13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Examination on a Criterion for a Debonding Fracture of Single Lap Joints from the Intensity of Singular Stress Field Tatsujiro Miyazaki1,*, Nao-Aki Noda 2, Rong Li 3, Takumi Uchikoba 3 and Yoshikazu Sano 2 1 Department of Mechanical Engineering Systems, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Nakagami-gun, Okinawa 903-0213, Japan 2 Department of Mechanical Engineering, Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata-ku, Kitakyushu-shi, Fukuoka, 804-8550, Japan 3 Department of Mechanical and Control Engineering, Graduate School of Engineering, Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata-ku, Kitakyushu-shi, Fukuoka, 804-8550, Japan * Corresponding author: t-miya@tec.u-ryukyu.ac.jp Abstract In this study, the experimental adhesive strength is newly considered in terms of the singular stress appearing at the end of interface between the adhesive and adherent. Here the critical intensity of singular stress field is examined as the debonding criterion for all types of single lap joints under different adhesive thickness and overlap length. The intensity of singular stress can be evaluated by the application of the finite element method focusing on the stress value at the end element of the interface. It should be noted that except for the case of small overlap length the separation always occurs at the edge of the interface causing unstable growth and final brittle fracture. In this type of fracture it is found that the critical intensity of the stress singular field is constant independent of the adhesive thickness and overlap length. Keywords Adhesion, Interface, Intensity of Singular Stress, Finite Element Method 1. Introduction The requirements to packaging technology of semiconductors diversify with the miniaturization and high-performance of the electronics [1, 2]. The packages of semiconductors contain many various interfaces. For example, the connection of the semiconductor to the substrate, resin seal of semiconductor, multilayer structures composed of the dissimilar semiconductor materials. In order to ensure the reliability of the packages of semiconductors, the method for evaluating the debonding fracture strength properly is required [3 - 5]. Generally, the debonding strength of the dissimilar material joints depends on the material combination, load condition, adhesive condition and so on. Because the experimental evaluation of the adhesive strength is time-consuming job, the practical and convenient debonding fracture criterion and evaluation method are asked for. Recently, the authors examined the experimental data for the butt joints of medium carbon steel bonded by epoxy resin under various adhesive thicknesses [6]. The debonding fracture criterion can be described by the constant value of the critical intensity of the singular stress field at the fracture, Kσ c, independent of the adhesive thickness [7]. When the joint is satisfied with the small scale yielding condition, the adhesive strength is predicted accurately by the debonding fracture criterion based on the intensity of the singular stress field [8, 9]. In this study, the debonding criterion for all types of single lap joints (SLJs) will be discussed under various adhesive thickness and overlap length in terms of the critical intensity of singular stress field as Kσ c = constant. The recent experimental results performed on SLJs by Park et al [10] will be used. In this experiment, Park et al evaluated the damage zone size at fracture while considering the non-linear deformation behavior of the adhesive and adherent. Although the various methods were examined, the debonding fracture criterion cannot be expressed simply and conveniently [11, 12].
RkJQdWJsaXNoZXIy MjM0NDE=