Professor and Director, Experimental Stress Analysis Laboratory, Illinois Institute of Technology, Chicago, Ill.
Assistant Research Engineer, IIT Research Institute, Chicago, Ill.
L. J. Broutman & Associates, Chicago, Ill.
Pages: 21 Published: Jan 1982
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
Paper ID: STP28492S