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 Us and Ud, and As and Ad, respectively. The energy release rate, Gs, for stable crack growth was determined using Us/As. The kinetic and non-elastic energies were measured and subtracted from Ud to evaluate the fracture energy for the dynamic process, Ef. The dynamic energy release rate, Gf, was then determined as Ef/Ad. Gd was also obtained as Ud/Ad to correlate with Gs and Gf, and the results are discussed.