Impact response in glass-epoxy system with and without perforated PTFE-bearing material at the mid-thickness

The work looks at the differences in impact response between plain glass fabric-epoxy and the same system containing PTFE-bearing layer having regular circular perforations inserted at the entire mid-thickness position during fabrication stage of the laminate by the hand lay-up technique. Instrumented impact data showed a drop in maximum load, total energy and ductility index following the insertion. There was a difference in the way the load–time data appeared between the plain and the mid-layer inserted PTFE bearing material cases. The plain ones showed a sharp drop after the peak whereas such a feature was absent for the mid-layer material inserted ones. Also noticed were the changes in the number of steps seen both before and after peak load following the insertion of the PTFE bearing material. These features are analyzed with the help of optical microscopy, which showed a delamination exactly at the PTFE inserted interface region while for the plain, i.e.for the non-mid-layer inserted cases, the separation seemed to occur along the ply that had the poor bonding. These and other features are analyzed in this work.