GeoStrut – Carbon Fiber Structures

Carbon fiber is known throughout the world as a superior material.  Carbon fiber has long been hampered from entering the broad market due to its high cost and low production rate potentials.  However, as a high-end material carbon fiber is virtually unmatched in its structural characteristics.  The Boeing 787 Dreamliner demonstrates one of the world’s most visible carbon fiber applications. 

With the GeoStrut technology, ACTR has successfully developed a carbon fiber structure along with the method for mass production thus providing this high-end material in a cost-effective embodiment.  The lattice structure of the GeoStrut technology successfully maintains the strength properties of the material while reducing the amount of material necessary and reducing overall costs.  In most cases, GeoStrut outperforms other carbon fiber structures and can be had at a fraction of the price. 

GeoStrut Technology benefits include

Note, GeoStrut is capable of cylindrical, triangular and square shapes among many others.  The most common application for GeoStrut is in straight members as a basic building material.  In applications such as the automotive industry, bent shapes inclusive of various cross-sectional areas are also possible.  Please contact ACTR for a design to suit your specific application at (801) 356-1488.

Carbon Fiber, The superior material

As a high-end material, carbon fiber has performances characteristics well beyond that of standard materials.  Table 1 shows the comparison of carbon fiber to other materials.  Notice the tensile strength of the carbon fiber is more than 9 times the strength of 304 stainless steel.  The elasticity is another way of viewing material stiffness.  Notice carbon fiber is the stiffest material in Table 1.  

These amazing material properties are combined with very light weight in the final product.  Notice how 304 stainless steel is more than 5 times the density of carbon fiber.  The combination of lower density in carbon fiber and higher tensile strength allow the designer to create new structures to carry the same loads which can end up being less than 6% of a steel structure in weight.

Table 1:  Material comparison demonstrating the significant tensile strength of carbon fiber.

GeoStrut Superiority in Every-Day Applications

GeoStrut excels as the structure of choice in every-day applications.  In vehicle structures, GeoStrut can be covered with a plastic-based or carbon-based skin for aerodynamic purposes.  Generally implemented as a lattice structure, GeoStrut provides excellent performances by reducing the fluid forces (water or air) to half of what is seen by an equivalent cylindrical structure. 

Table 2 compares two simple tube structures.  For direct comparison, assume two 100 ft wind turbine towers built to 36 inches in diameter.  This keeps the differences between the towers as low as possible and highlights the superiority of a GeoStrut tower design.  Notice in Table 2, the structures are considered to give the same projected area and are subjected to the same wind load (40 psf, which is 100 mph winds).  Since the lattice design of GeoStrut allows air to pass through the structure, the drag coefficient is half that of a geometrically comparable cylinder of any material.  Resulting from this lower drag coefficient, the total wind force on the GeoStrut structure is also half that of the solid structure.  The load reduction allows the designer some freedom to reduce the amount of material needed.

GeoStrut Wind Turbine Tower Component

Using the same comparison, GeoStrut also provides significant advantages in material transportation and tower erection.  The steel structure outlined in Table 2 is assumed to be fabricated from 1/8” thick self-supporting sheet metal.  This is comparable to a tower with a steel frame coated with 1/32” thick sheet metal.  Notice the weight differences.  The GeoStrut tower comes in at 275 lbs for a 100 ft structure.  The steel tower is more than twenty times that weight.  The GeoStrut tower can be transported, in pieces even, by a standard pick-up truck or easily flown in by helicopter.  The steel tower requires heavy equipment for transportation as well as erection along with a significant lead time.  Further, the GeoStrut tower can be practically erected by hand with minimal labor in comparison to the steel structure. 

Table 2:  Comparison of wind forces on a 100 ft wind turbine tower made as a solid cylinder and of GeoStrut tube.

*  The tower weight is based on an equivalent 100 ft steel cylinder of 1/8” wall thickness.