For a long time, measuring structural changes within lightweight design components had only been possible to achieve through ultrasonic or tomographic processes. In many industrial areas but also in everyday life, intact structures often play a vital role: the early detection of hidden defects in airplane structures and automobile bodies or invisible defects in rotor blades of wind turbines is crucial in order to prevent a sudden failure of the components and serious accidents. Particularly carbon-fiber-reinforced plastic (CFRP) components with complex geometries and fiber layers make it difficult to predict strains and stresses inside of the components based on finite element methods. Moreover, such predictions are, depending on the actual strain of the component, rather vague.
Optical Fourier Domain Reflectometry enables to measure strain gradients and temperature changes underneath the surface by using optical fibers. Consequently, damages and strains within fiber-reinforced composites can be unveiled. Unlike traditional straingauges, fiber-optic measurement processes do not require a high amount of cabling since one single sensor fiber supports up to several million measuring points. The small diameter of optical fibers, which is similar to that of a human hair, enables the embedding of sensors in the material during production.
In structural health monitoring, fiber-optic sensors can be used for the early detection of interior and exterior damages of components. Measurements in different time lapses enable to obtain a solid understanding of the strains and signs of ageing under realtime conditions. Improved form geometries, target-oriented input and customized production processes on the basis of measured data will save material and costs, resulting in higher resource efficiency.
- Measurement of strain gradients
- Bending monitoring
- Evaluation of material behavior (relaxation, hysteresis)
- Monitoring of temperature and shrinkage characteristics in bonding processes