Scientometric Analysis and Systematic Review of Multi-Material Additive Manufacturing of Polymers

Fabrication of Composite Material by Directly Printing Resin on Aluminum Foam by 3D Printer

Aluminum foam has relatively low tensile and flexural strengths because it is composed of many pores with thin cell walls. One method of strengthening aluminum foam is to fabricate a composite material with a dense lightweight resin. In this study, the fabrication of composite materials by directly printing resin on an aluminum foam surface using a 3D printer was attempted. The resin was directly printed on both heated and unheated aluminum foam. It was shown that composite materials consisting of aluminum foam and resin can be fabricated by directly printing resin with a 3D printer on both heated and unheated aluminum foam. The resin was softened during the printing process in the case of directly printed resin on heated aluminum foam, allowing more resin to penetrate into the pores than in the case of directly printed resin on unheated aluminum foam. In addition, it was shown that resin can be directly printed on the aluminum foam with a high bonding strength, as a large amount of resin penetrated into the pores, resulting in an anchor effect. That is, composite materials consisting of aluminum foam and arbitrary-shaped resin with relatively high bonding strength can be fabricated when a large amount of resin is allowed to penetrate into the pore.

Design of Experiments to Compare the Mechanical Properties of Polylactic Acid Using Material Extrusion Three-Dimensional-Printing Thermal Parameters Based on a Cyber-Physical Production System

The material extrusion 3D printing process known as fused deposition modeling (FDM) has recently gained relevance in the additive manufacturing industry for large-scale part production. However, improving the real-time monitoring of the process in terms of its mechanical properties remains important to extend the lifespan of numerous critical applications. To enhance the monitoring of mechanical properties during printing, it is necessary to understand the relationship between temperature profiles and ultimate tensile strength (UTS). This study uses a cyber-physical production system (CPPS) to analyze the impact of four key thermal parameters on the tensile properties of polylactic acid (PLA). Layer thickness, printing speed, and extrusion temperature are the most influential factors, while bed temperature has less impact. The Taguchi L-9 array and the full factorial design of experiments were implemented along with the deposited line's local fused temperature profile analysis. Furthermore, correlations between temperature profiles with the bonding strength during layer adhesion and part solidification can be stated. The results showed that layer thickness is the most important factor, followed by printing speed and extrusion temperature, with very close influence between each other. The lowest impact is attributed to bed temperature. In the experiments, the UTS values varied from 46.38 MPa to 56.19 MPa. This represents an increase in the UTS of around 17% from the same material and printing design conditions but different temperature profiles. Additionally, it was possible to observe that the influence of the parameter variations was not linear in terms of the UTS value or temperature profiles. For example, the increase in the UTS at the 0.6 mm layer thickness was around four times greater than the increase at 0.4 mm. Finally, even when it was found that an increase in the layer temperature led to an increase in the value of the UTS, for some of the parameters, it could be observed that it was not the main factor that caused the UTS to increase. From the monitoring conditions analyzed, it was concluded that the material requires an optimal thermal transition between deposition, adhesion, and layer solidification in order to result in part components with good mechanical properties. A tracking or monitoring system, such as the one designed, can serve as a potential tool for reducing the anisotropy in part production in 3D printing systems.

A Review on Multiplicity in Multi-Material Additive Manufacturing: Process, Capability, Scale, and Structure

Additive manufacturing (AM) has experienced exponential growth over the past two decades and now stands on the cusp of a transformative paradigm shift into the realm of multi-functional component manufacturing, known as multi-material AM (MMAM). While progress in MMAM has been more gradual compared to single-material AM, significant strides have been made in exploring the scientific and technological possibilities of this emerging field. Researchers have conducted feasibility studies and investigated various processes for multi-material deposition, encompassing polymeric, metallic, and bio-materials. To facilitate further advancements, this review paper addresses the pressing need for a consolidated document on MMAM that can serve as a comprehensive guide to the state of the art. Previous reviews have tended to focus on specific processes or materials, overlooking the overall picture of MMAM. Thus, this pioneering review endeavors to synthesize the collective knowledge and provide a holistic understanding of the multiplicity of materials and multiscale processes employed in MMAM. The review commences with an analysis of the implications of multiplicity, delving into its advantages, applications, challenges, and issues. Subsequently, it offers a detailed examination of MMAM with respect to processes, materials, capabilities, scales, and structural aspects. Seven standard AM processes and hybrid AM processes are thoroughly scrutinized in the context of their adaptation for MMAM, accompanied by specific examples, merits, and demerits. The scope of the review encompasses material combinations in polymers, composites, metals-ceramics, metal alloys, and biomaterials. Furthermore, it explores MMAM's capabilities in fabricating bi-metallic structures and functionally/compositionally graded materials, providing insights into various scale and structural aspects. The review culminates by outlining future research directions in MMAM and offering an overall outlook on the vast potential of multiplicity in this field. By presenting a comprehensive and integrated perspective, this paper aims to catalyze further breakthroughs in MMAM, thus propelling the next generation of multi-functional component manufacturing to new heights by capitalizing on the unprecedented possibilities of MMAM.

Triplet Fusion Upconversion for Photocuring 3D-Printed Particle-Reinforced Composite Networks

High energy photons (λ < 400 nm) are frequently used to initiate free radical polymerizations to form polymer networks, but are only effective for transparent objects. This phenomenon poses a major challenge to additive manufacturing of particle-reinforced composite networks since deep light penetration of short-wavelength photons limits the homogeneous modification of physicochemical and mechanical properties. Herein, the unconventional, yet versatile, multiexciton process of triplet-triplet annihilation upconversion (TTA-UC) is employed for curing opaque hydrogel composites created by direct-ink-write (DIW) 3D printing. TTA-UC converts low energy red light (λ_max  = 660 nm) for deep penetration into higher-energy blue light to initiate free radical polymerizations within opaque objects. As proof-of-principle, hydrogels containing up to 15 wt.% TiO₂ filler particles and doped with TTA-UC chromophores are readily cured with red light, while composites without the chromophores and TiO₂ loadings as little as 1-2 wt.% remain uncured. Importantly, this method has wide potential to modify the chemical and mechanical properties of complex DIW 3D-printed composite polymer networks.

Multi-Material Additive Manufacturing of High Temperature Polyetherimide (PEI)-Based Polymer Systems for Lightweight Aerospace Applications

Rapid innovations in 3-D printing technology have created a demand for multifunctional composites. Advanced polymers like amorphous thermoplastic polyetherimide (PEI) can create robust, lightweight, and efficient structures while providing high-temperature stability. This work manufactured ULTEM, a PEI-based polymer, and carbon-fiber-infused ULTEM multi-material composites with varying layering patterns (e.g., AAABBB vs. ABABAB) using fused filament fabrication (FFF). The microstructure of fractured surfaces and polished cross-sections determined that the print quality of layers printed closer to the heated bed was higher than layers closer to the top surface, primarily due to the thermal insulating properties of the material itself. Mechanical properties of the multi-material parts were between those of the single-material parts: an ultimate tensile strength and elastic modulus of 59 MPa and 3.005 GPa, respectively. Multi-material parts from the same filaments but with different layering patterns showed different mechanical responses. Prints were of higher quality and demonstrated a higher elastic modulus (3.080 GPa) when consecutive layers were printed from the same filament (AAABBB) versus parts with printed layers of alternating filaments (ABABAB), which showed a higher ultimate strength (62.04 MPa). These results demonstrate the potential for creatively designing multi-material printed parts that may enhance mechanical properties.

Research on metallic glasses at the atomic scale: a systematic review

Metallic glasses (MGs) have been long investigated in material science to understand the origin of their remarkable properties. With the help of computational simulations, researchers have delved into structure-property relationships, leading to a large number of reports. To quantify the available literature, we employed systematic review and bibliometric analysis on studies related to MGs and classical molecular dynamics simulations from 2000 to 2021. It was found that the total number of articles has increased remarkably, with China and the USA producing more than half of the reports. However, high-impact articles were mainly conducted in the latter. Collaboration networks revealed that top contributor authors are strongly connected with other researchers, which emphasizes the relevance of scientific cooperation. In regard to the evolution of research topics, according to article keywords, plastic behavior has been a recurrent subject since the early 2000s. Nevertheless, the traditional approach of studying monolithic MGs at the short-range order evolved to complex composites with characterizations at the medium-range order, including topics such as nanoglasses, amorphous/crystalline nanolaminates, rejuvenation, among others. As a whole, these findings provide researchers with an overview of past and current trends of research areas, as well as some of the leading authors, productivity statistics, and collaboration networks.

Scientometric Review for Research Patterns on Additive Manufacturing of Lattice Structures

Over the past 15 years, interest in additive manufacturing (AM) on lattice structures has significantly increased in producing 3D/4D objects. The purpose of this study is to gain a thorough grasp of the research pattern and the condition of the field's research today as well as identify obstacles towards future research. To accomplish the purpose, this work undertakes a scientometric analysis of the international research conducted on additive manufacturing for lattice structure materials published from 2002 to 2022. A total of 1290 journal articles from the Web of Science (WoS) database and 1766 journal articles from the Scopus database were found using a search system. This paper applied scientometric science, which is based on bibliometric analysis. The data were subjected to a scientometric study, which looked at the number of publications, authorship, regions by countries, keyword co-occurrence, literature coupling, and scientometric mapping. VOSviewer was used to establish research patterns, visualize maps, and identify transcendental issues. Thus, the quantitative determination of the primary research framework, papers, and themes of this research field was possible. In order to shed light on current developments in additive manufacturing for lattice structures, an extensive systematic study is provided. The scientometric analysis revealed a strong bias towards researching AM on lattice structures but little concentration on technologies that emerge from it. It also outlined its unmet research needs, which can benefit both the industry and academia. This review makes a prediction for the future, with contributions by educating researchers, manufacturers, and other experts on the current state of AM for lattice structures.