From prototyping to functional parts: A review of mechanical reinforcing procedures for polymeric parts fabricated via material extrusion

In recent years, there has been a growing focus among researchers on enhancing the mechanical performance of Additively Manufactured (AM) polymers. The ultimate goal is to extend their applications beyond prototyping and into real-word scenarios. Within the published literature of this research domain, studies can be broadly categorized into two primary areas of investigation: the reinforcement of AM materials, and the strengthening of AM components. The first category concentrates on enhancing the feedstock material by incorporating additives, drawing on knowledge from traditional polymer-based composites. Additionally, various in- and post-processing methods aimed at improving layer bonding have been explored. These methods seek to strengthen the weakest links in Material Extrusion (MEX) printed parts, thereby enhancing their mechanical performance. Concurrently, other methodologies, primarily involving hybrid manufacturing through the addition of local reinforcement, have been researched with the goal to improve the endurance and mechanical performance of MEX structures. While each of the mentioned techniques can provide some degree of mechanical enhancement, their ease of use and availability may vary. Therefore, a deeper understanding of these methods, along with their pros and cons, can assist users in selecting the most suitable reinforcement technique for improved mechanical performance. This review paper discusses the progress to date in the improvement of mechanical performance of MEX fabricated polymer parts. Towards this objective, the study examines the reported data to identify the fundamental factors influencing the reinforcement process, while also evaluating the efficacy of the suggested techniques. Furthermore, this work duly acknowledges and addresses the research gaps, challenges, and drawbacks associated with the endeavor to strengthen MEX components within the context of the study.