecular level. Herein, molecular models are developed to study, for the first time, the geopolymer-aggregate interface. Chemically, various forms of interfacial bonding are characterized, including Al-O-Si bonding through condensation reactions, NaO and H-bonding. An atomic-level interfacial transition zone (ITZ) is identified, attributed to the concentration of –OH groups. Increasing the Si/Al ratio of geopolymer is found to decrease the ITZ density, but have limited effect on the ITZ width. A heterogeneous diffusion characteristic occurs in geopolymer, due to the weak interfacial interaction. Mechanically, lowering the Si/Al ratio promotes the interfacial strength due to the stronger interfacial interaction and higher cross-linking degree in geopolymer. Under loading the interfacial fracture undergoes three stages: crack propagation, chain bridging (including aluminosilicate and ionic bridging) and breakage. The above atomic-level findings may facilitate a better design of geopolymer concrete in engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Hierarchically Structured Vitrimer Biocomposites for Sustainable Manufacturing

Polymers containing dynamic covalent bonds (DCBs) exhibit thermoplastic-like flow above their topology freezing temperature (T v ) while maintaining thermoset-like properties below it, making them promising for sustainable manufacturing. However, their large-scale adoption remains limited due to challenges in accurately determining T v and achieving efficient fiber-matrix bonding in composite applications. Here, hierarchically structured epoxy-anhydride-based polyester vitrimer composites reinforced with cellulosic filaments is demonstrated, where hydroxyl groups on fiber surfaces participate directly in transesterification with the matrix. Further, this dynamic interfacial bonding delivers exceptional mechanical properties, including ≈70 MPa shear strength and >10% strain-to-failure, while enabling thermal malleability. Using a combination of nuclear magnetic resonance and nano-infrared spectroscopies, direct evidence is provided that chemical bond exchange begins well below the conventionally measured T v , supporting the hypothesis that rheologically determined T v reflects a combination of chemical exchange and frictional dynamics rather than a discrete transition. The composites demonstrate excellent processability through vacuum-assisted resin transfer molding and maintain >90% of their mechanical properties after multiple thermal reforming cycles. These findings advance both the fundamental understanding of vitrimeric transitions and the practical development of sustainable, high-performance composite materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Unraveling disadhesion mechanism of epoxy/CSH interface under aggressive conditions

Almost all FRP-reinforced concrete exposed to the marine environment are susceptible to durability deficiencies due to failure of the FRP/epoxy/concrete interface, especially the vulnerable epoxy/concrete interface, which is frequently attacked by water and ions. Herein, molecular dynamics simulations of epoxy/CSH interface under different environmental exposures are utilized to specifically elucidate the degradation principles of water and ions on the bonding properties and mechanical responses of the epoxy/concrete interface. The environmental sequences associated with the interfacial bonding degradation are arranged as Na{sub 2}SO{sub 4} + NaCl>NaCl>Na{sub 2}SO{sub 4} > Water>Dry. Remarkably, water molecules weaken the interaction between the epoxy and CSH by robbing interfacial H- and Ca-O bonds, thereby reducing the energy barrier to interfacial peel and shear failure. The weakening effects are exacerbated by the presence of aggressive ions, as Na{sup +} ions attracted to the CSH surface accumulate more water molecules in the interfacial region by forming hydrated ions clusters, which ultimately accelerates the epoxy/CSH interfacial degradation.

36 MATERIALS SCIENCE↗
DOE OSTI2024

LLNL-LDRD-Final report

The main focus of this study is the X-ray spectroscopy and complementary modeling characterization of the range of perovskite materials. Specific areas covered in this study include: • Quantitative characterization of individual (both CB and VB) band edge movement as a function of Sn concentration; • The effects of creating an interface with the charge transport layer and back contact on both the interfacial bonding and unoccupied band structure – i.e., how does the interfacial eDOS evolve when the interface is assembled; • How does this interface change (local bonding, CB edge) evolve with degradation – this includes depth profiling; • Additional insights from the spectroscopy – e.g., the pathway of degradation (Sn(II) oxide formation to a significant depth before Sn(IV) oxide formation, etc.), do different charge transport layers have distinct properties in slowing degradation, etc.

14 SOLAR ENERGY↗
NASA NTRS1979

Metal-dielectric interactions

There is a wide variety of situations wherein metals are in solid state contact with dielectric materials. The paper reviews some of the factors that influence solid state interactions for metals in contact with dielectric surfaces. Since surfaces play an important part in these reactions, the use of analytical tools in characterizing surfaces is discussed. Adhesion, friction, and wear are utilized as indicators of the nature of interfacial bonding between metals and dielectrics can be effectively determined with adhesion and friction force measurements. Films present on the surface, such as oxygen or water vapor, markedly alter adhesive bond strength which in turn affects friction force and interfacial fracture when attempts are made to separate the contact regions. Analytical surface tools such as the field ion microscope, Auger emission spectroscopy, and X-ray photoelectron spectroscopy are very effective in providing insight into the effect of contact on the surfaces of metals and dielectrics.

Buckley, D. H.↗
DOE OSTI2022

Plasma surface modification coupled with thermal and step-over distance effects on significant fracture improvement of adhesively-bonded metal-$\mathrm{CFRTP}$ dissimilar materials

Here, this work proposes an approach to improve the interfacial bonding between carbon-fiber-reinforced thermoplastic polymers (CFRTP) and thermoset adhesive by using the surface modification with the combination of air plasma, thermal, and step-over effects. Thanks to the proper heating which causes the exposure of carbon fibers on the CFRTP surface, both polymer matrix and these exposed carbon fibers can have improved bonding with adhesive due to air plasma treatment. By conducting the Double Cantilever Beam (DCB) tests performed on adhesively-bonded AA5052/CFRP-PA66 dissimilar joints, it was shown in this work that the average Mode I specific fracture energy can be improved up to about 180% compared to non-treated counterparts. The foregoing improvement can be further increased by considering the step-over distance of the surface treatment, which triggers the tortuous damage path in the failure process of adhesively-bonded structures. By manipulating this treatment parameter, often overlooked in the literature, and other parameters (i.e., treatment speed, nozzle tip-to-surface distance, etc.) investigated in this study, the average Mode I specific fracture energy of adhesively-bonded AA5052/CFRP-PA66 dissimilar joints can be improved reaching up to about 410% compared to non-treatment counterparts.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1993

Ceramic matrix composites properties/microstresses with complete and partial interphase bond

A multilevel substructuring technique which includes a unique fiber substructuring concept is used for the analysis of continuous fiber reinforced ceramic matrix composites. This technique has four levels of substructuring--from laminate to ply, to supply, and then to fiber. A stand-alone computer code CEMCAN (Ceramic Matrix Composites Analyzer), incorporating this technique and specifically for the simulation of ceramic matrix composites behavior, is currently under development at NASA Lewis Research Center in Cleveland, Ohio. The thermal and mechanical properties, along with the microstresses, for a SiC/RBSN (silicon carbide fiber and reaction bonded silicon nitride matrix) composite at different fiber volume ratios and varying degrees of interfacial bond around the fiber circumference are computed. Values predicted by CEMCAN computer code are shown to bound the experimentally measured values. Results also show that transverse tensile strength test can be a sensitive test method to assess interfacial conditions.

Mital, Subodh K.↗
DOE OSTI2022

Criteria for electronic growth of Au on layered semiconductors

An electronic growth mode has been reported to occur in several noble metals on MoS2 but has not been observed on other layered semiconductors. In this work, the experiments show that Au(111) islands initially follow an electronic growth mode on WS2, matching the quantization seen in Au/MoS2. However, while epitaxial nanostructures with similar features are observed on WSe2, there is no sign of electronic growth. Binding energy calculations show that multiple bonding sites have nearly the same energy on both WS2 and MoS2, while Au strongly prefers a single bonding site on WSe2. Having multiple sites with the same energy gives flexibility in interfacial bonding that can alleviate strain from the 9+% lattice mismatch in these systems, which would, otherwise, easily suppress quantum size effects from electronic growth modes. These results should be useful in predicting which systems undergo quantized electronic growth on layered semiconductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗