Search NASA⌕ Search

SEARCH · Search NASA

Results for “High Strain Composites”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Sintering and Interface Strain Tolerance of Plasma-Sprayed Thermal and Environmental Barrier Coatings

Ceramic thermal and environmental barrier coatings will be more aggressively designed to protect gas turbine engine hot section SiC/SiC Ceramic Matrix Composite (CMC) components in order to meet future engine higher fuel efficiency and lower emission goals. A coating system consisting of a zirconia-based oxide topcoat (thermal barrier) and a mullite/BSAS silicate inner coat (environmental barrier) is often considered a model system for the CMC applications. However, the coating sintering, and thermal expansion mismatch between the zirconia oxide layer and the silicate environmental barrier/CMC substrate will be of major concern at high temperature and under thermal cycling conditions. In this study, the sintering behavior of plasma-sprayed freestanding zirconia-yttria-based thermal barrier coatings and mullite (and/or barium-strontium-aluminosilicate, i.e., BSAS) environmental barrier coatings was determined using a dilatometer in the temperature range of 1200-1500 C. The effects of test temperature on the coating sintering kinetics were systematically investigated. The plasma-sprayed zirconia-8wt.%yttria and mullite (BSAS) two-layer composite coating systems were also prepared to quantitatively evaluate the interface strain tolerance of the coating system under thermal cycling conditions based on the dilatomentry. The cyclic response of the coating strain tolerance behavior and interface degradation as a function of cycle number will also be discussed.

Zhu, Dongming↗
NASA NTRS2010

Single Spatial-Mode Room-Temperature-Operated 3.0 to 3.4 micrometer Diode Lasers

Compact, highly efficient, 3.0 to 3.4 m light emitters are in demand for spectroscopic analysis and identification of chemical substances (including methane and formaldehyde), infrared countermeasures technologies, and development of advanced infrared scene projectors. The need for these light emitters can be currently addressed either by bulky solid-state light emitters with limited power conversion efficiency, or cooled Interband Cascade (IC) semiconductor lasers. Researchers here have developed a breakthrough approach to fabrication of diode mid-IR lasers that have several advantages over IC lasers used for the Mars 2009 mission. This breakthrough is due to a novel design utilizing the strain-engineered quantum-well (QW) active region and quinternary barriers, and due to optimization of device material composition and growth conditions (growth temperatures and rates). However, in their present form, these GaSb-based laser diodes cannot be directly used as a part of sensor systems. The device spectrum is too broad to perform spectroscopic analysis of gas species, and operating currents and voltages are too high. In the current work, the emitters were fabricated as narrow-ridge waveguide index-guided lasers rather than broad stripe-gain guided multimode Fabry-Perot (FP) lasers as was done previously. These narrow-ridge waveguide mid-IR lasers exhibit much lower power consumptions, and can operate in a single spatial mode that is necessary for demonstration of single-mode distributed feedback (DBF) devices for spectroscopic applications. These lasers will enable a new generation of compact, tunable diode laser spectrometers with lower power consumption, reduced complexity, and significantly reduced development costs. These lasers can be used for the detection of HCN, C2H2, methane, and ethane.

Frez, Clifford F.↗
NASA NTRS2008

Micromechanics-Based Progressive Failure Analysis of Composite Laminates Using Different Constituent Failure Theories

Predicting failure in a composite can be done with ply level mechanisms and/or micro level mechanisms. This paper uses the Generalized Method of Cells and High-Fidelity Generalized Method of Cells micromechanics theories, coupled with classical lamination theory, as implemented within NASA's Micromechanics Analysis Code with Generalized Method of Cells. The code is able to implement different failure theories on the level of both the fiber and the matrix constituents within a laminate. A comparison is made among maximum stress, maximum strain, Tsai-Hill, and Tsai-Wu failure theories. To verify the failure theories the Worldwide Failure Exercise (WWFE) experiments have been used. The WWFE is a comprehensive study that covers a wide range of polymer matrix composite laminates. The numerical results indicate good correlation with the experimental results for most of the composite layups, but also point to the need for more accurate resin damage progression models.

Moncada, Albert M.↗
DOE OSTI2025

Phase segregation dynamics in mixed-halide perovskites revealed by plunge-freeze cryo-electron microscopy

Mixed-halide lead perovskites, with photoexcited charge-carrier properties suitable for high-efficiency photovoltaics, hold significant promise for high-efficiency tandem solar cells. However, phase segregation under illumination, where an iodide-rich phase forms carrier trap states, remains a barrier to application. This study employs plunge-freeze cryoelectron microscopy to visualize nanoscale phase segregation dynamics in CsPb(Br x I 1–x ) 3 films. By rapidly freezing the illuminated samples, we preserve transient photoexcited ion distributions for high-resolution structural and compositional analysis at the nanoscale. Cryogenic scanning transmission electron microscopy (STEM) techniques (electron energy loss spectroscopy [EELS] and 4D-STEM) captured the dynamics of photo-induced iodine migration from grain boundaries to centers, identified the buildup of anisotropic strain, and captured the heterogeneous evolution of this process within a single grain. These findings provide insight into microscopic phase segregation mechanisms and their dynamics, enhancing our understanding of mixed-halide perovskite photostability.

42 ENGINEERING↗
NASA NTRS1979

Internal coating of air cooled gas turbine blades

Six coating systems were evaluated for internal coating of decent stage (DS) eutectic high pressure turbine blades. Sequential deposition of electroless Ni by the hydrazine process, slurry Cr, and slurry Al, followed by heat treatment provided the coating composition and thickness for internal coating of DS eutectic turbine blades. Both NiCr and NiCrAl coating compositions were evaluated for strain capability and ductile to brittle transition temperature.

Ahuja, P. L.↗
NASA NTRS1991

Microfracture in high temperature metal matrix crossply laminates

Microfracture (fiber/matrix fracture, interphase debonding, and inter-ply delamination) in high temperature metal matrix composites (HTMMC), subjected to both mechanical and thermal loading, is computationally simulated. A crossply 0.3 fiber volume ratio SiC/Ti15 composite with 0/90/0 lay-up is evaluated for microfracture using a multicell finite element model. A computational simulation procedure based on strain energy release rates is used to predict the fracture process and establish the hierarchy of fracture modes. Microfracture results for various loading cases are presented and discussed.

Mital, Subodh K.↗
NASA NTRS1990

HITCAN: High temperature composite analyzer

A computer code, HITCAN (High Temperature Composite Analyzer) was developed to analyze/design metal matrix composite structures. HITCAN is based on composite mechanics theories and computer codes developed at NASA LeRC over the last two decades. HITCAN is a general purpose code for predicting the global structural and local stress-strain response of multilayered (arbitrarily oriented) metal matrix structures both at the constituent (fiber, matrix, and interphase) and the structure level and including the fabrication process effects. The thermomechanical properties of the constituents are considered to be nonlinearly dependent on several parameters including temperature, stress, and stress rate. The computational procedure employs an incremental iterative nonlinear approach utilizing a multifactor-interaction material behavior model. HITCAN features and analysis capabilities (static, load stepping, modal, and buckling) are demonstrated through typical example problems.

Singhal, Surendra N.↗
NASA NTRS1995

Failure Mechanisms During Isothermal Fatigue of SiC/Ti-24Al-11Nb Composites

Failure mechanisms during isothermal fatigue of unidirectional SiC/Ti-24Al-11Nb (at.%) composites have been determined by microstructural analysis of samples from tests interrupted prior to the end of life and from tests conducted to failure. Specimens from three regions of life were examined based on the maximum strain from a fatigue life diagram: Region 1 (high strain), Region 2 (mid-strain) and Region 3 (low strain). Crack lengths were also measured from interrupted samples and compared based on temperature (23-815 C), region of life and numbers of cycles. Region 1 was controlled by fiber-dominated failure. A transition zone was observed between Regions 1 and 2 due to competition between failure mechanisms. Failure in Region 2 was generally described as surface-initiated cracking with varying amounts of fiber bridging. However, the specific descriptions of crack propagation through the fibers and matrix varied with strain and temperature over this broad region. Region 3 exhibited endurance behaviour at 23 C with no cracking after lO(exp 6) cycles. However at 425 C, surface-initiated cracking was observed after 10(exp 6) cycles with fractured fibers in the crack wake. If endurance behaviour exists for conditions of isothermal fatigue in air at temperatures of greater than or equal to 425 C, it may only be found at very low strains and at greater than 10(exp 6) cycles.

Brindley, P. K.↗
NASA NTRS1977

Elastic properties and fracture strength of quasi-isotropic graphite/epoxy composites

A research program is described which was devised to determine experimentally the elastic properties in tension and bending of quasi-isotropic laminates made from high-modulus graphite fiber and epoxy. Four laminate configurations were investigated, and determinations were made of the tensile modulus, Poisson's ratio, bending stiffness, fracture strength, and fracture strain. The measured properties are compared with those predicted by laminate theory, reasons for scatter in the experimental data are discussed, and the effect of fiber misalignment on predicted elastic tensile properties is examined. The results strongly suggest that fiber misalignment in combination with variation in fiber volume content is responsible for the scatter in both elastic constants and fracture strength.

Sullivan, T. L.↗
DOE OSTI2020

Structural stability of mechanically alloyed amorphous (FeCoNi) 70 Ti 10 B 20 under high-temperature and high-pressure

Nanostructured (FeCoNi) 70 Ti 10 B 20 (at%) alloy was synthesized by mechanical alloying from elemental powder mixture of Fe, Co, Ni, Ti and B using ball milling. The effect of ball milling time on the evolution of structure and morphology was investigated by X-ray diffraction, scanning and transmission electron microscopy and differential thermal analysis. It was observed that the formation of solid solution of (FeCoNi) 70 Ti 10 B 20 started from the very onset of the milling process. Crystallite size and lattice strains seemed to be leveled off after 20 h of milling with no further major changes. The milling process for longer periods introduced severe plastic deformations causing formation of amorphous phase of (FeCoNi) 70 Ti 10 B 20 . The amorphous alloy composition was confirmed by energy dispersive X-ray spectroscopy analysis that showed an excellent homogeneity of the alloying elements. The phase stability of the mechanically alloyed amorphous sample was further verified by employing high-temperature and high-pressure studies. The alloy samples heat-treated at 700 °C revealed crystallization of the amorphous phase. However, synchrotron-based high-pressure ambient temperature X-ray diffraction studies confirmed that the amorphous phase of the alloy remained stable up to the pressure of 30 GPa. Here, the 50 h milled sample after being annealed at 350 °C showed improvement in the soft magnetic properties of the alloy, which was due to the probable elimination of the residual stress in the amorphous phase of the alloy powders.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Measurement of impact-induced delamination buckling in composite laminates

High-velocity impact tests were performed on graphite/epoxy laminates with embedded delaminations. High-speed photography of the transversely impacted laminates shows that dynamic local buckling of the sublaminate region formed by the delamination can cause a mode-I-dominated propagation of that delamination. Simultaneous recordings of the dynamic strain histories at several locations in the buckled sublaminate region are used to measure the laminate and sublaminate responses to the impact loading. Flexural motion resulting from transverse impact is shown to reduce local buckling of the sublaminate. This buckling causes a progressive separation of the delaminated surfaces and subsequent extension of the delamination in a mode-I dominated fashion.

Grady, J. E.↗
NASA NTRS1989

Compressive strength of a B2 matrix NiAl-Nb intermetallic at 1200 and 1300 K

The effect of a large Nb addition to a NiAl, to a final composition 43.5Ni-45.2Al-0.8Fe-10.5Nb (in at. pct), on the high-temperature compressive strength of NiAl was investigated using cylindrical samples which were compression tested in air at 1200 K and 1300 K under constant-velocity conditions. The compressive strength of the Ni-45Al-10.5Nb was compared to data from all known solid solution-strengthened and/or precipitation-strengthened NiAl-based materials. It was found that, for strain rates higher than 5 x 10 to the -6th/sec, the Ni-45Al-10.5Nb is stronger than NiAl. However, this advantage disappears at lower strain rates. A comparison of NiAl-based materials indicated that a NiAl+TiB2 composite containing 20 vol pct 1-micron-diam particles has a strength superiority over all the solid solution and precipitation-hardened aluminides at strain rates below 10 to the -7th/sec.

Whittenberger, J. Daniel↗
NASA NTRS2005

Crack Driving Forces in a Multilayered Coating System for Ceramic Matrix Composite Substrates

The effects of the top coating thickness, modulus and shrinkage strains on the crack driving forces for a baseline multilayer Yttria-Stabilized-Zirconia/Mullite/Si thermal and environment barrier coating (TEBC) system for SiC/SiC ceramic matrix composite substrates are determined for gas turbine applications. The crack driving forces increase with increasing modulus, and a low modulus thermal barrier coating material (below 10 GPa) will have no cracking issues under the thermal gradient condition analyzed. Since top coating sintering increases the crack driving forces with time, highly sintering resistant coatings are desirable to maintain a low tensile modulus and maintain a low crack driving force with time. Finite element results demonstrated that an advanced TEBC system, such as ZrO2/HfO2, which possesses improved sintering resistance and high temperature stability, exhibited excellent durability. A multi-vertical cracked structure with fine columnar spacing is an ideal strain tolerant coating capable of reducing the crack driving forces to an acceptable level even with a high modulus of 50 GPa.

Ghosn, Louis J.↗
DOE OSTI2024

Assessment of a Grade 91 Steel Forging and Seamless Pipe Section After 141,000-Hours of Operation in a Superheat Outlet Header

In this work, two unique heats of 9Cr creep strength enhanced ferritic (CSEF) steels extracted from a retired superheat outlet header after 141,000 hours of service were evaluated. These two CSEF steels were a forging manufactured to SA-182 F91 (F91) reducer and a seamless pipe produced to SA-335 P91 (P91) pipe. Their creep deformation and fracture behavior were assessed using a lever arm creep frame integrated with in-situ high-temperature digital image correlation (DIC) system. Critical metallurgical and microstructure factors, including composition, service damage, grain matrix degradation, precipitates, and inclusions were quantitatively characterized to link the performance of the two service aged F91 and P91 CSEF steels. The creep test results show the F91 and P91 steels exhibit a large variation in creep strength and creep ductility. The F91 steel fractured at 572 hours while P91 steel fractured at 1,901 hours when subjected to a test condition of 650 °C and 100 MPa. The nominal creep strains at fracture were 12.5% (F91) and 14.5% (P91), respectively. The high-resolution DIC strain measurements reveal the local creep strain in F91 was about 50% while the local creep strain in P91 was >80%. The characterization results show that the F91 steel possessed pre-existing creep damage from its time in service, a higher fraction of inclusions, and a faster matrix grain coarsening rate. These features contribute to the observed reduction in performance for the F91 steel. The context for these findings, and the importance of metallurgical risk in an integrated life management approach will be emphasized.

Wang, Yiyu↗
NASA NTRS1991

Mechanical characterization and modeling of non-linear deformation and fracture of a fiber reinforced metal matrix composite

The nonlinear anisotropic mechanical behavior of an aluminum alloy metal matrix composite reinforced with continuous alumina fibers was determined experimentally. The mechanical behavior of the composite were modeled by assuming that the composite has a periodical microstructure. The resulting unit cell problem was solved with the finite element method. Excellent agreement was found between theoretically predicted and measured stress-strain responses for various tensile and shear loadings. The stress-strain responses for transverse and inplane shear were found to be identical and this will provide a simplification of the constitutive equations for the composite. The composite has a very low ductility in transverse tension and a limited ductility in transverse shear that was correlated to high hydrostatic stresses that develop in the matrix. The shape of the initial yield surface was calculated and good agreement was found between the calculated shape and the experimentally determined shape.

Jansson, S.↗
NASA NTRS1993

Structural tailoring of aircraft engine blade subject to ice impact constraints

Results are presented for the minimum weight design of SR2 unswept blade made of (titanium/graphite-epoxy/titanium) sub s fiber composite. The blade which is rotating at high RPM is subject to ice impact. The root chord length, blade thicknesses at five stations, and graphite-epoxy ply orientation are chosen as design variables. Design constraints are placed on the behavior variables: local leading edge strain and root damage parameter (combined stress failure criteria) as a function due to ice impact, maximum spanwise centrifugal stress at the root of the deformed blade due to local damage, first three natural frequencies, and resonance margin after impact. The method of feasible directions is employed to solve the inequality constrained minimization problem. The effect of ice speed and the ice impact location on the final design are discussed.

Reddy, E. S.↗
NASA NTRS1992

Structural tailoring of aircraft engine blade subject to ice impact constraints

In this paper, results are presented for the minimum weight design of SR2 unswept blade made of (Titanium/Graphite-Epoxy/Titanium)s fiber composite. The blade which is rotating at high RPM is subject to ice impact. The root chord length, blade thicknesses at five stations, and graphite-epoxy ply orientation are chosen as design variables. The design constraints are placed on the behavior variables: leading edge strain and root damage parameter due to ice impact, maximum post-impact bending stress at the root due to rotation, first three natural frequencies and resonance margin after impact. The method of feasible directions is employed to solve the inequality constrained minimization problem. The effect of ice speed and the ice impact location on the final design are discussed.

Reddy, E. S.↗
NASA NTRS1988

High temperature tensile testing of ceramic composites

The various components of a high temperature tensile testing system are evaluated. The objective is the high temperature tensile testing of SiC fiber reinforced reaction bonded Si3N4 specimens at test temperatures up to 1650 C (3000 F). Testing is to be conducted in inert gases and air. Gripping fixtures, specimen configurations, furnaces, optical strain measuring systems, and temperature measurement techniques are reviewed. Advantages and disadvantages of the various techniques are also noted.

Gyekenyesi, John Z.↗