Effects Of Unit-Cell Boundary Type On The Electromechanical Properties Of Randomly Distributed Multifunctional Composite Structures

The unit-cell composition of three-dimensional finite element models for 3-0 and 3-1 type polymer (PVDF) - ceramic (BaTiO3) and ceramic (PZT-7A) - ceramic (BaTiO3) structures are compared to determine the effects of fiber interaction at the surface of the unit-cell on the effective elastic, piezoelectric and dielectric properties of the multifunctional composite systems. The first unit-cell type examined has enclosed fibers that are completely contained within its boundaries, the second type has fibers that are contained within the sides of the unit-cell but can be cut at the top and bottom surfaces, and the third type has fibers that can be cut on the top, bottom and side surfaces of the unit-cell. All cut fibers are matched on opposing surfaces for continuity. Randomly distributed and aligned circular fibers, randomly distributed and randomly oriented circular fibers, and one central enclosed fiber with varying volume fractions and aspect ratios are compared with these three unit-cell structures. Results show that fiber models display greater or equal values of C"" when compared to aligned or randomly oriented fibers for all cases except aspect ratio 1 polymer-ceramic structures. The third type of unit-cell shows the highest e""values for single, aligned and randomly oriented fiber structures, except for the aspect ratio 10 polymerceramic case where the second type of unit-cell has greater results for aligned and single fibers. Finally, it can generally be seen that randomly oriented fibers have smaller values than similar aligned and single fiber structures with the exception being C"" of the ceramic-ceramic structures.