Accession Number : ADA304421

Title :   Lamination Residual Stresses in Fiber Composites.

Descriptive Note : Interim rept. 1 Aug 72-30 Jun 74,

Corporate Author : IIT RESEARCH INST CHICAGO IL

Personal Author(s) : Daniel, I. M. ; Liber, T.

PDF Url : ADA304421

Report Date : MAR 1973

Pagination or Media Count : 480

Abstract : An experimental investigation was conducted to determine the magnitude of lamination residual stresses in angle-ply composites and to evaluate their effects on composite structural integrity. The materials investigated were Boron/Epoxy, Boron/Polyimide, Graphite/Low Modulus Epoxy, Graphite/High Modulus Epoxy, Graphite/Polyimide and S-Glass/Epoxy. These materials were fully characterized. Static properties of 02/+ OR -45 were also determined. Experimental techniques using embedded strain gages were developed and used to measure residual strains during curing. The extent of relaxation of lamination residual stresses was investigated. It was concluded that the degree of such relaxation is low. The behavior of angle-ply laminates subjected to thermal cycling, tensile load cycling and thermal cycling with tensile load was investigated. In most cases these cycling programs did not have any measurable influence on residual strength and stiffness of the laminates. The only exceptions were the Graphite/Low Modulus Epoxy and S-Glass/Epoxy which failed during elevated temperature thermal cycling under load and showed degradation during low temperature thermal cycling under load. In the tensile load cycling tests, the Graphite/ Polyimide showed the highest endurance with 10 million cycle runouts at loads up to 90 percent of the static strength. The S-Glass/Epoxy had the lowest endurance failing to survive 10 million cycles even at 25 percent of ultimate. The effects of fiber volume ratio, ply orientation and ply stacking sequence were also investigated for Graphite/ Polyimide. Residual strains during curing, static strength and residual properties after thermal cycling under load were determined. The 0 SUB 2/+ OR - 15s specimens with the lowest residual stresses showed somewhat higher residual strength. (MM)

Descriptors :   *LAMINATES, *FIBER REINFORCED COMPOSITES, *RESIDUAL STRESS, *EPOXY COMPOSITES, *EPOXY RESINS, STRESS STRAIN RELATIONS, LOW TEMPERATURE, AIRCRAFT, DEGRADATION, STRESS ANALYSIS, HIGH TEMPERATURE, TENSILE STRESS, STIFFNESS, TENSILE PROPERTIES, COMPOSITE STRUCTURES, GRAPHITE, MATRIX MATERIALS, STRAIN(MECHANICS), FAN BLADES, STRENGTH(MECHANICS), ALUMINUM OXIDES, FLEXURAL STRENGTH, STRAIN GAGES, EMBEDDING, CURING, BORON, FAILURE(MECHANICS), COMPRESSIVE STRENGTH, THERMAL STRESSES, ELONGATION, AXIAL LOADS, CYCLIC LOADS, CYCLIC TESTS, GRAPHITE EPOXY COMPOSITES, POLYIMIDE PLASTICS, POLYIMIDE RESINS, REINFORCED PLASTICS, STRUCTURAL INTEGRITY.

Subject Categories : Laminates and Composite Materials
      Plastics

Distribution Statement : APPROVED FOR PUBLIC RELEASE