Impact fracture specimen preparation

With specimens prepared in different ways, the results of quasi-static testing using spherical indenters of different diameters and those of fracture observation after impact tests using 1 mmcf) spherical particle were compared. 

The surface morphologies of fractured surfaces of nanobiocomposites were observed with scanning electron microscope (SEM, S-4800, Hitachi, Japan) and energy dispersive X-ray (EDX). The fractured surface of biocomposites was prepared with impact test specimens. Prior to the observation, all the specimens were coated with Au in order to prevent electrical discharge. The acceleration voltage used was 15-25 kV. 

The procedure outlined above can be useful if the specimens are prepared carefully to ensure that LEFM applies. The specimen should be as thick as is practicable, and the notches should be very sharp. If a razor blade is used for cutting, a compressive plastic zone must be avoided at the notch tip. This can be accomplished by slicing the notch tip rather than by pressing the blade into the notch. If the fracture surface contains plastic flow, the crack size most hkely has to be corrected. The method for determining fracture tou mess can be extended to tensile impact of a notched specimen (28). 

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