Accession Number : ADA305939

Title :   Performance of a Quantitative Study of Instability-Related Delamination Growth.

Descriptive Note : Contract rept.,

Corporate Author : NORTHROP CORP HAWTHORNE CA AIRCRAFT DIV

Personal Author(s) : Ramkumar, R. L.

PDF Url : ADA305939

Report Date : MAR 1983

Pagination or Media Count : 100

Abstract : An experimental program was conducted to quantify instability-induced imbedded delamination growth. Static tests on double cantilever beam (DCB) specimens yielded the critical mode I strain energy release rate for T300/5208 graphite/epoxy. Static tests on mixed mode cracked lap shear (CLS) specimens, and a nonlinear finite element analysis (NFEA) of the CLS specimen to separate mode I and mode II effects, yielded the critical mode II strain energy release rate for T300/5208. Constant amplitude fatigue tests on DCB and CLS specimens, along with the NFEA results on CLS specimens, quantified mode I and mode II contributions to delamination growth rate. Fatigue tests were conducted at a frequency of 10 Hertz, maintaining the minimum to maximum cyclic load ratio at 0.05. Static compression and constant amplitude compression fatigue tests were also conducted on specimens with imbedded through-the-width (ITTW) delaminations. Kapton imbeddments were located below 3, 4 or 6 plies in a 64-ply laminate, during layup, to simulate ITTW delaminations. The onset of instability (local buckling), the transverse displacement of the delaminated region, and the load level corresponding to the propagation of the ITTW delamination to the tab boundary (delamination failure) were monitored during the static tests. Under cyclic compressive loading delamination growth rates were measured at various maximum cyclic compressive load values. (MM)

Descriptors :   *EPOXY LAMINATES, *DELAMINATION, *GRAPHITE EPOXY COMPOSITES, COMPRESSION, FINITE ELEMENT ANALYSIS, TENSILE STRESS, DISPLACEMENT, MODULUS OF ELASTICITY, STRENGTH(MECHANICS), STRAIN RATE, CRACK PROPAGATION, POLYMERIC FILMS, BUCKLING, AMPLITUDE, FAILURE(MECHANICS), INSTABILITY, ELONGATION, FATIGUE TESTS(MECHANICS), CYCLIC LOADS, POISSON RATIO, CANTILEVER BEAMS, POLYIMIDE RESINS.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE