Active composites based on shape memory polymers: overview, fabrication methods, applications, and future prospects

Shape memory polymers (SMPs) have received immense attention from materials research community thanks to their unrivaled properties such as high recoverable strains (up to 400%), low weight, tailorable properties, easy processing, and multiple activation methods. Researchers in both academia and industry have been proposing, experimenting, analyzing, and reporting on various aspects of these materials from synthesis to their applications. Such efforts have led to skyrocketing research output in terms of published papers, especially in the last half a decade. Despite the flourishing research, numerous challenges that hinder advanced applications still exist with the predominant one being the low mechanical properties. To circumvent these challenges, various types of reinforcements have been utilized, leading to significant enhancements and widened potential applications. This work presents an overview of the present research on active composites. Areas covered include the background of SMPs, reinforcements, fabrication techniques, stimulus methods, and applications. Our review is particularly unique in that we included discussions on the various fabrication techniques for SMP composites including their merits and demerits which, to the best of our knowledge, is the first review to include such discussion, thus making it a complete reference material.