A numerical study on the thermal expansion coefficients of fiber

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ACKNOWLEDGEMENTS I would like to thank to my supervisor Assist. Prof. Dr. Dilek KUMLUTAŞ for her guidance, valuable advises, incomparable helps and considerable concern in carrying out the <strong>study</strong>. I would especially like to thank to my family for their helpful encouragement and valuable support. Finally, I would like to thank my fiancée for her unconditional friendship, unlimited patience, moral support and unconditional love. iii
A NUMERICAL STUDY ON THE THERMAL EXPANSION COEFFICIENTS OF FIBER REINFORCED COMPOSITE MATERIALS ABSTRACT In the present work, the effective CTE of different kinds of fiber reinforced composites is studied by micromechanical modeling using finite element method. To determine the both longitudinal and transverse CTEs of composites, three dimensional steady state analyses were undertaken. Representative unit cell models, cylinder which is embedded in a cube with unit dimension, having different fiber volume fractions were produced using finite element program ANSYS. Fibers are assumed to have a square packing arrangement. To compare the results of finite element solutions for different types of composites with the results of the analytical methods and to determine the expansion behavior of different material systems with respect to fiber content, models having fiber volume fractions from 10% to 80% with increments of 10% have been composed. Furthermore, comparison between finite element solutions and experimental results have been made upon the models having 40%, 47%, 48%, 54%, 57%, 63%, 65%, and 68% fiber volume fractions. Present <strong>numerical</strong> finite element solution by ANSYS is in excellent agreement with the analytical solution by Rosen and Hashin and in sufficient agreement with other analytical solutions. The comparisons of these model predictions with experimental data show that for some material the agreement is very good, but for others there is some discrepancy between the experimental results and model predictions. The reason may be that the fiber-matrix interface bond which was assumed to be perfect was not really so in the experimental materials. The interface may either contain interfacial cracks or it might have elastic properties different from those of matrix and fiber. Keywords: Coefficient of thermal expansion, fiber reinforced composites, ANSYS, micromechanical modeling. iv
Page 1 and 2: DOKUZ EYLÜL UNIVERSITY GRADUATE SC
Page 3: M.Sc THESIS EXAMINATION RESULT FORM
Page 7 and 8: CONTENTS Page THESIS EXAMINATION RE
Page 9 and 10: 4.2.1 Geometry Creation............
Page 11 and 12: 2 coefficients of thermal expansion
Page 13 and 14: 4 coefficients coincide to give res
Page 15 and 16: 6 concentration from pure metal to
Page 17 and 18: 8 high strength-to-weight and stiff
Page 19 and 20: 10 polymers. Thermosetting polymers
Page 21 and 22: 12 Metals are strong and tough. The
Page 23 and 24: 14 Table 2.1 Properties of reinforc
Page 25 and 26: 16 2.2.2.2 Carbon Fibers Carbon is
Page 27 and 28: 18 use is in aircraft industry foll
Page 29 and 30: 20 strength and a reasonable Young
Page 31 and 32: 22 1. Processing the conventional f
Page 33 and 34: 24 (orthorhombic) of polyethylene h
Page 35 and 36: 26 Whiskers are monocrystalline sho
Page 37 and 38: 28 3.2 Factors Affecting the Coeffi
Page 39 and 40: 30 3.2.4 Thermal Cycling The primar
Page 41 and 42: 32 3.3.1 Mechanical Dilatometry Thi
Page 43 and 44: 34 absolute accuracy of about ± 0.
Page 45 and 46: 36 3.3.3 Strain Gauges This relativ
Page 47 and 48: 38 • The composite is macroscopic
Page 49 and 50: 40 3.4.1.3 Equation of Van Fo Fy In
Page 51 and 52: 42 and the thermal expansion coeffi
Page 53 and 54: 44 P P 11 33 2 A 22 − A = Det A A
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46 • A perfect bonding exists at
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CHAPTER FOUR FINITE ELEMENT METHOD
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50 No matter how the geometry is cr
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52 displacements and/or rotations a
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CHAPTER FIVE MICROMECHANICAL ANALYS
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56 5.2 Mesh Creation 10-node tetrah
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58 carbon fibers were assumed to ha
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60 Figure 5.6 The displacement fiel
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62 small differences between these
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64 Table 6.1 Comparison of the expe
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66 Longitudinal CTE (1/°C) 2.25E-0
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74 Ishikava, T., Koyama, K., & Koba
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A numerical study on the thermal expansion coefficients of fiber

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