Conventional impact tests (without instrumentation) are performed to measure the energy required to break a notched specimen under dynamic loading. Instrumented impact tests not only measure the notched specimen breaking energy but also quantify the energy required to form a crack at the root of the notch and the energy required to propagate the crack through the material. Instrumented test systems use strikers which have strain gages so that the load-deflection curve during the impact event can be derived. These data provide load, deflection, and energy data which can be correlated with engineering parameters such as fracture toughness, ductility, and fracture resistance.

This paper compares instrumented impact results obtained using both the Charpy and Izod test procedures. Several possible limitations of the instrumented test procedure have been identified and test procedures to overcome these limitations have been proposed. In addition, an important potential limitation of the Izod test, specimen clamping pressure, has been studied.