High precision
composite panels

TRB Lightweight Structures has successfully developed composite solar panel substrates for the aerospace industry. The carbon fibre panels with an aluminium honeycomb core structure provide an extremely lightweight and durable substrate to bond solar panels to satellites. For this project, TRB engineered a tooling-based manufacturing system that could guarantee the quality of each panel to meet the high specification requirements of satellite applications. 

Key facts

• Lightweight, durable, high-level flatness tolerance
• Carbon fibre composite with aluminium core
• High precision
• Reduced outgassing

Challenge

Space provides a unique set of environmental conditions that only a few materials can endure. Satellite structures need to fulfil stringent criteria to be safely placed into orbit, including high flatness tolerances to prevent cracks and damage, lightweight designs to avoid adding parasitic weight, and limited outgassing to withstand extreme pressures. TRB was approached by an aerospace research team to manufacture uniformly flat, high-strength and lightweight composite panels over a perforated aluminium core, to act as a substrate for the mounting of photovoltaic cells. 

An additional challenge for this project was the precise placement of metal inserts within the composite panel. Typically, these are added during manufacture, then drilled and tapped to allow threaded fasteners to be used. However, it is difficult to consistently achieve stringent positional tolerances with combined carbon fibre and metallic manufacture, due to the differing coefficient thermal expansion (CTE) of the materials. Devising a suitable manufacturing method that would produce consistently flat panels, with a standardised positioning of aluminium inserts, was crucial to the success of this project.

Solution

Tooling was at the heart of this challenge, and TRB developed a unique approach that allows the CTE of the tool to be matched to that of the end product. This custom-made mould tool guarantees the perfect positioning of metal inserts every time, and was combined with a specialized jig that could reliably produce uniform panels to achieve consistent manufacturing. 

The panels were manufactured from high specification carbon fibre and adhesives to reduce outgassing and provide an efficient weight-saving strategy, while the aluminium honeycomb core was perforated to allow the transition of gasses through the panel, reducing pressure differentials. A capped-on coating was then applied to each side of the panel using the bespoke jig design, providing the perfect surface for solar panel attachment. Following manufacture, each panel was thoroughly inspected by the team using a Faroarm® and laser metrology tool to certify the flatness and ensure the highest quality. 

Outcome

Following production and acceptance of the prototype, TRB successfully manufactured 20 additional solar array substrates using this novel production method, which were all accepted by the customer, who was very happy with the result. Since then, the same tooling concept has been applied to other aerospace projects, providing the same reliable outcome every time, giving customers confidence in this approach for the production of reproducible, high quality products.