Predictive Manufacturing of V-22 Composite Grips

The V-22 engineering and manufacturing development (EMD) grip is a complex rotor component fabricated from advanced composite materials. Due to its loading and position in the rotor system, it has an irregular tubular shape, a thick clevis on the end attached to the blade, and sculpted wall thicknesses at different attachment points (Fig. 1). The wall thickness varies between approximately 0.4 and 1.5 inches. During full-scale development (FSD) and testing of the V-22 rotor system, a significant effort was expended to develop the tooling and processing techniques required for grip manufacture. Many subscale specimens and finally full-scale grip components were fabricated to optimize fabrication and cure processes. A two-piece clamshell carbon/epoxy tool was used to obtain good outer mold line (OML) surfaces and fiber alignment . The part and tool were bagged and sealed, then the part was compacted and expanded to the tool surface with autoclave pressure. The FSD grip cure cycle, which was approximately 14 hours, was designed to prevent runaway exotherm and to provide even heatup throughout the varying thickness. Exotherm is the heat given out as a result of chemical reaction in the epoxy resin. In the EMD phase of the V-22 program the grip is being redesigned. A new composite material system has been selected, E7T1-2/IM7, which is a toughened graphite/epoxy system with recommended curing temperature between 300°F and 350°F. To achieve cost and quality targets, the number of subcomponents has been reduced, automation is being implemented, and an improved cure approach is being investigated.