High resolution description of a crack front in a heterogeneous Plexiglas block

We study experimentally the propagation of an in-plane fracture into a tran sparent and heterogeneous Plexiglas block. A stable crack propagation in mo de I is monitored by an imposed displacement. The experimental setup allows a high resolution observation of the crack front in situ. Self-affine prop erties of the crack front are described over more than three decades using several techniques: variable bandwidth, return probability, Fourier spectru m, and wavelet analysis. The different methods lead to a roughness exponent of 0.63 +/- 0.03, consistent with a previous work. [S1063-651X(99)01608-6] .