Studies, fracture topography

The mechanical properties of rapidly polymerizing acrylic dispersions, in simulated bioconditions, were directly related to microstructural characteristics. The volume fraction of matrix, the crosslinker volume in the matrix, the particle size distribution of the dispersed phase, and polymeric additives in the matrix or dispersed phase were important microstructural factors. The mechanical properties were most sensitive to volume fraction of crosslinker. Ten percent (vol) of ethylene dimethacrylate produced a significant improvement in flexural strength and impact resistance. Qualitative dynamic impact studies provided some insight into the fracture mechanics of the system. A time scale for the elastic, plastic, and failure phenomena in Izod impact specimens was qualitatively established. The time scale and rate sensitivity of the phenomena were correlated with the fracture surface topography and fracture geometry in impact and flexural samples. 

TEM observations were performed in the as-received and deformed samples in order to reveal the effects of microstructure on the fatigue response of the studied alloy. Fracture surfaces of the deformed fatigue test specimens were comprehensively examined in a scanning electron microscope (JEOL JSM6500F) equipped with field emission gun to determine the macroscopic fracture mode and characterize the fine-scale topography and microscopic mechanisms governing fatigue fracture. 

The test specimen, which may be smooth or notched, is fixed in a tensile testing machine permitting to program the strain rate. A slow constant strain rate is applied and maintained throughout the experiment until the specimen fractures. During the test one measures the stress strain curve, a = f(e) and after the test one studies the cross sectional area and the topography of the fracture surface. 

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