Additive Manufacturing of Low CTE Open Isogrid Composite Structure

Continuous Composites Inc. (CCI) has developed and patented a continuous fiber 3-D printing technology known as CF3D®. CF3D has unique capabilities to reduce cost, accelerate design cycles, scale throughput, and create highly tailorable structures (e.g., in terms of design and material properties). By utilizing continuous fiber reinforcement, snap curing aerospace-grade photopolymers, and robotics, CF3D can drastically reduce the time and cost of creating continuous fiber-reinforced composites. CF3D allows for fabrication of unique structures that would be impractical to produce with traditional methods requiring autoclave or vacuum bag pressure during curing. One such structure is an open iso-grid rib structure. Iso-grid composite structures are not a new technology and have been built and flown on space structures, however traditionally are very expensive to produce.CF3D is very conducive to the manufacturing of iso-grid composite structures, either with a skin or as an open lattice concept. The single carbon fiber tow can be put on a support surface of any shape (e.g., flat, cylindrical, or spherical). Each tow is then stacked on top of the previous tow and UV cured in-situ, resulting in any rib pattern desired for the target strength and stiffness of the structure. A unique property of the composite open iso-grid structural concept is its bulk thermal expansion properties. As each rib of the iso-grid structure is composed of all unidirectional fibers oriented along the length of the member, the CTE is very low. Published studies on T800 unidirectional laminates show CTE to be in the range of -.4 (10-6 X K-1) in the fiber direction. This results in a structure that is overall lightweight and isotropic given the nature of the iso-grid concept with a very low CTE. Using high strength, low-cost intermediate modulus fibers to build a lightweight, low CTE structure has the potential to greatly decrease the weight, cost, and lead time of dimensionally stable structures.

Potential NASA applications include dimensionally stable space structures and light weight space payloads and vehicles structures.

Potential Non-NASA applications include commercial dimensionally stable space structures and light weight space payloads and vehicles structures. In addition, other aerospace applications where lightweight open iso-grid structures can add value to a program such as fixed wing aircraft, helicopter, VTOL, or other high performance aerospace composite structures.

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