Stresses and Deformations in Composite Tubes Due to a Circumferential Temperature Gradient

1986 ◽  
Vol 53 (4) ◽  
pp. 757-764 ◽  
Author(s):  
M. W. Hyer ◽  
D. E. Cooper
Keyword(s):  
Thermal Expansion ◽  
Temperature Gradient ◽  
Hoop Stress ◽  
Single Layer ◽  
Transversely Isotropic ◽  
Axial Direction ◽  
Axial Deformation ◽  
Composite Tubes ◽  
Displacement Approach ◽  
Overall Bending

This paper presents a linear elasticity solution for determining the response of composite tubes subjected to a circumferential temperature gradient of the form ΔTo+ ΔT1 cos(θ). The temperature does not vary with distance along the tube nor through the wall. Temperature-independent material properties are assumed and a displacement approach is used. The results are limited to tubes with the fibers in each layer oriented axially or circumferentially, so-called cross-ply tubes. It is shown that for both single layer and multiple layer tubes, one constant characterizes overall bending of the tube and one constant characterizes overall axial deformation. Numerical results show that fiber orientation strongly influences the stresses in a single layer tube. When the fibers are aligned axially, all components of stress in the tube are small. When the fibers are aligned circumferentially, the hoop stress becomes large. This is due to the large difference between the radial and circumferential coefficients of thermal expansion when the fibers are oriented circumferentially. Also, for a single layer tube constructed of a material with no thermal expansion in the axial direction, the overall change of length of the tube due to the temperature gradient will be zero only if the material is transversely isotropic. However, even if the material is transversely isotropic, the tube will still experience overall bending.

Determination of Poisson's Ratio of Thin low-k Films using Bidirectional Thermal Expansion Measurement

2006 ◽  
Vol 914 ◽  
Author(s):  
Jiping Ye ◽  
Satoshi Shimizu ◽  
Shigeo Sato ◽  
Nobuo Kojima ◽  
Junnji Noro
Keyword(s):  
Thermal Expansion ◽  
Temperature Gradient ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Silicon Oxide ◽  
Young's Modulus ◽  
Polymer Materials ◽  
Poisson's Ratio ◽  
Thermal Expansion Measurement ◽  
Low K

AbstractA recently developed bidirectional thermal expansion measurement (BTEM) method was applied to different types of low-k films to substantiate the reliability of the Poisson's ratio found with this technique and thereby to corroborate its practical utility. In this work, the Poisson's ratio was determined by obtaining the temperature gradient of the biaxial thermal stress from substrate curvature measurements, the temperature gradient of the whole thermal expansion strain along the film thickness from x-ray reflectivity (XRR) measurements, and reduced modulus of the film from nanoindentation measurements. For silicon oxide-based SiOC film having a thickness of 382.5 nm, the Poisson's ratio, Young's modulus and thermal extension coefficient (TEC) were determined to be Vf = 0.26, αf =21 ppm/K and Ef =9,7 GPa. These data are close to the levels of metals and polymers rather than the levels of fused silicon oxide, which is characterized by Vf = 0.17 and Er = 69.6 GPa. The alkyl component in the silicon oxide-based framework is thought to act as an agent in reducing the modulus and elevating the Poisson's ratio in SiOC low-k materials. In the case of an organic polymer SiLK film with a thickness of 501.5 nm, the Poisson's ratio, Young's modulus and TEC were determined to be Vf = 0.39, αf =74 ppm/K and Er =3.1 GPa, which are in the typical range of V= 0.34~0.47 with E =1.0~10 GPa for polymer materials. From the viewpoint of the relationship between the Poisson's ratio and Young's modulus as classified by different material types, the Poisson's ratios found for the silicon oxide-based SiOC and organic SiLK films are reasonable values, thereby confirming that BTEM is a reliable and effective method for evaluating the Poisson's ratio of thin films.

PREDICTING PROCESSING INDUCED RESIDUAL- STRESSES IN CARBON FIBER-THERMOPLASTIC MICRO-COMPOSITES

2021 ◽  
Author(s):  
NITHIN K. PARAMBIL ◽  
BRANNDON R. CHEN ◽  
JOSEPH M. DEITZEL ◽  
JOHN W. GILLESPIE, JR. ◽  
LOAN T. VO ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Residual Strain ◽  
Coefficient Of Thermal Expansion ◽  
Fiber Composite ◽  
Transversely Isotropic ◽  
Axial Direction ◽  
Single Fiber ◽  
Temperature Dependent ◽  
Test Configuration ◽  
Polypropylene Composites

A computational model of residual stress is developed for AS4/polypropylene composites and implemented via user material subroutine (UMAT) in ABAQUS. The main factors included in the model are the cooling-rate dependent crystallinity, temperature-dependent elastic modulus, and temperature-dependent coefficient of thermal expansion (CTE) of the matrix, and the temperature-independent transversely isotropic properties of the carbon fiber. Numerical results are generated for the case of a single fiber embedded in a thin film of polypropylene sample to replicate the process history and test configuration. During single fiber composite processing, a precalculated weight (tensile preload) is applied at the fiber ends to eliminate buckling/waviness of the carbon fiber induced by matrix shrinkage in the axial direction of the fiber. Experiments and Finite element (FE) analysis have been conducted with different preloads (1g, 4g, and 8g) at 25°C. Micro-Raman spectroscopy is utilized to validate the residual strain with different preloads at the bulk. The measured strain values show a good correlation with the predicted residual strain for various preload conditions.

Thermal-Mechanical Study of 3D Printing Technology for Rail Repair

2018 ◽  
Author(s):  
Ershad Mortazavian ◽  
Zhiyong Wang ◽  
Hualiang Teng
Keyword(s):  
Thermal Analysis ◽  
Thermal Expansion ◽  
3D Printing ◽  
Stress Distribution ◽  
Temperature Gradient ◽  
Initial Temperature ◽  
Mechanical Analysis ◽  
Von Mises Stress ◽  
Additive Materials ◽  
Von Mises

The complicated steel wheel and rail interaction on curve causes side wear on rail head. Thus, the cost of maintenance for the track on curve is significantly higher than that for track on a tangent. The objective of this research is to develop 3D printing technology for repairing the side wear. In this paper, the study examines induced residual thermal stresses on a rail during the cooling down process after 3D printing procedure using the coupled finite volume and finite element method for thermal and mechanical analysis respectively. The interface of the railhead and additive materials should conserve high stresses to prevent any crack initiation. Otherwise, the additive layer would likely shear off the rail due to crack propagation at the rail/additive interface. In the numerical analysis, a cut of 75-lb ASCE (American Society of Civil Engineers) worn rail is used as a specimen, for which a three-dimensional model is developed. The applied residual stresses, as a result of temperature gradient and thermal expansion coefficient mismatch between additive and rail materials, are investigated. At the beginning, the worn rail is at room temperature while the additive part is at a high initial temperature. Then, additive materials start to flow thermal energy into the worn rail and the ambient. The thermal distribution results from thermal analysis are then employed as thermal loads in the mechanical analysis to determine the von-Mises stress distribution as the decisive component. Then, the effect of preheating on residual stress distribution is studied. In this way, the thermo-mechanical analysis is repeated with an increase in railhead’s initial temperature. In thermal analysis, the temperature contours at different time steps for both the non-preheated and preheated cases indicate that preheating presents remarkably lower temperature gradient between rail and additive part and also represents a more gradual cooling down process to allow enough time for thermal expansion mismatch alignment. In mechanical analysis, the transversal von-Mises stress distribution at rail/additive interface is developed for all cases for comparison purposes. It is shown that preheating is a key factor to significantly reduce residual stresses by about 40% at all points along transversal direction of interface.

Mechanical Properties of Kevlar® KM2 Single Fiber

2005 ◽  
Vol 127 (2) ◽  
pp. 197-203 ◽  
Author(s):  
Ming Cheng ◽  
Weinong Chen ◽  
Tusit Weerasooriya
Keyword(s):  
Isotropic Material ◽  
Axial Stress ◽  
Axial Loading ◽  
Strain Range ◽  
Transversely Isotropic ◽  
Axial Direction ◽  
Strain Response ◽  
Transversely Isotropic Material ◽  
Stress Strain ◽  
Strain Behavior

Kevlar® KM2 fiber is a transversely isotropic material. Its tensile stress-strain response in the axial direction is linear and elastic until failure. However, the overall deformation in the transverse directions is nonlinear and nonelastic, although it can be treated linearly and elastically in infinitesimal strain range. For a linear, elastic, and transversely isotropic material, five material constants are needed to describe its stress-strain response. In this paper, stress-strain behavior obtained from experiments on a single Kevlar KM2 fiber are presented and discussed. The effects of loading rate and the influence of axial loading on transverse and transverse loading on axial stress-strain responses are also discussed.

Development of a Negative Thermal Expansion Capsular Object Using Phase Change Material

2003 ◽  
Author(s):  
Y. Yamaguchi ◽  
K. Takanashi
Keyword(s):  
Thermal Expansion ◽  
Phase Change ◽  
Phase Change Material ◽  
Fluid Layer ◽  
Negative Thermal Expansion ◽  
Axial Direction ◽  
Steam Pressure ◽  
Expansion Behavior ◽  
Motion Characteristics ◽  
Change Material

Driving device for heat transfer enhancement in a fluid layer heated from above was developed. The device was composed of two closed vessels of which the size differs. They are flexible in axial direction, and the lager vessel is filled with air and the smaller one is filled with phase change material (PCM). By the change of the steam pressure of the PCM, the device shrinks and sinks under water when it is hot, and it expands and floats on water when it is cold. The device has a negative thermal expansion behavior, so the authors named it negative thermal expansion capsular object, NTE capsule for short. In this study, the NTE capsule using phase change material (PCM) was developed. It was composed of the large vessel enclosing the air and small vessel enclosing the PCM. Perfluorocyclobutane (RC318) was used for the PCM. The vapor pressure of the PCM changes widely according to the temperature. The motion characteristics of the NTE capsule using PCM were investigated experimentally. As a result, it was confirmed that the new NTE capsule falls downward and rises upward spontaneously in a fluid layer heated from above.

Thermal Expansion of Three-Phase Composite Materials

1989 ◽  
Vol 56 (2) ◽  
pp. 418-422 ◽  
Author(s):  
George J. Dvorak ◽  
Tungyang Chen
Keyword(s):  
Thermal Expansion ◽  
Heterogeneous Media ◽  
Transversely Isotropic ◽  
Local Fields ◽  
Stress Fields ◽  
Cylindrical Shape ◽  
Thermal Expansion Coefficients ◽  
Decomposition Procedure ◽  
Transverse Geometry ◽  
Expansion Coefficients

Exact expressions are found for overall thermal expansion coefficients of a composite medium consisting of three perfectly-bonded transversely isotropic phases of cylindrical shape and arbitrary transverse geometry. The results show that macroscopic thermal expansion coefficients depend only on the thermoelastic constants and volume fractions of the phases, and on the overall compliance. The derivation is based on a decomposition procedure which indicates that spatially uniform elastic strain fields can be created in certain heterogeneous media by superposition of uniform phase thermal strains with local strains caused by piecewise uniform stress fields, which are in equilibrium with prescribed surface tractions. The procedure also allows evaluation of thermal stress fields in the aggregate in terms of known local fields caused by axisymmetric overall stresses. Finally, averages of local fields are found with the help of known mechanical stress and strain concentration factors.

Investigation on Thermal Energy Storage Characteristics of Thermocline Tank with Mixture Filler Materials

2014 ◽  
Vol 687-691 ◽  
pp. 3512-3515
Author(s):  
Jing Xiao Han ◽  
Yong Ping Yang ◽  
Jia Rui Wu ◽  
Hong Juan Hou
Keyword(s):  
Temperature Gradient ◽  
Axial Direction ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Filler Materials ◽  
Indirect Contact ◽  
Lower Velocity ◽  
Air Inlet ◽  
Sand Filler ◽  
Storage Characteristics

An experimental setup for indirect contact sensible heat TES was built. Air was chosen as the heat transfer fluid to flow inside the tubes and carry heat, while the mixture in the tank contacts the outside of the tubes. The results were also compared with pure sand filler material. It can be found that and the TES efficiency of mixture increased by 18% compared with pure sand, what’s more, its temperature gradient along the radical direction was also lower, while its temperature gradient along the axial direction was higher, so the mixture was better. Under various air inlet temperature (60-70°C), TES performances were similar, but for real power generation, further work on optimism temperature range was needed. Air velocity was also important to TES tank, lower velocity can not only increase the TES efficiency, but also enlarge the thermocline temperature gradient.

Thermal Deformation Modeling of Space Optical Systems With Variable Coefficient of Thermal Expansion

2005 ◽  
Author(s):  
Jennifer Batson ◽  
Ab Hashemi
Keyword(s):  
Thermal Expansion ◽  
Temperature Gradient ◽  
Wave Front ◽  
Thermal Deformation ◽  
Coefficient Of Thermal Expansion ◽  
Optical Element ◽  
Thermal Control ◽  
Temperature Gradients ◽  
Optical Systems ◽  
Space Optical Systems

In modeling space optical systems, an important property affecting the wave front error is the coefficient of thermal expansion (CTE) of the materials. The change of deformation that an optical element experiences due to thermal loads is proportional to both the CTE and the change in temperature gradient. This deformation affects the performance of the optical system by introducing error in the wave front. The deformation can be reduced in part by using materials with low CTE. Alternatively, using high conductivity materials to minimize temperature gradients through the mirror can also reduce deformation. Usually, a combination of these approaches is used to optimize the performance and meet the requirements of the system. Even with the utmost attention to thermal control, often the temperature gradients cannot be completely avoided. Low CTE materials have been developed to reduce thermal deformation, including ULE (Ultra-low Expansion), Zerodur, and Silicon Carbide. However, the manufacturing process can result in non-uniformities throughout the optics. For optical systems requiring highly precise performance, modeling these non-uniformities becomes important. The non-uniformity in the CTE of a material in effect compounds the deformation in the same manner as introducing additional temperature gradient through the optics. This paper describes the methodology for integrated thermal/mechanical modeling to predict the deformation response of an optical element with assumed CTE variations and thermal disturbances. A mirror with an assumed CTE variation was modeled in a changing thermal environment and using IDEAS/TMG analysis tools, thermal deformations were predicted. Results show excellent agreement with engineering predictions. Clearly knowing the CTE variation of the material is a critical step for modeling. However, measuring and specifying the material CTE is out of the scope of this paper.

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