Accession Number : ADA312004

Title :   Hopkinson Bar Perforation of Laminated Graphite/Epoxy Composite.

Descriptive Note : Interim rept. 10 Dec 93-31 Dec 94,

Corporate Author : DILLARD UNIV NEW ORLEANS LA

Personal Author(s) : Nwosu, Sylvanus N.

PDF Url : ADA312004

Report Date : 10 MAY 1995

Pagination or Media Count : 77

Abstract : A Dillard University split Hopkinson pressure bar (SHPB) test apparatus was developed for dynamic quantification of energy expenditure in the perforation process of composite laminates. This report describes the basic features of the Hopkinson bar system for wave propagation and perforation experiments to characterize the perforation process, the nature of energy absorption process, and to explain and predict the extent of damage sustained during high strain rate perforation. Preliminary results for graphite/epoxy laminates show that the nature of energy expended in the perforation process depends on the thickness of the laminate, the fiber lay-up, the impact parameters and the incident stress delivered to the composite. The mode of laminate failure can be characterized by the level of energy absorption. The average impact energy per ply needed for damage initiation in graphite/epoxy were 7 plus or minus 1 J/ply, 10 J/ply and 11 plus or minus 3 J/ply for crack initiation on the rear surface, perforation and plug push-out, respectively. The reflected stress waves show the presence of multiple peaks, possibly caused by reflection from the incident bar/indentor interface (due to the impedance mis-match at the interface). Although such reflection has a negligible effect on the results, the indentor will be modified to eliminate this anomaly.

Descriptors :   *IMPACT, *DAMAGE, *LAMINATES, *STRESS WAVES, *GRAPHITE EPOXY COMPOSITES, *PERFORATION, STRESSES, VELOCITY, THICKNESS, FIBERS, PARAMETERS, COMPOSITE MATERIALS, CRACKING(FRACTURING), FAILURE, FABRICATION, TEST EQUIPMENT, REFLECTION, STRAIN RATE, SURFACES, WAVE PROPAGATION, EPOXY LAMINATES, KINETIC ENERGY, PRESSURE, ENERGY CONSUMPTION, ENERGY ABSORBERS, REINFORCED PLASTICS.

Subject Categories : Laminates and Composite Materials
      Physical Chemistry
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE