5-2001  It's so simple

'Jigsaw' approach to repairable honeycomb

Problem: Honeycomb structures have proved their worth in a multitude of different applications.

Its combination of strength, rigidity and weight make it ideal for a number of structural applications where weight, specifically, is a major part of the design brief. Modern advances have given engineers the ability to modify the shape of the material from plain sheets to complex curves which follow the contours of the design.

Unlike other materials commonly used is structural application, honeycomb can be difficult to repair. Repair is possible, but imparting any repaired region with the original mechanical properties can be hard.

Solution: TWI has developed a new form of material called Ex-Struct. Similar in principal to existing honeycomb sandwich structures, Ex-Struct exhibits one important difference – the individual cells can be slotted together using an approach analogous to a jigsaw puzzle's lugs and holes.

honey 1.jpg (18753 bytes)honey 2.jpg (17085 bytes)

The design of the projections and slots can be varied to take into account the demands of the specific application such as load paths and impact resistance. Once assembled the structure can then have a 'skin' added by stake welding using lasers which will penetrate the skin and the material immediately below. Individual panels can also be linked, using the same projection and slot system, to create a larger area.

In the event of damage, individual panels can be replaced or, if the damage is more localised, the skin can be removed from the area and individual cells can be replaced.

Applications: TWI suggests a number of applications for this material concept. They include lightweight car decking for ships, bridge construction, interchangeable armour, railway carriages and heavy duty flooring for cargo aircraft.

The properties of honeycomb make it a viable material in a multitude of other applications. Where damage, and the repair of damage, is a real concern Ex-Struct could come into its own.  MF

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