Periodic Reporting for period 2 - COMBUSS (Composite tooling for business jet lower wing stiffened panel manufacturing)
Reporting period: 2020-01-01 to 2020-12-31
For the COMBUSS project the major objective for the first reporting period (P1) was to design a prototype tooling system to produce the composite stiffened panel of the lower wing of a business jet. The design was on M9 of the project after a Critical Design Review (CDR) in collaboration with the TM. The tooling features the following key characteristics:
a. Full functionality for the processing in fewer steps of the integrated stiffened panel design.
b. Lightweight with long service life and flexibility.
c. Built-in quality assurance tools to guarantee reliable processing of the selected material systems according to technical specifications.
d. Tooling documentation for accurate dimensioning, modification protocols and health check during the tool service life.
In order to materialize this outcome, the COMBUSS Consortium has introduced, adapted and validated a set of innovative technologies covering materials, sensors, models, tools and devices. All these technologies will be physically integrated on the prototype tooling, which will acquire the required qualities in manufacturing.
Eventually, COMBUSS aims to develop and demonstrate an innovative tooling configuration for the manufacturing of all components of a composite stiffened panel, while considering sustainable production with integration of innovative modelling, monitoring, and optimization and control systems.
The project has completed the “Tool design phase”: In the first two technical WPs (WP2 & WP3) the tool design, including all components (heat/cool systems), thermal management, process monitoring, and positioning of inlet/outlet ports has been finalized through a number of iterations.
The concept of the COMBUSS manufacturing system is the use of robust self-heated composite tools for preforming, injection and cure of the stiffened panel components. The composite tools are designed for long life and effectively integrate temperature and material property sensing elements with the view to facilitate control system for low cost, energy efficient and quality assured production of the composite stiffened panels. The main concept of the COMBUSS manufacturing system is the use of robust self-heated composite tools for preforming, injection and cure of the stiffened panel components. COMBUSS concept is depicted in Figure 1. Figure 2 shows the CATIA model of the closed mould for the manufacturing of the stiffened panel and Figure 3 shows the early stages of master mould fabrication.
After the TM’s approval of the design, the tool is being fabricated, will be checked for conformance with the specification and eventually transported to the TM premises and commissioned. The partners will provide full documentation on the tooling system and its use and will support the TM with the demonstrator fabrication.
In Reporting Period 2 The composite tool production and delivery phases have been completed.
In WP4 the tool manufacturing was completed accounting for all components and automation systems (heating, monitoring) and in WP5 the tool was verified in terms of geometrical fidelity and overall functionality and tested in representative manufacturing conditions. The manufacturing of the tool started with the production of the positive tool (Figure 4), the curing of the composite tool and the subsequent additional of the thermal management components (Figure 5 and Figure 6). In WP5 the performance of the tool was assessed in a number of test runs. Dimensional tolerances, tool surface evaluation and optimization for production has been part of the performance assessment. A life cycle analysis and an estimation of energy savings in the expected life of the tool has been conducted as well.
The tool was delivered to the Topic Manager site as part of WP6 activity. Commissioning and technical training (OMI and TWI) as well as and follow up activities with the Topic Manager have been performed via virtual meetings and remote sessions due to COVID 19 pandemic. The pandemic impacted COMBUSS project, mainly by inflicting delays in time schedule and inhibiting face to face meetings. The duration of the project had to be prolonged and deliverables and milestones rescheduled but despite that COMBUSS consortium was able to deliver the originally envisaged capabilities (Figure 7).
In COMBUSS certain challenges have been addressed as far as the innovative tooling is concerned. The self-heating capability was combined with the requirement of long service life of the RTM tooling. The development of the innovative tool has the following characteristics:
• A precise temperature control system is employed that allows for very close following of the optimal temperature profile throughout the part curing. Up to eleven independent heating zones can be utilized.
• The electrical system is able to heat the part safely at 180°C. The heating elements can be readily incorporated in the composite structure and tested to 220oC.
• The heating elements support possible autoclave post-curing of the tool up to 220°C and max 7 bar.
• The use of in-process sensors for the continuous measurement of material properties in the part. This allows rapid adjustment of energy balance in the tooling and on-line quality control of the produced aeronautical composite structures.
• Integration with state-of-the-art process optimization algorithms to establish an eco-efficient curing system.
Currently, one of the major cost items of fiber reinforced composite production is curing. The energy required is very high and can make up close to 50% of the total embedded energy of the final product. Hence, methodologies that reduce the required energy will provide a major opportunity for cost reduction that can lead to:
• Increased appeal of fiber reinforced composites through lower cost
• Reduction of embedded carbon footprint, and
• Improved product quality
COMBUSS is promoting the use of a self-heated fully controlled processing tool that will minimize the required energy budget and offer unparallel quality assurance. In terms of energy savings, payback period of the proposed processing method can be much shorter when compared with conventional oven or autoclave.