Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials

This study elucidates the mechanistic relationship between cooling rate and interfacial bubble evolution in direct bonding of commercially pure titanium (Ti) to polyethylene terephthalate (PET). Joints were fabricated via a thermal press-bonding process under two distinct cooling regimes—rapid and s...

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Main Authors: Katsuyoshi Kondoh, Nodoka Nishimura, Kazuki Shitara, Shota Kariya, Ke Chen, Abdillah Sani Bin Mohd Najib, Junko Umeda
Format: Article
Language:English
Published: Elsevier 2025-12-01
Series:Journal of Advanced Joining Processes
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Online Access:http://www.sciencedirect.com/science/article/pii/S2666330925000664
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author Katsuyoshi Kondoh
Nodoka Nishimura
Kazuki Shitara
Shota Kariya
Ke Chen
Abdillah Sani Bin Mohd Najib
Junko Umeda
author_facet Katsuyoshi Kondoh
Nodoka Nishimura
Kazuki Shitara
Shota Kariya
Ke Chen
Abdillah Sani Bin Mohd Najib
Junko Umeda
author_sort Katsuyoshi Kondoh
collection DOAJ
description This study elucidates the mechanistic relationship between cooling rate and interfacial bubble evolution in direct bonding of commercially pure titanium (Ti) to polyethylene terephthalate (PET). Joints were fabricated via a thermal press-bonding process under two distinct cooling regimes—rapid and slow cooling—and the dynamic behavior of residual gas bubbles was analyzed through in-situ optical observation. Slow cooling was found to markedly reduce both the size and population density of interfacial bubbles, attributed to enhanced gas re-dissolution and diffusion within the softened PET matrix at elevated temperatures. Quantitative image analysis revealed that the bubble area fraction decreased by >50 % under slow cooling conditions. Tensile shear testing showed that joints fabricated under slow cooling exhibited significantly higher bond strength—up to 1.5 times greater than those produced under rapid cooling—highlighting the deleterious role of residual bubbles as interfacial defects. Fractographic observations further indicated that slow cooling altered bubble morphology from network-like, dome-shaped structures to isolated, spherical forms, thereby increasing the effective bonded area and promoting interfacial adhesion. These findings provide critical insight into thermally driven interfacial phenomena in metal–polymer joining and underscore the importance of thermal management strategies for optimizing joint integrity.
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id doaj-art-95f80c2ee7394a00b20079f258e68a95
institution Kabale University
issn 2666-3309
language English
publishDate 2025-12-01
publisher Elsevier
record_format Article
series Journal of Advanced Joining Processes
spelling doaj-art-95f80c2ee7394a00b20079f258e68a952025-08-23T04:49:13ZengElsevierJournal of Advanced Joining Processes2666-33092025-12-011210034510.1016/j.jajp.2025.100345Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materialsKatsuyoshi Kondoh0Nodoka Nishimura1Kazuki Shitara2Shota Kariya3Ke Chen4Abdillah Sani Bin Mohd Najib5Junko Umeda6Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 Japan; Corresponding authors.Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 JapanJoining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 JapanJoining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 JapanSchool of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR ChinaFaculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, MalaysiaJoining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 Japan; Corresponding authors.This study elucidates the mechanistic relationship between cooling rate and interfacial bubble evolution in direct bonding of commercially pure titanium (Ti) to polyethylene terephthalate (PET). Joints were fabricated via a thermal press-bonding process under two distinct cooling regimes—rapid and slow cooling—and the dynamic behavior of residual gas bubbles was analyzed through in-situ optical observation. Slow cooling was found to markedly reduce both the size and population density of interfacial bubbles, attributed to enhanced gas re-dissolution and diffusion within the softened PET matrix at elevated temperatures. Quantitative image analysis revealed that the bubble area fraction decreased by >50 % under slow cooling conditions. Tensile shear testing showed that joints fabricated under slow cooling exhibited significantly higher bond strength—up to 1.5 times greater than those produced under rapid cooling—highlighting the deleterious role of residual bubbles as interfacial defects. Fractographic observations further indicated that slow cooling altered bubble morphology from network-like, dome-shaped structures to isolated, spherical forms, thereby increasing the effective bonded area and promoting interfacial adhesion. These findings provide critical insight into thermally driven interfacial phenomena in metal–polymer joining and underscore the importance of thermal management strategies for optimizing joint integrity.http://www.sciencedirect.com/science/article/pii/S2666330925000664Sheating and pressure bonding processTitanium–polymer bonding interfaceCooling rateResidual bubble morphologyTensile shear strengthInterfacial adhesion
spellingShingle Katsuyoshi Kondoh
Nodoka Nishimura
Kazuki Shitara
Shota Kariya
Ke Chen
Abdillah Sani Bin Mohd Najib
Junko Umeda
Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials
Journal of Advanced Joining Processes
Sheating and pressure bonding process
Titanium–polymer bonding interface
Cooling rate
Residual bubble morphology
Tensile shear strength
Interfacial adhesion
title Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials
title_full Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials
title_fullStr Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials
title_full_unstemmed Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials
title_short Mechanistic insight into cooling-rate-driven bubble evolution and interfacial bonding strength in directly bonded Ti–PET materials
title_sort mechanistic insight into cooling rate driven bubble evolution and interfacial bonding strength in directly bonded ti pet materials
topic Sheating and pressure bonding process
Titanium–polymer bonding interface
Cooling rate
Residual bubble morphology
Tensile shear strength
Interfacial adhesion
url http://www.sciencedirect.com/science/article/pii/S2666330925000664
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