Related Experiment Video
Updated: Jun 23, 2026
09:39
Characterizing Dissipative Elastic Metamaterials Produced by Additive Manufacturing
Published on: June 28, 2024
A unified viscoelastic-viscoplastic constitutive framework for optically clear adhesives: Experiments, modeling, and
Zhaoxu Zhou1,2, Qiying Liu1, Yujia Chen1
1KeyLaboratory of Transients in Hydraulic Machinery, Ministry of Education, School of Power and Mechanical Engineering, Wuhan University, Wuhan, China.
Microsystems & Nanoengineering
|June 21, 2026
Summary
This study introduces a new model for optically clear adhesives (OCAs) used in foldable displays. The model accurately predicts how these materials deform under bending, improving the design and reliability of flexible electronic devices.
Area of Science:
- Materials Science
- Mechanical Engineering
- Polymer Science
Background:
- Optically clear adhesives (OCAs) are critical bonding layers in modern display manufacturing, particularly for foldable devices.
- The time- and temperature-dependent deformation of OCAs during repeated bending necessitates accurate constitutive modeling for reliable stress prediction and design.
- Existing models often neglect the coupled viscoelastic-viscoplastic response, limiting their predictive accuracy for foldable display applications.
Purpose of the Study:
- To develop and validate a unified constitutive framework for characterizing the coupled viscoelastic-viscoplastic behavior of OCAs.
- To provide a reliable tool for stress analysis and design optimization of foldable displays incorporating OCAs.
- To enhance the long-term reliability assessment of flexible OLED devices through accurate material modeling.
Main Methods:
- A unified constitutive framework combining a generalized Maxwell model with the Qian-Liu viscoplastic formulation was developed.
- The proposed model was calibrated using stress-relaxation experimental data obtained at 30, 60, and 85°C.
- The framework was implemented into an ABAQUS UMAT for finite-element simulations and validated against experimental observations.
Main Results:
- The calibrated model successfully captured the coupled viscoelastic-viscoplastic behavior of OCAs under various temperature conditions.
- Finite-element simulations using the implemented UMAT corroborated the experimental findings, validating the model's predictive capabilities.
- The study demonstrated the framework's effectiveness in simulating the mechanical response of a simplified foldable display structure.
Conclusions:
- The developed unified constitutive framework effectively models the complex mechanical behavior of OCAs in foldable displays.
- This research fills a critical gap in OCA constitutive modeling, offering a validated tool for structural optimization.
- The validated framework is essential for improving the design and ensuring the long-term reliability of flexible OLED devices.
Related Concept Videos
01:19Viscosity of Fluid
Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
01:28Classification and Mechanical Properties of Synthetic Polymers
Synthetic polymers are classified as elastomers, fibers, or plastics based on their crystallinity. Crystallinity, the degree of long-range order in the solid state, influences the mechanical properties (stretching or contracting) of elastomers. Elastomers are flexible polymers that can expand or contract easily upon the application of an external force. They have numerous crosslinks that pull them back into their original shape when stress is removed. Silicones, for instance, are highly elastic...
01:20Elastic Strain Energy for Shearing Stresses
As discussed in previous lessons, strain energy in a material is the energy stored when it is elastically deformed, a concept crucial in materials science and mechanical engineering. This energy results from the internal work done against the cohesive forces within the material. When a material undergoes shearing stress and corresponding shearing strain, the strain energy density, which is the energy stored per unit volume, is calculated. Within the elastic limit, where the stress is...
01:15Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Deformation occurs in axial and transverse directions when an axial load is applied to a slender bar. This deformation impacts the cubic element within the bar, transforming it into either a rectangular parallelepiped or a rhombus, contingent on its orientation. This transformation process induces shearing strain. Axial loading elicits both shearing and normal strains. Applying an axial load instigates equal normal and shearing stresses on elements oriented at a 45° angle to the load axis.
01:21Plastic Behavior
A material's elastic behavior is characterized by the disappearance of stress once the load is removed, allowing the material to return to its original state. However, when stress surpasses the yield point, yielding commences, marking the onset of plastic deformation or permanent set. This change from elastic to plastic behavior is influenced by the peak stress value and the duration before the load is removed. An intriguing observation occurs when a specimen is loaded, unloaded, and reloaded.
01:19Members Made of Elastoplastic Material
The behavior of elastoplastic materials under bending stresses, particularly in structural members with rectangular cross-sections, is crucial for predicting material responses and understanding failure modes. Initially, when a bending moment is applied, the stress distribution across the section follows Hooke's Law and is linear and elastic. This distribution means the stress increases from the neutral axis to the maximum at the outer fibers, up to the elastic limit.
As the bending moment...
As the bending moment...