1.1 Concept and objectives

1.1.1 Socio-Economical demands and technical challenges on composite manufacturing

By reason of their high weight specific mechanical properties, fibre reinforced composite materials are increasingly employed for high performance structures (cf. Figure 1). Yet, their exploitation is still limited due to rather high costs as well as particular design and manufacturing requirements, which cannot be met today, especially within automotive, aeronautic, marine and railway application. In order to increase exploitation, industry and SME request for more robust but flexible composite production processes, which enable to significantly increase ramp-up times and process reliability as well as to reduce material and energy consumption, rework and post-processing. Especially for high product changes and material substitution aspects, a very strong effort is currently required to find optimum process parameters and thus, often hinders technological advances in the final product.

Within the following, current socio-economic demands for manufacturing of high performance composites are emphasized for three main categories of industrial application: volume parts, complex parts and large parts.

By reason of potential weight savings (up to 20%), e.g. automotive industry is increasingly asking for solutions of material substitution for volume parts (high throughput). By this means, resource consumption and CO2/NOx (e.g. fuel burn) can be reduced significantly during service. Yet, manufacturing processes of high performance composites, such as carbon fibre reinforces plastics (CFRP), are either too inefficient (high process time, material and energy consumption) or they are lacking of required robustness. Current

process variations already lead to unacceptable loss of required quality (e.g. structural performance, surface quality). Moreover, inevitable rework and post-processing tasks also hinder economical manufacturing of volume parts. Therefore, a new composite manufacturing concept is required in order to ensure required robustness while significantly reducing manufacturing costs within automotive industry. Thus, to exploit lighter and high performance composite volume parts.

So-called complex parts may have complex geometric shapes (e.g. with strong curvatures or thickness variations) or complex multi-material designs in order to integrate joints for load introduction purpose or to serve specific (multi-functional) requirements. By reason of their flexibility, composites can meet these particularities for a wide range of application and thus, offer exploitation of new product properties (e.g. light-weight composite propeller with acoustic damping capabilities). But yet, an immense effort and investment has to be spent on process design (tooling, process temperatures, etc.), hinders first-time-right manufacturing and prevents from further exploitation. In order to increase sustainable exploitation of complex parts (e.g. involving potentials of multi-functional capabilities), especially SMEs are requiring a new composite manufacturing processes technique, which significantly reduces ramp-up times and production costs. This is necessary to exploit

Figure 1: Attractivity and competiveness of significant materials for industry Error! No se encuentra el origen de la referencia..

European leadership (suppliers and end users) for high technology applications, even across markets (e.g. automotive, aeronautic, marine, railway).

High performance large parts are mostly weight driven. But also geometric tolerances

(e.g. aerodynamic shape of an aeronautic wing cover) are of high importance in order to achieve current socio-economical requirements. E.g. European commission is demanding 75% CO2 reduction and 90% NOx reduction (cf. Flighpath 2050 Error! No se encuentra el origen de la referencia.) until 2050, for which reason fuel consumption has to be reduced significantly by structural weight reduction and increased aerodynamic efficiency. To this, unnecessary safety margins of composite design (by 10-20%) have to be exploited by identifying and minimizing manufacturing defects. Currently, extremely low manufacturing tolerances are applied, leading to very high process costs (time and energy), and yet, relatively high effort (up to 20%) is spent on non-added value processes like rework and post-processing. Moreover, rejection rates (up to 10%) are to be prevented in order to increase process efficiency, thus reducing overall energy and material consumption as well as CO2 and NOx emissions.

Due to these industrial demands ECOMISE addresses all three product types: volume, complex and large parts. For this purpose a scientific approach is followed by investigating the respective particularities of each product type and developing a new and innovative manufacturing technology, which suits all three product types. As depicted within Figure 2, this manufacturing technology is validated and demonstrated by three different industrial use-cases: Car Suspension (volume part), Aeronautic Wing Cover (large part) and Ship Propeller (complex part).

Volume Part Large Part Complex Part

Car Suspension

Aeronautic Wing Cover

Ship Propeller

Figure 2: Three representative industrial sectors for volume, large and complex part application.

Within this context the project is addressing the following impacts:

- Higher utilization of composites by 15% with improved performance without a cost increase for new composite applications by significantly improving composite quality through structural evaluation and selective adjustment of manufacturing tolerances

- Decrease in raw materials and energy consumption up to 45% during

manufacturing by increased process efficiency due to first-time-right process design (no manufacturing trials), in-situ process control, net-shape fibre placement, significantly reduced curing times

- Reduction of waste and emissions up to 45% during manufacturing and post-processing (no rework or shimming during assembly) by robust net-shape manufacturing based on in-situ evaluation and immediate process adjustment

1.1.2 Concept of the project In spite of extensive effort within several research projects, the current development process of composite structures still shows a mostly sequential work flow (cf. on the left of Figure 3)

along Process Design, Production, Quality Assurance and Rework phases. Several different empirical and numerical methods and tools are applied within these phases in order to solve particular questions. Accompanying it, a heterogeneous set of systems and tools with mostly incomplete interfaces hinders a throughout development process with a high degree of automation. This directly affects process efficiency both short-term ramp-up as well as long-term robustness. Hence, a high number of iterations is usually needed for an initial Process Design and frequent Process Adjustments; nonetheless, Part rejection cannot be avoided.

Facing the high complexity of composite manufacturing processes and the high sensitivity of the final composite quality with respect to inevitable process tolerances a new holistic, knowledge-based manufacturing approach is required, which enables high performance composite application at significant reduction of production time and costs as well as related material and energy consumption.

An innovative breakthrough technology will therefore be developed within ECOMISE by:

Enabling Next Generation COmposite Manufacturing by

In-Situ Structural Evaluation and Process Adjustment.

For the first time, an in-situ evaluation of the real determining composite properties will be provided already during manufacturing, directly coupled with an immediate, individual process adjustment. Thus, initial requirements with very low tolerances/ safety margins can be ensured for future composite application without costly rework/ repair at a late production state.

As depicted on the right of Figure 3, this breakthrough will be achieved by the new holistic ECOMISE Manufacturing System, which is not available yet. This manufacturing system combines the following four innovative technology modules:

- Probabilistic Process Prediction, taking into account statistical process tolerances,

- On-line Process Monitoring, for capturing comprehensive process data and related

composite properties,

- In-Situ Evaluation of present as-built composite quality affected by detected process deviations and composite properties

- In-Situ Process Adjustment measures to prevent or compensate deviations.

Figure 3: Innovations of ECOMISE Manufacturing System with four advanced modules.

Before introducing the innovations of these four required technology modules in greater detail the following remark shall be highlighted: The ECOMISE Manufacturing System with its four modules (Probabilistic Process Prediction, Online Process Monitoring, In-Situ Evaluation and In-Situ Process Adjustment) must not be mistaken with current process control techniques within composite manufacturing plants. Current techniques are monitoring dedicated process conditions, such as global process temperature, pressures, process speed or alike. But no information is directly captured regarding the real composite properties. For this reason, experience-based rules (e.g. rough estimation of degree of cure relating on global process temperature) are currently applied, in order to decide about process modifications without direct assessing the affected composite quality (e.g. shape, stiffness or strength). Yet, due to the complex manufacturing of composites, very high process sensitivities have to be accounted for. Therefore, industrial production has to take the loss of either overestimated process times or high reject rates and rework effort.

Probabilistic Process Prediction Module

The new module of Probabilistic Process Prediction will be developed and integrated within the early process design phase. In comparison with current state-of-the-art design methods, which are mainly empirically based with few simulations of selected process conditions, the new module will address the following innovations. More reliable, physically based process simulation methods are developed in order to predict the continuous manufacturing process from first preforming of fabrics, via subsequent moulding, resin injection and curing, up to final de-moulding. Beyond, sensitive manufacturing particularities are considered for more realistic predictions. Exemplarily, preform tolerances (e.g. fabric shearing, misalignments, ondulations) lead to varying material properties and thickness distribution and therefore influence the precision of subsequent infiltration. The resulting fibre volume content variation will determine the subsequent

State-of-the-art

manufacturing process

- Empirical experience

- Single deterministic

calculations

ECOMISE Manufacturing System

beyond state-of-the-art

Process

Design

Rework

& Post-

Processing

Production

Quality Assurance

Extensive process redesign and tooling

modification

Probabilistic Process Prediction for reliable and robust process

design

No rework/ repair No rejection Significantly reduced post-processing

Robust process window

Online Process Monitoring for immediate and reliable

information of complete part

In-Situ Evaluation

of composite

quality as-built

In-Situ Process Adjustment

by fast

optimization

In-situ (re-) qualification

measures Part rejection

Figure 4: Probabilistic Process Prediction Module

composite curing and final part distortion. Building on the new continuous simulation chain, a throughout transfer of the determining distributions of process and material parameters is enabled instead of isolated applications. Moreover, these simulation methods are enhanced for robust prediction of process behaviour. To this, the determining process constraints and inevitable process tolerances (e.g. fabric thickness, gaps, temperature distribution) are integrated by probabilistic methods and the influence on the resulting composite properties is evaluated by detailed sensitivity and reliability analyses. It shall be highlighted, that not only process parameters are considered, but the quality of the virtually manufactured composite is evaluated in order to assess new processing strategies.Particular sensitive parameters can be identified and a reliable process window can be predicted for fast process ramp-up without extensive manufacturing trials and tooling modification. In order to increase simulation speed more efficient surrogate models (analytical approximation functions) are derived to predict the resulting composite properties with respect to inevitable process variations. Based on the required accuracy the most efficient models are selected and implemented into the process chain for process optimization taking into account process reliability.

Online Process Monitoring Module

During production phase, an innovative Online Process Monitoring is developed in order to capture all prior identified sensitive process and material properties, which are determining the composite quality and defects during preforming, infusion and curing processes. Most important are: spatial fibre orientation, curvature, thickness, gaps, foreign objects, composite temperature, heat flow, resin flow front, resin gelation, glass transition or degree of cure. Although some can already be captured with current industrial measurement systems (e.g. temperature, flow front), the measurement of further determining parameters (e.g. fibre orientation of highly curved parts) has to be enhanced also for new material systems and tested for robust industrial use. This includes both, development of respective sensor hardware (e.g. new lightening concept with reduced reflections during fibre orientation measurement or more robust tooling-integrated curing sensors for volume production) as well as implementation of more reliable and more efficient algorithms for real-time analysis and post-processing of required properties from indirect measurements (e.g. deriving fibre architecture from grey scales or correlation of degree of cure with electrical resistance). To this, a pre-selection and dedicated training of the underlying data analysis methods (phenomenological needs and numerical efficiency) is performed and statistical analysis methods are exploited for increased reliability and efficiency. By on-line comparison of the measured and the numerically predicted data (from detailed process design phase), an early assessment of possible deviations can be accomplished. Imminent violations of process envelopes can be indicated and simulation models (from probabilistic process prediction) can be updated. Investigations are performed for a variety of process conditions and test samples related to the final industrial project

use-cases. Hereupon, specifications and guidelines will be derived for the required monitoring systems. The pilot implementation of monitoring systems will first be tested within laboratories in order to evaluate reliability of tracking the real process parameters and resulting component properties. Subsequently, the monitoring systems are tested within production environment to demonstrate scalability towards industrial needs.

In-Situ Evaluation Module

Figure 5: Online Process Monitoring Module

Due to very high sensitivities of various process parameters, violations of process tolerances can hardly be avoided within industrial settings. Yet, not all violations are affecting the final product quality by the same critical amount. Exemplarily, slight deviations of fibre orientation or lower fibre volume content might be critical within highly loaded complex areas of the composite part, but insignificant for low loaded areas of the same part. Therefore, an innovative In-Situ Evaluation of the affected composite quality (based on previously measured process parameters from Online Process Monitoring) is performed during production in case of violations. At first, a feedback of the measured as-built data (from Online Process Monitoring) into the structural model takes place, e.g. of fibre orientation, thickness or degree of cure. On this, enhanced tools are developed to automatically analyse the hereby effected structural material properties (e.g. reduced stiffness from deviating fibre orientation) as well as to map the complex 3D-field data onto the respective structural simulation models. Subsequently, an automated as-built analysis is performed for the real composite properties, and the resulting composite quality is evaluated (e.g. load bearing capacity) with respect to the occurring manufacturing deviations. In order to meet the required speed of in-situ analysis and evaluation, a new approach is followed. Before manufacturing, numerical and semi-analytical sensitivity analyses are performed in order to derive response functions of the composite properties with respect to underlying process deviations. Further, these derived response functions are implemented into a new post-processing routine, which is applied on as-built structural models. Thus, a breakthrough method and tool is provided for evaluating structural

performance and composite quality instead of running time-consuming analyses of high-resolution finite element models. Concluding, the proposed method of In-Situ Evaluation is based on a new comprehensive approach, which integrates online measured process deviations and beyond, immediately evaluates the resulting composite quality by new efficient methods, which are suitable for in-situ application. Within industrial use, this evaluation will lead to an in-situ decision whether corrective actions are necessary or not. In the best case, the particular investigated effect may be locally negligible, and the production can be continued without costly stopping of the process.

In-Situ Process Adjustment Module

Nominal Design CAE-Model without manufacturing

aspects

FPM- or CAD-Model providing manufactured fibre

alignment

Multiscale Analysis providing effective material

properties

1. As-Built CAE-Model including

effective material properties + fibre orientation

Manufactured sample FPM Data Nominal Design Local Global

FImax=0.96

FImax=0.37

Feedback CAE model including fibre information

Figure 6: In-Situ Evaluation Module

If the required composite quality is not ensured, automatic process correction measures are provided during production by the In-Situ Process Adjustment module. This will replace current procedures of continuing subsequent process steps as initially planned and eventually allocating very high effort for later rework/ repair activities such as grinding and post-curing of porous areas or if the case may be even rejecting the failed product (after completing costly production). The main challenges of the new Process Adjustment arise from the required in-situ decision making capability. Thus, previously developed surrogate models (from Probabilistic Process Prediction and In-Situ Evaluation modules) are exploited to described structural response as a function of varying process parameters much faster than finite-element-based process simulations. Moreover, they can be integrated into more efficient global optimization procedures. Their robustness and accuracy are

investigated by detailed studies within the required parameter space to ensure reliable application. Depending on the respective process step, optimization time is expected within few minutes in order to determine adjusted process parameters. Exemplarily, fibre orientations of next plies are adjusted in order to balance current deviations and to compensate defects. Within a further example, temperatures of time-lagging large part production are controlled within an early process state in order to prevent from later overshooting with related material degradation. These measures lead to a significant reduction of waste of material and energy while ensuring the required part quality.

In addition to the above mentioned benefits, the developed ECOMISE Manufacturing System integrates major quality assurance aspects at the earliest (in-situ) process stage. For this reason, subsequent non-destructive inspection/testing tasks (NDI/NDT) for quality assurance, such as time consuming ultrasonic testing, are reduced for certain applications. Furthermore, rework/repair tasks, such as subsequent trimming of edges, grinding of

porous areas and post-curing can be prevented. Due to the predictive evaluation of final geometrical shape of the composite and continuous process adjustments, assembly tolerances are met with much higher precision. Therefore, costly joining and assembly tasks will be considerably simplified by minimizing non-added value post-processing, such as manual shimming or grinding.

1.1.3 Scientific & technological objectives The current state of composite manufacturing is limited to conservative restriction. For example expensive pre-impregnated fabrics are used to reduce fibre misalignment and to eliminate problems during injection. The application of cheaper dry fibre materials within injection processes is commonly associated with a loss of accuracy. Hence, inevitable process tolerances are occurring during manufacturing and therefore have to be paid attention to. Within the top part of Table 1 typical process tolerances are listed for the main process steps of fabric layup, resin injection and curing. Depending on the respective environment, the degree of automation, specific part geometry and selected process parameters these tolerances lead to several defects within the composite structures, such as gaps, overlaps, folds, pores, dry spots, cracks, delamination, residual stresses and distortions (cf. middle part of Table 1).

The product of ECOMISE is a new Manufacturing System, by which the following cost savings are assessed for the different production phases by increased robustness (less waste, rework and rejection) and reduced process time (less energy, higher volume): 5-10% during fabric layup, 5-15% during infiltration and up to 40% during curing (cf. bottom part of

t

T

Figure 7: In-Situ Process Adjustment Module

Knowledge-based process paramter optimization

Layup

adjustment

Layup

deviation

exothermic

overshoot

Temperature

adjustment

Comentario [WT1]: Hier Krzungspotenzial und auf 1.2 verweisen. Jeweils Bezug auf Table 1

herstellen

Table 1). Within the ECOMISE Manufacturing System four innovative technology modules are developed and integrated, resulting in the following technological and scientific objectives:

Po

ten

tia

l c

os

t

sav

ing

s 5-10% by increased

process robustness,

5-10% by reduced process

time

10-15% by increased process robustness

5-10% by reduced process

time

5-20% by increased process robustness

10-40% by reduced process

time

Table 1: Typical process tolerances and resulting structural defects of composites.

1) Probabilistic Process Prediction Module: New simulation techniques are investigated and software is developed by research institutes and software provider. It will be provided for Industry and SME end users in order to predict the process behaviour by advanced simulation methods, which also make use of reliability analysis to account for statistical process variations.

- Enhanced investigation of material behaviour and implementation of advanced material models to capture viscoelastic material behaviour of resin and composite

- Investigation of process boundaries conditions with respect to their effect on the resulting composite properties

- Derivation of probabilistic process simulation methods/ models to account for tolerances; derivation of simulation guideline and (pre-normative) data format,

- Implementation of probabilistic analysis framework to account for uncertainties/ parameter variations during process simulation

2) Online Process Monitoring Module: Advanced sensor system hardware and data acquisition/ analysis software are developed by research institute and sensor system

Pro

ce

ss

ste

ps

Fabric layup

Resin infiltration

Curing

Pro

ce

ss

tole

ran

ce

s

- Fibre orientation

- Waviness, undulation

- Fibre gaps

- Overlapping

- Shearing of fabric

- Foreign objects

- Pressure

- Resin and tool temperature

- Cavity size and shape

- Permeability

- Resin viscosity

- Air entrapments

- Temperature distribution

- Exothermic reaction

- Degree of cure distribution

- Glass transition

- Chemical shrinkage

- Thermal expansion

Ma

nu

fac

turi

ng

de

fec

ts

folds pores distortions

variation of degree of cure

cracks, delamination

fibre volume variation

residual stresses foreign objects

undulation, shearing, kinks

resin rich or dry areas

gaps, overlaps

provider (SME). They will be provided for Industry and SME end users for monitoring preforming, injection and curing processes.

- Development of new process monitoring strategies as well as required measurement systems for preforming (containing lightening, camera and computation hardware devices) and flow front/ curing (electrical resistivity sensor hardware)

- Development of new analysis methods and software implementation for real-time evaluation of monitored properties with required resolution and reliability for preforming (fibre angles, curvatures, thickness, gaps, overlaps as well as foreign objects) and infiltration/ curing (degree-of-cure, glass transition temperature, shrinkage or stiffness changes)

3) In-Situ Evaluation Module: Advanced software is developed and implemented by research institutes and simulation software provider. This software for real-time evaluation of the composite quality (structural behavior depending on the real as-built composite properties) makes use of online process measurement data. Advanced as-built feedback methods, efficient evaluation strategies and new corresponding evaluation criteria are developed and implemented for Industry and SME end users.

- Development of advanced as-built feedback method as well as implementation of missing software and CAD-CAE-CAM interfaces to map measured or simulated data onto different (3D/2D) structural analysis models

- Development of an in-situ process evaluation method and automated as-built analysis software to verify the structural properties during manufacturing with respect to inevitable process tolerances

- Investigation of advanced surrogate models to increase efficiency for in-situ capability

4) In-Situ Process Adjustment Module: New software is developed and implemented for in-situ prediction of process adjustment measures. Feedback loop is closed to manufacturing facility (especially placement machine, heating device)

- Advanced process adjustment/optimization strategy implemented into framework and tailored for robust industrial use

- Development and verification of surrogate models for efficient in-situ adjustment capability of subsequently required process parameters to rebuild composite quality by fast on-time optimization

- Development of automated decision support and process correction measures/ machine control

5) Manufacturing System Integration:

- Enhancement of promising manufacturing methods and guideline definition (dry fibre placement) to increase flexibility (adaptive preforming speed close to accuracy limits) to apply new materials like dry fibre and fast curing resin systems

- Detailed definition of the ECOMISE Manufacturing System with respect to different product types of volume, complex and large parts (guideline, patent) and integration of the four modules (hardware and software installation)

- Installation and programming of robots for guided online process monitoring and for automated process adjustment

- Validation of the newly developed methods on coupon and small component level; industrial testing and demonstration by three use-cases: 1) Car Suspension, 2) Aeronautic Wing Cover, 3) Ship Propeller (cf. detailed explanation in chapter 1.1.4)

1.1.4 Validation and demonstration of ECOMISE The ECOMISE Manufacturing System is especially developed for high performance fibre reinforced composites in order to significantly improve production efficiency and product performance without cost increase, decrease raw materials and energy consumption as well

as reduce waste and emission. As explained in the previous chapters a holistic approach is followed by adding four innovative technology modules to current manufacturing plants. In this way, several composite manufacturing processes can be addressed, whereas the project focus is laid upon dry preforming with subsequent infiltration and curing processes.

In order to prove validity, to evaluate efficiency and to demonstrate applicability of the new ECOMISE System three industrial relevant use-cases are chosen, which represent three different types of application: Use-Case 1: Car Suspension (Volume part), Use-Case 2: Aeronautic Wing Cover (Large part), Use-Case 3: Ship Propeller (Complex part).

For all three use-cases, the ECOMISE System (including the four technology modules containing monitoring hardware and analysis/evaluation/optimization software) is integrated likewise at the respective end-users plant of Hutchinson, Bombardier and Airborne. As can be seen from Table 2 different combinations of preforming, infiltration and consolidation processes are applied to assess generality: Manual layup + Resin Transfer Moulding (RTM), Advanced Fibre Placement (AFP) + Resin Transfer Injection (RTI), Automated Pick&Place + Resin Transfer Moulding (RTM).

By manufacturing 10 car suspensions, 2 wing covers and 3 ship propellers the overall requirements are assessed by following measures: Time and cost savings, Material and energy/ CO2/ NOx savings, Process robustness and reliability, Accuracy and product quality, Industrial applicability. A more detailed description of the use-cases is given in the subsequent sections.

Volume part Large part Complex and thick part

Use case 1:Car Suspension

Use case 2: Wing Cover

Use case 3:Ship Propeller

Hutchinson (IND) Bombardier (IND) Airborne (SME)

Layup + RTM process AFP + RTI process Pick&Place + RTM process

10 pieces 2 pieces 3 pieces

Metal inserts, bonding, rubber Co-Bonding Metal inserts

Overall requirements for all three use cases

- High structural quality

- High process reliability

- Minimum waste (material and energy)

- Low geometrical tolerance

- High process robustness

- Minimum process costs

Table 2: Use case Cases for Validation and Demonstration of ECOMISE.

Use case 3: Ship Propeller (Airborne)

The use case of Airborne is on multi-material composite ship propellers for a navy ship with 2.5m diameter. These blades are a solid laminate, made of glass and carbon fabric laminates with metal inserts for load introduction. The main design drivers are stiffness of the blade (any deviation can have an effect on hydro-dynamic performance) and strength at the root, at the connection to the metal hub. Since the blades are currently made with the RTM process with manual preforming the following improvements are investigated within this project.

Towards automation of preforming by pick&place, the ECOMISE system will be used to measure the distortions (image analysis) and feed that back to the placement software. Laser measurement will be used to on-line detect the edge of a ply, and in-situ adjust the control of the robot to place the ply directly next to the previous ply. By transferring measured

0,4m 4,5m 2,5m

fibre orientations and alignments into the structural analysis, a prediction e.g. the final stiffness is enabled during production (before injection and curing). If the predicted stiffness is out-of-spec, the dry preform can either be modified before injection, or the preform can be scrapped before injection and curing instead of afterwards, which saves a lot of material and energy. Improved injection simulation methods for thick-walled laminates will be developed that include through-thickness flow prediction, and can differentiate between fabric and UD based laminates. Flow-front and degree-of-cure sensors will be used to optimise the injection and curing strategy, and actively monitor and steer the process in production. Simulation tools will be developed to predict residual stress, especially for the highly-loaded thick-walled part at the root of the blade. Moreover, faster curing resin systems are investigated to reduce process time and energy. Since current practice requires individual specific propeller design for each ship the ECOMISE System is expected to significantly reduce the development effort and time as well as related energy consumption by ECOMISE. Finally, the improved engineering process is evaluated.