Large-scale high-rate automated composite deposition

An integral part to delivering the next generation of environmentally friendly, sustainable aircraft is to accelerate the use of composite materials, especially for large-scale aerostructures such as wing skins and fuselage sections. Novel manufacturing techniques are required to provide a step change in capability and enable composite structures to achieve cost parity with the equivalent metallic structures.
Current automated manufacturing techniques, such as automated fibre placement (AFP) and automated tape laying (ATL), which revolutionised the manufacture of composite aerostructures over the past two decades, are limited by their relatively low deposition rates. When working with large scale parts that require high-volume production, they must be compensated with more machines. As a consequence, it requires additional costs with the associated investment in real estate, energy and manpower, rendering it uneconomical for this purpose.

New deposition method set to revolutionis

A new method for the lay-up of large-scale parts, which has been steadily gaining interest across major aerospace manufacturers, moves away from depositing a series of tows or tapes. Instead, it involves depositing complete plies in one pass. This manufacturing technique has the potential to deposit in excess of 200 kilogrammes of material per hour. Manufacturers who have the capability to handle and manipulate larger plies will be able to reduce the total number of plies required for a panel, and therefore the time required to lay up a preform. For example, a wing skin that currently requires over 100,000 individual tows or tapes is cut down to 150 with complete ply deposition.
On top of this, moving towards high-volume capability has the potential to consume 40% less energy, in 30% of the space required and at a 50% reduced cost when compared to other systems, such as AFP processes that are only capable of depositing in the region of 20 kg of material per hour.

Introducing FibreFORM®

One such machine providing this capability is Loop Technology’s FibreFORM®, a conformal pick-and-place end effector that can be deployed on a robot or gantry system (see Figure 1). The machine can pick up large pieces of pre-cut fabric, manipulate it into a 3D shape to match the surface of the mould, then lay it down and repeat the process with highly repeatable accuracy.
The system is based on a series of splines running across the width of the unit (see Figure 2). 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 rate. Splines can be manipulated independently of their neighbours in order to achieve a double-curvature surface. This allows FibreFORM to control the material’s shear behaviour in the system in a deterministic manner, thereby achieving a very repeatable lay-up process. Designed to handle prepreg and dry fibre, the individually-controlled lifting elements enable FibreFORM to pick and place a wide variety of ply sizes and shapes, including irregular sections and cut-outs. The system can be built to handle ply sizes up to 2m wide and for lengths from 0.4m up to 20m, or even longer. It also includes integrated vision systems to facilitate high-accuracy ply location. The high-accuracy system does not rely on path tracking accuracy, and is extremely tolerant of ply and surface geometry.

Unveiling the latest innovation

The latest iteration was recently unveiled at The Farnborough International Airshow (see Figure 3). The company were invited to exhibit alongside leading global manufacturer of factory automation FANUC, who are committed to exploring the niche solutions in composite manufacturing that Loop Technology provide.
As with all manufacturing techniques, there sysare advantages and disadvantages. One of the challenges with FibreFORM is that the machine must be as long and as wide as the largest ply, and it can consume a fair amount of energy during the process.
Dry fibre often requires a high airflow rate to generate lift when handling materials. Depending on material properties, this can be expensive to run. These challenges are being addressed as part of Loop Technology’s composite automation development programme to improve the accessibility of the technology, including into other industries such as renewable energy.

The new design unveiled at the airshow, compared to the previous iteration of Fibre-FORM, includes:
– Lighter construction to allow the machine to be deployed on smaller robotic systems
– Reduction to the overall profile while achieving the same pick area, shapes, and geometries
– Redesign of the lifting elements to provide a step-change reduction in energy consumption

Process development and evaluation

The benefits from investing in this type of process are clear, but involve an initial investment to first procure the equipment and then for in-process development. To diminish this barrier, Loop Technology invested in a £2.4 million demonstrator: the ADvanced Automated Preforming Technology (ADAPT) cell. It will enable the company to provide in-person demonstrations of the capabilities, and to perform evaluation studies for manufacturers to study different materials and preform shapes.
The ADAPT cell, including the new design of FibreFORM, is one of many work packages under ASCEND (Aerospace and Automotive Supply Chain Enabled Development), a UK industry consortium that aims to accelerate the development of composite material and process technologies for the next generation of energy-efficient aircraft and future mobility. It will also include equipment for ply cutting and trimming, preform stabilisation, and another ply deposition tool, Fibre-ROLL, which is designed to handle long, simple ply shapes.

This article has been published in the JEC Composites Magazine N°148.

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