| Summary: | 碩士 === 國立交通大學 === 土木工程系所 === 106 === We study the potentials and fields of multiferroic fibrous composites with gradient effects. Earlier experiment shows that when the material sizes come to micrometers or nanometers, the classic elasticity theory is no longer valid due to the gradient effect. In this research, we extend the strain gradient theory proposed by Aifantis (1992) and Yue et. al. (2014) to the multiferroic fibrous composites, which contain the coupling among mechanics, electricity, and magnetism. We use the eigenvalue method to decouple the multi-physics problem and use strain gradient theory to investigate the influences of each characteristic length to the generalized potentials and generalized strains.
Numerical calculations are first demonstrated for piezoelectric material PZT-4 with micro-void and are shown in good agreement with earlier study. Following, we study the behavior of PZT-4 – CoFe2O4 composites and investigate the influences of the characteristic length to the generalized potentials and generalized strains. The results show that the extremum of the generalized potential no longer appears at the interface but offsets to the matrix or inclusion direction when the characteristic length increases. Further, the generalized strains of matrix approach to the classical result of the case with no gradient effects when the characteristic length decreases. In contrast to the generalized strains of matrix, the generalized strains of inclusion are mainly
affected by the strain continuous interface condition instead of the characteristic length.
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