Accession Number : ADA304553

Title :   The Effects of Discontinuities on Compression Fatigue Properties of Advanced Composites.

Descriptive Note : Final rept. 1 May 79-30 Sep 80,

Corporate Author : NORTHROP CORP HAWTHORNE CA AIRCRAFT DIV

Personal Author(s) : Grimes, G. C. ; Adams, D. F. ; Dusablon, E. G.

PDF Url : ADA304553

Report Date : OCT 1980

Pagination or Media Count : 346

Abstract : This study is directed at assessing the static compression and R = 10 compression fatigue properties of graphite epoxy composites with ply drop-off discontinuities under severe operating environments including room temperature dry and wet, -65 F wet, and 218 F dry and wet. In 30-ply (+/-45)5/016/904c laminates, two 0 deg plies or four 45 deg plies are dropped off symmetrically in the middle of the specimen. Static strengths and moduli of elasticity are unaffected by these discontinuities, however, some proportional limit and Poisson's ratio values are changed significantly. At 1.25x106 cycles of constant frequency fatigue the maximum endurance limit stress level is degraded significantly in all cases by the two 0 deg ply dropoffs, but for the four 45 deg ply dropoffs it is unaffected or increased significantly. Surviving specimens exhibit residual strength that varies directly with the maximum applied cyclic compressive stress up to a threshold level. Detail data tables and plots are included. Scanning electron microscopy observations of the failed specimen fracture surfaces combined with micromechanics/point stress analysis and the analysis of ply dropoff effects are also included. (MM)

Descriptors :   *LAMINATES, *FATIGUE(MECHANICS), *GRAPHITE EPOXY COMPOSITES, COMPRESSION, STRESS STRAIN RELATIONS, SCANNING ELECTRON MICROSCOPES, STRESS ANALYSIS, COMPOSITE MATERIALS, FINITE ELEMENT ANALYSIS, FIBER REINFORCED COMPOSITES, ELASTIC PROPERTIES, MOISTURE CONTENT, STRENGTH(MECHANICS), ELECTRON MICROSCOPY, NAVAL AIRCRAFT, QUALITY ASSURANCE, YIELD STRENGTH, DISCONTINUITIES, MICROMECHANICS, POISSON RATIO, SPECIFIC GRAVITY.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE