Fused-Deposition Modeling 3D Printing of Short-Cut Carbon-Fiber-Reinforced PA6 Composites for Strengthening, Toughening, and Light Weighting.

Additive manufacturing of carbon-fiber-reinforced polymer (CFRP) has been widely used in many fields. However, issues such as inconsistent fiber orientation distribution and void formation during the layer stacking process have hindered the further optimization of the composite material's performance. This study aimed to address these challenges by conducting a comprehensive investigation into the influence of carbon fiber content and printing parameters on the micro-morphology, thermal properties, and mechanical properties of PA6-CF composites. Additionally, a heat treatment process was proposed to enhance the interlayer bonding and tensile properties of the printed composites in the printing direction. The experimental results demonstrate that the PA6-CF25 composite achieved the highest tensile strength of 163 MPa under optimal heat treatment conditions: 120 °C for 7.5 h. This corresponds to a significant tensile strength enhancement of 406% compared to the unreinforced composites, which represents the highest reported improvement in the current field of CFRP-fused deposition 3D printing. Additionally, we have innovatively developed a single-layer monofilament CF-OD model to quantitatively analyze the influence of fiber orientation distribution on the properties of the composite material. Under specific heat treatment conditions, the sample exhibits an average orientation angle µ of 0.43 and an orientation angle variance of 8.02. The peak frequency of fiber orientation closely aligns with 0°, which corresponds to the printing direction. Finally, the study explored the lightweight applications of the composite material, showcasing the impressive specific energy absorption (SEA) value of 17,800 J/kg when implementing 3D-printed PA6-CF composites as fillers in automobile crash boxes.

Preparation of Thermoplastic Polyurethane/Multi-Walled Carbon Nanotubes Composite Foam with High Resilience Performance via Fused Filament Fabrication and CO2 Foaming Technique.

Wearable flexible sensors with high sensitivity and wide detection range are applied in motion detection, medical diagnostic result and other fields, but poor resilience and hysteresis remain a challenge. In this study, a high-resilience foam sensor was prepared through a combination of additive manufacturing and green physical foaming method. The conductive filaments were prepared by using MWCNTs-modified TPU by the physical method of melt blending. Samples were prefabricated using the FFF printer and then saturated with CO2 in an autoclave before being removed and heated to foam. The composite foam effectively reduced residual strain, demonstrating the high resilience of the 3D-printed composite materials with a foam porous structure. The residual strain of the sample before foaming was >6% after a single cycle, and then gradually increased. The residual strain of the foamed samples is less than 5%. In addition, composite foam has high sensitivity and can monitor subtle pressure changes (0~40 kPa). The sensing performance of the composite foam was evaluated, and the current signal remained stable under different loading rates and small compression strains (2~5%). By using this highly resilient conductive composite material, a hierarchical shoe insole was designed that successfully detected human walking and running movements.

Progress in the Preparation, Properties, and Applications of PLA and Its Composite Microporous Materials by Supercritical CO2: A Review from 2020 to 2022.

The development of degradable plastic foams is in line with the current development concept of being pollution free and sustainable. Poly(lactic acid) (PLA) microporous foam with biodegradability, good heat resistance, biocompatibility, and mechanical properties can be successfully applied in cushioning packaging, heat insulation, noise reduction, filtration and adsorption, tissue engineering, and other fields. This paper summarizes and critically evaluates the latest research on preparing PLA microporous materials by supercritical carbon dioxide (scCO2) physical foaming since 2020. This paper first introduces the scCO2 foaming technologies for PLA and its composite foams, discusses the CO2-assisted foaming processes, and analyzes the effects of process parameters on PLA foaming. After that, the paper reviews the effects of modification methods such as chemical modification, filler filling, and mixing on the rheological and crystallization behaviors of PLA and provides an in-depth analysis of the mechanism of PLA foaming behavior to provide theoretical guidance for future research on PLA foaming. Lastly, the development and applications of PLA microporous materials based on scCO2 foaming technologies are prospected.

The Micro-Macro Interlaminar Properties of Continuous Carbon Fiber-Reinforced Polyphenylene Sulfide Laminates Made by Thermocompression to Simulate the Consolidation Process in FDM.

Three-dimensional (3D) printing of continuous fiber-reinforced composites has been developed in recent decades as an alternative means to handle complex structures with excellent design flexibility and without mold forming. Although 3D printing has been increasingly used in the manufacturing industry, there is still room for the development of theories about how the process parameters affect microstructural properties to meet the mechanical requirements of the printed parts. In this paper, we investigated continuous carbon fiber-reinforced polyphenylene sulfide (CCF/PPS) as feedstock for fused deposition modeling (FDM) simulated by thermocompression. This study revealed that the samples manufactured using a layer-by-layer process have a high tensile strength up to 2041.29 MPa, which is improved by 68.8% compared with those prepared by the once-stacked method. Moreover, the mechanical-microstructure characterization relationships indicated that the compactness of the laminates is higher when the stacked CCF/PPS are separated, which can be explained based on both the void formation and the nanoindentation results. These reinforcements confirm the potential of remodeling the layer-up methods for the development of high-performance carbon fiber-reinforced thermoplastics. This study is of great significance to the improvement of the FDM process and opens broad prospects for the aerospace industry and continuous fiber-reinforced polymer matrix materials.

Effect of POSS-Modified Montmorillonite on Thermal, Mechanical, and Electrical Properties of Unsaturated Polyester Nanocomposites.

Montmorillonite (MMT) displays excellent cohesion with an unsaturated polyester (UP) matrix to generate a material which exhibits an extensive range of commercial applications. The organic modification of MMT using polyhedral oligomeric silsesquioxanes (POSS) and the effect of POSS-MMT on the thermal, mechanical, and electrical properties of UP are reported here. Transmission electron microscopy (TEM) images were used to characterize the modification of MMT using POSS. Modified MMT (POSS-MMT) was incorporated, at different wt.% (0.5, 1, 3, 5), into UP via in-situ polymerization. The presence of POSS-MMT enhanced the characteristic properties of UP as a consequence of good dispersion in the polymer matrix. Scanning electron microscopy (SEM) images support effective POSS-MMT dispersion leading to tensile strength enhancement of a UP/POSS-MMT nanocomposite (3 wt.% POSS-MMT) by 54.7% as compared to that for unmodified UP. TGA displays a 35 °C improvement of thermal stability (10% mass loss) at 5% POSS-MMT incorporation, while the electrical conductivity is improved by 108 S/m (3 wt.% POSS-MMT) in comparison to that for unmodified UP. The conventional obstacle of UP associated with shrinkage weight loss during curing seems to be moderated with POSS-MMT incorporation (3%) resulting in a 27.8% reduction in shrinkage weight loss. These fabricated nanocomposites expand the versatility of UP as a high-performance material owing to enhancements of properties.

A Novel Approach to Enhance Mechanical and Thermal Properties of SLA 3D Printed Structure by Incorporation of Metal-Metal Oxide Nanoparticles.

Silver (Ag) ornamented TiO2 semiconducting nanoparticles were synthesized through the sol-gel process to be utilized as nanofillers with photo resin to enhance the mechanical and thermal properties of stereolithography 3D printed objects. The as-prepared Ag-TiO2 nanoparticles (Ag-TNP) were typified and qualified by XRD, XPS, Raman, and FESEM; TEM analysis dissected the morphologies. The enhancement in the tensile and flexural strengths of SLR/Ag-TNP nanocomposites was noted as 60.8% and 71.8%, respectively, at the loading content of 1.0% w/w Ag-TNP within the SLR (stereolithography resin) matrix. Similarly, the thermal conductivity and thermal stability were observed as higher for SLR/Ag-TNP nanocomposites, equated to neat SLR. The nanoindentation investigation shows an excerpt hike in reduced modulus and hardness by the inclusion of Ag-TNP. The resulted thermal analysis discloses that the introduction of Ag-TNP can appreciably augment the glass transition temperature (Tg), and residual char yield of SLR nanocomposites remarkably. Hence, the significant incorporation of as-prepared Ag-TNP can act as effective nanofillers to enhance the thermal and mechanical properties of photo resin.

Novel Unsaturated Polyester Nanocomposites via Hybrid 3D POSS-Modified Graphene Oxide Reinforcement: Electro-Technical Application Perspective.

The latest trends in technologies has shifted the focus to developing innovative methods for comprehensive property enhancement of the polymer composites with facile and undemanding experimental techniques. This work reports an elementary technique to fabricate high-performance unsaturated polyester-based nanocomposites. It focuses on the interactive effect of polyhedral oligomeric silsesquioxanes (POSS)-functionalized graphene oxide (GO) within the unsaturated polymermatrix. The hybrid framework of POSS-functionalized graphene oxide has been configured via peptide bonding between the aminopropyl isobutyl POSS and graphene oxide. The synergistic effect of POSS and graphene oxide paved the way for a mechanism to inculcate a hybrid framework within the unsaturated polyester (UP) via in situ polymerization to develop UP/GO-POSS nanocomposites. The surface-appended POSS within the graphene oxide boosted its dispersion in the UP matrix, furnishing an enhancement in tensile strength of the UP/GO-POSS composites by 61.9%, thermal decomposition temperature (10% mass loss) by 69.8 °C and electrical conductivity by 108 S/m, in contrast to pure UP. In particular, the homogenous influence of the POSS-modified GO could be vindicated in the surging of the limiting oxygen index (%) in the as-prepared nanocomposites. The inclusive property amelioration vindicates the use of fabricated nanocomposites as high-performance nanomaterials in electrotechnical applications.

Enhanced Mechanical and Thermal Properties of Stereolithography 3D Printed Structures by the Effects of Incorporated Controllably Annealed Anatase TiO2 Nanoparticles.

Fabrication of low-cost, durable and efficient metal oxide nanocomposites were successfully synthesized and reinforced with photo-resin via 3-dimensional printing. Here, we put forward a novel approach to enhance the mechanical and thermal behaviors of stereolithography (SLA) 3D printed architecture by adding TiO2 nanoparticles (TNPs) in different crystalline phases (anatase and rutile), which were obtained at different annealing temperatures from 400 °C to 1000°C. The heat-treated anatase TNPs were scrutinized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, diffusive reflectance spectroscopy (DRS), and transmission electron microscopy (TEM) analysis. Among all the samples, at 800 °C, annealed anatase TNPs exposed a highly crystalline anatase phase, having a low energy bandgap and a comparably high tensile strength (47.43 MPa) and high elastic modulus (2.261 GPa) for the 3D printed samples, showing improvement by 103% and 32%, respectively, compared with the printed pristine stereolithography resin (SLR) sample. Moreover, enhanced storage modulus and tan δ values were achieved via the better interfacial interactions between the incorporated nanofillers and the SLR matrix. In addition to this, enhanced thermal conductivity and thermal stability of the SLR matrix were also noted. The low energy bandgap and nanoscale size of the fillers helped to achieve good dispersion and allowed the UV light to penetrate at a maximum depth through the photo resin.

Controllably Alloyed, Low Density, Free-standing Ni-Co and Ni-Graphene Sponges for Electrocatalytic Water Splitting.

Synthesis of low cost, durable and efficient electrocatalysts that support oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are the bottlenecks in water electrolysis. Here we propose a strategy for the development of controllably alloyed, porous, and low density nickel (Ni) and cobalt (Co) based alloys - whose electrocatalytic properties can be tuned to make them multifunctional. Ni and Co based alloy with the chemical structure of Ni1Co2 is identified as an efficient OER catalyst among other stoichiometric structures in terms of over potential @ 10 mAcm(-2) (1.629 V), stability, low tafel slope (87.3 mV/dec), and high Faradaic efficiency (92%), and its OER performance is also found to be on par with the benchmarked IrO2. Tunability in the porous metal synthesis strategy allowed the incorporation of graphene during the Ni sponge formation, and the Ni- incorporated nitrogen doped graphene sponge (Ni-NG) is found to have very high HER activity. A water electrolysis cell fabricated and demonstrated with these freestanding electrodes is found to have high stability (>10 hours) and large current density (10 mAcm(-2) @ 1.6 V), opening new avenues in the design and development of cost effective and light weight energy devices.