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Previous studies have provided evidence that reinforcement of epoxy adhesives with nanostructures such as carbon nanofibers (CNFs) produces higher strength bonded joints between carbon fiber reinforced polymer (CFRP) laminates and shifts bond-line failure modes from the adhesive into the laminate. Despite this, there has been no research dedicated to applying reinforced adhesives to the bonding of nano-reinforced CFRP such as CNF z-threaded carbon fiber reinforced polymer (ZT-CFRP) laminates, which have been proven to exhibit increased interlaminar shear strength, mode-I delamination toughness, and compressive strength over traditional CFRP. This study examined the effectiveness of using CNF reinforced epoxy adhesives for unidirectional ZT-CFRP laminate bonding through single-lap shear tests using the ASTM D5868-01 standard. Unidirectional CFRP laminate samples bonded with both epoxy adhesive and CNF reinforced epoxy adhesive were also tested for comparison. It was found that the average shear strength observed for ZT-CFRP samples bonded with CNF reinforced epoxy adhesive was approximately 44% and 26 % higher than that of CFRP samples bonded with epoxy adhesive and CNF reinforced epoxy adhesive, respectively. Microscopic image analysis was performed to examine the mode of bond failure. The roles of nanomaterials in the fracture mechanism of the adhesives and the composite laminates are also discussed.
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Non-destructive evaluation (NDE) of bond-line using carbon nanofiber and nanotube modified film adhesive and infrared thermography
A film adhesive is commonly used to form the bond line between composite or metal parts. The bond line's quality and performance can be affected by defects such as voids, impurities, agglomerations, and other structural issues found within it; in addition, defects can form due to damage or delamination. Identifying these defects is possible with non-destructive evaluation (NDE). In this paper, the joule-heating effect through carbon nanofibers (CNF) and carbon nanotubes (CNT) modified film adhesive will be used along with infrared thermography for bond line defect inspection. Due to the difference in the electrical conductivity between the modified epoxy and the defect, joule heating can cause a different temperature at the defect; thus, in theory, the defect can be viewed by infrared thermography. The percentage of carbon nanofiller in a film adhesive changes the measurement quality due to its relationship to electrical conductivity. An Acrylonitrile Butadiene Styrene (ABS) equilateral triangle defect with 30 mm sides was used inside bond line samples. These bond lines were composed of epoxy and nanofillers of CNF and CNT at various concentrations. Each concentration was evaluated individually and bonded onto two single-ply CFRP coupons. In this study, the feasibility of using carbon nanofillers of different concentrations as a medium for identifying and characterizing defects through NDE infrared thermography was investigated and validated the effectiveness of this new NDE approach. In the future, aligning nanofiller for bond lines could be a potential research direction to improve upon what this study strives to achieve.
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- Award ID(s):
- 2044513
- PAR ID:
- 10386716
- Date Published:
- Journal Name:
- CAMX Conference Proceedings. Anaheim, CA, October 17-20, 2022
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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