Fibre-Steering technology for advanced composite panels

Abstract

A Dutch company is specialized in design and manufacturing of advanced composite structures for aerospace, maritime and civil applications. One of their key technologies is ‘Fibre Steering’. Fibre Steering enables lightweight composite structures to be produced with a high resistance against vibration loads and buckling. Panels made with this process can be up to 30% lighter compared to conventional lay-ups, without loss of specific mechanical properties in the load case that is applied.

Description

In the space market, everything is dominated by weight. The costs to launch 100 kg into space are still very high; so all the components should be as light as possible. The company designs and produces ultra-lightweight composite structures, in accordance with the quality standards required by the space industry. One of their key technologies is ‘Fibre Steering’.

The most critical load case for a composite structure (e.g. a sandwich solar array panel) is the vibration load during the rocket launch. The natural frequency of the panel should therefore be high enough to survive these severe vibrations. The current state-of-the-art always uses straight fibre paths in the composite design, which leads to constant stiffness designs, but these are not weight optimised for this dominant load case. With FibreSteering and new processes such as automated fibre placement, curved fibre paths can be manufactured to create variable stiffness laminate designs.

Innovations and advantages of the offer

Fibre Steering allows us to distribute the stiffness over the panel in a smart way. Thus, the natural modes can be influenced and brought to higher levels. It has been shown that for a typical solar array panel, a 30% higher natural frequency can be achieved for the same weight of the panel.

Further Information

With a uniform (conventional) design the global layup is optimised to give the best response for a uniform layup. Patches and doublers are then applied in cases where local strengthening is required, as shown in Figure 1 below (left), but this increases mass, manufacturing complexity and cost. With fibre steering the designer optimises through controlling the load paths, such that the mechanical response can be tweaked as shown Figure 1 below (right). Panels with optimised fibre directions exhibit higher natural frequencies at equal weight compared to conventionally manufactured parts – or lower weight for identical frequency specifications.

The company has demonstrated and validated the Fibre Steering technology to TRL 3 (TRL = Technology Readiness Level) on a large solar array substrate sandwich panel, which was subjected to vibration testing. Changing the layup of the skin has optimized this fibre-steered platform panel, while core material and other structural parts were assumed to be fixed in the design. A fibre path formula with two variables was used to optimise this particular panel, which resulted in a first natural frequency that was over 44% above an equivalent conventional panel with straight fibre paths and the same mass.

Recently, the company has taken the previous study a step further and considered a stowed solar array wing. The wing consists of a stacked arrangement of 4 array panels and the mechanical behaviour (both in air and in vacuum) was modelled. As before, baseline (conventional) versus variable stiffness (fibre-steered) panels were considered. The results of the critical Eigenfrequency of the baseline and variable stiffness solar array wings are summarized in Table 1.

The technology can also be used for other composite structures that are critical to vibration or buckling, such as structural panels for satellites or high-speed machine components.

Application

The technology enables to design and manufacture parts like structural panels for satellites or high-speed machine components with a very high performance, enables innovative new designs and is a repeatable process to achieve a high and consistent quality.


Additionally the technology can be used to reduce weight of a structure when keeping the performance constant. In this way a weight reduction is possible for the same geometric design.

Comments on the technology by the broker

The company has developed the technology within their own R&D programme to increase the Technology Readiness Level. The current level amounts to TRL 4. Recently the company has acquired an ESA GSTP project to further develop the technology and increase the TRL.

Description of Space Heritage

The company has developed a solar panel to cope with the heaviest load case for panels: withstanding vibrations during launch. The Eigenfrequency (stiffness) of the panel is not allowed to be close to the frequencies generated by the launcher. Due to the increasing demand on power, solar panels tend to become larger and therefore the Eigenfrequency becomes more critical. Using Fibre Steering the Eigenfrequency of the panel was increased to a value that was 30% higher compared to a conventional ply lay-up product of the same weight. Therefore Fibre Steering has the potential to introduce breakthrough space applications.

Category
Mechanical Components
Reference No.
TDO0205
Could this technology benefit your business? Please contact Len van der Wal TNO Space (Netherlands)
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