Accession Number : ADA300677

Title :   Static and Dynamic Large Deflection Flexural Response of Graphite-Epoxy Beams.

Descriptive Note : Contractor rept.,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG

Personal Author(s) : Sensmeier, Mark D. ; Griffin, O. H., Jr. ; Johnson, Eric R.

PDF Url : ADA300677

Report Date : MAR 1988

Pagination or Media Count : 251

Abstract : In support of crashworthiness studies of composite airframes, the present study was undertaken to understand the large deflection flexural response and failure of graphite-epoxy laminated beams. The beam specimens were subjected to eccentric axial impact loads and to static eccentric axial loads, in order to assess the damage caused by impact. A geometrically and materially nonlinear analysis of the response and failure of the static test specimens is presented. The analysis employed an incremental, noniterative finite element model based on the Kantrovich method and a corotational solution technique. Width-wise effects are included by assuming specific forms of the displacements across the width, with length-wise variation introduced as a degree of freedom. This one-dimensional, 22 degree of freedom finite element accurately predicted the load-deflection and strain-deflection responses of the static test specimens. Inclusion of nonlinear material behavior was found to be important in correctly predicting load-deflection response of uniaxial materials, while inclusion of width-wise effects was determined to be more important for laminates with off-axis plies due to the existence of coupling between bending and twisting curvatures (Die and D26). Once material nonlinearity begins to occur in flexure, even symmetric laminates exhibit bending-stretching coupling due to different material response in tension and compression.

Descriptors :   *BEAMS(STRUCTURAL), *DEFLECTION, *COMPOSITE STRUCTURES, *AIRFRAMES, *GRAPHITE EPOXY COMPOSITES, *CRASHWORTHINESS, STRESS STRAIN RELATIONS, TENSILE STRENGTH, IMPACT, LAMINATES, FINITE ELEMENT ANALYSIS, LOADS(FORCES), STATIC LOADS, STIFFNESS, DISPLACEMENT, BENDING, STRENGTH(MECHANICS), DEGREES OF FREEDOM, SHEAR STRESSES, DATA ACQUISITION, NONLINEAR ANALYSIS, FAILURE(MECHANICS), GRAPHITED MATERIALS, COMPRESSIVE STRENGTH, EPOXY RESINS, FLEXURAL PROPERTIES, STATIC TESTS, AXIAL LOADS, POISSON RATIO, ECCENTRICITY.

Subject Categories : Aircraft
      Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE