Fractoluminescence from brittle and ductile homogeneous solids

Cracks in loaded solids propagate through multiple ruptures of chemical bonds with generating photon emission from reconfiguring electronic structures. Single crystals SiO2, SiC and Al2O3, and samples of polymethylmethacrylate (PMMA) were subjected to impact damaging by a falling weight. Time series of pulses of light emission induced by mechanical action from the samples (triboluminescence or fractoluminescence, FL) were detected with the time resolution of 10 ns. The statistical analysis of the FL time series showed that the amplitude distributions in crystals follow the power law. The power law dependences of number of FL pulses on pulse amplitude (scaling) signalize the presence of long-range interactions between newly-forming primary defects in fracturing brittle homogeneous crystals when the defects affect each other at distances exceeding the radius of a damaged site. The formation of damaged sites in ductile PMMA was found to be fully random.