Forming methodology for highly aligned discontinuous fiber composite blanks via epoxy matrix staging

Abstract

A methodology for rapid manufacturing of complex geometry stretch formed parts from highly aligned discontinuous fiber (ADF) epoxy matrix multiaxial composite blanks is demonstrated in this paper. During typical forming processes, forming and curing occur within the same tool, leading to bottlenecks in processing time. In this new methodology, the epoxy resin is partially cured to increase glass transition temperature above room temperature. Advanced matrix staging allows a blank to be easily removed from a room temperature tool after forming. In a production environment, blanks would be (i) staged in an oven vacuum bag process, (ii) preheated in an IR oven, (iii) rapidly stamp formed into a room temperature tool, (iv) ejected as a near net shape part, and then (v) fully cured/formed in a parallel batch process. To implement this methodology, accurate relationships between viscosity, cure, and glass transition temperature are established and used to manufacture partially cured material for mechanical testing and extensibility characterization. Several key benefits are realized by using partially cured material; namely, the ability to rapidly form and eject a preformed part from tooling and reduced resin bleed during cure and consolidation. The staging process is also shown to retain similar formability and mechanical properties relative to the uncured material form.