Search NASA⌕ Search

SEARCH · Search NASA

Results for “thermal stress”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The effect of multiple compliant layers at the fiber-matrix interface on residual thermal stresses in metal matrix composites

The large mismatch in thermoelastic properties of the fiber and matrix phases in advanced metal matrix composites, coupled with high consolidation temperatures, produces severe residual stresses that can be large enough to initiate microcracks in the matrix phase adjacent to the fiber/matrix interface. Previous investigations have demonstrated that the use of a compliant interfacial layer between fiber and matrix phases has the potential for reducing these residual stresses. In this paper, the influence of multiple compliant layers in reducing residual thermal stresses is investigated.

Pindera, Marek-Jerzy↗
NASA NTRS1993

Thermal stress analysis of composites in the space environment

A finite element micromechanics approach was utilized to investigate the thermally induced stress fields in continuous fiber reinforced polymer matrix composites at temperatures typical of spacecraft operating environments. The influence of laminate orientation was investigated with a simple global/local formulation. Thermal stress calculations were used to predict probable damage initiation locations, and the results were compared to experimentally observed damage in several epoxy matrix composites. The influence of an interphase region on the interfacial stress states was investigated.

Bowles, David E.↗
NASA NTRS1988

Thermal stress in high temperature cylindrical fasteners

Uninsulated structures fabricated from carbon or silicon-based materials, which are allowed to become hot during flight, are attractive for the design of some components of hypersonic vehicles. They have the potential to reduce weight and increase vehicle efficiency. Because of manufacturing contraints, these structures will consist of parts which must be fastened together. The thermal expansion mismatch between conventional metal fasteners and carbon or silicon-based structural materials may make it difficult to design a structural joint which is tight over the operational temperature range without exceeding allowable stress limits. In this study, algebraic, closed-form solutions for calculating the thermal stresses resulting from radial thermal expansion mismatch around a cylindrical fastener are developed. These solutions permit a designer to quickly evaluate many combinations of materials for the fastener and the structure. Using the algebraic equations developed, material properties and joint geometry were varied to determine their effect on thermal stresses. Finite element analyses were used to verify that the closed-form solutions derived give the correct thermal stress distribution around a cylindrical fastener and to investigate the effect of some of the simplifying assumptions made in developing the closed-form solutions for thermal stresses.

Blosser, Max L.↗
NASA NTRS1993

Strain energy of thermally stressed multilayer panels and its sensitivity coefficients

A study is made of the effect of lamination and material parameters of thermally stressed multilayer composite panels on the strain energy and its sensitivity coefficients obtained by the three-dimensional thermoelasticity model. The sensitivity coefficients measure the sensitivity of the strain energy to variations in the different lamination and material parameters of the panel. The strain energy and sensitivity coefficients obtained by the three-dimensional model are used as the basis for assessing the accuracy of the corresponding quantities obtained by two-dimensional first-order shear deformation theory. Numerical results are presented for antisymmetrically laminated angle-ply panels subjected to linear temperature variation through the thickness. The numerical results demonstrate the accuracy of the strain energy and its sensitivity coefficients obtained by the first-order shear deformation theory, for the range of parameters considered, and the importance of the particular terms in the strain energy, which vanish for single-layer panels.

Noor, Ahmed K.↗
NASA NTRS1992

Residual thermal stresses in composites for dimensionally stable spacecraft applications

An overview of NASA LaRC's research on thermal residual stresses and their effect on the dimensional stability of carbon fiber reinforced polymer-matrix composites is presented. The data show that thermal residual stresses can induce damage in polymer matrix composites and significantly affect the dimensional stability of these composites by causing permanent residual strains and changes in CTE. The magnitude of these stresses is primarily controlled by the laminate configuration and the applied temperature change. The damage caused by thermal residual stresses initiates at the fiber/matrix interface and micromechanics level analyses are needed to accurately predict it. An increased understanding of fiber/matrix interface interactions appears to be the best approach for improving a composite's resistance to thermally induced damage.

Bowles, David E.↗
NASA NTRS1989

Analysis of thermal stresses in polymer matrix composites

In the present micromechanics study of the thermally-induced stress field which emerges at very low temperatures in the matrix and fibers of continuous fiber-reinforced polymer composites, the results obtained by a specialized FEM analysis are compared to an analytical solution of the composite cylinder model for several composite materials. Attention is given to the influence of microstructural geometry and constituent properties; it is established that the distributions and magnitudes of the thermally-induced stresses are affected by the assumed microstructural geometry of the sample. While matrix stresses are not a strong function of fiber properties, the temperature dependence of the matrix properties significantly affects the magnitudes of thermally-induced matrix stresses.

Bowles, David E.↗
DOE OSTI2021

Impact of Thermal Stress on Attachment and Stability of High Temperature Strain Sensors

Static and dynamic strain sensing is required in high-temperature (HT), harsh-environments (HE) for industrial, aerospace, and energy sector applications to ensure equipment and process safety, reduce the cost of operation and maintenance, and increase process efficiency. Challenges that arise in HT HE sensing applications include device mounting, packaging, integrity, and stability to HT HE conditions. In previously reported work, static and dynamic strain surface acoustic wave resonator (SAWR) sensors were fabricated on langasite (LGS) and mounted on Inconel 625 strain beams for wireless testing up to 400°C. In this work, it has been identified that after subjecting the mounted SAWR strain sensor to thermal cycling between 100°C and 425°C, the measured sensitivity to dynamic strain decreased by 73% due to cracking at the adhesive/LGS interface, further deteriorating after additional thermal cycles. Strain modeling of the mounted LGS sensor chip up to 400°C revealed the existence of concentrated strain at the borders of the LGS chip. Microcracks caused by dicing make the chip boarders the most susceptible location for cracks to initiate when the sensor is subjected to thermal stress. In an attempt to mitigate the high strain at the LGS chip borders due to heating, adhesive shaping is proposed in this work. Simulations indicate a strain reduction of 50% at the border is achieved using both circular and triangular adhesive shapes, while also reducing the maximum strain over the entire adhesive/LGS interface by around 30%. Furthermore, the technique is thus promising for improving the integrity, reliability, and stability of static and dynamic strain sensors, particularly while operating under HT HE with several hundreddegree Celsius temperature excursions.

47 OTHER INSTRUMENTATION↗
NASA NTRS1974

Thermal stresses in chemically hardening elastic media with application to the molding process

A method has been formulated for the determination of thermal stresses in materials which harden in the presence of an exothermic chemical reaction. Hardening is described by the transformation of the material from an inviscid liquid-like state into an elastic solid, where intermediate states consist of a mixture of the two, in a ratio which is determined by the degree of chemical reaction. The method is illustrated in terms of an infinite slab cast between two rigid mold surfaces. It is found that the stress component normal to the slab surfaces vanishes in the residual state, so that removal of the slab from the mold leaves the remaining residual stress unchanged. On the other hand, the residual stress component parallel to the slab surfaces does not vanish. Its distribution is described as a function of the parameters of the hardening process.

Levitsky, M.↗
NASA NTRS1999

Numerical Investigation of Thermal Stress Convention in Nonisothermal Gases Under Microgravity Conditions

Reported here are our results of our numerical/theoretical investigation into the effects of thermal stress in nonisothermal gases under microgravity conditions. The first part of the report consists of a brief summary of the accomplishments and conclusions of our work. The second part consists of two manuscripts, one being a paper presented at the 1998 MSAD Fluid Physics workshop, and the other to appear in Physics of Fluids.

Mackowski, D. W.↗
NASA NTRS1992

Three-dimensional solutions for the free vibrations and buckling of thermally stressed multilayered angle-ply composite plates

Analytic three-dimensional elasticity solutions are developed for the free vibration and buckling of thermally stressed rectangular multilayered angle-ply anisotropic plates which are assumed to have an antisymmetric lamination with respect to the middle plane. Sensitivity derivatives are evaluated and used to investigate the sensitivity of the vibration and buckling responses to variations in the different lamination and material parameters of the plate. A Duhamel-Neumann-type constitutive model is used, and the material properties are assumed to be independent of temperature. Numerical results are presented, showing the effects of variations in the material characteristics and fiber orientation of different layers, as well as the effect of initial thermal deformation on the vibrational and buckling responses of the plate.

Noor, Ahmed K.↗
NASA NTRS1993

Thermal-Stress Reducer For Metal/Composite Joint

Simple insert called "thermal link" reduces stresses caused by mismatches between thermal expansions of metal part and nonmetallic part made of fiber/matrix composite material. Link conceived for use in casing of advanced jet engine.

Glinski, Robert L.↗
NASA NTRS1973

Release of Bacterial Spores from the Inner Walls of a Stainless Steel Cup Subjected to Thermal Stresses and Mechanical Shock

The release and fallout of particulates from surfaces afforded thermal or impact stress is of concern for control of contamination of Mars from planetary landing vehicles. A metal vessel contaminated by aerosols of spores was used as a model system and the fallout of spores as affected by various mechanisms was examined. Thermal stresses simulating those expected on the Mars lander dislodged approximately .01% of the aerosol deposited surface burden as did a landing shock of 8 to 10G deceleration. Spores imprinted by finger or swab contact yielded similar results. In all cases where repeated cycling of temperature, motion, or shock were employed the majority of fallout occurred in the first cycle. Particles released from the surface were predominantly in the size range 1 to 5 microns.

Wolochow, H.↗
NASA NTRS1989

Prediction of thermal-stress and deformations due to phase change in solidifying objects via flux/stress based finite element representations

The paper presents numerical simulations for the prediction of thermal-stress and deformation fields resulting from phase change in solidifying bodies employing new finite element representations. The formulations herein demonstrated provide different perspectives and physical interpretation for the modeling/analysis of thermo-mechanical problems and possess several inherent advantages. In comparison to traditional approaches for solving similar problems, the paper employs new flux/stress based representations to enhance the overall effectiveness. Comparative numerical applications validate applicability of the formulations for predicting the temperature induced deformations and stresses resulting from effects due to phase change.

Tamma, K. K.↗
NASA NTRS1977

Fluid shifts during thermal stress with and without fluid replacement

Six unacclimatized men rested for 4 hr in a hot, dry environment without fluid replacement (DH). Another group of six men were exposed to the same thermal stress, replacing evaporative fluid loss with warm 0.1% NaCl solution (FRP). Total grams of circulating hemoglobin, determined by CO immediately prior to and again during the last minutes of heat exposure, increased an insignificant 1.6 and 1.3% during DH and FRP, respectively. With DH, body weight loss of 2.6% was accompanied by a 7.8% reduction in calculated plasma volume (PV). Even when body weight was maintained (FRP), PV decreased 2.9% during the heat exposure. Total circulating serum protein did not change as a result of the heat stress with either DH or FRP. In a test-retest series of experiments on four men, DH was not detrimental to sweat rate. It is shown that hemodilution is not a general response to acute heat exposure. The disproportionately large reduction in PV during thermal dehydration is confirmed.

Myhre, L. G.↗