Effect of particle distribution on initial cracks forming from notch tips of composites with hard particles embedded in a soft matrix

This paper studied the size of a so-called initial crack occurring at a not ch tip caused by strain concentration in a particulate composite. The compo site had hard and strong particles embedded in a soft and weak matrix mater ial. Therefore, the crack formed in the matrix material but not in particle s. This study discusses a computational model and a criterion to predict le ngths of initial cracks. The predicted results agree well with average valu es obtained from the experiments. However, the experimental data showed sca ttering. Zn order to understand such scattered data, the effect of particle distribution on the initial crack size was studied numerically. The study showed that a variation in particle volume fraction did not affect the crac k length as long as the specimen had a uniform particle distribution. Howev er, a local variation of particle distribution in a specimen had a signific ant effect on the initial crack length confirming the scattered data. The s ize of the localized zone was about 2 mm or less which was the smallest siz e of the specimen to represent the smeared homogeneous properties of the co mposite material. (C) 2001 Elsevier Science Ltd. All rights reserved.