Tensile fracture behavior of a biodegradable polymer, poly(lactic acid)

The stable and dynamic fracture behavior of a biodegradable polymer, poly(lactic acid) (PLA), was investigated using single-edge-cracked tensile specimens. To study the dynamic effect of brittle facture, the specimens were pin-loaded using a special jig that allowed them to split and fly off in the loaded direction after fracture. The non-elastic effect of viscoelastic and plastic deformations was also measured using an optical high-speed extensometer, which consisted of an optical fiber and a position-sensing detector (PSD). For the stable and dynamic fracture process, external work applied to the specimen and its fracture surface was partitioned into U-s and U-d, and A(s) and A(d), respectively. The energy release rate, G(s), for stable crack growth was determined using U-s/A(s). The kinetic and non-elastic energies were measured and subtracted from U-d to evaluate the fracture energy for the dynamic process, E-f. The dynamic energy release rate, G(f), was then determined as E-f/A(d). G(d) was also obtained as U-d/A(d) to correlate with G(s) and G(f), and the results are discussed. (C) 2006 Elsevier Ltd. All rights reserved.