Paper number 1322

EFFECTS OF STRAIN RATE AND FIBER WAVINESS ON THE COMPRESSIVE BEHAVIOR OF COMPOSITE LAMINATES

I. M. Daniel¹ and H. M. Hsiao²

1Robert R. McCormick School of Engineering and Applied Science
Northwestern University, Evanston, IL 60208 USA
2Hexcel Composites, Dublin, CA 94568 USA

Summary

Experimental methods, including falling weight and split Hopkinson bar, were developed and applied for characterization of mechanical behavior of unidirectional and crossply carbon/epoxy laminates at strain rates up to 1,800 ms-1. Dynamic stress-strain curves to failure were obtained at various strain rates under longitudinal and transverse compression and shear for the unidirectional material, and under axial compression for crossply laminates. The behavior of the crossply laminate is governed primarily by that of its 0-deg. plies, with a constant initial modulus and ultimate strain and strength increasing significantly with strain rate. One characteristic difference is that the ultimate strains of the crossply specimens are higher than those of the 0-deg. material at the same strain rates. This can be attributed to the fact that the 0-deg layers in the crossply specimen are supported by the adjacent 90-deg. layers and thus can sustain higher stresses and strains before failure.

Keywords

Strain rate effects, fiber waviness, dynamic response, compressive testing of composites, impact testing, Hopkinson bar technique, carbon/epoxy laminates, dynamic stress-strain behavior.