Stress and Deformation Behavior of 2D Composite Cellular Actuator Structures of Ceramic Building Blocks and Epoxy Resins

Abstract

2D actuator composite structures are fabricated of lead zirconate titanate (PZT) and Al2O3 building blocks with an epoxy resin matrix. This novel modular concept gives the possibility to create complex geometric structures where the structure itself tailors the physical properties. To improve the possibilities of excitation or loading and determine the influence of the geometric parameters as slenderness ratio t2 · g−1 and active area Aactive finite element (FE) simulations are used. The stress distribution σyy within the unit cell and the resulting strain amplification ay are tested with different mechanically coupled thermal excitation modes. A homogeneous excitation of the PZT building blocks and a maximum Aactive of 24% led to a maximum of strain amplification and a reduction of induced tensile stresses. In addition, zero deformation could be generated by modifying the structure design with a slenderness ratio of 0.5. Further geometric variations offer the potential to increase the strain amplification.

Improved Mechanical Amplification of Monolithic PZT and PZT Composite via Optimized Honeycomb Macrostructures

“…A soft PZT powder Pb(Zr x Ti 1-x )O 3 with x = 0.44 − 0.52 and spray granules with an average grain size of d 50 = 1.8 µm (NCE51, Noliac Group, Kvistgaard, Denmark) was used to fabricate the cellular composite according to the design of Eichhorn et al [16,33] with 23 unit cells. The ceramic building blocks were produced using a PZT injection mold with a filler content of 48.3 vol-% [16,34,35] and cast into three different 3D silicone forms [35,36] generated by casting 3D-printed positive forms (Printing material "DL260", 3D printer "028 J", both DWS Systems, Zane, Italy) (Figure 1). Filling and cooling were carried out at 120 • C and with a cooling rate of 1 K min −1 in a tempering furnace ("Type K1252", Heraeus Holding GmbH, Hanau, Germany) to reduce thermal induced stress.…”

“…The production of this filled silicone resin is described below. In comparison to [16,33], the connecting phase of epoxy resin was replaced by PZT-filled silicone resin without conversion or further processing to the ceramic, and to improve the singular piezoelectric properties of the complete structure.…”

“…The production of this filled silicone resin is described below. In comparison to [16,33], the connecting phase of epoxy resin was replaced by PZT-filled silicone resin without conversion or further processing to the ceramic, and to improve the singular piezoelectric properties of the complete structure. A reference structure with identical geometrical dimensions was fabricated from monolithic PZT ceramic (Figure 1b) consisting of the same PZT injection mold used for the building blocks of the composite lattice structures.…”

“…The piezoelectric constants can be optimized by tailoring the cellular design. Based on this research, Eichhorn et al [15,16] analyzed the mechanical and pseudopiezoelectric deformation behavior of modular, honeycomb-based cellular solids by FE simulations. The lattice structures consisted of modular units (building blocks), which were connected by a piezoelectric passive epoxy and were excited individually.…”

“…In addition to FE simulations [14][15][16], experimental investigations on active lattice structures made of pure piezoelectric ceramics, polymers, or composite materials are reported [2,6,[17][18][19]. A basic piezoelectric cellular, auxetic lattice structure based on PZT laminates (single thickness 0.53 mm) was reported by Fey et al [2].…”