A multiscale flexoelectric theory and a new method for real-time detection of microcracks in dielectric materials
Duration: 01. 10. 2018 – 30. 09. 2021
Teamleader: J. Sladek
Team members: V. Sladek, M. Repka, L. Sator, M. Vrabec
Scientific base of the structural health monitoring (SHM) systems should be developed to prevent catastrophic failure of structures, decrease maintenance cost and guide construction. The SHM is especially important for high performance structures, where failure would lead to disasters. It requires a real-time monitoring of micro-cracks in structures. Usually piezoelectric materials are utilized in SHM as sensors. Conventional piezoelectric materials contain toxic lead and they have lower thermal stability. Therefore, the goal of the project is to design lead-free piezoelectric metamaterials with a functionality and piezoelectric response comparable to those of lead-oxide based piezoelectrics. While the piezoelectric property is non-zero only for select materials (noncentrosymmetric),the flexoelectricity is in principle non-zero for all materials. Flexoelectricity is a phenomenon widely existing in all dielectric materials. It couples the strain gradient developed in a dielectric material with its polarization. To utilize the flexoelectric effect the strain gradients have to be large and they are generated easily only at the nanoscale. A reliable computational method based on gradient theory has to be developed. Both material parameters higher order elastic and flexoelectric coefficients are determined on the base of atomistic model. The governing equations with the corresponding boundary conditions are derived from the variational principle. The FEM formulation is developed from the governing equations of gradient theory. The C1-continuous elements are applied to guarantee the continuity of variables and their derivatives in the element boundaries. Experimental methods are applied to verify new theoretical and computational approaches in flexoelectricity.