Stress Intensity Factor of Micro-Scale Crack in Parallel Fiber Direction

• Main Authors: Chia-Tsung Chen, 陳佳聰
• Other Authors: Chun-Ron Chiang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/35837908013324021708

碩士 === 國立清華大學 === 動力機械工程學系 === 93 === The stress distribution of composite material at the crack tip is determined by Stress Intensity Factor (SIF), K, which is the significant target in material strength evaluation. In this paper, ANSYS is applied to simulate and analyze crack problems and discuss how the Stress Intensity Factor is affected by non-homogeneous materials. The SIF of orthotropic composite material is macroscopically assumed 1, used to decide the relative nondimensional SIF of crack, paralleled to the direction of fiber in microscope scale. In order to simplify our analysis moderately, we put our emphasis on Mode-I. Equivalent elastic theory of composite material is employed to calculate the boundary condition of the model, and further analysis is conducted to obtain the influence on K with different (Volume Fraction of Fiber)Vf, (Ratio of Elastic Modulus)Ef/Em, and Poisson’s Ratio. The results show that the KI value of crack tip in the matrix lowers with larger volume fraction of fiber. Larger Elastic Modulus of fiber leads to a smaller KI of crack tip under the same volume ratio of fiber while there is no obvious influence to KI of crack tip with different Poisson’s ratios