Towards a model-based control for thermoplastic automated fiber placement

Commercial aviation must become climate neutral in the next decades, a key factor are lightweight fuselages that may increase fuel efficiency of an aircraft over its lifetime. New manufacturing processes such as in-situ, thermoplastic Automated Fiber Placement (AFP) enable larger and more complex carbon fiber reinforced components. In order to increase material performance process parameters, have to be controlled precisely. A sensible approach is introduced in this work by implementation of Model-Based Control (MPC), which can accommodate for process specific challenges. A finite element model of the process is designed and integrated in to the control. Subsequently, layup trials validate the improvements and thus show the potential of the control approach

Upscaling of in-situ Automated Fiber Placement with LM-PAEK – from Panel to Fuselage

The application of thermoplastic CFRPs in large aerospace components enables a modern and differential approach to Aircraft manufacturing. Most importantly the opportunity of dust-free joining of components by means of thermoplastic welding technologies allow subassemblies to be pre-equipped with system and cabin elements that are then subsequently joined. The Institute for Structures and Design of the German Aerospace Center (DLR) has been working on in-situ Automated Fiber Placement (AFP) with different thermoplastic matrix materials with the goal to develop a suitable single stage manufacturing process for thermoplastic CFRPs. Different aspects of the scale-up were investigated including the overall ply design, manufacturability of complex areas of a fuselage, first ply adhesion, and the overall laminate quality with regard to weldability. The manufacturing of a test shell with 4 m diameter is presented in this work. It identified key areas of the process that require further refinement in order to assure manufacturability and weldability of AFP-produced parts. Using the results, a holistic approach to the manufacturing process is proposed for the direct manufacturing of large-scale components made with the in-situ AFP Process

Thermocouple based process optimization for laser assisted automated fiber placement of CF/LM-PAEK

Self-commitments and increasing legal requirements lead to the compulsion to reduce carbon dioxide emissions in commercial aerospace. One viable approach is the reduction of structural mass, that would reduce emissions for every flight. This is especially true for high cadence singe aisle aircrafts. However, high quantities are required in this segment. To achieve these goals the newly developed low-melt Poly-Aryl-Ether-Ketone (LM-PAEK), a high-performance carbon fiber-reinforced thermoplastic composite was chosen to build a full-scale multi-functional fuselage demonstrator (MFFD) in order to delevelop an automated process that shows these savings. Single-step automated Fiber Placement (AFP) with in-situ consolidation offers distinct advantages in this field with its short curing times and especially by eliminating high amounts of waste otherwise caused by vacuum bagging and related tasks for post-consolidation in an autoclave. In order to ready this technology for future aircraft production this paper demonstrates how the processing window for LM-PAEK tape (TC1225) provided by TORAY was established. By closely linking robot and end-effector data with positionally accurate thermocouple measurements, the determined mechanical properties at coupon level and micro-sections of the manufactured specimens can be precisely correlated. This holistic approach is independent of the placement equipment and may enable global comparability within the community working in the field of thermoplastic AFP. In conclusion the procedure is evaluated and possible simplifications are discussed

Inline Quality Control for Thermoplastic Automated Fiber Placement by 3D Profilometry

Thermoplastic Automated Fiber Placement (T-AFP) is a promising technology for the manufacturing of complex aerospace parts. In contrast to tapelaying of duromere prepregs TAFP has the potential of in-situ consolidating the laminate as well as the opportunity for a dustfree ssembly based on thermoplastic welding. Subsequent rework is challenging in this single-stage process due to the direct consolidation onto the substrate. In result inline quality control gains even more importance. Starting from AIPS 0302019 at DLRs Center of Lightweight Production Technology in Augsburg we investigated the feasibility of a fully automated inspection system based upon a high-performance light sheet sensor that is capable of detecting most crucial defect types such as gaps and overlaps inline, allowing an early correction by the user or by a control system. We found that especially overlaps between tracks in lower plies have the potential of introducing extreme undulations at higher plies. In order to assure a constant minimum gap between placed tracks in production, measuring overlaps as well as gaps has been our focus. Since steering effects and other influences are complex all received data is associated with machine data and stored in a data management system for further algorithmic and AI-based evaluation

Full-Scale Application of in-situ Automated Fiber Placement for the Production of a Fuselage Skin Segment

The CleanSky II multi-functional fuselage demonstrator is the world’s largest known aviation structure made of thermoplastic composites. The Center for Lightweight Production Technology (ZLP) in Augsburg together with Premium Aerotec, supported by Aernnova and Airbus was responsible for the delivery of the 8 m long upper half shell. The first step in the upper shell production is the skin placement which is done by means of in-situ automated fiber placement (in-situ T-AFP). The process is a lean, single-stage additive manufacturing process for thermoplastic CFRPs. In order to ensure a sufficient quality in the laminate the ZLP has worked intensively on dedicated design principles for the process, material quality requirements and an optimization of process parameters. Major advancements on the way towards a full-scale fuselage have been displayed in the past by the manufacturing of a scaled demonstrator. This paper presents the evolution to the recently manufactured full-scale component with a total length of 8 m, a diameter of 4 m and a composite part design that includes reinforcements for the door cut-outs and two different welding interfaces. The latter will be leveraged for the joining of two half-shells by means of thermoplastic welding. In this work the methodology for a scale up to an actual airplane geometry and the associated challenges are emphasized. Critical aspects of the scale up and potential mitigation of future issues for in-situ process are discussed with regards to design, process and manufacturing. Finally, a way towards industrial, full-scale productions by means of in-situ AFP is proposed

Simulation based draping of dry carbon fibre textiles with cooperating robots

Carbon fibre-reinforced plastic (CFRP) is a promising material for aircraft and other lightweight applications. To be competitive with low-cost metal based solutions highly effective and flexible production technologies are required. For this purpose production systems comprising automated fibre placement or automated tape laying technology are on the market for several years and widely spread. However, there is still a lack of automated systems capable of producing preforms efficiently and flexibly from textile semi-finished goods. Non-crimp fabrics (NCF) and weaves have to undergo considerable shear and reshaping during the layup of 3D-curved preforms in order to properly fit the 2D cut pieces to the moulds. At the Center for Lightweight Production Technology (ZLP) a digital and automated process for the easy draping of large NCF and weave cut pieces with several robots according to the previous draping simulation has been set up and tested in a robotic work cell. The details of converting the draping simulation into correct and easy to setup motions for cooperating robots and how to execute the entire process autonomously, i.e. without teaching the robots, are described. On the basis of preliminary tests the system’s capabilities on a large scale demonstrator part resembling an airplane’s rear pressure bulkhead are evaluated. An overview of the system’s architecture from simulation based planning to detecting, correct gripping, collision free autonomous transport and laydown of the cut pieces is also given

Autonomous Composite Production by Robotic Pick & Place

During the last decade the DLR Center of Lightweigth Production Technology (ZLP) in Augsburg investigated the potential of the autonomous production of composite parts by means of pick and place executed by industrial robots. Starting from conventional teaching the research focus was extended to the development of technology bricks for computer vision based gripping, automated derivation of grip- and drop coordinates from CAD data, digital process description and workflow, autonomous cut-piece transfer by means of collision free path planning and a multi-robot synchronization and execution layer. The technology bricks are enriched by a process data acquisition system and controlled by a manufacturing execution system embedded into a high-level process control system. In this work we give an overview of the developed technologies and achievements based upon several use cases from the field of composite production

Automated layup of spherical GLARE components using cooperating robots

The use of Fiber-Metal-Laminates (FML) for aircraft fuselages offers a wide range of opportunities regarding mechanical properties like weight and impact tolerance. One example for an FML is glass reinforced aluminum (GLARE) which is currently used in the A380 fuselage. The production process for existing components is highly manual and therefore the use of GLARE is limited due to high production costs. A promising approach to reduce costs is the development of a fully automated production process for GLARE components. Challenges of an automated production include the handling of large aluminum sheets and especially the layup of sheets on spherical surfaces. The Center for Lightweight Production Technology investigated the use of cooperating robots to build an example layup. A main focus was to determine if the setup provides a sufficient repeatability and accuracy. The layup showed that the maximum width of the sheets needs to be limited in order to avoid kinks and waviness. These occur in spherical curved areas of the mold. A possible solution to avoid the waviness as well as inner stresses is the use of preformed spherical aluminum sheets for the layup. The feasibility of a preformed layup is experimentally investigated and opportunities for the process are discussed