Piercing Process by Punch Press with Negative Clearance for CFRP Laminates

Abstract

This paper presents effects of negative clearance on open hole compressive strengths and machining qualities of circular piercing hole produced by punch press in thermosetting CFRP laminates. First, a hole was produced by using a punch with flat surface at positive and negative clearances. After the piercing process, damages, delamination, and burrs on the surfaces and the cutting planes around the hole were observed. These internal total damage amount of the hole was then observed using radiography. It was proved from these observations of holes after the piercing processes that the negative clearance give as the smooth machining surface and slightly long delamination than positive clearance. In addition, the open hole compressive strength after piercing process at negative clearance was same as that at positive clearance.