Portable Glass Transition Temperature Device

Caltrans and other DOT agencies have been conducting extensive programs to manufacture and retrofit bridges using composite materials. The composites in retrofit applications are typically wrapped in place and allowed to cure with time. Full cure is necessary in order to completely utilize the mechanical and thermal properties of the composite structure.

Portable Tg test unit used to measure the Tg of composite overwraps at the fabrication route.

The glass transition temperature (Tg) of the resin within a composite usually gives a good indication as to the degree of cure. The Tg is the temperature at which the resin undergoes a solid-to-rubber phase transition. If contamination, partial cure, or an improper mixing of the components in a resin has occurred, the measured Tg will give an indication of a problem. Typically, the Tg is measured by cutting a portion of the sample and analyzing the composite in a laboratory. Techniques such as dynamic mechanical analysis, dielectric analysis, and thermal expansion are commonly used. However we have invented a device that can identify the Tg of a composite both rapidly and on-site using a portable probe. The instrument tests a small area in which a thermal proble only disturbs a few millimeters of the sample. This portable instrument can be used in the field without the need to perform costly destructive analysis. In addition, due to its very high probe resolution, a number of measurements can be performed on selected areas of composite hardware to verify consistency of cure.

We are currently working with a manufacturer to bring this device to market.