TY - JOUR
T1 - Research on epoxy resin curing monitoring using laser ultrasonic
AU - Zhang, Yanjie
AU - Wang, Xiaochen
AU - Yang, Quan
AU - Xue, Renjie
AU - Zhang, Jiamin
AU - Sun, Youzhao
AU - Xu, Dong
AU - Krishnaswamy, Sridhar
N1 - Funding Information:
This work was supported by Beijing Natural Science Foundation (Grant No.3182026), National Natural Science Foundation of China (Grant No.51975043 and No.51604024), Guangxi Special Funding Program for Innovation-Driven Development (Grant No.GKAA17202008) and Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-19-002A3). The experiments were performed using the facilities of the Center for Smart Structures and Materials at Northwestern University.
Funding Information:
This work was supported by Beijing Natural Science Foundation (Grant No. 3182026 ), National Natural Science Foundation of China (Grant No. 51975043 and No. 51604024 ), Guangxi Special Funding Program for Innovation-Driven Development (Grant No. GKAA17202008 ) and Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-19-002A3 ). The experiments were performed using the facilities of the Center for Smart Structures and Materials at Northwestern University .
Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/7/1
Y1 - 2020/7/1
N2 - Adhesive bonding is widely used in the structural assembly of aircraft, and assessing the curing state of the adhesive is important to ensure the safe operation of the assembly. In this paper, the curing process of epoxy resin is monitored by laser ultrasonics. The propagation of ultrasonic waves in a composite structure is discussed, and the curing of epoxy resin and its influence on ultrasonic characteristics are studied. In the fast-drying epoxy resin, the molecular cross-linking rate is fast, the difference of acoustic impedance between the epoxy resin and aluminum gradually decreases, so the transmission coefficient becomes larger and the reflection coefficient decreases. The calculation of absorption attenuation and dispersion should take this change into account. The relationship between amplitude and reflection coefficient is established by far-field ultrasound. The difference in molecular mobility causes the relaxation process, which results in absorption and dispersion of the ultrasonic waves. Making use of the broadband characteristic of laser ultrasonics, the transmission waves are analyzed. As the epoxy resin changes from liquid to solid, the relaxation time is gradually shortened, and the center frequency of the transmitted wave is gradually increased, the absorption attenuation is approximately linear with frequency. The results show that the curing process has a significant effect on ultrasonic characteristics, and laser ultrasonics could be used as an online monitoring method.
AB - Adhesive bonding is widely used in the structural assembly of aircraft, and assessing the curing state of the adhesive is important to ensure the safe operation of the assembly. In this paper, the curing process of epoxy resin is monitored by laser ultrasonics. The propagation of ultrasonic waves in a composite structure is discussed, and the curing of epoxy resin and its influence on ultrasonic characteristics are studied. In the fast-drying epoxy resin, the molecular cross-linking rate is fast, the difference of acoustic impedance between the epoxy resin and aluminum gradually decreases, so the transmission coefficient becomes larger and the reflection coefficient decreases. The calculation of absorption attenuation and dispersion should take this change into account. The relationship between amplitude and reflection coefficient is established by far-field ultrasound. The difference in molecular mobility causes the relaxation process, which results in absorption and dispersion of the ultrasonic waves. Making use of the broadband characteristic of laser ultrasonics, the transmission waves are analyzed. As the epoxy resin changes from liquid to solid, the relaxation time is gradually shortened, and the center frequency of the transmitted wave is gradually increased, the absorption attenuation is approximately linear with frequency. The results show that the curing process has a significant effect on ultrasonic characteristics, and laser ultrasonics could be used as an online monitoring method.
KW - Adhesion
KW - Interface
KW - Non-destructive testing
KW - Process monitoring
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U2 - 10.1016/j.measurement.2020.107737
DO - 10.1016/j.measurement.2020.107737
M3 - Article
AN - SCOPUS:85082020808
SN - 0263-2241
VL - 158
JO - Measurement: Journal of the International Measurement Confederation
JF - Measurement: Journal of the International Measurement Confederation
M1 - 107737
ER -