Effect of thermal and hygrothermal aging on the plane stress fracture toughness of poly(ethylene terephthalate) sheets
T. Barany, E. Foldes, T. Czigany
Vol. 1., No.3., Pages 180-187, 2007
DOI: 10.3144/expresspolymlett.2007.28
DOI: 10.3144/expresspolymlett.2007.28
Corresponding author: T. Barany 
GRAPHICAL ABSTRACT
ABSTRACT
The in-plane (plane stress) fracture toughness of two polyester (PET, PETG) sheets were assessed using the essential work of fracture (EWF) method after thermal and hygrothermal aging performed just below glass temperature. This ensured that physical aging takes place. On the aged sheets the yield stress (σy), enthalpy relaxation (ΔH) and EWF parameters were determined. It was observed that the essential work of fracture component related to the specific yielding (we,y) is suitable for assessing physical aging - independently of the humidity content. A good linear correlations exists between we,y, σy and ΔH.
