STP864

    Elastic Representation Surfaces of Unidirectional Graphite/Epoxy Composites

    Published: Jan 1985


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    Abstract

    Unidirectional graphite/epoxy composites exhibit high elastic anisotropy and unusual geometrical features in their elastic-property polar diagrams. From the five-component transverse-isotropic elastic-stiffness tensor we compute and display representation surfaces for Young's modulus, torsional modulus, linear compressibility, and Poisson's ratios. Based on Christoffel-equation solutions, we describe some unusual elastic-wave-surface topological features. Musgrave considered in detail the differences between phase-velocity and group-velocity surfaces arising from high elastic anisotropy. For these composites, we find effects similar to, but more dramatic than, Musgrave's. Some new, unexpected results for graphite/epoxy include: a shearwave velocity that exceeds a longitudinal-wave velocity in the plane transverse to the fiber; a wave that changes polarization character from longitudinal to transverse as the propagation direction sweeps from the fiber axis to the perpendicular axis.

    Keywords:

    graphite/epoxy, acoustic properties, elastic properties, energy-flux deviation, group velocity, mode conversion


    Author Information:

    Kriz, RD
    Materials research engineer and research metallurgist, Fracture and Deformation Division, Center for Materials Science, National Bureau of Standards, Boulder, CO

    Ledbetter, HM
    Materials research engineer and research metallurgist, Fracture and Deformation Division, Center for Materials Science, National Bureau of Standards, Boulder, CO


    Paper ID: STP32819S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP32819S


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