Session: Methods for Uncertainty Quantification, Sensitivity Analysis, and Prediction

Paper Number: 157771

157771 - Modeling, Experimental Characterization, and Uncertainty Quantification of Aged Dielectric Materials 

Abstract: 

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Dielectric materials hold considerable potential for enhancing the energy storage density of film capacitors, particularly on a per-volume basis, which is essential for meeting growing power demands in modern applications. Capacitors, by design, rely on dielectric materials to store electrical energy in the form of an electric field. The effectiveness of a dielectric material is largely determined by its dielectric permittivity, which measures how much electric charge the material can store, and its dielectric loss, which refers to the amount of energy lost as heat during operation. In recent years, advancements in materials science have led to significant improvements in the dielectric permittivity of various materials, allowing capacitors to store more energy. However, little is known about the aging and breakdown of these materials, which causes concerns about their long-term performance.

While dielectric materials show promise in meeting high energy demands, over time, these materials may undergo aging and potential breakdown, both of which can reduce energy storage density and increase dielectric loss, ultimately compromising the efficiency and reliability of capacitors. Understanding the effects of aging and breakdown on dielectric materials is particularly important for applications where long-term stability is essential. However, comprehensive data on the aged mechanical behavior of these materials over extended periods are limited, making it challenging to predict their durability and effectiveness.

In this study, the mechanical behavior of two dielectric materials, biaxially oriented polypropylene (BOPP) and VHB4910, is characterized and modeled over time. BOPP is commonly used in large wound film capacitors, while VHB4910 is commonly used in actuator applications. The study focuses on experimentally characterizing the cyclic stress response of BOPP and the fracture stress response of VHB4910. By examining these responses, the study aims to provide insights into the materials' mechanical behavior under varying conditions and over different aging periods, which is essential for predicting their long-term performance.

To model the mechanical behavior of BOPP and VHB4910, Bayesian uncertainty analysis is applied. This approach allows for a systematic evaluation of key modeling parameters, helping quantify the hyperelastic and, where applicable, viscoelastic properties of the materials. For BOPP, the study compares Neohookean and nonaffine hyperelastic models combined with fractional-order viscoelasticity, while Ogden and nonaffine hyperelastic models are used for VHB4910. These models represent different approaches to capturing the elasticity and deformation behavior of materials, with hyperelastic models describing the elastic response under large deformations and viscoelastic models accounting for time-dependent deformation. The application of Bayesian uncertainty analysis helps ensure the reliability of the modeling process by providing prediction and confidence intervals for the parameters.

The materials are tested across a range of stretch rates, from 0.07 to 20 Hz, and aging periods of 0, 6, and 12 months, enabling the study to capture how material properties evolve over time and under different loading conditions. The findings reveal that when hyperelastic and viscoelastic models are coupled, a distinct set of hyperelastic parameters can be identified, independent of the stretch rate. This suggests that certain mechanical properties remain stable across various loading rates, which could simplify the modeling of these materials in practical applications. 

Ultimately, this study provides valuable insights into the aged mechanical behavior of BOPP and VHB4910, highlighting the potential of these materials to meet the demands of high-energy-density applications while addressing concerns regarding long-term reliability. By characterizing and modeling their stress responses under different conditions, the research offers a framework for predicting how these dielectric materials will perform in capacitors over extended periods. This information is essential for designing capacitors and actuators with improved durability and reliability, supporting the development of more efficient and resilient power systems across a wide range of industries.

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Presenting Author: Eugenia Stanisauskis Weiss Naval Undersea Warfare Center- Divison Newport

Presenting Author Biography: Dr. Eugenia Stanisauskis Weiss holds a Ph.D. in Materials Science and Engineering, with a research focus on the stress responses of functional and soft materials. Dr. Stanisauskis Weiss is also a Department of Defense SMART Scholar and SMART SEED grant recipient on her work focusing on the aging and breakdown of aged dielectric materials. Dr. Stanisauskis Weiss's research combines her expertise in material modeling and Bayesian uncertainty analysis to improve the reliability and durability of materials in demanding environments.

Authors:

Eugenia Stanisauskis Weiss Naval Undersea Warfare Center- Divison Newport
Emily Guzas Naval Undersea Warfare Center- Division Newport