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This is some of the work that was carried out during my short post-doctoral stint at Prof. Roderick Melnik's group at Wilfrid Lautier University, Waterloo, Canada. This was part of a major collaborative project with the Department of Continuum mechanics at the University of Seville, Spain.
Our group built advanced models to describe non-linear and size-dependent electromechanical couplings in piezoelectric composites using which we explored the effect of various parameters such as polycrystallinity of piezo-inclusions, auxeticity of matrices, composite architectures conducive to flexoelectric enhancement, and so on.
Can polycrystalline piezoelectric inclusions be better than single crystals in piezoelectric composite design?
Can polycrystalline piezoelectric inclusions be better than single crystals in piezoelectric composite design?
Tuning the microcrystalline structure of piezoelectric crystals (e.g. BaTiO3) is known to improve their piezoelectric response, specially the e31 and e33 coefficients. However, in the context of polycrystalline inclusions in piezocomposites, this improvement is not straightforward. One might need to tweak the dielectric environment around the inclusions, in the matrix, to see the benefits. This finding leads to a generic design rule for polycrystal based piezocomposites - using nanomodified matrices incorporated with percolating networks of metallic nanoparticles or carbonic nanomaterials (nanotubes, and graphene) can produce an optimal dielectric environment in which polycrystalline inclusions lead to a marked improvement in piezoelectric response. The models developed look at intricacies related to agglomeration of nanomaterials within the matrices, presence of atomic vacancies in the nanomaterials, and their effect on the overall piezoelectric response of the composite.
Smart Materials and Structures. 2019 Jun 12;28(7):075032, Composite Structures, 2019, 224, 111033, Smart Materials and Structures. 2019 Dec 2;29(1):015021, Mechanics of Materials, Volume 142, 2020, 103275
Nonlocal and nonlinear coupling in piezocomposites: Towards accurate electromechanical description of functional piezomaterials and devices
Nonlocal and nonlinear coupling in piezocomposites: Towards accurate electromechanical description of functional piezomaterials and devices
In describing the behavior of electromechanically coupled materials, specially piezoelectric composites, it is important to understand and incorporate certain key coupled effects in addition to linear coupling between strain and electric fields (linear piezoelectricity). These effects are nonlocal couplings such as between strain-gradients and electric fields (flexoelectricity) and nonlinear couplings (e.g electrostriction). This aspect of research looks at the development of advanced theoretical models to accurately describe the behaviour of a piezoelectric composite material. Further, these models are used to derive insights towards efficiently structuring composite materials at optimal length scales to harness size-dependent coupling amplifications towards designing highly strain-sensitive materials for sensors/energy harvester device architectures.
Composite Structures, Volume 238, 2020, 111967, International Journal of Mechanical Sciences, Volume 182, 2020, 105745
Can auxetic polymeric structures enhance strain coupling in piezocomposites? Multiscale matrix structures for enhanced piezosensitivity and directional selectivity
Can auxetic polymeric structures enhance strain coupling in piezocomposites? Multiscale matrix structures for enhanced piezosensitivity and directional selectivity
A wide explored form of a piezoelectric composite material consists of piezoelectric inclusions (micro- and nano- particles) embedded in a matrix, usually polymeric. In trying to improve the response of the piezoelectric material, commonly chosen routes include additional nano-functionalization using materials such as carbon nanotubes, graphene etc. However, is there an alternative route, through material structuring, that is viable for implementation using emerging 3D printing techniques? This aspect of my research looks at introducing auxetic polymeric structures into the matrix of the composite to boost the strain-sensitivity of the piezocomposite and hence its response. Further, through proper choice of matrix structural anisotropy and polycrystallinity of the piezoelectric inclusions, it is possible to boost the directional anisotropy in strain sensitivity making the new design approach suitable for directional sensing applications.
Smart Materials and Structures, Vol. 29, 5, 2020; Composite Structures, Volume 255, 1 January 2021, 112909
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