Morphological aspects on the fracture surfaces in brittle materials and their correlation with crack velocity and acoustic emission.

摘要

Linear Elastic Fracture Mechanics (LEFM) provides a quantitative description of the crack motion that agrees well with observations in brittle materials as long as the crack growth is sufficiently slow. However, several issues remain unsolved: (i) – experimental' observations reveal that at high velocity, the crack speed is systematically smaller than the one predicted by LEFM and (ii) above a given velocity, a dynamically growing crack creates a structure of its own as evidenced from roughening of fracture surfaces at high speed. We have designed an experimental setup in which we control the dynamical crack propagation in opening mode in two brittle materials, Plexiglas and glass, with mean velocities ranging from 100 m /s to half the Rayleigh wave speed. Crack velocity is recorded in real time during fracture, and the morphology of fracture surfaces is observed post mortem by optical microscopy and profilometry. We have characterized in details their statistics and their relations with crack velocity.