Accession Number : ADA310579

Title :   Vibration Testing of Impact-Damaged Composite Laminates.

Descriptive Note : Technical memorandum,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Grady, Joseph E. ; Meyn, Erwin H.

PDF Url : ADA310579

Report Date : JUN 1989

Pagination or Media Count : 11

Abstract : A new test is described that can be used to measure changes in the vibration properties of impact-damaged composite materials. Impact-induced delamination was observed to significantly affect natural frequencies of vibration and damping properties in cross-ply graphite/epoxy laminates. Natural frequencies are shown to drop by as much as half of their original value, and modal damping ratios can increase by a factor of up to eight when large amounts of damage are present. A simple finite-element model of the damaged impact specimens was used to predict the effect of delamination on certain vibration properties. A comparison of the finite-element calculations with the experimental measurements suggests that delamination was the dominant mechanism of flexural stiffness loss resulting from the transverse impact.

Descriptors :   *VIBRATION, *EPOXY LAMINATES, *GRAPHITE EPOXY COMPOSITES, STRESS STRAIN RELATIONS, MATHEMATICAL MODELS, NONDESTRUCTIVE TESTING, FINITE ELEMENT ANALYSIS, IMPACT TESTS, STRUCTURAL ANALYSIS, STIFFNESS, CRACKING(FRACTURING), DAMAGE ASSESSMENT, DAMPING, IMPACT STRENGTH, RESONANT FREQUENCY, FLEXURAL PROPERTIES, DELAMINATION.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE