Nondestructive Inspection of Graphite-Epoxy Composites for Heat Damage Using Laser-Induced Fluorescence

W. G. Fisher, J. M.E. Storey, S. L. Sharp, C. J. Janke, E. A. Wachter

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Laser-induced fluorescence has been applied to the nondestructive inspection of graphite-fiber-reinforced polymer-matrix composites. Upon curing, the epoxy resin in these materials forms a highly cross-linked network of aromatic sub-units. This result yields a material with significant absorptivity from the ultraviolet through the near-infrared and a fluorescence bandwidth covering 200 to 300 nm. When subjected to temperatures beyond the recommended upper service temperature, these materials experience thermally induced degradation and a reduction in mechanical strength. Furthermore, these heat-damaged materials exhibit significant changes in fluorescence intensity and in the wavelength of maximum fluorescence intensity. These spectroscopic changes can be correlated with the extent of heat damage. An imaging approach has been developed to monitor these fluorescence signatures, allowing rapid nondestructive inspection of large surface areas. This capability provides qualitative and quantitative information about the location and severity of damage.

Original languageEnglish
Pages (from-to)1225-1231
Number of pages7
JournalApplied Spectroscopy
Volume49
Issue number9
DOIs
StatePublished - Sep 1995

Funding

Research sponsored by U.S. Department of Energy under Contract DE-AC05–84OR21400 with Martin Marietta Energy Systems, Inc.

Keywords

  • Fiber-reinforced composites
  • LIF
  • Laser-induced fluorescence
  • NDE
  • PMCs
  • Thermal damage

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