Residual stiffness and strength of Kevlar/epoxy laminates impulsively loaded to 7. 9 ktaps

Technical Report · Sun Nov 01 04:00:00 EST 1987

OSTI ID:5679480

Guess, T R

An experimental investigation of impulse-damaged composites is described. The purpose was to assess material property degradation in Kevlar/epoxy composites that had been subjected to impulse loads up to about 7.9 ktaps. These impulse loads produced intense short-duration compressive stress waves in flat composite panels. In most tests 25% to 45% of the initial composite thickness was delaminated (spalled) and removed from the back surface of the target. Optical inspection of residual target material did not reveal any matrix microcracking or delaminations away from the immediate vicinity of the spall surface of 0.125 and 0.25 inch thick targets; the 0.5 inch thick targets had some tensile stress induced delaminations. Specimens cut from residual targets and from as-fabricated materials were tested in tension, compression, four-point bend and three-point bend. There was basically no difference between the stress-strain responses of residual, impacted composite and as-fabricated composite samples. The load carrying capacity of the residual, impacted composites was reduced in proportion to the thickness of the material removed by spallation. Predictions of composite elastic properties were in good agreement with experimental values. Combined evidence of optical inspection and experimental results suggests that intense compression stresses did not significantly degrade the basic lamina properties of the Kevlar/epoxy composites investigated. 12 refs., 7 figs., 7 tabs.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5679480
• Report Number(s): SAND-87-1885; ON: DE88003724
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure & Phase Studies
360603* -- Materials-- Properties
42 ENGINEERING
420500 -- Engineering-- Materials Testing
ARAMIDS
COMPARATIVE EVALUATIONS
COMPOSITE MATERIALS
COMPRESSION
CRACKS
DAMAGE
EPOXIDES
FAILURES
IMPACT TESTS
LAYERS
MATERIALS
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
RESIDUAL STRESSES
SHEAR
STRESSES
SYNTHETIC MATERIALS
TESTING