Experimental Investigation of Graphite/Polyimide Sandwich Panels in Edgewise Compression.

Abstract

This study experimentally and analytically investigates the local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression. Material properties of sandwich panel constituents (adhesive and facings) were determined from flatwise tension and sandwich beam flexure tests. An adhesive bond study resulted in the selection of a suitable cure cycle for FM-34 polyimide film adhesive and, a bonding technique using a liquid cell-edge version of that adhesive resulted in considerable mass savings. Tensile and compressive material properties of the facings (quasi-isotropic, symmetric laminates of Celion/PMR-15) were determined at 116, R.T., and 589K (-250, R.T., and 600 F) using the sandwich beam flexure test method. Results indicate that Gr/PI is a usable structural material for short term use at temperatures as high as 589K (600 F). Buckling specimens were 30.5 x 33.0 cm (12 x 13 in.), had quasi- isotropic symmetric facings and a glass/polyimide honeycomb core (HRH-327-3/8-4). Core thicknesses varied (0.635, 1.27, 1.91, and 2.54 cm (0.25, 0.50, 0.75, and 1.0 in.)) and three panels of each thickness were tested in edgewise compression at room temperature to investigate failure modes and corresponding buckling formulas. Specimens 0.635 cm (0.25 in.) thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the wrinkling tests indicate that several buckling formulas were unconservative and therefore not suitable for design purposes; recommended wrinkling equations are presented. In conclusion, the buckling behavior of Gr/PI sandwich panels, predicted analytically, has been characterized experimentally and results compare favorably. (MM)

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Document Details

Document Type
Technical Report
Publication Date
Oct 01, 1990
Accession Number
ADA303914

Entities

People

  • Charles J. Camarda

Organizations

  • Langley Research Center

Tags

Communities of Interest

  • Air Platforms
  • Space

DTIC Thesaurus Topics

  • Aircraft Industry
  • Aircrafts
  • Composite Materials
  • Elastic Properties
  • Fabrication
  • Failure Mode And Effect Analysis
  • Honeycomb Cores
  • Materials Laboratories
  • Materials Processing
  • Materials Testing
  • Measurement
  • Mechanical Working
  • Modulus Of Elasticity
  • Sandwich Construction
  • Sandwich Panels
  • Shear Modulus
  • Stress Strain Relations

Readers

  • Structural Dynamics.
  • Structural Health Monitoring of Composite Structures.