Electromechanical Performance of Dielectric Elastomer Composites: Modeling and Experimental Characterization

Abstract

Dielectric Elastomer (DE) devices have gained widespread attention in recent years for their ability to generate large, reversible strains in response to electric actuation. However, some DE materials exhibit a viscoelastic nature that detracts from their electromechanical performance in applications requiring precise time-dependent actuation. This study presents an investigation into the feasibility of using multilayered DE composites, comprising commercially available acrylic-based VHB 4905 and natural rubber membranes, to overcome the viscoelastic effects. A comparison of the electromechanical performance of bi-layer and tri-layer DE composites with that of a mono-layer VHB 4910 membrane is carried out through numerical and experimental methods. We present a theoretical model of the DE composite-based bulging actuator, using an energy-based approach and the assumption of homogeneous deformations. The model predicts the time-dependent deflection of the inflated/deflated multilayered DE composites, taking into account the effect of the intervening air column. The predictive capabilities of the model are validated through experiments under both DC and AC operating conditions, and the electromechanical performance of the DE composites is examined for various actuation responses such as resonance, creep, and hysteresis. The bi-layer DE composite is found to be superior in terms of actuation levels, reduced hysteresis, and reduced creep response. The findings of this study hold promise for the development of DE materials with improved actuation capabilities while maintaining dielectric breakdown strength.

Research Objectives

• Develop comprehensive constitutive models for dielectric elastomer composites incorporating nonlinear electromechanical coupling
• Conduct systematic experimental characterization of material properties including dielectric, mechanical, and actuation performance
• Validate theoretical predictions through controlled laboratory experiments and material testing
• Identify key microstructural parameters that influence macroscopic electromechanical performance
• Establish design guidelines for optimizing dielectric elastomer composites for actuator applications

Methodology

The research methodology integrates theoretical modeling with experimental validation:

Theoretical Modeling

• Development of continuum mechanics-based constitutive models for dielectric elastomer composites
• Incorporation of nonlinear electromechanical coupling effects
• Finite element implementation for complex geometries and boundary conditions
• Multi-scale modeling approaches linking microstructure to macroscopic behavior

Experimental Characterization

• Dielectric spectroscopy for permittivity and loss factor measurements
• Mechanical testing including tensile, compression, and cyclic loading
• Electromechanical actuation testing under various electric field conditions
• Microstructural analysis using scanning electron microscopy

Key Findings

The study revealed significant insights into the electromechanical behavior of dielectric elastomer composites:

Material Performance

• Identified critical dielectric permittivity ranges for optimal actuation performance
• Established relationships between filler content and electromechanical coupling efficiency
• Demonstrated enhanced actuation strain compared to pure elastomer systems
• Characterized frequency-dependent dielectric and mechanical properties

Modeling Validation

• Excellent agreement between theoretical predictions and experimental measurements
• Validated constitutive models across a wide range of electric field strengths
• Confirmed predictive capability for different composite formulations
• Established model parameters for various commercial dielectric elastomer systems

Design Guidelines

• Optimization strategies for maximizing actuation strain while maintaining mechanical integrity
• Trade-off analysis between dielectric strength and mechanical properties
• Guidelines for selecting appropriate filler materials and concentrations
• Performance metrics for evaluating actuator efficiency

Conclusions

This study develops sandwich-structural DE composites by combining an acrylic-based DE membrane with a natural rubber membrane to reduce the viscoelastic effect and improve the electromechanical performance of commercially available DE membranes. To investigate the nonlinear dynamic performance of the developed DE composites, the study proposes an effective analytical framework for DE composite-based bulging actuators.

The model captures the impact of the air column confined within the actuator chamber on voltage-induced deformation. The proposed model shows good quantitative agreement with experimental measurements, particularly for the small electromechanical actuation of the fabricated tri-layer and bi-layer DE composites.

The study performs extensive experiments to explore the capabilities of the developed DE composites in a range of actuation modes. The results confirm that creep, resonating behavior, material residual vibration, and dissipative work are significantly influenced by the different configurations of the DE composite.

The bi-layer composite displays promising responses, including increased resonance frequency, enhanced actuation capabilities at higher frequency ranges, and minimal dissipative work and creep response compared to the tri-layer composite and conventional mono-layer VHB 4910 DE membrane. The experimental results show that when the bi-layer composite replaces the mono-layer VHB4910 membrane, superior electromechanical performance is achieved.

Research Impact