Monitoring

FREEFORM CONSTRUCTION STRUCTURAL MONITORING

Embedding Active and Passive fibres within Adaptive Metal Structure by Ultrasonic Consolidation

Phill Dickens, Choon Yen Kong, Rupert Soar

Loughborough University IMCRC, EPSRC, MoD/DSTL, Solidica Inc, North West Aerospace Alliance

BACKGROUND

Freeform Construction will allow ‘nervous systems’ to be integrated within a building as it is ‘printed’ by embedding fibre optic sensing systems and actuator mechanisms. The building will ‘feel’ its environment and respond to changes, such as wind shear for example, to maintain integrity and notify where limits are exceeded or where failure occurs in the system. This is the concept of emerging engineering materials, known as Adaptive or ‘Smart’ Structures. This will go beyond integrated wiring and actuators systems to include embedded fibre-optic mesh structures throughout the building to ‘pipe’ natural light from receivers on the roof and project the world outside to the rooms inside, potentially removing the requirement for windows. The same systems will allow the images and optical data streams to be projected into each room through thousands of tiny fibre ends protruding into the room to represent each pixel of the image.

OBJECTIVES

Ultrasonic Consolidation (UC) is a novel technique which allows thermally sensitive shape memory alloy (SMA) actuators and damage intolerant optical fibre sensors to be embedded within, and on, metal structures using high frequency, low amplitude, mechanical vibrations. Ultrasonic Consolidation is a solid-state, fabrication technique possessing little pre-processing of material, fast bonding times, multiple material combinations, low process temperatures (at typically 25-50% of the melting temperature of the base metal) and low pressures.

The Ultrasonic Consolidation technology is being developed as an in-situ ‘direct writing’ process for advanced metal structures, capable of depositing functional fibres. The current work is being applied to a range of aerospace applications but will equally be applicable to construction applications such as:

Structural health monitoring - Optical fibre sensors are attracting considerable attention. When surface mounted or embedded within structures, the sensors give the structures capabilities which would be very difficult to achieve by other means, including continuous assessment of damage processes, the ability to determine performance relative to the design, or the ability to provide real-time data for feedback and control. Structural health monitoring involves the use of strain, temperature, vibration and chemical sensors to infer integrity of the structure.

Self-healing/control structures - SMA fibres, representing active fibres, are flexible and have a high damping capacity. They are currently being exploited for the development of adaptive or smart structures with control, healing or adaptation properties. The use of active control systems is a promising approach to minimize structural damage to buildings and other structures due to dynamic loadings such as earthquake and wind vibrations.

Wireless communications (WiFi) – Micro-electromechanical systems (MEMS) with built-in wireless modules can be embedded within structures. Wireless networks in the home also means music, video and pictures to be "beamed" from one room to the other, and films and TV programmes played on any screen in the house without wires. Embedded MEMS may serve as a mobile phone masts (signal station) for the local area.

Security systems - Embedded systems will run through the building to feed data from one device (e.g. MEMS) to others. Embedded ‘network’ systems will work in the same way as current ‘smart home’ security and entertainment systems, which will be laid into the building as it is built.

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