This paper reviews recent advances at LaRC in quantitative measurement science applied to characterizing materials in a nondestructive environment. Recent demands on NDE have resulted in new thrusts to achieve measurements that represent material properties rather than indications or anomalies in a background measurement. Good physical models must be developed of the geometry, material properties, and the interaction of the probing energy with the material to interpret the results quantitatively.
In this paper are presented NDE models that were used to develop measurement technologies for characterizing the curing of a polymer system for composite materials. The procedure uses the changes in ultrasonic properties of the material to determine the glass transition temperature, the degree of cure, and the cure rate. A practical application of this technology is a closed feedback system for controlling autoclave processing of composite materials.
An additional example is in the area of thermal NDE. Thermal diffusion models combined with controlled thermal input/measurement have been used to determine the thermal diffusivity of materials. These measurements are remote, require no contact with the material under test and thus have interesting promise for NDE applications.