The inaugural International Composites Summit (ICS) was held in London on the 8th and 9th of September 2021. Loop Technology were invited to speak at the Open Forum for the ‘Innovation in Composites: New Technologies and Materials’ session. Alun Reece, Managing Director of Loop Technology, presented on the topic: ‘High Rate Composite Deposition for Large Scale Aerostructures’. It highlighted two automated technologies that provide high-rate alternatives to automated fibre placement (AFP) and automated tape laying (ATL) to meet the growing demand for large aerostructures.
Alun began with a brief overview of the industry challenge driven by future single aisle aircraft programmes. With target outputs of up to 100 shipsets/month, it requires 200kg/hr of material deposition for components such as wing skins. He went on to explain how this is difficult to do using existing technologies which includes hand layup, AFP and ATL. These struggle to keep up with their low deposition rates (up to 20kg/hr) which can only produce 11 shipsets/month. To compensate, more machines are required which would result in additional costs with the associated investment, real estate, energy and manpower. It is clear a novel approach is required for large scale structures.
This was followed on by Alun describing the proposed approach which moves away from AFP/ATL to wide format materials. Instead of depositing a series of tows or tapes, complete plies can be deposited in one pass with two new methods: a conformal pick and place end effector, and a roller-based end effector. The technology introduces the capability to deposit up to 200kg/hr of material.
The end effectors can be deployed on either a gantry or robot, based on the application, and can be combined with a toolkit of peripheral equipment to support the preforming process. “Given the wide array of structures, we do not believe there is a one size fits all system, and consequently we don’t want to take the approach of some companies that offer a fixed solution with no room to optimise” Alun explained.
He likened the approach to an old-fashioned sweet shop, with the option to pick and mix. But instead of sweets, a customer can choose from a portfolio of modular and scalable equipment, designed explicitly for producing structures at a high rate.
The portfolio spans the entire preforming process, from rolls of material in, to preform out – with options for automated cutting, sorting, kitting, deposition, inspection, stabilisation and trimming. “All elements are important, but arguably, the crux of the solution lies in the ability to deposit material into moulds at a high rate and obviously to the right specification”.
He used the subsequent slides to explain how each deposition method works, illustrated each method with a video, and offered some ‘rule of thumb’ guidelines to bear in mind when considering to procure these types of systems. Alun explained that Loop Technology offer two seemingly competing methods but each prioritise different capabilities and have their own strengths and weaknesses.
The first method, the conformal pick and place end effector (FibreFORM shown in the video above) can pick plies from a cutting table, or material store, and form it into a 3D double curvature form before lowering it onto a mould tool.
The system is based on a series of splines running across the width of the unit. Mounted onto these are active lifting elements. Each spline is manipulated via a series of motors that allows the system to achieve a fifth order polynomial with a theoretical zero error. Splines can be manipulated independently of its neighbours in order to achieve a double curvature surface. This allows FibreFORM to control material sheer in the system in a deterministic manner, thereby achieving a very repeatable layup.
It is suitable for prepreg and dry fibre ply, and can handle irregular sections and cut outs with ease. The system can be built to handle ply sizes up to 2m wide and for lengths from 0.4m up to 20m. It also includes integrated vision systems to facilitate high accuracy ply location. The system is highly accurate, does not rely on the deployment system path accuracy, and is extremely tolerant of ply and surface geometry. However, the drawback is that FibreFORM must be as long and wide as the largest ply.
The second method, the roller-based end effector (FibreROLL shown in the video above), uses two rollers: a primary roller to control pickup and placement, and a secondary detachable roller used for material storage and for end control. It includes a number of integrated 2D and 3D vision systems to provide alignment, guidance and verification.
The system is available in widths from 0.5 to 5m, and can accommodate plys in excess of 20m. “This means a phenomenal amount of material can be deposited in one pass. For example, a multiaxial fabric with a gsm of 500 could result in 50kg of material deposited in a matter of minutes.” However, despite the clear benefits in terms of rate capability, it does have some drawbacks compared to conformal pick and place; the system is less tolerant of material types and ply geometry and it is less accurate overall due to minor movement during rolling. This accuracy degrades as a function of system width and surface curvature. It can also include an integrated ply stabilisation capability used to bond one layer to the next. This provides the potential for a ply to be deposited, inspected and tacked in a single pass.
After describing the two deposition methods, Alun reviewed the main benefits offered by the approach:
- A step change in rate deposition from 20kg/hr to 200kg/hr. He also noted there is a roadmap to raise this further still – for both end effector types.
- The ability to handle and manipulate larger plies to reduce the number of plies required for a part. For example, a wing which currently needs 100,000 pieces, is cut down to only 150.
- All tools are available with automatic tool changer interfaces allowing multiple end effector types to be deployed. Consequently, more structures can be manufactured in the same factory footprint with the same or fewer people. This drives the cost down significantly and is a big step in bringing the cost of composite structures closer to their metallic counterparts.
- The systems are modular and scalable and the flexible nature of the deployment stage allows for simple optimisation and expansion, or reconfiguration and change in the future.
To conclude the presentation, Alun reiterated the problem and solution: “The industry requires a way of manufacturing large structures at high rate and at a commercially acceptable cost. We believe the modular approach using wide format materials facilitates this.”
He ended with a summary of the two deposition methods presented and how to select between them: “Conformal pick and place provides the highest absolute accuracy, is highly tolerant of material characteristics and geometry and is consistent across a wide range of complex surface forms. If your application necessitates one or all of these attributes, we recommend conformal pick and place. If, however, the process can tolerate lower accuracy, the ply shapes are simple, and the surface curvature low, roller systems can offer an effective solution, with arguably, an even higher deposition capability.”