Fused deposition modelling (FDM) is one of the fastest-growing additive manufacturing methods used in printing fibre-reinforced composites (FRC). The performances of the resulting printed parts are limited compared to those by other manufacturing methods due to their inherent defects. Hence, the effort to develop treatment methods to overcome these drawbacks has accelerated during the past few years. The main focus of this study is to review the impact of those defects on the mechanical performance of FRC and therefore to discuss the available treatment methods to eliminate or minimize them in order to enhance the functional properties of the printed parts. As FRC is a combination of polymer matrix material and continuous or short reinforcing fibres, this review will thoroughly discuss both thermoplastic polymers and FRCs printed via FDM technology, including the effect of printing parameters such as layer thickness, infill pattern, raster angle and fibre orientation. The most common defects on printed parts, in particular, the void formation, surface roughness and poor bonding between fibre and matrix, are explored. An inclusive discussion on the effectiveness of chemical, laser, heat and ultrasound treatments to minimize these drawbacks is provided by this review.

FDM-Based 3D Printing of Polymer and Associated Composite: A Review on Mechanical Properties, Defects and Treatments.

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. To fit functional demand, materials with desired physical, chemical, biological, biomechanical, and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Biomedical applications of biodegradable polymers

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has boomed over the last 30 years, and its use has accelerated during the last 5 years AM is a materials-oriented manufacturing technology, and printing resolution versus printing scalability/speed trade-off exists among various types of materials, including polymers, metals, ceramics, glasses, and composite materials Four-dimensional (4D) printing, together with versatile transformation systems, drives researchers to achieve and utilize high dimensional AM Multiple perspectives of the AM of structural materials have been raised and illustrated in this review, including multi-material AM (MMa-AM), multi-modulus AM (MMo-AM), multi-scale AM (MSc-AM), multi-system AM (MSy-AM), multi-dimensional AM (MD-AM), and multi-function AM (MF-AM) The rapid and tremendous development of AM materials and methods offers great potential for structural applications, such as in the aerospace field, the biomedical field, electronic devices, nuclear industry, flexible and wearable devices, soft sensors, actuators, and robotics, jewelry and art decorations, land transportation, underwater devices, and porous structures

Additive manufacturing of structural materials

This is an accepted manuscript of an article published by Elsevier in Additive Manufacturing on 02/10/2021, available online: https://doi.org/10.1016/j.addma.2021.102378 
The accepted version of the publication may differ from the final published version.

Fused Deposition Modelling: Current Status, Methodology, Applications and Future Prospects

Polylactic acid (PLA) is the most widely used raw material in extrusion-based three-dimensional (3D) printing (fused deposition modeling, FDM approach) in many areas since it is biodegradable and environmentally friendly, however its utilization is limited due to some of its disadvantages such as mechanical weakness, water solubility rate, etc. FDM is a simple and more cost-effective fabrication process compared to other 3D printing techniques. Unfortunately, there are deficiencies of the FDM approach, such as mechanical weakness of the FDM parts compared to the parts produced by the conventional injection and compression molding methods. Preparation of PLA composites with suitable additives is the most useful technique to improve the properties of the 3D-printed PLA parts obtained by the FDM method. In the last decade, newly developed PLA composites find large usage areas both in academic and industrial circles. This review focuses on the chemistry and properties of pure PLA and also the preparation methods of the PLA composites which will be used as a raw material in 3D printers. The main drawbacks of the pure PLA filaments and the necessity for the preparation of PLA composites which will be employed in the FDM-based 3D printing applications is also discussed in the first part. The current methods to obtain PLA composites as raw materials to be used as filaments in the extrusion-based 3D printing are given in the second part. The applications of the novel PLA composites by utilizing the FDM-based 3D printing technology in the fields of biomedical, tissue engineering, human bone repair, antibacterial, bioprinting, electrical conductivity, electromagnetic, sensor, battery, automotive, aviation, four-dimensional (4D) printing, smart textile, environmental, and luminescence applications are presented and critically discussed in the third part of this review.

Extrusion-Based 3D Printing Applications of PLA Composites: A Review

Additive Manufacturing technology has a significant impact on the modern world because of its ability to fabricate highly complex computerized geometrics. Pure 3D-printed polymer parts have limited potential applications due to inherently inferior mechanical and anisotropic properties. For more utilization and versatility, the addition of fillers has enhanced their functionalities. 3D printing has innovative advantages including low cost, minimal wastage, customized geometry, and ease of material change. This review reveals the development of 3D printing techniques of matrix composite materials with improving properties and their applications in the fields of aerospace, automotive, biomedical, and electronics. A general introduction is given on AM techniques mainly fused deposition modeling (FDM), Powder-liquid 3D printing (PLP), selective laser sintering (SLS), stereolithography (SLA), digital light processing (DLP), and robocasting. Process methodologies and behavior of different filler additives, reinforcement fibers, nanoparticles, and ceramic polymer composites are discussed. Also, some major issues of difficulty including printing parameters, homogeneous desperation of fillers, nozzle clogging due to filler aggregation, void formation, augmented curing time, and anisotropic attributes are addressed. In the end, some capabilities and shortcomings are pointed out for further development of 3D-printing technology.

A review on 3D printed matrix polymer composites: its potential and future challenges

Blending graphite nanoplatelets (GNPs) with polylactic acid (PLA) is a conventional approach endowing the GNPs/PLA nanocomposites with enhanced mechanical and thermal properties. Meanwhile, l-Arginine (l-Arg) has been proved to be effective GNPs modifiers, which can be used to improve the solubility and compatibility of GNPs in PLA. On the other hand, additive manufacturing offers a novel and unique way to fabricate components with complex structure and special functions, which can significantly expand the application of material in many fields. This study demonstrated the fused deposition modeling (FDM) 3D printing l-Arg/GNPs/PLA nanocomposites with enhanced mechanical property and thermal stability in conjunction with its potential application as biomaterials. Nanocompsites were prepared by solvent-based mixing method and extruded into filaments for FDM printing. The addition of l-Arg/GNPs significantly improved the tensile and flexural strength of PLA matrix, 43.6% in tensile strength and 28.5% in flexural strength with optimal loading of 2 wt% l-Arg/GNPs. The thermal stability of l-Arg/GNPs/PLA nanocomposites gradually improved, with 60 °C increase in degradation temperature and 7% increase in remaining residual weight. Furthermore, MTT cytotoxicity assay of the 3D printed nanocomposites showed the good biocompatibility of the l-Arg/GNPs/PLA nanocomposites, which indicates the promising prospect of being applied as biomaterial in bone tissue engineering.

3D printing biocompatible l-Arg/GNPs/PLA nanocomposites with enhanced mechanical property and thermal stability

Atomic-scale and experimental investigation on the micro-structures and mechanical properties of PLA blending with CMC for additive manufacturing

Multi-scale investigation on the phase miscibility of polylactic acid/o-carboxymethyl chitosan blends

Tissue-engineered skin grafts have long been considered to be the most effective treatment for large skin defects. Especially with the advent of 3D printing technology, the manufacture of artificial skin scaffold with complex shape and structure is becoming more convenient. However, the matrix material used as the bio-ink for 3D printing artificial skin is still a challenge. To address this issue, sodium alginate (SA)/carboxymethyl cellulose (CMC-Na) blend hydrogel was proposed to be the bio-ink for artificial skin fabrication, and SA/CMC-Na (SC) composite hydrogels at different compositions were investigated in terms of morphology, thermal properties, mechanical properties, and biological properties, so as to screen out the optimal composition ratio of SC for 3D printing artificial skin. Moreover, the designed SC composite hydrogel skin membranes were used for rabbit wound defeat repairing to evaluate the repair effect. Results show that SC4:1 blend hydrogel possesses the best mechanical properties, good moisturizing ability, proper degradation rate, and good biocompatibility, which is most suitable for 3D printing artificial skin. This research provides a process guidance for the design and fabrication of SA/CMC-Na composite artificial skin.

Ying Guo

Papers

A review on 3D printed matrix polymer composites: its potential and future challenges

3D printing biocompatible l-Arg/GNPs/PLA nanocomposites with enhanced mechanical property and thermal stability

Atomic-scale and experimental investigation on the micro-structures and mechanical properties of PLA blending with CMC for additive manufacturing

Multi-scale investigation on the phase miscibility of polylactic acid/o-carboxymethyl chitosan blends

Design and Fabrication of Sodium Alginate/Carboxymethyl Cellulose Sodium Blend Hydrogel for Artificial Skin