MEASUREMENT OF MICROSCOPIC DISPLACEMENTS IN GRAPHITE EPOXY COMPOSITE-MATERIALS USING SEM-GENERATED FIDUCIAL MARKERS Academic Article uri icon

abstract

  • AbstractGraphite fiberreinforced resin composite materials are widely used in commercial applications where high strength and low weight are critical factors. In order to predict the fracture toughness of a composite material from the constitutive properties of the resin and fibers, experimental methods for the analysis of microscopic displacements and strain fields that develop at the fracture crack tip within the composite material are required. Information derived from measurement of displacements, and calculation of strain fields can then be used to test micromechanical models of matrixdominated fracture. A method was developed in which it is possible to conduct near realtime fracture analysis of epoxybased composite materials, and to subsequently obtain micrometerscale measurements of displacements in the region of the crack tip. A map matrix was generated on the surface of test specimens in an SEM equipped with a tensile stage, along with an xray spectroscopy and image analysis system. A 40 40 point digital map was introduced onto the surface of the specimen using the digital xray mapping function of the xray analysis system which produced a surface matrix with point spacing of 10 m. The quality of maps varies with test specimens and therefore it is necessary to optimize microscope operation parameters for each resin tested. Reproducible results were obtained with both neat resins and graphite/epoxy composites. In situ analysis of a region of a propagating crack tip grown using the tensile stage reveals a deformation zone ahead of the crack tip and images of the stages of microcracking were captured by the image analyzer for subsequent measurement of displacement. Direct measurement of crack tip displacements from SEM electron beaminduced reference matrices provide an important tool in characterizing the fracture behavior of both neat resin and composite materials.

published proceedings

  • SCANNING

author list (cited authors)

  • BURGHARDT, R. C., EHRMAN, J. M., STEPHENS, T. C., HIBBS, M. F., & BRADLEY, W. L.

citation count

  • 1

publication date

  • January 1991

publisher