An Investigation of the Formability of Long Fiber Thermoplastic Composite Sheets

Abstract

An experimental and analytical investigation was undertaken to improve understanding of the form of long fiber reinforced thermoplastic sheets. The materials tested contained 30 percent by weight of glass fibers in a polypropylene matrix, with the fibers approximately randomly oriented in the plane of sheet. The forming tests covered a range of forming temperatures between the glass transition temperature and the melting point of the polypropylene matrix. The testing geometry was that of a Swift flat-bottomed cup test, which primarily tests bending and drawing behavior of the sheet. An analysis of the process was developed in terms of a continuum model of material behavior with normal anisotropy and rotational symmetry. Results of the forming tests are compared with analytical predictions. Limitations of both the form of the material and the modeling approach are discussed.