Characterization, Modeling, and Experimental Testing of 3D Printed Polymer Composite Laminate Morphing Structures

Heat dissipation can be significantly improved in thermal management systems using pumped two-phase cooling, but maldistribution and fluid flow instabilities are more prevalent. Traditional temperature and pressure sensing does not offer in-situ and real-time flow monitoring and detection of local anomalies within heat exchangers. To this end, functional metamaterials can be employed to react to various stimuli to provide signals based on material properties. These types of structures utilize properties which react to external stimuli and record information based on interaction, acting as a health monitoring system when connected within a network. Our research is exploring the design space and functionalities of these materials, and specifically, this paper will focus on the fabrication and material characterization of 3D-printed polymer composite laminates as well as an experimental setup designed to validate an FEA numerical model for the morphing response of these structures. The composite laminates are made of two top/bottom layers of PLA with a layer of TPU in the middle, and each layer has varying layer orientation, thickness, and print settings. By utilizing manufacturing-dependent material properties such as pre-strain and storage modulus, these structures can change shape at various temperatures based on two main driving factors: pre-strain within the materials and CTE mismatch between the layers. The results offer novel material data on 3D-printed off-the-shelf polymers (PLA and TPU) and demonstrate how these materials can be additively manufactured to create a responsive system. The fabrication method using TPU and PLA layers is detailed including key printing parameters that enable successful manufacturing. It is concluded that parameters such as fan speed and print temperature can have a drastic impact on the stiffness and pre-strain of PLA, and that the greatest shape change occurs when all materials in the composite are in the glassy phase. These samples are tested within a thermal chamber and compared to the predictions of an FEA model that predicts the displacement direction and magnitude at various temperatures. The results demonstrate correlation between the model-predicted and experimentally measured displacement, which provide the basis for a further validation to be completed. This work contributes toward the ultimate goal of creating a system of passively actuating sensors that can respond to temperature and pressure inputs, creating a more robust and resilient thermal management system.