A composite material is defined as a material that is made of two or more different materials, combined to create a unique material with new characteristics, different from the starting components. Sensing of composites parts during manufacture and in-service is often limited due to the complexity and high cost of currently available technologies. A low-cost wireless solution suitable for integration into composites parts would open new opportunities for composites, allowing their benefits to be applied to new areas. The ability to use low-cost sensing techniques during manufacture, assembly processes and in-service could give many benefits such as device identification, tracking, and in-service part inspection.

The National Composites Centre (NCC), based in Bristol, UK, is part of the Government’s UK Composites Strategy, with a mission to accelerate the growth of UK industrial output by enabling design and manufacturing enterprises to deliver winning solutions in the application of composites. The NCC brings together dynamic companies and enterprising academics to develop new technologies for the design and rapid manufacture of high-quality composite materials products. The NCC has partnered with CPI to design and manufacture a low-cost, printed wireless sensor that can be used to monitor a composite part during manufacture and in-service.

The objectives

It is beneficial to monitor the performance of a material during manufacture and in service. To this end, a strain sensor that can monitor the physical response of a structure to an applied force is of critical importance to apply composite materials into new areas where performance sensing is compulsory.

The NCC is working with CPI to produce such an embedded strain sensor that can withstand composites processing, whilst maintaining the integrity of the printed electronics and advanced composites. This project will produce a proof-of-concept prototype that will show an embedded sensor within an advanced composite laminate that is suitable for both wireless and non-wireless power and communication.

The activities

CPI and the NCC have carried out a series of tests to ascertain the compatibility of printed electronics with advanced composite materials (glass and carbon composites). These tests have been carried out to find the best integration approach to print lightweight circuitry and easy-to-embed strain sensors that will be important in advanced polymer composites.

A strain sensor, printed on a flat, flexible polymeric film, will be embedded or integrated into an advanced composites structure that can demonstrate real-time structural health monitoring via a PC display interface, and also through wireless communication for data-based maintenance and specific life assessment of the composites infrastructure.

The outputs

Based on the results of the tests carried out during this study, CPI and NCC have determined a method suitable for embedding sensing electronics into composites parts. CPI has designed several printable strain sensors and has developed a system for testing these with composites for real-time structural health monitoring from a PC display, using data acquisition software. CPI has also designed, developed and is currently assembling a wireless communication method suitable for use with glass fibre composites. CPI is currently working with NCC to finalise a proposal for a follow-on project to tackle the challenges of wireless communication in carbon fibre composites, which are known to have challenges with wireless connectivity.

The outcome

The long-term vision for this project is to print a network of sensors directly onto a composite structure (or embedded into one), to introduce a “sensing ability??” for continuous health and usage monitoring to give extra safety features and responsiveness to composites structures. The design, development and implementation of printable electronics by CPI, combined with the design, process and advanced composites manufacturing capability of the NCC, have been brought together to create greater intrinsic learning for embedding and sensing in composites.

The ability to use low-cost sensing techniques during manufacture, assembly processes and in-service allows for the exploitation of composites in new areas. The outcome from this project will be a substantial reduction in part count and assembly complexity, as well as the creation of simple, low-cost methods to integrate structural health monitoring in composites structures.