Instrumented impact test and evaluation of fracture toughness in PMMA.

Abstract

In the present study, fracture toughness of PMMA is evaluated based on the instrumented impact test and static three-point bending test. In the measurement of true fracture load in the instrumented impact test, a very difficult problem associated with a remarkable inertial loading effect is pointed out. However, it is shown that the inertial loading effect can be controlled by changing the period (τ) of vibration in specimen. It is also shown that the fracture toughness (KI) is affected by the loading rate (K^.). It is observed in the tested range of K^. (3.8 10-32.3 104MNm -3/2 S-1) that the changing tendency can be divided into three types. That is, KI increases monotonously at first, then decreases, and increases once again with increasing loading rate. Furthermore, it is observed that a feature of fracture morphology is the change from a stable fracture to an unstable one with increasing in K^..