STP808

    Transverse Compressive Stress-Strain Behavior of Thick Kevlar/Epoxy Laminates

    Published: Jan 1983


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    Abstract

    The room-temperature compressive stress-strain response of quasi-isotropic Kevlar 49 fabric/epoxy composites was studied. Cylindrical specimens with porosities up to 20% were loaded normal to the plane of fiber reinforcement. Sample porosity was an important factor affecting the shape of the compressive stress-strain curve, modulus, strength, strain to failure, and Poisson's ratio. As a porous specimen was loaded in compression the tangent modulus first decreased due to void collapse and then increased as complete consolidation was approached. Increasing the porosity from 1 to 20% caused (a) the initial modulus to decrease from 6.0 to 1.4 GPa, (b) the strength to reduce from 1150 to 580 MPa, (c) Poisson's ratio to change from 0.15 to 0.06, and (d) the failure strain to increase from 16 to 26%.

    Most of the axially compressed cylindrical specimens failed along inclined planes by shearing through many layers of fabric. Broken fibers were observed on the fracture surfaces. A macroscopic shear stress failure process can be inferred from the data. Computed maximum shear stresses along 45-deg planes were of the same magnitude as measured strengths from shear tests using samples oriented to produce shear across layers of fabric.

    Keywords:

    composite materials, fiber composites, laminates, Kevlar 49 composites, epoxy resins, static tests, failure, elastic properties, Poisson's ratio, anisotropy, compressive strength, compressive modulus, porosity, uniaxial stress, orthotropism, quasi-isotropic, strain


    Author Information:

    Guess, TR
    Sandia National Laboratories, Albuquerque, N.M.

    Ericksen, RH
    Sandia National Laboratories, Albuquerque, N.M.


    Paper ID: STP36206S

    Committee/Subcommittee: E28.10

    DOI: 10.1520/STP36206S


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