Fracture Criterion of Braided Composite Plates Containing a Circular Hole

• Main Authors: Sue-fen Wang, 王淑芬
• Other Authors: Kun-Hsieh Tsai
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/15752436239109469383

碩士 === 逢甲大學 === 紡織工程所 === 97 === In this work, the primary purpose is to study the fracture criterion of braided composite plates containing a circular hole. First, the engineering moduli of braided composite plates were calculated. This calculation method considered the crimp arrangement of the shape of yarns and they were treated as a sine wave. The simulated sine wave is then divided into many small sections, and the engineering moduli of braided composite plates were calculated by means of Stiffness Averaging Method. The plain strength and notched strength of braided composite plates were measured by experiments. Those strengths and engineering moduli calculated above were putted into ANSYS to analyze the stress distribution around the hole. Then average stress criterion was used to calculate the characteristic length for each hole size. It was found the characteristic length decreased with the ratio of the hole diameter and the specimen width (D/W) by a power-law relationship. Through observation using metallurgical microscopy it is found that the damage caused by drilling around the hole is not severe. Initial damage occurs at the point of stress concentration around the hole. Then debonding occurs between yarns and matrix. At some point cracks deflect and break yarns resulting in the breakage of the specimen.