STP1230: Stacking Sequence Effects and Delamination Growth in Graphite/Epoxy Laminates Under Compression-Dominated Fatigue Loading

    Komorowski, JP
    Senior research officer, Structures and Materials Laboratory, Institute for Aerospace Research, National Research Council, Canada, Ottawa, Ontario

    Lefebvre, D
    Professor, professor, and graduate student, Faculty of Applied Science, University of Sherbrooke, Sherbrooke, PQ

    Roy, C
    Professor, professor, and graduate student, Faculty of Applied Science, University of Sherbrooke, Sherbrooke, PQ

    Randon, C
    Professor, professor, and graduate student, Faculty of Applied Science, University of Sherbrooke, Sherbrooke, PQ

    Pages: 19    Published: Jan 1995


    Abstract

    The effect of free-edge stresses on the fatigue of graphite/epoxy laminates was evaluated numerically and experimentally. Reported are results of static and compression-dominated (R = -3.75) fatigue tests on AS4/3501-6 and IM6/5245C using unnotched specimens. Two different stacking sequences of 18-ply laminates were tested. The lamination was (0°/45°/90°) (44.4%, 44.4%, 11.1%). Damage development was monitored using ultrasonic C-scans, photoelastic coatings, and optical microscopy.

    Stacking sequence had a significant influence on compressive failure strength. Differences in the fatigue lives of the two stacking sequences were close to two orders of magnitude. Damage always initiated at the edge and was related to the magnitude of interlaminar shear stresses. Well-defined stages of the fatigue process leading to final failure were observed.

    A computer code was used to predict the life of the specimens. The code has yet to be calibrated for an unnotched delamination failure mode.

    Keywords:

    composite materials, graphite/epoxy, fatigue, compression tension, stacking sequence, edge delamination, test, prediction


    Paper ID: STP14018S

    Committee/Subcommittee: D30.06

    DOI: 10.1520/STP14018S


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