SIMULTANEOUS DEEP DRAWING AND STRETCH FORMING OF KNITTED FABRIC COMPOSITE SHEET

In sheet metal forming, the occurrence of localized necking sets the limit in which the blank can be further formed. Previous studies have shown that sheet formability is governed by the complex interplay between pure stretching and pure deep drawing. Knitted fabric composite sheets, which exhibit excellent stretchability and drapeability, can be easily formed into shells of revolution. As in sheet metal forming, the forming conditions (such as blank holding load, blank size and tool geometry) govern the extent to which the fabric composite sheets can be formed. This paper first introduces a new parameter X which describes the amount of stretching relative to drawing during forming. It will be seen that forming processes, specified by the use of various combinations of forming conditions, can be characterized by the parameter X. Finally, the overall formability of knitted fabric composite sheet is discussed with reference to X.