Search NASA⌕ Search

SEARCH · Search NASA

Results for “THERMAL EXPANSION”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Thermal expansion of composites using Moire interferometry

An experimental technique for precise measurement of the thermal response of fiber-reinforced composite materials uses moire interferometry with fringe multiplication which yield a sensitivity of 833 nm (32.8 mu in.) per fringe. Results from the technique are compared with those obtained from electrical resistance strain gages, and also those predicted from classical lamination theory. Temperature dependent coefficients of thermal expansion for composite materials subjected to thermal cycling in the temperature range of 297 K (75 F) to 422 K (300 F) were determined for four laminate configurations (0, 90, 0/ + or - 45/90 sub s and 0/90/ + or - 45 sub s) of T300/5208 graphite epoxy, and ranged from -0.107 mu epsilon K/1 (-0.059 mu epsilon deg F/-) for the 0 laminate to 32.18 mu epsilon K/1 (17.88 mu epsilon F/1) for the 90 laminate. Moisture was found to greatly influence the thermal response of a quasi-isotropic laminate, resulting in hysteresis and residual compressive strain as the moisture content was reduced. Comparisons between moire and strain gage measurements were inconclusive with both techniques giving consistent but systematically different results. Differences of as much as 29% were observed.

Bowles, D. E.↗
NASA NTRS1975

A strut with infinitely adjustable thermal expansivity and length

A tubular strut with an integral mechanism for adjusting its thermal expansivity and length was developed to fulfill the stringent thermal stability requirements anticipated for the metering truss in the Large Space Telescope. Its features may be advantageously applied to a general variety of structures and precision mechanisms where dimensional control of component elements in a dynamic thermal environment is required. Detail, design, fabrication, and test of a developmental strut are discussed.

Nelson, P. T.↗
NASA NTRS1982

Moire interferometry for thermal expansion of composites

Moire interferometry by reflection is described and demonstrated for the case of a real reference grating of 1200 lines/mm. Extraneous beams can be displaced and stopped by using a wedge-shaped air gap between reference and specimen gratings. Double-order dominance, the use of diffraction sequences for reflection, the isolation of preferred sequences, and the use of two-beam interference are discussed. Experimental accuracy is enhanced significantly by using several data points to establish displacements along a line, and random errors characterized by one standard deviation can be as small as one microstrain. The method is well adapted to thermal environments, coefficients of thermal expansion of selected graphite-epoxy laminates being determined in the temperature range of 297-422 K. Very good precision was achieved for a wide range of thermal expansion coefficients, from approximately zero to 27 microstrains/K.

Bowles, D. E.↗
NASA NTRS2017

Thermal Expansion from Stochastic Nonlinear Acoustic Fields

The methods of stochastic mechanics are applied to nonlinear acoustic fields generated by random acoustic radiation sources associated with oscillating lattice sites in nonlinear lattices. The assumption of stochastically independent zero-point and temperature-dependent acoustic fields leads to expressions of the thermodynamic internal and Helmholtz free energies per unit mass in terms of modal energies per unit mass that account for the nonlinearity of the propagation modes. The thermodynamic state functions canonically transform to the familiar results of a system of quantized, simple harmonic oscillators in the linear field limit. The thermal expansion coefficient, derived from the Helmholtz free energy per unit mass, is obtained as a sum of the zero-point modal nonlinearity parameters, weighted by temperature-dependent, modal heat capacities. The relationship is fully anharmonic, in contrast to commonly used quasi-harmonic models, and predicts with excellent agreement the experimentally observed null thermal expansion of vitreous silica at the ‘cross-over’ temperature corresponding to the balance between long wavelength modes that contribute negative nonlinearity parameters to the modal sum and short wavelength modes that contribute positive nonlinearity parameters.

Cantrell, John H., Jr.↗
NASA NTRS1979

Thermal Expansion and Swelling of Cured Epoxy Resin Used in Graphite/Epoxy Composite

The thermal expansion and swelling of resin material as influenced by variations in temperature during moisture absorption is discussed. Comparison measurements using composites constructed of graphite fibers and each of two epoxy resin matrices are included. Polymer theory relative to these findings is discussed and modifications are proposed.

Adamson, M. J.↗
NASA NTRS2003

High Accuracy Thermal Expansion Measurement At Cryogenic Temperatures

A new, interferometer based system for measuring thermal expansion to an absolute accuracy of 20 ppb or better at cryogenic temperatures has been developed. Data from NIST Copper SRM 736 measured from room temperature to 15 K will be presented along with data from many other materials including beryllium, ULE, Zerodur, and composite materials. Particular attention will be given to a study by the Space Optics Manufacturing Technology Center (SOMTC) investigating the variability of ULE and beryllium materials used in the AMSD program. Approximately 20 samples of each material, tested from room temperature to below 30 K are compared as a function of billet location.

Stallcup, Michael↗
NASA NTRS1989

Thermal expansion and elastic anisotropy in single crystal Al2O3 and SiC whiskers

The crystalline thermal expansion and elastic anisotropies of SiC and Al2O3 whiskers are considered in the process of evaluation of the anisotropy of the alpha-E product, the thermoelastic stress index. It is demonstrated to exhibit considerable crystalline anisotropy and a substantial temperature dependence, both of which will influence the thermal and residual stresses in composites using these materials for reinforcement.

Salem, J. A.↗
NASA NTRS2012

Thermal expansion compensator having an elastic conductive element bonded to two facing surfaces

A thermal expansion compensator is provided and includes a first electrode structure having a first surface, a second electrode structure having a second surface facing the first surface and an elastic element bonded to the first and second surfaces and including a conductive element by which the first and second electrode structures electrically and/or thermally communicate, the conductive element having a length that is not substantially longer than a distance between the first and second surfaces.

Determan, William↗
NASA NTRS1982

Development of a Priest interferometer for measurement of the thermal expansion of a graphite epoxy in the temperature range 116-366 K

The thermal expansion behavior of graphite epoxy laminates between 116 and 366 degrees Kelvin was investigated using as implementation of the Priest interferometer concept. The design, construction and use of the interferometer along with the experimental results it was used to generate are described. The experimental program consisted of 25 tests on 25.4 mm and 6.35 mm wide, 8 ply pi/4 quasi-isotropic T300-5208 graphite/epoxy specimens and 3 tests on a 25.4 mm wide unidirectional specimen. Experimental results are presented for all tests along with a discussion of the interferometer's limitations and some possible improvements in its design.

Short, J. S.↗
NASA NTRS1992

Thermally induced changes in the focal distance of composite mirrors - Composites with a zero coefficient of thermal expansion of the radius of curvature

Calculations are presented of the coefficient of thermal expansion (CTE) of the radius of curvature of the reflector face sheets made of a quasi-isotropic composite. It is shown that, upon cooling, the change of the CTE of the focal distance of the mirror is equal to that of the radius of the curvature of the reflector face sheet. The CTE of the radius of the curvature of a quasi-isotropic composite face sheet depends on both the in-plane and the out-of-plane CTEs. The zero in-plane CTE of a face sheet does not guarantee mirrors with no focal length changes.

Dolgin, Benjamin P.↗
NASA NTRS2003

High Accuracy Thermal Expansion Measurement at Cryogenic Temperatures

A new, interferometer-based system for measuring thermal expansion to an absolute accuracy of 20 ppb or better at cryogenic temperatures has been developed. Data from NIST Copper SRM 736 measured from room temperature to 15 K will be presented along with data from many other materials including beryllium, ULE, Zerodur, and composite materials. Particular attention will be given to a study by the Space Optics Manufacturing Technology Center (SOMTC) investigating the variability of ULE and beryllium materials used in the AMSD program Approximately 20 samples of each material, tested from room temperature to below 30 K are compared as a function of billet location.

Tucker, Jim↗
NASA NTRS1973

A solar engine using the thermal expansion of metals.

A thermal engine which uses solid metal as the single-phase working substance to convert solar energy into small amounts of mechanical energy is described. Test data are given for an engine whose working substance was annealed 304-type steel welded into a thin-walled tube that was mounted in a bearing at each end (making it free to rotate about its axis) with a flywheel mass at its midpoint. When heated on its upper surface, the tube rotates producing steady power. The theory of the engine is outlined.

Beam, R.↗
NASA NTRS2003

Transverse Coefficient of Thermal Expansion Measurements of Carbon Fibers Using ESEM at High Temperatures

The transverse coefficient of thermal expansion (CTE) of single IM7, T1000, and P55 carbon fibers are measured at elevated temperatures. The specimens are prepared by press-fitting fiber tows into 0.7mm-diameter cavity in a graphite disk of 5mm in diameter and 3mm high. The specimens are placed on a crucible in an ESEM, and images of the fiber cross section are taken as the fibers are heated up to 800 C. Holding time, heating and cool down cycles are also introduced. The geometrical changes are measured using a graphics tablet. The change in area/perimeter is calculated to determine the strain and transverse CTE for each fiber. In a complimentary computational effort, displacements and stresses are calculated with finite element models.

Ochoa, O.↗
NASA NTRS2021

Thermal Expansion Coefficients of Ca2Y8(SiO4)6O2 and Ca2Yb8(SiO4)6O2 Apatite-type Silicates

High temperature X-ray diffraction (XRD) scans of Y2Si2O7 and Yb2Si2O7 reactions with calcium-magnesium-aluminosilicates (CMAS) were utilized to determine thermal expansion coefficients (CTEs) of Ca2Y8(SiO4)6O2 and Ca2Yb8(SiO4)6O2 apatite materials. In order to validate these measurements, the CTEs of Y2Si2O7, Yb2Si2O7 and SiO2 were also determined from the same scans. The directional CTEs for γ-Y2Si2O7 were determined to be αa=5.84×10-6/K, αb=6.81×10-6/K and αc=0.81×10-6/K, and β-Yb2Si2O7 was determined to have values of αa=6.89×10-6/K, αb=4.81×10-6/K and αc=2.78×10-6/K. The average CTEs of γ-Y2Si2O7 and β-Yb2Si2O7 were determined to be 4.5×10-6/K and 4.7×10-6/K, respectively, which agreed with previous analyses. Ca2Y8(SiO4)6O2 exhibited directional CTEs of αa=9.36×10-6/K and αc=7.95×10-6/K (averaged between two sets of data), whereas Ca2Yb8(SiO4)6O2 had values that were very similar (αa=9.63×10-6/K, αc=7.45×10-6/K). Both results for the Ca2RE8(SiO4)6O2 apatites correlated well with the limited data on apatite-type silicates available in literature.

rare earth↗