Advantages of 3D woven composite fabric
Three-dimensional (3-D) weaving of composite fabrics can produce complex single-piece constructions that are structurally robust and lightweight.
Compared to traditional two-dimensional (2-D) fabrics, 3D weaving reduces weight, eliminates the delamination that often occurs in two-dimensional fabrics, reduces crack risk, and reduces production time. 3-D fabrics also provide direct and indirect manufacturing and operating cost reductions.
What is 3D weaving?
Most fabrics are woven in two dimensions – the X-axis (length) and the Y-axis (width). Three-dimensional woven fabrics include woven through thickness or Z-axis. This creates a complex one-piece structure.
Looms are the primary tool for woven fabrics. The loom is almost as old as the civilization itself and is the ideal machine for weaving two-dimensional fabrics, including webbing, tape, belts and tape. However, without a lot of tools, they cannot weave 3D fabrics.
In 1991, Bally Ribbon Mills (BRM) received a research contract from the US Air Force Research Laboratory that enabled the company to begin developing the technology needed for 3D weaving. The experience gained through research and final construction of the first fully automatic three-dimensional bias looms provides knowledge and experience for the development of other 3D woven composites for BRM, including: orthogonal plates, thermal protection systems, near net shape and complex Net shape prefabricated parts for the aerospace, automotive, construction, military and security industries.
The benefits of three-dimensional weaving
Three-dimensional weaving is an emerging technology that offers several advantages over two-dimensional composite production and more traditional building materials such as steel and aluminum. Key benefits include weight reduction, delamination, reduced crack risk, reduced production time and reduced costs.
Three-dimensional braided composites are much lighter than metal structures. This is especially relevant to the aerospace industry. The estimated weight per pound saved from the aircraft allows the aircraft operator to save approximately $1 million in operating expenses, primarily fuel costs, over the life of the aircraft. Intelligent use of 3D braided composite structures in aircraft design can reduce aircraft weight by up to 30%, saving significant operating costs.
Layering occurs when two or more layers of 2-D woven composite material are separated or layered from each other. Layering destroys the strength and reliability of the part and must be replaced to prevent damage and serious safety issues. Layering is the main cause of damage to two-dimensional laminated composites.
3-D weave produces a near net shape composite structure that is completely interconnected by its yarns, rather than a 2-D composite, which includes many different layers of material that are manually bonded together. This means that 3D woven composites are free of delamination risks, ensuring they remain strong and reliable.
Reduce crack risk
2-D laminate composites are susceptible to cracking, particularly in structures with bends, such as T-shaped structures. Due to the curvature limitations in the layers, many 2-D shapes have considerable gaps at the joints and intersections. These spaces and pockets are usually filled with resin and the resin may break.
Even three-dimensional braided composites of complex shapes have no empty pockets because their structural integrity extends along all three axes. Therefore, the crack rate of the three-dimensional woven composite material is much lower than that of the two-dimensional laminated composite material.
Reduce production time
Two-dimensional composite production is a long and precise process. Many 2-D material layers are woven individually or in larger form and then cut to size. These layers are then pre-impregnated with certain resins to make them so-called “prepreg” materials. These materials are then stacked and formed into the necessary form in a process known as plying. Plying shares are usually done by hand and are expensive and time consuming. The layers are then laminated together by injecting additional resin – some processes and structures even require stitching the layers of material together prior to lamination. Finally, the structure is set for a period of time during which the resin cures.
After the structure is properly cured, further processing is required to form the finished product. The required secondary processing techniques can include cutting, scraping, sanding, deburring and drilling.
In contrast, 3-D weaving of composite structures is simpler, faster, and more cost effective. Similar to the 2-D loom, the 3-D loom weaves the weft and warp yarns along the X and Y axes. The difference between 3-D weaving machines is that the fabric does not continue along the Y-axis, but is constructed vertically – the weft and warp yarns are not only woven together in one plane, but one plane is woven together with the next plane.
In addition to designing 3-D weaving that requires highly skilled design engineers, the 3-D weaving process is fully automated, forming a net shape or a near net shape component. Despite the increased complexity of the 3-D weaving process, this greatly reduces manufacturing time.
By weaving the entire structure in 3-D, the slow and expensive plying process – the longest and most expensive part of the 2-D laminated composite structure – can be completely eliminated – significantly speeding up production and reducing costs.
The use of three-dimensional braided composite structures instead of traditional metal or two-dimensional laminated composites can save costs through the manufacturing process and the life of the product. Automated 3-D weaving technology and near net shape capabilities reduce direct labor and secondary processing costs.
Saving operating costs saves indirect costs, such as reducing fuel. In addition, because 3-D woven composites are stronger, more flexible, and less prone to breakage than 2-D laminated composites, they can be replaced frequently, reducing replacement and maintenance costs.
Example of 3D weaving application
The use of polymer composites in aircraft engines has long been a challenge due to the high temperatures and complex geometries involved in aircraft engine manufacturing. However, polymer composites are desirable because, as noted above, the aerospace industry has been seeking to reduce aircraft weight and fuel efficiency. Replacing conventional titanium parts with carbon fiber composites in large engine parts helps to reduce weight because these composite parts are much lighter than similar parts in metal. In addition, composite engine components reduce the noise level of aircraft engines.
3D weaving is particularly successful in advancing aviation insulation technology. The Thermal Protection System (TPS) is a mission-critical component in space exploration vehicles. The ability to change yarn type, density, thickness and width, and resin type allows for the creation of fully customizable TPS to meet specific mission needs. For example, quartz compression pads are woven from BRM for Orion capsules to ensure structural strength during firing and heat resistance during re-entry. In addition, NASA’s Extremely Entering Environmental Technology (HEEET) program is developing carbon TPS for extreme items designed to survive in the challenging environment of Saturn or Venus. Both technologies were developed through extensive additional research.
In addition to the slabs and engine components, the three-dimensional braided components work well when joining the two structures together. Due to the nature of the 3-D weave, the strength and support are converted in all three dimensions, thus enabling the connection to enhance the strength of the load path along the joined substructures. These 3-D braid shapes for attachment can be customized to accommodate the structure of the structure itself, as well as the connected sub-assemblies.
Replacing traditional metal or 2D composites can bring benefits
The use of three-dimensional braided composite structures instead of traditional metal or two-dimensional laminated composites can save costs through the manufacturing process and the life of the product.