Time-temperature dependent fracture toughness of PMMA

A toughness-biased Ree-Eyring relationship gives a good description of fracture toughness data of PMMA over a range of temperatures (283 to 353 K) and crack velocities (10 −5 to 1 m sec −1 ). Fracture toughness was measured by Gurney's sector method. The activation energy associated with the equation supports earlier work which suggests that, in the same temperature and velocity range, cracking in PMMA is controlled by craze growth, which is governed by secondary ( β ) molecular processes. Unstable cracking at moderate velocities (10 −2 to 1 m sec −1 ) seems to be produced by an isothermal/adiabatic transformation; an analysis for the onset of instability is given. At temperatures below 283 K, changes in toughness behaviour are seen, and below 243 K no stable cracking at all was obtained. A discussion is given of various methods of characterizing resistance to cracking, and methods of transforming R (à, T ) and K (à, T ) data are compared.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44668/1/10853_2004_Article_BF00540829.pd