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.

Thermomechanical Stability of Graphite/Epoxy Composites

W. R. Goggin
Appl. Opt. 13(2) 444-450 (1974)

Composite polymer membranes for laser-induced fluorescence thermometry

Francisco González-Martínez, Oscar González-Cortez, Reinher Pimentel-Domínguez, Juan Hernández-Cordero, and Guillermo Aguilar
Opt. Mater. Express 8(10) 3072-3081 (2018)

Nondestructive evaluation of aircraft composites using transmissive terahertz time domain spectroscopy

Christopher D. Stoik, Matthew J. Bohn, and James L. Blackshire
Opt. Express 16(21) 17039-17051 (2008)

Nondestructive in situ thermoluminescence using CO₂ laser heating

John L. Lawless, S. K. Lam, and D. Lo
Opt. Express 10(6) 291-296 (2002)

Applications of holographic interferometry to structural and dynamic analysis of an advanced graphite-epoxy composite component

Howard Fein
Opt. Express 3(1) 35-44 (1998)