Thermal Stress in a Coated Short Fibre Composite

1986 ◽  
Vol 53 (3) ◽  
pp. 681-689 ◽  
Author(s):  
Yozo Mikata ◽  
Minoru Taya
Keyword(s):  
Stress Field ◽  
Thermal Stresses ◽  
Fibre Composite ◽  
Extreme Case ◽  
Short Fibre ◽  
Thermal Expansion Coefficients ◽  
Stress Functions ◽  
Expansion Coefficients ◽  
Short Fibre Composite ◽  
Good Agreement

When a coated short fibre composite is subjected to temperature change, thermal stresses in and around the coated fibres are induced due to the mismatch of thermal expansion coefficients of the constituents, resulting in a possibility of cracking in the coating. The problem of the above thermal stresses in a coated short fibre composite is solved by using the Boussinesq-Sadowsky stress functions. The present results are compared with Eshelby’s solutions for an extreme case and good agreement between the two methods is obtained. A parametric study is then conducted to examine the effect of the geometry and thermo-mechanical properties of the coating on the stress field in and around a coated short fibre. It is found in this study that the stress field in the coating is sensitive to the properties and geometry of the coating.

Thermal Stress in a Coated Short Fiber Composite

1987 ◽  
Vol 109 (1) ◽  
pp. 59-63 ◽  
Author(s):  
Hiroshi Hatta ◽  
Minoru Taya
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Stress Field ◽  
Thermal Stresses ◽  
Fiber Composite ◽  
Short Fiber ◽  
Critical Parameters ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Short Fiber Composite

When a coated short fiber composite is subject to temperature change, thermal stresses in and around the coated fibers are induced due to the mismatch of thermal expansion coefficients of the constituents. The problem of the above thermal stresses in a coated short fiber composite is solved by using the Eshelby’s equivalent inclusion method under the assumption of thin coating. A parametric study is then conducted to examine the effect of thermo-mechanical properties of the coating on the stress field in an and around a coated short fiber. It is found in this study that critical parameters influencing the thermal stress field are the thermal expansion coefficients of the fiber and coating.

Thermal Stress Analysis of a Bi-Material Layered Structure

2010 ◽  
Vol 450 ◽  
pp. 161-164 ◽  
Author(s):  
Shiuh Chuan Her ◽  
Chin Hsien Lin ◽  
Shun Wen Yeh
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Dissimilar Materials ◽  
Beam Theory ◽  
Layered Systems ◽  
Thermal Expansion Coefficients ◽  
Parametric Studies ◽  
Expansion Coefficients ◽  
Good Agreement

Thermal stress induced by the mismatch of the thermal expansion coefficients between dissimilar materials becomes an important issue in many bi-layered systems, such as composites and micro-electronic devices. It is useful to provide a simple and efficient analytical model, so that the stress level in the layers can be accurately estimated. Basing on the Bernoulli beam theory, a simple but accurate analytical formulation is proposed to evaluate the thermal stresses in a bi-material beam. The analytical results are compared with finite element results. Good agreement demonstrates that the proposed approach is able to provide an efficient way for the calculation of the thermal stresses. It is shown that thermal stresses are linear proportion to the ratio of thermal expansion coefficients between the two materials. Parametric studies reveal that thermal stresses in each layer are decreasing with the increase of thickness, and are increasing with the increase of Young’s modulus ratio between the two materials.

Thermal Expansion Coefficients and Thermal Stresses in an Aligned Short Fiber Composite With Application to a Short Carbon Fiber/Aluminum

1985 ◽  
Vol 52 (4) ◽  
pp. 806-810 ◽  
Author(s):  
Y. Takao ◽  
M. Taya
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Carbon Fiber ◽  
Thermal Stresses ◽  
Short Fiber ◽  
Short Carbon Fiber ◽  
Thermal Expansion Coefficients ◽  
Equivalent Inclusion Method ◽  
Expansion Coefficients ◽  
Short Carbon

A formulation to compute the effective thermal expansion coefficients (αc) of an anisotropic short fiber-reinforced composite and the thermal stress (σ) induced in and around the fiber is developed. The formulation is based on the Eshelby’s equivalent inclusion method. Main emphasis is placed on short Carbon fiber/Aluminum. The thermal stress due to a uniform temperature rise ΔT is computed at points just outside the fiber. The effects of various parameters on αc and σ are also investigated.

Interfacial Thermal Stresses in Layered Structures: The Stepped Edge Problem

1995 ◽  
Vol 117 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Wan-Lee Yin
Keyword(s):  
Stress Field ◽  
Elastic Layer ◽  
Thermal Stresses ◽  
Free Edge ◽  
Multilayered Structure ◽  
Local Geometry ◽  
Temperature Load ◽  
Edge Problem ◽  
Stress Functions ◽  
Multilayer Substrate

The intense, localized stress field produced by a temperature load in a multilayered structure may be significantly affected by the local geometry of the free edge. We examine here the stepped edge problem associated with bonding an elastic layer (silicon chip) to a single or multilayer substrate with a slightly larger length. Stress functions are introduced in various rectangular regions and the continuity of tractions are enforced across all inter-region boundaries. Furthermore, continuity of displacements is enforced across the junction of the two segments of the base laminate. The analysis results indicate that even a minute protrusion of the edge of the base laminate relative to the attached chip may cause significant changes in the peeling and shearing stresses in the end region of the interface.

Modelling of III-Nitride Epitaxial Layers Grown on Silicon Substrates with Low Dislocation-Densities

MRS Advances ◽  
2019 ◽  
Vol 4 (13) ◽  
pp. 755-760 ◽  
Author(s):  
Khaled H. Khafagy ◽  
Tarek M. Hatem ◽  
Salah M. Bedair
Keyword(s):  
Thermal Stresses ◽  
Life Time ◽  
Epitaxial Layers ◽  
Silicon Substrates ◽  
Thermal Expansion Coefficients ◽  
Dislocation Densities ◽  
Large Lattice ◽  
Expansion Coefficients ◽  
And Performance ◽  
Mesh Convergence

ABSTRACTLarge lattice and thermal expansion coefficients mismatches between III-Nitride (III N) epitaxial layers and their substrates inevitably generate defects on the interfaces. Such defects as dislocations affect the reliability, life time, and performance of photovoltaic (PV) devices. High dislocation densities in epitaxial layer generate higher v-shaped pits densities on the layer top surface that also directly affect the device performance. Therefore, using an approach such as the embedded void approach (EVA) for defects reduction in the epitaxial layers is essential. EVA relies on the generation of high densities of embedded microvoids (∼108/cm2), with ellipsoidal shapes. These tremendous number of microvoids are etched near the interface between the III N thin-film and its substrate where the dislocation densities present with higher values.This article used a 3-D constitutive model that accounts the crystal plasticity formulas and specialized finite element (FE) formulas to model the EVA in multi-junction PV and therefore to study the effect of the embedded void approach on the defects reduction. Mesh convergence and 2-D analytical solution validation is conducted with accounting thermal stresses. Several aspect and volume ratios of the embedded microvoids are used to optimize the microvoid dimensions.

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