Development of Mechanical Testing Machine for Microelements

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A specially designed testing machine (load range : 0.1mN - 5N, accuracy : less than 0.02muN, applied displacement range : 0 - 250mum) was developed, which enables mechanical testing including fatigue of microelements. Loads were applied to a specimen by means of an electromagnetic actuator, and the displacement was measured with a differential transformer (measuring accuracy : 0.1mum). Mechanical testing of microelements and fiber reinforcements could thereby be performed with a sufficient precision. By using this developed machine, quasi-static bending tests of single-crystalline silicon microelements fabricated by dicing and photoetching and lateral compression and longitudinal tensile tests of various types of fiber reinforcements including aramid fibers and ceramic fibers were performed. Single-crystalline silicon microelements deformed elastically until final catastrophic failure, showing a brittle nature, and the elastic modulus was dependent on crystal orientation. The influences of the fabrication process and specimen size on the fracture strength were investigated, and the dominating factor on the strength was discussed. In the case of mechanical tests of fiber reinforcements, the influence of environments including vacuum and humidified environments on the fracture strength were investigated. For both aramid fibers and ceramic fibers of Al_2O_3, SiC and Si-C-Ti-O, tensile strength decreased by existence of water in the environment or water absorption.