Scaling Up 4D Printing: Direct Pellet Extrusion of Shape Memory Polymer Composites

Abstract

Shape Memory Polymers (SMPs) exhibit responsiveness to stimuli, characterized by the Shape Memory Effect (SME) which enables them to temporarily store a shape and return to their permanent/original form upon the application of a stimulus. However, SMPs face challenges in being applied to large-scale applications due to their limited stress recovery response. A promising solution to this problem are Shape Memory Polymer Composites (SMPCs). This study aims to explore the feasibility of producing SMPCs with Additive Manufacturing (AM), which is also known as 4D printing, for large-scale manufacturing. In the future, the aim is eventually to be able to 4D print drone wings that can change their shape to maneuver in the air. Therefore, the goal is to leverage the unique properties of SMPCs, enhancing their applicability in the engineering field. In this work, a large-scale Extrusion Based 3D printing platform is modified and adapted with a pellet extruder. A polymer blend made of SMP polyurethane based MM4520 and PLA with 15% weight content of carbon fibers (CF) were used to create SMPC samples. Compositions of 0, 10, and 20 weight % CF15 PLA on SMP were manufactured and studied for shape recovery, shape recovery fixity ratio and shape recovery flexural stress. Results demonstrated that higher contents of CF15 PLA led to higher shape recovery flexural stresses that increased more than 400% compared to the raw printed material. However, a counter effect occurred to the shape recovery ratio and shape fixity. The shape recovery ratio decreases a maximum of 7% in comparison to the raw material. The shape fixity decreased from 22% from the raw material. This study is the first step to achieve scalability of 4D printing.