Selected mechanical properties of symmetrically (±45°) reinforced 16-lamina graphite/epoxy composites have been found to be affected by sub-Tg annealing. Postcured specimens of Thornel 300 graphite/Narmco 5208 epoxy were sub-Tg annealed at 140 °C for ca. 10, 102, 103, 104, and 105 min, with a prior quenching from above Tg. The ultimate tensile strength strain-to-break, and static toughness of the composite materials were found to decrease as a function of sub-Tg annealing time. No weight loss was observed during the sub-Tg annealing. The time-dependent change in properties can be explained on the basis of physical aging which is related to free volume decrease in the non-equilibrium glassy state of network epoxies. The results imply possible changes in composite properties with service time.
No takes yet. Share an insight, caveat, or question.
Eric Siu-Wai Kong (1981) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: