Technical Papers
The advantages of thermoplastic composites are well known and their use continues to grow as a result. Many fabrication technologies have been developed with the general goal of automated production of high performance structures using thermoplastic composite (TPC) materials. The most versatile of these technologies is in-situ consolidated TPC by automated fiber placement (AFP), a true out-of-autoclave (OoA) additive manufacturing (AM) process. Although TPC AFP is a mature technology that has been used in serial production for over 20 years, recent technical papers have cast some doubt. Several examples of high performance in-situ consolidated TPC AFP structures will be presented to dispel doubt. This paper clarifies erroneous technical assumptions in the existing literature, describes the current state-of-the-art of in-situ TPC AFP, describes the authors' current research and outlines future advancements.
Design, manufacturing, and operational requirements for Seawater Pressure Actuated (SPA) hydraulic intensifier pumps operating in water depths of up to 15,000 ft are driving the use of hybrid non-metallic and metallic materials in their fabrication. The principal goals for the design of the SPA intensifier pump are to minimize the number of components, to minimize weight, safe operation in water depths below 6,000 feet, and resistance to corrosive effects of seawater and marine biofouling. The size of an intensifier pump is approximately 240 inches long with an outer diameter of 24 inches and delivery volume of 29 gallons per stroke. Extensive use of continuously reinforced fiber placed thermoplastic composite and auxiliary polymer components have been identified as critical to managing weight, size, and subsea operation of the SPA intensifier pumps. The principal design challenges for the composite design are material selection, laminate design, and mechanical interface between composite and metallic elements. The principal manufacturing challenges for the composite are identified as fabrication of long tubular sections incorporating metallic and composite elements; maintenance of circularity, concentricity, and surface finish over the length of the dynamic seal contacting surface; incorporation of through-wall penetrations for maintenance; and reliability.
Thermoplastic composites are being recognized as very suitable material systems for many aerospace structures that require a high level of durability and toughness. These materials offer a lightweight, high strength and operational robustness that is able to surpass many metals and thermo-set composite materials. Additionally some of the process techniques that are currently available are able to offer overall manufacturing cost savings as well. Together, the material properties and manufacturing cost saving potential make these materials and their processing techniques favorable options in the aerospace community. In conjunction, there are many applications that either require, or can benefit from, a hybrid structure that includes composite and metal. However, the integration of these materials into a single structure is a non trivial task. Automated Dynamics and their in-situ fiber placement process are able to offer unique process techniques that are capable fabricating both all composite structures as well as metal/composite hybrids. This study concentrates on evaluating structural capabilities of these types of structures. Simple cylinders will be fabricated and evaluated to show the spectrum of capabilities of all metal, all composite and hybrid composite/metallic structures.
The growing demand to integrate electronics in composite structures has driven the development of a consistent and automated manufacturing process. Automated Dynamics's in-situ fiber placement technology, typically used with continuous fiber reinforced polymer prepreg, has been expanded to include continuous thermoplastic coated forms, such as wire and fiber optic cable. With multi-axis automated equipment, wire is melt-bonded to a thermoplastic substrate in controlled, repeatable patterns, atop various substrate contours to create transmitters, receivers, antennas, or other electronic devices. Additional composite plies placed on the wire layer provide structural integrity, and seal the assembly against extreme environmental conditions commonly seen in oilfield and aerospace applications. In addition, these plies can serve as the substrate for subsequent wire layers, and provide housing for embedded connectors that integrate electronic components. For applications requiring robust, non-metallic and non-magnetic housings, a high quality, electrically transparent fiber reinforced thermoplastic is used. This technology provides the basis for manufacturing the next generation of high performance downhole electronic tools. The development and proven process for embedding electronic components in thermoplastic composite structures will be outlined.
Abstract: Automated fiber placement of thermoplastic composite tapes using in-situ consolidation is a well established process for numerous industrial applications. Recent advances in the process, equipment, materials and fabrication methods coupled with several aerospace development programs indicate that significant cost and weight savings are possible with this out-of-autoclave process. These advances will be presented and key process and material parameters will be discussed. Examples of aerospace structures designed and fabricated using this process will be presented.
To overcome some of the limitations of the filament winding and automated tape laying (ATL) processes, automated fiber placement (AFP) was developed as a logical combination of the two processes. Filament winding uses continuous fiber tapes to wrap surfaces of revolution. ATL involves placing wide bands of prepreg tape onto relatively flat surfaces using a compaction roller. AFP also uses a compaction roller to precisely place multiple prepreg tapes in any position and orientation on complex surfaces. The ability to start of stop a strip at any point on the surface allows ATL and AFP to minimize waste. The use of multiple, narrow tapes allows AFP to steer the fibers over complex surfaces without buckling the fibers.
The AFP process has been used successfully with both thermoset and thermoplastic matrix composite prepreg. When thermoplastic prepreg is utilized, the materials are not only tacked together, but are fusion (or in-situ) bonded. This eliminates the need for a post process autoclave cycle and allows for integral attachment of internal composite components such as stiffeners. In-situ fiber placed thermoplastic matrix composites can offer an attractive alternative for many applications because of reduced processing costs combined with the improvement in impact resistance and fatigue strength over thermoset systems. The automated process typically results in substantial labor reduction and reduced material scrap, which justifies the cost of the robotic equipment in a reasonable time frame. This paper describes the AFP process in detail, and provides information on process limitations and design considerations. The manufacture of various components with the AFP process will be described.
In order to overcome some of the limitations of the filament winding and automated tape laying (ATL) processes, automated fiber placement (AFP) was developed as a logical combination of the two processes. Filament winding uses continuous fiber tapes to wrap surfaces of revolution. ATL involves placing wide bands of prepreg tape onto relatively flat surfaces using a compaction roller. AFP also uses a compaction roller to precisely place multiple prepreg tapes in any position and orientation on complex surfaces. The ability to start of stop a strip at any point on the surface allows ATL and AFP to minimize waste. The use of multiple, narrow tapes allows AFP to steer the fibers over complex surfaces without buckling the fibers. The AFP process has been used successfully with both thermoset and thermoplastic matrix composite prepreg.
This paper describes the AFP process in detail, and provides information on process limitations and design considerations. The manufacture of various components with the AFP process will be described.
The emphasis on lightweight large caliber weapons systems has placed the focus on the use of advanced composite materials. Using composite materials not only directly removes weight from the gun tube, but by better balancing the tube, allows the use of smaller gun stabilization drive systems, thus further enhancing system weight loss. Additionally the use of high stiffness composites helps with pointing accuracy and alleviating the dynamic strain phenomenon encountered with high velocity projectiles.
Traditionally though, using composites has been difficult due to the coefficient of thermal expansion mismatch between the steel substrate and the composite jacket, which causes a gap after manufacturing. Dealing with this mismatch has greatly complicated the manufacturing process in the past to the point where mass-producing the barrels would be problematic at best. By using a carbon fiber, thermoplastic resin prepreg and an in-situ, consolidation on the fly, process the manufacturability of the barrels has been greatly improved and the gap has been eliminated.
Although the aerospace composites industry is currently experiencing a good annual growth rate, the "cost of composites" is a continuing issue that tends to limit industry growth. Aerospace grade materials and manufacturing processes are still expensive. Manufacturing processes for composites are still predominately non-automated and aerospace grade materials are much more expensive than metals. Highly efficient automated processing equipment is available to the industry and utilization of automation has grown in recent years. However, automated composites equipment has historically been very expensive and this factor tends to limit the spread of automation throughout the industry. For example, Fiber Placement and Automated Tape Laying processes have been historically the exclusive domain of the largest aerospace companies in the world. In order for the aerospace composites industry to achieve full growth potential, automated processes must become more affordable and therefore more accessible to the multitude of smaller and mid-sized companies around the world who are producing composite structures. This paper provides the author's perspectives on reducing the cost of composites automation.
Magazine Article: "Right Sized" Tape Laying Head is Simple and Affordable.
Many Challenges and obstacles were overcome in orderot get final flight test approval for the fusion-bonded thermoplastic stabilizer. The part and material system were subjected to a battery of tests. The design and environmental requirements, and loads, are evolving concurrently as development of this stabilizer continues. There were also fabrication and assembly enhancement required to achieve quality. This groundwork or basis for the flight testing, including risk reduction tests, manufacturing improvements, design changes, and evolving criteria for the fusion-bonded stabilizer, will be outlined and detailed.
Some of the benefits of continuous fiber composites are well known to many in the oil and gas industry. 1,2 These benefits relative to metals include:
Recently, the industry has begun to use composites for downhole applications where these and other properties are being exploited. Some of these other properties include:
Some of the reported applications using composites include logging tools, drillable composite completion and workover tools, core sample holders, composite drill pipe and spoolable composite tubing. New high temperature, high pressure (HTHP) applications (≥350°F and ≥10,000 psi) pose a serious problem for thermoset composites because the required durability at the more severe HTHP conditions exceed the performance of most thermoset resins.
This NASA funded project involved the fabrication of a Polyetheretherketone (PEEK) / Graphite composite cryogenic fuel line for use on future reusable launch vehicles. The fuel line structure was a four (4) foot long, 90 degree elbow with integral flanges. The fuel line was fabricated with a 16 ply quasi-isotropic lay-up and an 8" inner diameter with 11.75" outer diameter flanges. PEEK was selected for its toughness and compatibility with the liquid oxygen fuel. Fabrication of the fuel line was done with Automated Dynamics' proprietary in-situ thermoplastic fiber placement equipment. The fabrication of the fuel line involved resolving several issues, including software programming, design and construction of break-down tooling and modification of Automated Dynamics' existing robotic technology. All of which will be discussed in this paper.
The advantages of continuous, fiber reinforced, thermoplastic composites in oilfield applications where corrosion and temperature resistance are required are discussed. Automated Dynamics' in-situ thermoplastic process for high speed fabrication of reinforced thermoplastic pipe and down hole structures is reviewed.
Manufacturing methods for a thermoplastic matrix composite horizontal stabilizer in support of Bell Helicopter Textron's fusion bonded horizontal stabilizer program were developed concurrently with the design and testing of the horizontal stabilizer. This allowed the incorporation of the appropriate manufacturing techniques and material forms into the structure design. The horizontal stabilizer was designed to use carbon fiber reinforced PEEK (polyetheretherketone) for the entire structure. Internal components including two spars, trailing edge and ribs were manufactured by a variety of methods, primarily in-situ thermoplastic fiber placement and injection molding. The skin was fabricated using the in-situ thermoplastic fiber placement process using low-cost aluminum tooling. This tooling both positioned and held the internal structure of the stabilizer, while leaving the flanges of individual components exposed. The skin was then integrally melt-bonded to the internal structure, as it was fiber placed. This paper describes the manufacturing techniques required for the fabrication of this horizontal stabilizer, including tooling considerations, processing conditions and design limitations due to manufacturing.
The program objective was to develop a low-cost composite tailboom for the light-to-medium category helicopter. Using existing metal tailbooms as a baseline, the goal was a lighter, cheaper tailboom. To achieve this goal, a thermoplastic in situ fiber placement material system was chosen. This paper address the design and development process using a thermoplastic material system. Thermoplastics are not unique, but their applications to helicopter tailbooms are, with a number of advantages such as inherently tough resin system that make thermoplastics very desirable for damage tolerance and high-temperature applications. Affordability of the in situ fiber placement process makes it very attractive from a production standpoint. However, there are a number of technical challenges. The design drivers that led to the need for thermoplastics will be discussed, as well as the design considerations, and the test program, including coupon, component, and full-scale testing.
The design, development and testing on an in situ consolidated thermoplastic composite support structure for the ducted tail rotor and vertical fin of a medium helicopter was preceded by a series of material characterization tests. The base material chosen for this component is APC-2/AS4. The thickness of the laminate ranges form 0.115 inch to 0.292 inch. The outer surface is covered by two plies of off-axis APC-2/S-2 glass fiber reinforced tape. A full-scale component was subjected to static tests, up to ultimate load, for five different maneuver conditions. It was then tested to failure for a yaw maneuver condition that has the greatest combined loading. Failure occurred at 237% of limit load. The cost saving exceeded program goals. Weight savings were more than twice as great as targeted. This was achieved by completely altering the structural concept from the metal prototype configuration, in order to minimize the part count and make optimum use of the strength tailoring possible with composites.
Tomorrow's fuselage will have to meet increasingly urgent performance optimization and cost reduction objectives. The use of composite materials, associated with the development of new industrial scenarios should enable both of these objectives to be achieved. For the last three years, a thermoplastic composite fuselage has been under study [1] and development in the framework of a research project associating Aerospatiale Aircraft, Eurocopter and Dassault-Aviation. Two technological processes studied in this research project, a thermoplastic sheet forming process and a process called in-situ consolidation, are presented and several examples of aeronautical applications are given.
As fiber placement becomes a more accepted technology throughout the composite industry, more and varied applications are becoming candidates for this fabrication technique. The flexibility of this approach to composites manufacturing is illustrated by its adaptability to a variety of robotic platforms and ability to be applied to diverse applications ranging from industrial to aerospace to medical. The paper will discuss several of these applications. For each example, the relationship between equipment configuration and the application will be detailed. A brief history of automated fiber placement, its advantages, recent technological advances, and expectations for the future will be outlined
Hand layup and post processing have always been discouraging factors to cost-effective thermoplastic and thermoset composite structure manufacturing. The standard filament winding systems most commonly available are generally too expensive to justify potential savings in many areas of production. Their physical size is often too great to follow complex wind paths or place material on smaller, more elaborate component surfaces. These limitations have enabled ADC Acquisition Company (Automated Dynamics) to provide cost conscious industry with an affordable alternative in custom robotic equipment, targeting both development and production orientated environments. Multiple or single tape and tow placement technology comprised of Automated Dynamics hardware and software can be integrated into a complete, fully automated workcell or the fiber placement head and discreet controls can be provided as an autonomous unit to be utilized in conjunction with an existing winding platform. This intentional modular design is indicative of the range of need from university and government laboratories to demanding production applications. Affordable, reliability proven, automated, fiber placement equipment will be depicted saving millions of dollars in manufacturing costs and enabling continued international research into the logical future of composite structure fabrication.
Several examples of the use of both thermoset and thermoplastic matrix composite fiber placement for the fabrication of complex production and prototype aircraft structures are discussed. Each example highlights the reasons for automated fiber placement, its advantages and recent technological advances. For a number of years, Automated Dynamics has been developing robotic, in-situ processing of fiber reinforced thermoplastic tape. This development was initially done solely for military applications, but as material prices dropped and processing technology matured, the process has found its place in a number of commercial markets. Some of these applications include industrial rolls and shafts and piping. A major limitation associated with this material and process has been its high cost relative to lower performance thermoset resins and their corresponding processing methods. Recent ongoing research has shown promise in the area of development of customized composite materials that offer characteristics that enhance the capabilities of in-situ processing. These custom materials offer in-situ processing improved part properties with substantial decreases in processing cost. This translates to increased feasibility for the use of in-situ processing of thermoplastic composites for a much larger variety of demanding commercial applications.
Several examples of the use of both thermoset and thermoplastic matrix composite fiber placement for the fabrication of complex production and prototype aircraft structures are discussed. Each example highlights the reasons for automated fiber placement, its advantages and recent technological advances.
Eight years of developing fiber placement technologies at Automated Dynamics has resulted in a robust manufacturing process for both commercial and aerospace applications. In-situ consolidation technologies for thermoplastic matrix composites have been adapted to the commercial market to include recreational products, piping and industrial rolls and shafts. High performance thermoplastics such as PEEK, nylon and PPS have been the candidate materials for these applications. Increased performance of these materials over thermosets in the areas of damage tolerance, fatigue resistance, and chemical resistance has been well documented. The limitation of thermoplastic matrix composite products from broad scale commercialization to date has been cost. This paper describes new approaches which have been investigated to increase throughput of in-situ thermoplastic fiber placement to reduce manufacturing costs for thermoplastic composite components
This paper addresses the design, manufacture, and testing of a thermoplastic composite primary aircraft structural component. The goal of this program was two-fold: (1) to demonstrate the durability of a thermoplastic component and (2) to achieve a 40% cost reduction. The component chosen for this project was the right hand folding horizontal stabilizer (metal baseline) of an OH-58D aircraft. The project was executed by a concurrent engineering team effort with emphasis on incorporating the appropriate material forms and manufacturing processes to produce a cost- effective product. Two enabling technologies, an in-situ fiber placement manufacturing process and injection molding technology, resulted in the most significant cost reductions. Three horizontal stabilizers were produced and subjected to static tests, fatigue tests, ballistic shots, lighting strike and residual strength tests. All tests were based on actual flight loads and flight scenarios. The results of this program have shown that thermoplastics provide a significantly more durable structure than metal at a reduced cost.
The production cost of manufacturing the V-22 grip was reduced by over 60% with the implementation of fiber placement. Design changes allowed the fabrication process of this thick composite structure to be automated. The designer set aside the paradigm of bonded metal craft that has shaped many composite parts. The principles of laminate design were challenged as ply edge definition and shape took on a new look as low-cost methods drove the bases of the ply shapes. Strength and weight were not sacrificed as cost was lowered, and the critics that wanted a more conventional solution soon faded into the background. Tools that made these savings possible which were not available at the start of the V-22 program are 3-D modeling systems, knowledge based design systems, and fiber placement equipment with personal computers. The people at Bell Helicopter Textron Inc. brought the tools together to build one of the most complex composite parts ever designed in a cost-effective way.
Automated Dynamics' in-situ thermoplastic fiber placement technology is reviewed. A detailed description of how the process is used to fabricate a low-cost PPS/carbon fiber industrial drive shaft is provided.
This paper assesses the application of advanced thermoplastics in rotorcraft components, by presenting an overview of three of the current thermoplastic programs being developed at Bell Helicopter Textron, Inc. These programs utilize three totally different manufacturing methods of fabricating thermoplastic components: (1) injection-molded nonstructural components (drive system, rotors, etc.), (2) a diaphragm-formed Model 212/412 baggage door (secondary structure), and (3) an in situ consolidated Model 206/OH-58 tailboom (primary structure). The primary objectives of these programs, however, ate the same: to reduce weight, to reduce cost, and to decrease manufacturing cycle time, while improving reliability and maintainability. Development of these programs is described, including material and processing, design considerations, fabrication techniques, and test methods.
This paper reports on the developments of a low-cost composite helicopter tailboom. The aim is to develop a structure which takes advantage of the performance benefits offered by composite materials, while remaining cost competitive with a production metal baseline. The in-situ consolidation technology for fiber-reinforced thermoplastic materials, which was developed by Automated Dynamics, shows promise for achieving this goal.
The role of helicopters on the battlefield depends on their capability to survive against a variety of hostile and lethal threats. These threats include the use of ever increasing conventional and unconventional weapons. In developing features for survivability enhancement against these threats for rotorcraft designs, the designer is faced with the increasing challenge of making rotorcraft more affordable, in terms of cost and weight. This paper will address the synergistic design approach used to design a thermoplastic composite helicopter tailboom against a variety of High Explosive Incendiary (HEI) and Directed Energy Weapons (DEW) threats.
