Abstract: The effect of strain rate(v) on the tensile behavior of PBT was studied. As the loading rate grew, the fractography transformed from ductile to brittle. The flat region ratio(A_p/A_o)increased rapidly with increasing loading rate initially and leveled off at 1000 mm/min. The study also showed that the roughness of fracture surface(Rs) increased linearly w ith strain rate according to Rs=2.10-4.72x10^-4v. The yield stress( σ_y) increased rapidly with increasing strain rate and leveled off at 1000 mm/min. And the relationship between the yield stress and the strain rate was consistent with Eyring theory, and could be explained by the molecular chain sliding mechanics.

Key words: polybutylene terphthalate;tensile fracture, loading rate, fractography, roughness