Paper number 580

THE CHARACTERIZATION OF OPEN HOLE STRENGTHS OF STITCHED POLYMER COMPOSITE LAMINATE

Gregory D. Tracy and Keith T. Kedward

Department of Mechanical and Environmental Engineering,
University of California at Santa Barbara, Santa Barbara, Ca. 93106, USA

Summary

The open hole compressive (OHC) and tensile (OHT) strengths of a stitched hybrid composite material were experimentally, analytically and numerically investigated. The material tested was a hybrid AS4/IM7/3501 stitched laminate with the 0o plies composed of IM7 fibers, AS4 fibers in the off-axis plies and through-thickness Kevlar stitching at a stitch density of 6.2 stitches/cm2. The tensile test samples were similar to those required for ASTM D-3039 but with a 28-cm. length. The compressive properties were examined using the short block compression (SBC) test method. The linear elastic fracture mechanics, point stress and average stress criteria were used to predict the open hole strength. The finite element analysis correlated analytic and numeric point stress damage lengths. Results show that all three criteria can be used to determine compressive and tensile open hole strength for this material, with the average stress criterion slightly more accurate than the others.

Keywords

strength prediction, open hole, tension, compression, stitched, hybrid.