Fracture toughness of thin polymer films using miniature specimens

Thin polymer films were tested to determine fracture toughness. This was done to provide a measure of the resistance of the materials to crack-related damage and as a method for material evaluation and selection. The films tested were of a transparent polymeric material and were in the range of 0.03-0.10 mm thick. The testing procedures required to determine the fracture toughness for these materials were new, so several aspects of the testing had to be developed. These included the design and machining of appropriate specimens, the test setup and fixtures needed, and the method of data evaluation. This paper describes the procedures used to do this. The development work was done on a model material, 3M transparency overhead film for copiers. Most of the results presented here are for that material.