SNSF project: Mechanical contact of skin and textiles: THz imaging of the interface
Irritations caused by the reaction of skin to textiles and other materials are a general concern in health care. Nevertheless, mechanical contact between the skin of patients and medical textiles and devices are inevitable or might be essential, e.g. for the monitoring of body functions through fabric sensors. Numerous factors influence the mechanical interaction, such as surface texture of skin and material or interfacial liquids. There is a lack in experimental investigations related to the in situ observation of the interface.
In this project we investigated the interaction of skin with textiles and reference material surfaces on different scales down to 50 μm lateral resolution and 10 μm height resolution appropriate for the hierarchical surface structure of the skin. Terahertz imaging is a promising technique, as it can directly access the skin-textile interface, even under contact pressure. While THz radiation penetrates relevant materials, it is reflected by the skin and partially absorbed by interfacial water. To attain the required spatial resolution we applied THz holography and developed synthetic aperture and ptychographic techniques to develop a high-resolution THz imaging set-up for assessing hidden material interfaces and to apply it to the interface between human skin and THz transparent textile materials during mechanical contact. The THz technique was developed beyond the state of the art, including reflection holography; procedures to separate surface topography of skin and textile and to identify water content; and synthetic aperture techniques based on multiple viewing angles.
The measurement of interfacial parameters, in particular of microscopic skin surface deformations and mechanical interactions with textiles as a function of interfacial moisture will improve the understanding of the mechanical behaviour of the skin and mean a major advancement in the physiological and medical field, e.g. by providing clues for optimising the surfaces of future smart textiles for health monitoring.
EU H2020 Clean Sky 2 Project DIMES
DIMES - Development of Integrated MEasurement Systems
The project aim is to develop advanced integrated testing methods that have the capability to detect a crack or delamination in a metallic or composite structure and have the potential to be deployed as part of an on-board structural health monitoring system for passenger aircraft. The project incorporates a new philosophy for monitoring damage in which the disturbance to the strain field in the structure caused by the damage is used to identify significant damage and to track its propagation. Recently, this approach has been demonstrated to be at least as effective in composite structures as traditional non-destructive evaluation techniques and, in Clean Sky2 project INSTRUCTIVE using infrared camera technology, it has been shown to be capable of identifying smaller cracks in metallic structures than any other available technique. These innovations are amalgamated with established techniques, such as strain gauges and fibre Bragg sensors. The objectives are designed to mature technologies from TRL 4 to 6 that are likely to have a disruptive impact on the structural health monitoring of next generation large passenger aircraft. The objectives are:
i) to develop a robust and innovative concept for integrating a diverse set of sensors and data acquisition systems for detecting and monitoring damage in an aircraft assembly;
ii) to produce an integrated system of sensors and data acquisition systems deployed on a test bench representing a centre fuselage section with integrated cabin and system elements, and;
iii) to conduct prototype demonstration and evaluation tests of the integrated system and test bench using independent systems.
The primary outcome is the demonstration, on a test bench consisting of an Airbus A320 wing section in a loadfing frame at Empa, of an integrated measurement system for ‘on-line’ detecting and monitoring damage, based on a diverse range of commercial off-the-shelf sensor systems.
EU H2020 Project MOTIVATE
MOTIVATE - Matrix Optimization for Testing by Interaction of Virtual And Test Environments
A significant step change is performed in the way virtual and test environments are used together in an industrial environment to reduce the cost, risks and time associated with product development. Enabling technologies, which have been demonstrated in laboratory conditions during a series of EU FP 5 and 7 projects, are transitioned into the industrial environment and demonstrated in a structural test on an aircraft subcomponent at Airbus UK, Filton.
Approaches to quantifying uncertainty in measurements of displacement and strain fields obtained using digital image correlation will be reviewed and a simple-to-use, robust methodology developed for use in industrial environments, with attention paid to the need to consider the entire measurement volume as well as within the same timescale as a structure test. In addition, recent advances in the validation of simulations, using image decomposition to compare predicted and measured data fields, will be incorporated into advanced structural test protocols taking account of uncertainties to provide statements on the extent to which the predictions represent reality, i.e. the validity of the simulations. Best practice guidelines will be developed to allow the test matrix to be optimised thus minimizing the cost and time required for tests while maximising the reliability and credibility of the simulations.
This research represents a significant and generic advance in the technologies and methodologies used to validate computational models of structures that will benefit a wide range of industrial sectors, including the aerospace industry where it will support the introduction of disruptive technologies, such as highly integrated structures, by enabling high fidelity simulations. A strong programme of exploitation and dissemination is proposed using traditional routes as well as digital shorts, webinars, and a blog as well as workshops linked to the revision of the prenormative
document published by CEN.