Dynamic mechanical analysis of carbon/epoxy composites for structural pipeline repair

The viscoelastic behavior of a carbon fiber/epoxy matrix composite material system used for pipeline repair has been evaluated though dynamic mechanical analysis. The effects of the heating rate, frequency, and measurement method on the glass transition temperature (Tg) were studied. The increase in Tg with frequency was related to the activation energy of the glass transition relaxation. The activation energy can be used for prediction of long term performance. The measured tan delta peak Tg’s of room temperature cured and post-cured composite specimens ranged from 60 to 129 °C. Analysis of Tg data at various cure states was used to determine use temperature limits for the composite repair system.