High Strain-Rate Compressive Properties of Carbon/Epoxy Laminated Composites - Effects of loading direction and temperature

The high strain-rate compressive characteristics of a cross-ply carbon/epoxy laminated composite in the three principal material directions or fibre (1-), in-plane transverse (2-) and through-thickness (3-) directions are investigated on the conventional split Hopkinson pressure bar (SHPB) over a range of temperatures between 20 and 80 degrees C. A nearly 10 mm thick cross-ply carbon/epoxy composite laminate fabricated using vacuum assisted resin transfer molding (VaRTM) was tested. Cylindrical specimens with a slenderness ratio (= length/diameter) of 0.5 are used in high strain-rate tests, and those with the slenderness ratios of 1.0 and 1.5 are used in low and intermediate strain-rate tests. The uniaxial compressive stress-strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine at elevated temperatures. A pair of steel rings is attached to both ends of the cylindrical specimens to prevent premature end crushing in the 1- and 2- direction tests on the Instron testing machine. It is shown that the ultimate compressive strength (or failure stress) exhibits positive strain-rate effects and negative temperature ones over a strain-rate range of 10(-3) to 10(3)/s and a temperature range of 20 to 80 degrees C in the three principal material directions.