Abstract
PLA, poly (lactic acid), was molded under different conditions to fabricate PLA samples of different crystallized structures. Mode I fracture toughness was then evaluated at five different loading-rates using two kinds of testing systems. It is interesting to see that for the materials molded at 130℃, the fracture toughness dramatically increased as loading-rate increased up to (10)^3mm/min, and rapidly decreased at 1m/s. It should be noted that the toughness obtained at 1m/s was almost equivalent to that evaluated at 1mm/min. Microstructures of the molded samples and fracture surfaces created at different loading-rates were also observed using optical microscopes. Dependence of loading-rate and microstructure on the fracture toughness was discussed on the basis of those experimental results.
