trusses and beams

Introduction
Carbon fiber composites provide an alternative to conventional materials, for example steel, aluminum, and fiberglass, for the construction of lightweight trusses and frame structures. Element 6 Composites has developed two methods for building carbon fiber tubular frames: one with high strength, robustness, and customizability, and the other with extremely low weight.

Square Tubes and Gussets
The first construction method for these types of carbon fiber structures is using tubes and gussets. The tubes range from as small as 3/4”x3/4” to 2”x4” and even larger. In addition to overall dimensions, wall thicknesses, gusset geometries, and layup schedules can be customized to meet the needs of each application. For example, uni-direction carbon fiber can be added to individual members to increase bending/axial stiffness and strength. Likewise, gusset thickness and geometry can be adjusted to ensure proper shear stress transfer through the joints. NeiNastran composite FEA calculations are used to optimize structures for minimum weight, while maintaining the specified strength and stiffness requirements.






Weighing in at only 6 pounds, this carbon fiber truss comprised of ” x ” tubes and gussets was subjected to a cantilever test with 800 pounds placed at the end without breaking.




UAV flight test truss: Captive testing of a small UAV was conducting using a 50-foot long wire-braced truss. All of the compression members of the truss were made using carbon fiber square tubes and gussets. The tension members were steel wire. FEA analysis was performed on the entire structure to ensure adequate strength and stiffness.

Pultruded Round Tubes and Connectors
An alternative lightweight, and often cost-effective, carbon fiber construction method is using our patent-pending connectors and pultruded carbon fiber tubes. The connectors give a great deal of versatility to the structural designer, with infinite combinations of lengths and angles, and a wide array of attachment components. In addition, the skills necessary for construction of this type of structure are relatively easy to master. Element 6 Composites specializes in both design and fabrication; however, many of our customers have the in-house capability to assemble the final structures once we have worked together through the design and prototyping phases of development. The picture to the right shows a cantilever load test of a pultruded carbon fiber truss that held over 500 pounds.

Carbon Fiber Beams
Many applications from robots to load-bearing structures require customized beams. Element 6 Composites specializes in designing and fabricating custom carbon fiber beams for a wide array of industries and users. Although carbon fiber beams are typically more expensive than a similar metal component, the substantial weight savings that can be achieved through advanced composites often outweighs this upfront investment.

Weighing in at only 9 pounds, this 8ft curved beam held 2500 pounds without breaking.

Multiple fabrication methods and material combinations are available, each with specific advantages. Using Nastran FEA modeling and proprietary fabrication processes, customized bending and torsional stiffnesses are possible to minimize weight. Often customers have a working assembly constructed from metal that would benefit greatly from reduced weight and increased stiffness; however, do not have the experience internally to redesign the structural members in carbon fiber composites. The engineers at Element 6 Composites are glad to discuss your project and how we can help both in the design/prototyping, as well as low and high volume production phases of your program.

Cantilever beam testing and corresponding finite element analysis results for a carbon fiber box beam. Using a combination of FEA and experimental testing, Element 6 Composites is able to build highly optimized beam structures for each customer and application.


A 24-foot long arched box beam was designed for an application that required a lightweight structure to support a heavy distributed load. Several rounds of analytical and finite element analyses drove optimization. A combination of selective carbon fiber placement and hole pattern provided a minimum weight design that met all strength specifications.

Small box beams used as wing spars for an unmanned airplane. The parts were built up out of off-the-shelf Dragonplate components, providing a cost effective solution and rapid turn-around time for the customer.

Applications
The applications for lightweight carbon fiber trusses and beams are endless. Some examples include robotic support structures and end-effectors, replacements for cantilevered beams in high-speed or portable applications, tradeshow booths, and unmanned vehicle frames. If the application requires minimum weight, yet high stiffness and strength, carbon fiber trusses or beams may be a solution worth investigating.


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