| Reliability of composite members necessitates determination of the structural significance of geometric discontinuities. Obtaining accurate stresses around perforations in even 2-D finite orthotropic components by purely theoretical or numerical techniques can be difficult, particularly when boundary conditions are complex or unknown. Moreover, measured data close to the edge of a discontinuity is often undependable. This thesis overcomes these challenges by synergizing measured moiré and thermoelastic information with analytical and numerical tools. Reliable hybrid methods are developed and demonstrated experimentally for evaluating the relevant stresses (strains, displacements) and/or stress intensity factors associated with cutouts or cracks in orthotropic composites based on distant measured input. Unlike previous approaches for orthotropy, the edge of the cutout need not be traction-free. Numerical concepts from p-version, hybrid and traditional finite elements and the displacement substitution technique are utilized. Although 2-D analyses are emphasized, a proposed algorithm for 3-D thermoelastic stress analysis is included.; Specific contributions include stress-intensity determination in orthotropic composites by combining a series representation of the stresses valid away from the crack tip with distant thermoelastically-measured data and by commingling the displacement substitution method with p-version finite elements and moiré-measured displacements, and developing an accurate and effective method for thermoelastically evaluating individual displacements (hence strains and stresses). Whereas traditional crack-tip elements contain only the r−1/2 and a constant term of the stress representation, the present p-version quarter-point crack-tip elements contain five stress terms (r−1/2 through r3/2). This enables using very few, but individually large, crack-tip elements—which is experimentally advantageous. The stress-intensity determinations are valid under mixed-mode. |
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