Session: 03-05-01: 8th Symposium on Fastening and Joining Research and Advanced Technology

Paper Number: 113687

113687 - Study of Adhesive Joints Quality Based on Multi-Camera DIC System 

Recently, carbon fiber reinforced plastic (CFRP) composites have been used in more and more factories, laboratories, and other applications due to their high strength-to-weight ratio, corrosion resistance, fatigue resistance, and design flexibility. The carbon fiber reinforced plastics are typically joined with other materials or with themselves using adhesives. Adhesive joints improve mechanical characteristics while also decreasing the extra cost of practical application. However, the strength of the bonding region may be impacted by the combination of various materials and substrate thicknesses. The modification may result in an uneven force distribution, increasing the bonding area's susceptibility to vibration, contact, fatigue, etc., and hastening the bonding area's aging process. In this study, the deformation and fracture processes of adherends during tensile tests were measured by the Double Side-Multi-Digital Image Correlation (DS-Multi-DIC) system in order to evaluate the effects of various adherend thicknesses and adherend material types on the fracture behavior of joints. Two sets of stereo vision DIC measurement systems, each made up of two GigE cameras are positioned on the front and back sides of the sample, respectively. The double-sided calibration approach by integrating the global coordinate systems of the front and rear DIC measurement systems enables a direct measurement of all three direction deformations as well as the determination of all three direction strains, i.e. e_x, e_y, and e_z. By using this technique, the fracture process of each side of a sample is intuitively captured by observing the specimen's full-field deformations/strains in x, y, and also in the thickness directions. Unlike conventional methods, which can measure only in-plane strains, this technique also enables a direction measurement of thickness strain and simultaneous measurement surface deformations on the double side. The DS-Multi-DIC system benefits the study and analysis of anisotropic materials, especially composite materials, for more accurate measurement of strain concentration and crack initiation in different sides in the bonding joint areas. The experiment using this system will be described in this paper and the practicability of this method is verified by the obtained experimental results. Through the analysis of the change in strain distribution and the maximum strain experienced during the stretching process using this DS-Multi-DIC system, the paper will present impacts of (1) adherend layer thickness on the joint strength, (2) the ductility of adherends on the maximal strain and the crack locations, (3) the strain concentration on the crack initiation and propagation, and (4) the bond substrates thickness on the strain distribution. Along with these considerations, the non-uniform strain distribution during the tensile test in the bonding region will also be discussed in the paper. 

Presenting Author: Bicheng Guo Oakland University

Presenting Author Biography: Bicheng Guo is currently a PhD. candidate working in the Optical Laboratory of Mechanical Engineering at Oakland University. He received his Bachelor of Engineering in mechanical engineering from both Oakland University,
USA, and Changchun University of Technology, China in 2018. He received his Master of Science in mechanical engineering from Oakland University in 2020. His research focuses on solving challenging problems in mechanical
engineering by using advanced optical methods, such as digital image correlation, digital shearography etc.

Authors:

Bicheng Guo Oakland University
Zhongfang Gao Oakland University
Marco Gerini-Romagnoli Oakland University
Lianxiang Yang Oakland University