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In situ manufactured carbon-thermoplast curved stiffened panel

Periodic Reporting for period 1 - INSCAPE (In situ manufactured carbon-thermoplast curved stiffened panel)

Reporting period: 2016-01-01 to 2017-06-30

Objectives of the project
INSCAPE’s main objective is to enhance the automated thermoplastic fiber placement process and machine to manufacture an in situ consolidated (AFPisc) double-curved structure including in situ joining of stiffener and skin laminate.
This production strategy is a fundamental change compared to the state of technology, where composite structures typically build within process chains. AFPisc is integrating the major steps of material deposition and consolidation and represents a technology today named as 3D printing or more precisely described as additive manufacturing.
Technical objectives:
• Development of the AFPisc process to meet aerospace requirements, including joining for reduced assembly efforts.
• Reduction of investment costs per manufactured part by 30%; integrated joining and skin manufacturing as a key driver.
• Weight reduction by 20% of final structure compared to state of the art joined panels (with mechanical fasteners).
• INSCAPE aims for an overall reduction of manufacturing time of 50% compared to todays mutli step processing chains.
• Reduction of additional downstream quality assurance procedures.
Scientific objectives:
• Parameter study on mechanical and physical properties of in situ placed laminates (laminate in-plane properties) and of in situ joined structures (inter-plane properties of joint)
• Feasibility to integrate lightning protection layer into fiber placement process
Ecological objectives:
• Reduction of manufacturing scrap by 15% compared to standard thermoset prepreg part production.
• No need for vacuum bagging and other consumables like backing papers, no frozen material logistic required.
• Energy efficient low carbon dioxid processing.
• Reduction of number of tools required to manufacture a stiffened panel assembly.
• Enabling new high performance recyclable thermoplastic polymers with excellent FST properties for future aerospace part production.
• The in situ joining process enables a one material design approach for future aerospace parts.
Summarizing INSCAPE develops a new manufacturing approach for future lightweight structures used in aerospace application with the impact of more ecological friendly material, production and improved recyclability after end of use, higher productivity due to an automated manufacturing setup with high reproducibility and flexibility and therefore shall strengthen the future production of aerospace structures in highly developed societies with the ambition of high ecological and social standards.
The technological base of the project is an AFP machine capable for in situ consolidation installed in 2012 at TUM and supplied by AFPT GmbH. The basic process development was initiated with projects like DEfcodoor (CleansSky project, ITD Green Rotorcraft) were the manufacturing of hollow frame structures were in focus and Combo (BayernFIT program) with the demonstration of this new manufacturing approach for next generation rocket booster at a larger scale.
INSCAPE implements the demands of the aerospace industry with additional requirements in terms of quality, productivity, flexibility and intensive use of full 3D placement as well as the integration of subcomponents like thermoformed stiffeners and spars.
Project activities:
• Developments on machine hardware
• Design work related to the demonstration hardware
• Material and Process development, process demonstration as well as material performance characterization
These activities correlate with the project partners experience whereby the AFPT GmbH is focused on machine hardware development and machine code generation, FACC AG as composite component supplier to the large aircraft manufactures, concentrate on demonstrator and tool design as well as succeeding processes like part inspection (nondestructive and dimensional) and the scientific partners who put emphasis on the material and process development topics.
Operation on 3D curved panels as well as improved performance in terms of material throughput and improved contour accurate layup required a higher complexity compared to the existing single tow head design. Two development trajectories were driven: A new head design for new hardware and a technology prove by modification of the existing hardware.
The design work was focused to transfer the requirements to a feasible demonstrator design, taken into account limitations by accessible processing equipment like placement machine and pressing unit for thermoforming stiffeners, design to process and manageable complexity level, design to cost, incorporation of required functions like accurate stiffener positioning even for expected lightly distorted components. The approach to integrate the stiffening elements at skin lamination process avoids later assembly efforts. The component design was performed within CATIA Composite Design for laminate definition, but transfer to an offline machine programming environment is limited. There’s no consistency between CAD and CAM. Individual approaches were required to enable the demonstrator manufacturing. Kuka Robot Language (KRL) based code is used for panels and winding operation, an adapted version of CGTech VERICUT software is used for 3D offline programming the skin placement code.
Even the main manufacturing stream of INSCAPE is based on AFPisc processing, two alternative routes had to be prepared by TUM for stringer manufacturing. Especially the T-stringer which can’t be pressed from flat blankets, requires a more complex processing setup, where a near end shape AFPisc winding process was chosen to provide L shaped preforms for succeding T-assembly. The interaction of both processing routes can be proved within the manufacturing and demonstration activities carried out in the succeeding project period.
PEEK and PEKK based CF tapes were investigated for their processability. Fiber and resin distribution as well as homogenity and resin flow behaviour are critical characteristics for AFPisc.
Project partner INEGI performed an intensive material characterization program based on panels produced with the demonstrator manufacturing setup.
The aim of the applied project is to develop an advanced additive manufacturing process beyond the state of the art which enables light-weight design at proper mechanical performance under ecological friendly conditions. INSCAPE’s new in situ manufacturing and joining process will be shown by the demonstrator article according to the industry’s demand, that will be realized using a combination of laser-assisted TP-AFP and thermoforming process (for stiffener elements only). Increasing the TRL for TP-AFP head machine with multi-tow capability is also aimed.
The main challenges are:
• In situ placement of customized blanks with the TP-AFP head; the thermoplastic tapes are laid and consolidated in one step (in situ) before hot forming instead of applying a cost and energy intensive additional consolidation process
• In situ joining of the stiffened structure; the skin layers are directly (in situ) placed on the stiffener flanges. No further joining between the parts is needed.
• Improve process performance in terms of material through put, process robustness and laminate quality also in terms of multi tow operation
A new way of future lightweight composite manufacturing shall be developed and demonstrated.
In situ placed PEKK-CF tape / Placement trials with modified processing head 4x ½” tape placement
Curved stiffened panel demonstrator / Developed demonstrator design for technology demonstration
AFP machine at TUM for manufacturing demonstration / Program code testing and accessibility tests