In a simple and direct manner, residual strengths of edge-notched gelatin and cellulose acetate (CA) films under tension have been related to a single stress intensity factor. The effective stress intensity factors, or the effective fracture toughnesses, of the 0.012mm gelatin and 0.13 mm CA films are 2.97 and 3.30 MN m-3/2, respectively. Plasticity and finite width effects of edge-notched films are accommodated based on the Fedderson analysis. Stable crack growth before the fracture instability was confirmed using a high-speed video camera. Since stable crack extension guarantees the generation of naturally sharp cracks, sharp notches by fatigue cracking are not necessary for the fracture toughness measurement of thin films. However, with all the specimen widths employed (15-100 mm ) edge-notched poly (ethylene terephthalate) (PET) films of 0.10 mm thickness showed net section yielding during fracture testing. This indicates that the fracture behaviour of PET films with widths up to 100 mm have to be analysed on the basis of the elastic-plastic fracture mechanisms, and the fracture toughness of PET film is much greater than 25.3 MN m-3/2.
Посилання на статтю:
Strength analysis of polymeric films / A. H. Tsou, J. S. Hord, G. D. Smith and R. W. Schrader // Polymer. – 1992. – Vol 33. – P. 2970-2974.