Slow crack growth in cellulose film

A simple photographic method for measuring the slow crack growth in transparent polymer film is described. Framing speeds up to 100 per second have been achieved. Experimental data for a cellulose film with centrally located initial cuts indicate that for 0 < t < 0.8t_b, the crack length c increases with time t according to where c₀ is the initial cut size, K a constant, and t_b the time to fracture.