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    Strain Rate Characterization of Unidirectional Graphite/Epoxy Composite

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    Unidirectional graphite/epoxy was characterized at various strain rates ranging from quasi-static to over 500 s−1. Properties were obtained by testing thin rings 10.16 cm (4 in.) in diameter, 2.54 cm (1 in.) wide, and 6 to 8 plies thick under internal pressure. Unidirectional 0, 90, and 10-deg off-axis rings were tested to obtain longitudinal, transverse, and in-plane shear properties. In the dynamic tests internal pressure was applied explosively through a liquid, and the pressure was measured with a calibrated steel ring. Strains in the calibration and specimen rings were recorded with a digital processing oscilloscope. The data were processed and the equation of motion solved numerically by a minicomputer attached to the oscilloscope. Results were obtained and plotted in the form of a dynamic stress-strain curve. Times to failure were as short as 30 μs. The 0-deg properties which are governed by the fibers do not vary much with strain rate with only a moderate increase in modulus. The 90-deg properties show a marked increase in modulus and strength with strain rate. In-plane shear properties follow a similar trend, although less pronounced than transverse properties. In all cases ultimate strains do not vary much with strain rate.


    composite materials, graphite/epoxy, dynamic response, test methods, strain rate effects, characterization, data processing, dynamic tension, dynamic inplane shear

    Author Information:

    Daniel, IM
    Professor and Director, Experimental Stress Analysis Laboratory, Illinois Institute of Technology, Chicago, Ill.

    Hamilton, WG
    Assistant Research Engineer, IIT Research Institute, Chicago, Ill.

    LaBedz, RH
    L. J. Broutman & Associates, Chicago, Ill.

    Committee/Subcommittee: D30.05

    DOI: 10.1520/STP28492S