Session: 04-21-01: Dynamics of Advanced Functional Materials and Structures

Paper Number: 164253

Strain Rate Effects on Bonding Strength and Fracture Morphology of Adhesive Joints: Experiments and Molecular Dynamics Simulations 

In recent years, fastener-less structures based on adhesive bonding technology have been developed for the innovative design of multi-material structures in order to reduce the structural weight and improve the functionality of transportation equipment. In order to improve the strength and reliability of adhesive bonding technology, it is essential to elucidate the strength development mechanism and fracture morphology of such adhesive joints. In addition, understandings of strain rate effect and loading mode effect (i.e. uniaxial tension and shear) on the strength are important for mechanical design of adhesive bonding, since the fracture criterion is well known to be dependent on hydrostatic pressure. In this study, the effects of strain rate and loading mode on the adhesive strength and fracture morphology of epoxy adhesive joints were systematically investigated using quasi-static tests and Split Hopkinson Pressure Bar (SHPB) method. It was found that the adhesive strength was strain-rate dependent in both uniaxial tensile and shear loading modes. Fracture morphology also differs depending on the loading mode, and in particular, it was found that voids are generated on the fracture surface during tensile deformation at high strain rates only. In order to elucidate this mechanism from the viewpoint of molecular structure, molecular dynamics (MD) simulations were conducted for uniaxial tension and shear loadings against epoxy resin adhesive. The detailed discussion at the molecular chain level has been made, revealing that molecular deformation of bond stretching contributes to void generation, and molecular deformation of torsional angle may affect strain rate dependence. Furthermore, fracture toughness was evaluated to understand the crack propagation resistance under Mode-I and Mode-II loadings. Thus, our results provide insights on strength design of adhesive joint under dynamic/impact loadings. 
References
Masayoshi Ogawa, Akihiro Shinozaki, Yuichi Hosoya, Jiayue Hu, Akio Yonezu, Ling Liu, Fatigue Fracture Mechanisms and Strength Improvement of Adhesive Joints: An Integrated Experimental and Molecular Dynamics Study, International Journal of Adhesion and Adhesives
Masayoshi Ogawa, Ayumu Morimura, Ikko Haba, Akio Yonezu, Coarse-Grained Molecular Dynamics Simulations of Nano-Deformation Behavior of Epoxy Adhesives’ Interface during Atomic Force Microscopy (AFM) Mechanical Testing, Polymer, 320 (2025) 128071 (19 pages). 
Aoi Takagi, Yoshikatsu Kimoto, Akihiro Shinozaki, Hiroyuki Yamada, Tomohisa Kojima, Akio Yonezu, Development of LaSAT and Bonding Strength Evaluation of Epoxy Adhesive over a Wide Range of Loading Rates, The Journal of Adhesion, pp.1-23, 2023
Kohei Kanamori, Yoshikatsu Kimoto, Shuto Toriumi, Akio Yonezu, On the Cyclic Fatigue of Adhesively Bonded Aluminium: Experiments and Molecular Dynamics Simulation, International Journal of Adhesion and Adhesives, Volume 107, June 2021, 102848.
 

Presenting Author: Akio Yonezu Chuo University

Presenting Author Biography: Dr. Akio Yonezu is Professor at Chuo University in Japan. He received his B.S. and M.S. degrees from Aoyama Gakuin University (AGU) of Japan in 1999 and 2001, respectively. He served on Canon Inc. between 2001 and 2002. He again enrolled in AGU on April in 2003, and received Ph.D (Doctor of Engineering) on March in 2006 from AGU. He worked as postdoctoral research fellow under the 21st COE program at AGU until December 2006. He served on the faculty of Osaka University as assistant professor between 2007 (January) and 2012 (March). He joined Chuo University in 2012 (April) as associate professor and was promoted to full professor in 2017 (April). Dr. Akio Yonezu has a background in materials science and mechanics. He has more than 20 years of research experience with 120+ international journal publications. Selected Awards include Young Researcher Award, Japanese Society of Non-Destructive Inspection　(Dec. 2005). Best Paper Award, Japanese Society of Non-Destructive Inspection (May. 2006). Best Paper Award, Japanese Society of Materials Science (May. 2006). Acoustic Emission Working Group (AEWG49), Student Award (Jun. 2006) and Best Paper Award, Japanese Society of Non-Destructive Inspection (May. 2012) etc.

Authors:

Masayoshi Ogawa Chuo University
Yuto Kasuya Chuo University
Masato Matsui Chuo University
Akio Yonezu Chuo University