Structural Performance Evaluation of Foldable Displays for Consumer Electronic Devices

An emerging trend for hand held consumer electronic devices is the inclusion of a folding display. These folding displays consist of a laminate of functional component layers such as flexible OLED, touch sensor, and others, bonded together by an Optically Clear Adhesive (OCA). Foldable displays are challenging to design as the bend radius of these displays can be below 5 mm, and the OCA needs to remain adhered to the functional layers while experiencing shear strains of 250% and above. Durability of the displays requires up to 100,000 folding cycles over the lifetime of the device. Failures of foldable displays has been observed in many commercial devices on the market today. These failures can result in high warranty costs and damage to the customer brand. Designing a robust foldable display requires the evaluation of a variety of components, materials, and geometries within each consumer device variant. Using a virtual twin of a foldable display assembly, physics based simulation can be used to accelerate structural performance validation. Potential benefits are improved reliability and customer perception of quality as well as reduced warranty costs. Use of the digital twin enables simulation driven design earlier in the design cycle allowing for the rapid investigation of design alternatives using a DOE (Design of Experiments) approach. This approach results in reduction or elimination of costly and time-consuming physical testing. Simulation of a foldable display with FEM is complex requiring non-linear and time based material behavior, non-linear geometric behavior (local and global buckling/wrinkling), adhesion and cohesion of the OCA, and fracture/failure of the functional component layers. Additional considerations of the FEM formulation such as selection of the objective stress rate with large shear strains and finite rigid body rotations need to be addressed to maintain high solution accuracy. These topics will be covered in detail within this presentation.