Advanced fiber placement of composite fuselage structures

The Hercules/NASA Advanced Composite Technology (ACT) program will demonstrate the low cost potential of the automated fiber placement process. The Hercules fiber placement machine was developed for cost effective production of composite aircraft structures. The process uses a low cost prepreg tow material form and achieves equivalent laminate properties to structures fabricated with prepreg tape layup. Fiber placement demonstrations planned for the Hercules/NASA program include fabrication of stiffened test panels which represent crown, keel, and window belt segments of a typical transport aircraft fuselage

Automated fiber placement composite manufacturing: The mission at MSFC's Productivity Enhancement Complex

Automated fiber placement is a manufacturing process used for producing complex composite structures. It is a notable leap to the state-of-the-art in technology for automated composite manufacturing. The fiber placement capability was established at the Marshall Space Flight Center's (MSFC) Productivity Enhancement Complex in 1992 in collaboration with Thiokol Corporation to provide materials and processes research and development, and to fabricate components for many of the Center's Programs. The Fiber Placement System (FPX) was developed as a distinct solution to problems inherent to other automated composite manufacturing systems. This equipment provides unique capabilities to build composite parts in complex 3-D shapes with concave and other asymmetrical configurations. Components with complex geometries and localized reinforcements usually require labor intensive efforts resulting in expensive, less reproducible components; the fiber placement system has the features necessary to overcome these conditions. The mechanical systems of the equipment have the motion characteristics of a filament winder and the fiber lay-up attributes of a tape laying machine, with the additional capabilities of differential tow payout speeds, compaction and cut-restart to selectively place the correct number of fibers where the design dictates. This capability will produce a repeatable process resulting in lower cost and improved quality and reliability

Comparative Analysis on Low Cost Continuous Carbon Fiber Polypropylene Composite Using Compression Molding and Automated Tape Placement

Carbon fiber reinforced plastics (CFRP) are widely used throughout the aerospace industry where a weight reduction remains the highest priority with less emphasis on cost. Textile grade carbon fiber (TCF) and other low cost carbon fiber (LCCF) alternatives have recently emerged for use in the automotive market where emissions regulations have pushed automotive manufacturers and research institutions to look for cost effective light weight materials. Fiber reinforced thermoplastics provide an effective solution that align with automotive design including low cost, high processing rates, high impact toughness, unlimited shelf life, and recyclability. TCF and Zoltek_PX35 fibers are two LCCF aimed at the automotive, wind energy and commercial markets that are helping to push the cost of CF down to approximately $5 per lb. In combination with a hot melt thermoplastic pultrusion impregnation technique, an intermediate low cost composite tape can be produced that is shown to have good mechanical performance when consolidated through hot compression molding (CM). Automation is critical to the required rapid part production and process control within the automotive industry. Research was conducted into the manufacturing process parameters of LCCF composite tapes through in-situ consolidation with an automated tape placement (ATP) or automated fiber placement (AFP) robotic system. This research focuses on the manufacturing of low-cost continuous polypropylene composites and explores the mechanical and morphological properties associated with compression molding and automated tape placement

Materials for Heated Head Automated Thermoplastic Tape Placement

NASA Langley Research Center (LaRC) is currently pursuing multiple paths to develop out of autoclave (OOA) polymeric composite materials and processes. Polymeric composite materials development includes the synthesis of new and/or modified thermosetting and thermoplastic matrix resins designed for specific OOA processes. OOA processes currently under investigation include vacuum bag only (VBO) prepreg/composite fabrication, resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM) and heated head automated thermoplastic tape placement (HHATP). This paper will discuss the NASA Langley HHATP facility and capabilities and recent work on characterizing thermoplastic tape quality and requirements for quality part production. Samples of three distinct versions of APC-2 (AS4/PEEK) thermoplastic dry tape were obtained from two materials vendors, TENCATE, Inc. and CYTEC Engineered Materials** (standard grade and an experimental batch). Random specimens were taken from each of these samples and subjected to photo-microscopy and surface profilometry. The CYTEC standard grade of APC-2 tape had the most voids and splits and the highest surface roughness and/or waviness. Since the APC-2 tape is composed of a thermoplastic matrix, it offers the flexibility of reprocessing to improve quality, and thereby improve final quality of HHATP laminates. Discussions will also include potential research areas and future work that is required to advance the state of the art in the HHATP process for composite fabrication

Experimental Calibration of a Numerical Model of Prepreg Tack for Predicting AFP Process Related Defects

Wrinkles, puckers, and fiber bridging are among the major defects encountered in the Automated Fiber Placement (AFP) process, and are all different manifestations of fiber misalignment. The main driver for these defects are the residual stresses introduced in the tow during the deposition stage by the AFP head. In contrast, the tack between the deposited tape and the substrate is the resisting force against the formation of such defects. Tack may be defined as the ability of a material to form a bond immediately on contact with another surface. Tack is a very complex phenomenon that is influenced by a variety of process parameters including temperature, head pressure and speed, as well as degree of cure, moisture content, and surface roughness A physics-based modeling framework for simulation of tack was developed in this study that allows for prediction of tack response. The developed tack model is incorporated in the AFP placement modelling framework developed to simulate AFP defects

In situ consolidation of thermoplastic prepreg tape using automated tape placement technology: Potential and possibilities

The key parameters of the in-situ consolidation of carbon fibre reinforced poly-ether-etherketone (AS4-CF/PEEK) by automated tape placement (ATP) process were investigated by manufacturing of continuous rings and by laying tape onto pre-consolidated laminates. In order to establish and understand correlations between the process parameters and mechanical properties, a number of parametric studies were performed by manufacturing and testing the interlaminar shear strength, single lap shear strength and fracture toughness samples. The main process parameters investigated were the compaction force, tape laying speed and tool temperature. To achieve a uniform heat distribution across the thermoplastic tape, a new nozzle was designed. Baseline samples were also manufactured using the autoclave process to provide a comparison for the ATP composites produced. Optical microscopy was used for investigating the microstructure of composites compared. It was found that increasing the tool temperature reduced the temperature gradient between the incoming tape and substrate, resulting in better lap-shear strength and fracture toughness properties

Advanced tow placement of composite fuselage structure

The Hercules NASA ACT program was established to demonstrate and validate the low cost potential of the automated tow placement process for fabrication of aircraft primary structures. The program is currently being conducted as a cooperative program in collaboration with the Boeing ATCAS Program. The Hercules advanced tow placement process has been in development since 1982 and was developed specifically for composite aircraft structures. The second generation machine, now in operation at Hercules, is a production-ready machine that uses a low cost prepreg tow material form to produce structures with laminate properties equivalent to prepreg tape layup. Current program activities are focused on demonstration of the automated tow placement process for fabrication of subsonic transport aircraft fuselage crown quadrants. We are working with Boeing Commercial Aircraft and Douglas Aircraft during this phase of the program. The Douglas demonstration panels has co-cured skin/stringers, and the Boeing demonstration panel is an intricately bonded part with co-cured skin/stringers and co-bonded frames. Other aircraft structures that were evaluated for the automated tow placement process include engine nacelle components, fuselage pressure bulkheads, and fuselage tail cones. Because of the cylindrical shape of these structures, multiple parts can be fabricated on one two placement tool, thus reducing the cost per pound of the finished part

In Situ Thermal Inspection of Automated Fiber Placement Operations for Tow and Ply Defect Detection

The advent of Automated Fiber Placement (AFP) systems have aided the rapid manufacturing of composite aerospace structures. One of the challenges that AFP systems pose is the uniformity of the deposited prepreg tape layers, which complicates detection of laps, gaps, overlaps and twists. The current detection method used in industry involves halting fabrication and performing a time consuming, visual inspection of each tape layer. Typical AFP systems use a quartz lamp to heat the base layer to make the surface tacky as it deposits another tape layer. The innovation proposed in this paper is to use the preheated base layer as a through-transmission heat source for inspecting the newly added tape layer in situ using a thermographic camera mounted on to the AFP hardware. Such a system would not only increase manufacturing throughput by reducing inspection times, but it would also aid in process development for new structural designs or material systems by providing data on as-built parts. To this end, a small thermal camera was mounted onto an AFP robotic research platform at NASA, and thermal data was collected during typical and experimental layup operations. The data was post processed to reveal defects such as tow overlap/gap, wrinkling, and peel-up. Defects that would have been impossible to detect visually were also discovered in the data, such as poor/loss of adhesion between plies and the effects of vacuum debulking. This paper will cover the results of our experiments, and the plans for future versions of this inspection system

Utilizing Vacuum Bagging Process to Prepare Carbon/Epoxy Composite Laminates

In the frame of this work, composite laminates based on unidirectional carbon/epoxy prepreg were produced by using of by Automated Tape Laying (ATL)/ Automated Fiber Placement (AFP) and vaccum bagging processes. This research based on unidirectional carbon fiber/epoxy composites shows the effect of fiber architecture on mechanical properties using a automated tape/fiber laying procedure followed by the vacuum bagging process method. The properties of the prepreg material have been tested and some mechanical properties of the obtained composite laminates has been performed. The vacuum bagging method showed improvement in tensile strength and modulus. Keywords: automation, layup, vaccum bagging, prepreg, laminates

Improving manufacturing of aeronautical parts with an enhanced industrial Robotised Fibre Placement Cell using an external force-vision scheme

Composite materials are increasingly used in the demanding field of aeronautics. To meet this growing need, the company Coriolis Composites has developed an Automated Fibre Placement device already on the market. This process uses an industrial manip-ulator robot. This fibre placement task requires a com-pacting strength adapted to the material used. For the robot, the reference trajectories in position of each tape are prescribed off-line. However, accuracy problems of tape placement appear when off-line programmed robot trajectories. The proposed approach to address the accuracy problem and the manufacturing constraints is an interactive manufacturing scheme based on exterocep-tive sensor loops. This paper shows an interactive manufacturing approach based on force servoing to control the compacting strength and on visual servoing to control the lateral position of the tape in order to improve the fibre placement accuracy and then the quality of manufactured parts