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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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Single-defect spectroscopy in the shortwave infrared
Abstract Chemical defects that fluoresce in the shortwave infrared open exciting opportunities in deep-penetration bioimaging, chemically specific sensing, and quantum technologies. However, the atomic size of defects and the high noise of infrared detectors have posed significant challenges to the studies of these unique emitters. Here we demonstrate high throughput single-defect spectroscopy in the shortwave infrared capable of quantitatively and spectrally resolving chemical defects at the single defect level. By cooling an InGaAs detector array down to −190 °C and implementing a nondestructive readout scheme, we are able to capture low light fluorescent events in the shortwave infrared with a signal-to-noise ratio improved by more than three orders-of-magnitude. As a demonstration, we show it is possible to resolve individual chemical defects in carbon nanotube semiconductors, simultaneously collecting a full spectrum for each defect within the entire field of view at the single defect limit.
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- Award ID(s):
- 1904488
- PAR ID:
- 10153420
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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