Brittleness of engineering ceramics is one of the most critical properties limiting their application as structural materials. Therefore mechanical tests providing toughness characteristics of these materials have special importance. The instrumented impact test represents a quick and simple method for characterizing the brittle/ductile behavior of different materials and provides valuable information about the damage process that take place over time. While this method is widely applied for metallic and polymeric materials, it is still rarely used for examining ceramics. This paper introduces new results on instrumented impact testing of Si_3N_4 based ceramics. Different aspects of the dynamic failure process are considered, providing various mechanical characteristics of the tested material. These results are completed with analysis of the fracture surfaces and failure mechanism using fractography. The main objectives of the first part of the experimental and theoretical work were as follows: Determining various dynamic mechanical characteristics of Si_3N_4 ceramics and investigating the effect of certain test parameters on the measured data; Introducing the problem of determination of the force belonging to the unstable crack propagation at high loading rates for notched and unnotched specimens; Analyzing the failure origin and fracture mechanisms of the investigated Si_3N_4 ceramics by fractography. A companion paper presents results for determination of dynamic fracture toughness, K_(Id).
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