The first step in accurately measuring the fracture toughness of a polymeric material is to generate a sharp crack in the sample. Often this is accomplished by tapping a razor blade into the sample, allowing a natural crack to grow; however, it can be difficult to control the crack propagation. Alternate methods for initial crack generation are investigated, including scoring the sample with a razor blade and inserting thin films or foils into the samples during cure. Fluoropolymer films and aluminum and stainless steel foils of various thicknesses are examined in a number of epoxy-amine resins with a range of toughness and glass transition values. None of the alternative methods replicate the results of starting with a natural crack. Furthermore, it is difficult to form satisfactory test samples using fluoropolymer films. For relative toughness comparisons, either the scoring method or thin, ≤25.4 μm, foils can be used to initiate cracks with similar results.
All Science Journal Classification (ASJC) codes
- Surfaces, Coatings and Films
- Polymers and Plastics
- Materials Chemistry