Acree Technologies has developed several advanced technologies for the manufacture of polymer composite structures. These technologies are used to construct large components, with excellent strength and mechanical properties at reduced cost.
E-Beam Curing
Electron beam (E-Beam) curing offers several advantages over traditional autoclave curing. E-beam curing is a room temperature cure without the need for an oven or autoclave, consequently there are no coefficient of thermal expansion (CTE) mismatch issues. E-beam curing costs are intrinsically lower. For example, a typical price for curing a 4 x 4 x 8 foot object is about ~$700, compared to about $8,000 per large autoclave curing of a similar part. In addition, E-beam curing allows the use of low cost tooling. Room temperature cured composites offer the ability to use very low cost tooling materials such as modeling foams and plastics. These are ideal for low rate of production parts. Tools fabricated from metals and alloys are expensive, difficult to repair, heavy, and unwieldy in larger dimensions. By contrast, foam is about five to ten times more affordable than bulk aluminum and 10 times lower in density. Weight and cost savings are even greater in comparison to more specialized alloys such as Invar 36. Foam also can be machined quickly. The tool itself is substantially lighter, reducing the associated rigging for handling and transportation.
Resin Film Infusion
Acree uses an innovative approach to Resin Film Infusion in conjunction with E-Beam curing. The E-Beam resin is viscous at room temperature, having the consistency of soft rubber, and is applied to the tool in sheets with backing paper. The perform fiber is laid on top of the resin film. Once the build-up is in place, the part is vacuum bagged using a single bag and the composite is warmed to about 160° F to 200° F using warming lamps. The warming reduces the viscosity of the resin, allowing the resin to impregnate the fibers. The method is an inexpensive and superior approach for building large parts.
Z-Weaving
In Z-weaving the fiber layers are woven together using a Z stitch in addition to the X and Y weaving. Inter-laminar shear, first ply failure and ballistic survivability are key attributes that can be improved through the use of Z-weaving. Z-weaving opens the possibility of weaving fabrics to 3D net shape. 3D multi-ply fabrics can reduce fabrication costs, even though the 3D fabric itself is more expensive. The overall cost is lower because of the reduced labor required to fabricate a multiple layer system. The off-axis 3D plies increases the composite’s torsional strength.
