Accession Number : ADA303914

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

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER

Personal Author(s) : Camarda, Charles J.

PDF Url : ADA303914

Report Date : OCT 1990

Pagination or Media Count : 147

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)

Descriptors :   *COMPOSITE MATERIALS, *GRAPHITE, *SANDWICH CONSTRUCTION, *SANDWICH PANELS, *POLYIMIDE PLASTICS, COMPRESSION, STRESS STRAIN RELATIONS, STRESS ANALYSIS, LAMINATES, TENSILE STRESS, STIFFNESS, TEST METHODS, GLASS, BENDING, BONDED JOINTS, BUCKLING, CURING, STRENGTH WEIGHT RATIO, COMPRESSIVE STRENGTH, FLEXURAL PROPERTIES, ADHESIVES, TENSILE TESTERS, ADHESIVE BONDING, HONEYCOMB CORES, MOIRE EFFECTS.

Subject Categories : Laminates and Composite Materials
      Plastics

Distribution Statement : APPROVED FOR PUBLIC RELEASE