A method will be described for determining the fracture toughness of polymers at high rates (up to 30 m/s) and thus short loading times (down to 10 us). The experiments consist of timing the fracture using contact strips and fracture initiation gauges and thus defining the displacement at fracture. This is then converted to static toughness values which must be corrected for kinetic energy effects.

Correction factors for both KC and GC are deduced from a dynamic beam model where the controlling factor is the contact stiffness between the striker and the specimen. Results for GC as a function of impact speed for several polymers will be given and in some cases there are pronounced reductions in toughness at high speeds.
 
 
Leiterin EMPA Akademie
Dr. Anne Satir