Browsing by Subject "fracture toughness"

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TESTING PROTOCOL DEVELOPMENT FOR FRACTURE TOUGHNESS OF PARTS BUILT WITH BIG AREA ADDITIVE MANUFACTURING
(University of Texas at Austin, 2023) Garcia, J.P.; Camacho, L.A.; Hasanyana, A.; Espalin, D.
Mechanical testing of additively manufactured parts has largely relied on existing standards developed for traditional manufacturing. While this approach leverages the investment made on current standards development, it inaccurately assumes that mechanical response of AM parts is identical to that of parts manufactured through traditional processes. When considering thermoplastic, material extrusion AM, differences in response can be attributed to an AM part’s inherent inhomogeneity caused by porosity, interlayer zones, and surface texture. Additionally, interlayer bonding of parts printed with large-scale AM is difficult to adequately assess as much testing is done such that stress is distributed across many layer interfaces; therefore, the lack of AM-specific standard to assess interlayer bonding is a significant research gap. To quantify interlayer bonding via fracture toughness, double cantilever beam (DCB) testing has been used for some AM materials, and DCB has been generally used for a variety of materials including metal, wood, and laminates. Mode I DCB testing was performed on thermoplastic matrix composites printed with Big Area Additive Manufacturing (BAAM). Of particular interest was the crack shape and deflection speed during testing. A modernization of the testing process was proposed using visual processing of a recording of the crack propagation to get more accurate calculations. Results discuss the differences when using two crack types and three deflection speeds.