Design and numerical simulation of an optic fibre sensor for damage assessment of structures

The paper presents the design of a new optic fibre sensor that simultaneously measures normal deformation, cross-sectional deformation and temperature with the minimum number of sensible elements. It is based on two assembled in phase quadrature traditional Fabry-Perot sensors. Lightness and the extreme compactness make the proposed sensor suitable to equipe composite materials with low specific weight and various percentage in fibre volume, that it can be used for aeronautical and/or automotive applications without modifying mechanical characteristics. The example host material is Ti-6Al-4V/SiC composite characterized with the volume fraction of carbon fibres of 35%; it permits to insert the sensor at low temperature by means of Cold-Gas Spray technology. Sensor construction is quite easy and does not require great economical effort in comparison with other types of optic fibre sensors reported in literature. The sensor has the capability of independently measuring the thermal and mechanical (bending and traction) loads. It has a great sensibility indeed it allows evaluating mu m displacements and bending angle of the order of one hundredth of degree, operating in a temperature range between -190 degrees C and 750 degrees C. The paper concludes with the description of the mathematical model of the proposed sensor and with the correspondent numerical characterization in order to estimate sensor capabilities. Numerical simulation points out the potentials of the new proposed sensor.