Impact compressive failure of a unidirectional carbon/epoxy laminated composite in Three Principal Material Axes

Abstract

The impact compressive failure behavior of a unidirectional T700/2521 carbon/epoxy laminated composite in the three principal material directions or fiber (1-), in-plane transverse (2-) and through-thickness (3-) directions is investigate on the conventional split Hopkinson pressure bar (SHPB). Cubic and rectangular block specimens with the same square cross section are machined from a 42-ply unidirectional composite laminate. The uniaxial compressive stress strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine. A pair of steel rings are attached to both ends of the rectangular block specimens to prevent premature end crushing only in the 1-direction tests on the Instron testing machine. A modified sleeved SHPB is applied to allow recovery o the failed specimen without being subjected to repeated compressive loading during the test It is shown that the ultimate compressive strength (or failure stress) exhibits no strain-rate effect in the 1-direction, but a slight strain-rate effect in the 2- and 3- directions over a strain-rate range of 10 -3 to 10 3/s. It is also shown that the ultimate compressive straii (or failure strain) decreases marginally with strain rate in all three directions. Dominant compressive failure mechanisms are found to significantly vary with strain rate, depending on the three principal material axes. ©2009 The Society of Materials Science, Japan.