Optimal Cool Down in Nonlinear Thermoviscoelasticity With Application to Graphite/Peek (APC-2) Laminates

1994 ◽  
Vol 61 (2) ◽  
pp. 367-374 ◽  
Author(s):  
K. Lee ◽  
Y. Weitsman
Keyword(s):  
Composite Laminates ◽  
Thermal Stresses ◽  
Resin Composite ◽  
Strong Dependence ◽  
Temperature Drop ◽  
Geometric Constraints ◽  
Temperature History ◽  
Thermoplastic Resin ◽  
Cooling Process ◽  
Optimal Cool

Many thermoplastic resin composite laminates, such as those made of APC-2, undergo a substantial temperature drop during their post-manufacturing cool down. This thermal excursion induces significant residual thermal stresses into the laminate due to the mutual geometric constraints among the multidirectional plies. In view of the considerable time-dependent relaxation which occurs during the cooling process, the residual thermal stresses exhibit strong dependence on the temperature history. However, in view of the high magnitudes of those stresses, the relaxation behavior is viscoelastically nonlinear. This paper demonstrates that it is possible to obtain an optimal cool-down path which minimizes the residual thermal stresses in APC-2 composites upon the termination of the cooling process.

Optimal Cool-Down in Linear Viscoelasticity

1980 ◽  
Vol 47 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Y. Weitsman
Keyword(s):  
Residual Stress ◽  
Optimal Path ◽  
Viscoelastic Plate ◽  
Geometric Constraints ◽  
Optimal Temperature ◽  
Cooling Process ◽  
Linear Viscoelastic ◽  
Stress Free State ◽  
Temperature Path ◽  
Optimal Cool

An optimal temperature path is derived for a thin viscoelastic plate which is cooled from a stress-free state against geometric constraints. The optimal path, which minimizes the final residual stress due to cool down, is shown to possess discontinuities at the initial and final times and to be smooth and continuous during all intermediate times. An iterative convergent scheme is provided for a wide class of linear viscoelastic responses and typical paths are determined for two specific cases. In addition, a time-temperature path which maintains constant stress values during cool-down is derived. The problem is motivated by the cooling process of composite materials.

Residual thermal stresses in bismaleimide/carbon fiber composite laminates

1995 ◽  
Vol 16 (4) ◽  
pp. 276-283 ◽  
Author(s):  
Luca Di Landro ◽  
Alberto Palonca ◽  
Giuseppe Sala
Keyword(s):  
Carbon Fiber ◽  
Composite Laminates ◽  
Thermal Stresses ◽  
Fiber Composite ◽  
Carbon Fiber Composite

Thermal Behavior of Aluminum Metal-Matrix Composite During Cooling Process

2001 ◽  
Author(s):  
F. Okumuş ◽  
A. Turgut
Keyword(s):  
Finite Element ◽  
Thermal Behavior ◽  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Thermal Stresses ◽  
Cooling Process ◽  
Aluminum Metal ◽  
Aluminum Metal Matrix Composite ◽  
Stainless Steel Fiber

Abstract The paper presents a thermal behavior analysis of metal matrix composite lamina and laminates during a cooling process. A long stainless steel fiber reinforced aluminum metal matrix composite lamina and laminate are used for this purpose. Metal matrix composites were manufactured by using modulus under the action of 30 MPa pressure and heating up to 600 °C. The thermal stresses generated during cooling have a profound effect on the distortion and strength of the composite materials. In this study, thermal stresses, residual stresses and effective thermal expansion coefficients as a function of orientation angle of the aluminum metal matrix composite during a cooling process are investigated. The finite element method was used for thermal stress analysis. For this purpose, four noded rectangular elements were used in the ANSYS finite element code.

3D Thermal Stresses in Composite Laminates Under Steady-State Through-Thickness Thermal Conduction

2020 ◽  
Vol 12 (06) ◽  
pp. 2050065
Author(s):  
Yan Guo ◽  
Yanan Jiang ◽  
Ji Wang ◽  
Bin Huang
Keyword(s):  
Steady State ◽  
Plane Stress ◽  
Composite Laminates ◽  
Stress Function ◽  
Thermal Conduction ◽  
Thermal Stresses ◽  
Virtual Work ◽  
Ritz Method ◽  
Stress Fields ◽  
Stress Functions

In this study, 3D thermal stresses in composite laminates under steady-state through thickness thermal conduction are investigated by means of a stress function-based approach. One-dimensional thermal conduction is solved for composite laminate and the layerwise temperature distribution is calculated first. The principle of complementary virtual work is employed to develop the governing equations. Their solutions are obtained by using the stress function-based approach, where the stress functions are taken from the Lekhnitskii stress functions in terms of in-plane stress functions and out-of-plane stress functions. With the Rayleigh–Ritz method, the stress fields can be solved by first solving a standard eigenvalue problem. The proposed method is not merely computationally efficient and accurate. The stress fields also strictly satisfy the prescribed boundary conditions validated by the results of finite element method (FEM) results. Finally, some of the results will be given for discussion considering different layup stacking sequences, thermal conductivities and overall temperature differences. From the results, we find that the thermal conductivity greatly affects the stress distributions and peak values of stresses increase linearly for the present model. The proposed method can be used for predicting 3D thermal stresses in composite laminates when subjected to thermal loading.

scholarly journals Thermal Stresses in the Wall Connections of Cast Grate Structures

2016 ◽  
Vol 16 (4) ◽  
pp. 11-16 ◽  
Author(s):  
A. Bajwoluk ◽  
P. Gutowski
Keyword(s):  
Heat Treatment ◽  
Cross Section ◽  
Hot Spots ◽  
Thermal Stresses ◽  
Cooling Process ◽  
Temperature Variations ◽  
Temperature Changes ◽  
Different Types ◽  
The Difference ◽  
The Impact

Abstract The purpose of this study was to establish a relationship between the type of wall connection used in the cast grates, which are part of the equipment operating in furnaces for heat treatment and thermal-chemical treatment, and stresses generated in these grates during the process of rapid cooling. The places where the grate walls are connected to each other are usually characterized by the thickness larger than the remaining parts of walls. Temperature variations in those places are responsible for the formation of hot spots, and in the hot spots temperature changes much more slowly. The type of wall connection shapes the temperature gradient in the joint cross-section, and hence also the value of thermal stresses generated during cooling. In this study, five different designs of the grates were compared; the difference in them was the type of the designed wall connection. The following design variants were adopted in the studies: X connections with and without holes, T connections with and without technological recesses, and R (ring) connection. Numerical analysis was performed to examine how the distribution of temperature changes in the initial phases of the cooling process. The obtained results served next as a tool in studies of the stress distribution in individual structures. The analysis were carried out by FEM in Midas NFX 2014 software. Based on the results obtained, the conclusions were drawn about the impact of different types of wall connections on the formation of thermal stresses in cast grates.

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