Additive manufacturing is distinguished from traditional manufacturing techniques such as casting and machining by its ability to handle complex shapes with great design flexibility and without the ...typical waste. Although this technique has been mainly used for rapid prototyping, interest is growing in direct manufacture of actual parts. For wide spread application of 3D additive manufacturing, both techniques and feedstock materials require improvements to meet the mechanical requirements of load-bearing components. Here, we investigated short fiber (0.2–0.4mm) reinforced acrylonitrile–butadiene–styrene composites as a feedstock for 3D-printing in terms of their processibility, microstructure and mechanical performance. The additive components are also compared with traditional compression molded composites. The tensile strength and modulus of 3D-printed samples increased ∼115% and ∼700%, respectively. 3D-printing yielded samples with very high fiber orientation in the printing direction (up to 91.5%), whereas, compression molding process yielded samples with significantly lower fiber orientation. Microstructure–mechanical property relationships revealed that although a relatively high porosity is observed in 3D-printed composites as compared to those produced by the conventional compression molding technique, they both exhibited comparable tensile strength and modulus. This phenomenon is explained based on the changes in fiber orientation, dispersion and void formation.
Advanced templating techniques have enabled delicate control of both nano‐ and microscale structures and have helped thrust functional materials into the forefront of society. Cellulose nanomaterials ...are derived from natural polymers and show promise as a templating source for advanced materials. Use of cellulose nanomaterials in templating combines nanoscale property control with sustainability, an attribute often lacking in other templating techniques. Use of cellulose nanofibers for templating has shown great promise in recent years, but previous reviews on cellulose nanomaterial templating techniques have not provided extensive analysis of cellulose nanofiber templating. Cellulose nanofibers display several unique properties, including mechanical strength, porosity, high water retention, high surface functionality, and an entangled fibrous network, all of which can dictate distinctive aspects in the final templated materials. Many applications exploit the unique aspects of templating with cellulose nanofibers that help control the final properties of the material, including, but not limited to, applications in catalysis, batteries, supercapacitors, electrodes, building materials, biomaterials, and membranes. A detailed analysis on the use of cellulose nanofibers templating is provided, addressing specifically how careful selection of templating mechanisms and methodologies, combined toward goal applications, can be used to directly benefit chosen applications in advanced functional materials.
Cellulose nanofiber templating is a promising approach to obtain advanced functional materials. The unique attributes of cellulose nanofibers can be exploited to impart distinct properties onto the final templated materials. Two major considerations of cellulose nanofiber templating are reviewed: the detailed mechanisms and methodologies used to produce the materials and the specific applications that utilize this templating strategy.
Additive manufacturing (AM) or 3D printing is well known for producing arbitrary shaped parts without any tooling required, offering a promising alternative to the conventional injection molding ...method to fabricate near-net-shaped magnets. In this viewpoint, we compare two 3D printing technologies, namely binder jetting and material extrusion, to determine their applicability in the fabrication of Nd-Fe-B bonded magnets. Prospects and challenges of these state-of-the-art technologies for large-scale industrial applications will be discussed.
This article presents a practical model for evaluating polymer feedstock materials as candidates for 3D printing across a variety of extrusion-based platforms. In order for a material to be ...successfully utilized for 3D printing operations, a series of fundamental conditions must be met. First, pressure-driven extrusion must occur through a given diameter nozzle at a specified flow rate. Second, the extruded material must form and sustain the desired shape. Third, the extruded structure must be able to bridge a specified gap and serve as a mechanically sound foundation for successive deposits. Finally, the deposited structure must be dimensionally stable during the transition to the final state (i.e. fully cured at room temperature). This article presents a framework for extrusion-based printing and a simple viscoelastic model for each of these conditions based on the rheological and thermo-physical properties of the candidate material and the processing parameters of the extrusion-based deposition platform. The model is demonstrated to be a useful tool for the evaluation of example test cases including: high temperature thermoplastics (polyphenylsulfone), fiber reinforced thermoplastics (acrylonitrile butadiene styrene), low-viscosity thermosets (epoxy resins), and thermoplastics with a high coefficient of thermal expansion (polypropylene).
In recent years, Carbon Fiber Reinforced Plastics (CFRP) or Glass Fiber Reinforced Plastics (GFRPs) have become a very common material for aircraft and wind turbine structures. These structures are ...often protected from lightning strikes using conventional metal-based protective films/foils. Non-conventional, non-metallic lightning strike protection (LSP) technologies have not yet been fully realized, but research on non-conventional LSP systems for CFRPs has gained momentum in the last few years. The discovery of new structural conductive materials and improvements in the processing of carbon nano-filler based composites have challenged the conventional metal-based LSP systems by providing the potential for lightweight, non-metallic alternatives. However, a major challenge in using non-conventional LSP is the complex nature of a lightning strike event and its complicated thermal and mechanical impact on CFRP structures. Understanding the direct effect of a lightning strike on a CFRP structure requires understanding multiple transient loads, such as electrical, thermal, magnetic, acoustics, shock, and inertia. This review article focuses on new findings and discusses the complex direct effects of lightning on CFRPs. The focus is to find the important factors that regulate and control the damage to FRPs and they are classified and discussed with the help of available literature based on experimental results. Possibilities and limitations to these new findings are also discussed.
•An aqueous phase reaction has been applied for surface modification of MFC.•Surface modified and oven dried MFC has significantly reinforcement effect for PLA.•Modified MFC has improved ...compatibility and dispersion in PLA matrix.
Microfibrillated cellulose (MFC) is widely used as a reinforcement filler for biocomposites due to its unique properties. However, the challenge of drying MFC and the incompatibility between nanocellulose and polymer matrix still limits the mechanical performance of MFC-reinforced biocomposites. In this study, we used a water-based transesterification reaction to functionalize MFC and explored the capability of oven-dried MFC as a reinforcement filler for polylactic acid (PLA). Remarkably, this oven-dried, vinyl laurate–modified MFC improved the tensile strength by 38 % and Young’s modulus by 71 % compared with neat PLA. Our results suggested improved compatibility and dispersion of the fibrils in PLA after modification. This study demonstrated that scalable water-based surface modification and subsequent straightforward oven drying could be a facile method for effectively drying cellulose nanomaterials. The method helps significantly disperse fibrils in polymers and enhances the mechanical properties of microfibrillar cellulose-reinforced biocomposites.
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•A combination of phenolic hardener with DVB is mixed with DBSA-doped polyaniline complex to make a thermosetting conductive composite.•The phenol-DVB complex can be polymerized ...catatonically in the presence of acid doped-PANI without any additional catalyst.•The new structure of phenol-DVB resin, effectively reduced the de-doping of PANI, rendering high electrical conductivity.•The combination of phenol-DVB also increases the flexural modulus of the prepared composites.
Phenolic resin was mixed with a cross-linking agent divinylbenzene (DVB) to prepare a polyaniline-based electrically-conductive thermosetting polymer composite. It has been shown that this Phenol-DVB mixture can undergo cationic polymerization in the presence of the dodecylbenzene sulfonic acid (DBSA)-doped polyaniline (PANI). Composites with different weight ratios of phenolic resin and DVB were mixed with a fixed weight of DBSA-PANI (i.e. 30 wt. %). Increasing the phenol content in the resin system was found to improve the electrical conductivity of the composite to almost 2700%. This improvement has been assigned to the reduced de-doping of polyaniline in phenol-DVB resin. Active sites of phenol effectively attached to the β carbon of DVB and reduced the proton subtracting species of DVB, leading to reduced de-doping of PANI. This behavior was studied through various characterization techniques including differential scanning calorimetry (DSC), FT-IR spectroscopy and Scanning Electron Microscopy (SEM). Electrical conductivity measurement, mechanical properties, and in-situ electrical conductivity measurements were performed to find the optimized properties of the composite. Optimized composites prepared with the composition of 30 wt. % DBSA-PANI and 70 wt. % of phenol-DVB (50 wt. % each), have shown electrical conductivity of 0.20 S/cm and a flexural modulus of 2.1 GPa, which is a significant improvement in the flexural properties of polymer based-thermosetting composites with similar electrical conductivity. This material can be a potential candidate for the lightning strike protection of fiber reinforced plastics.
Plate-based lattices are predicted to reach theoretical Hashin–Shtrikman and Suquet upper bounds on stiffness and strength. However, simultaneously attaining high energy absorption in these ...plate-lattices still remains elusive, which is critical for many structural applications such as shock wave absorber and protective devices. In this work, we present bi-material isotropic cubic + octet sandwich plate-lattices composed of carbon fiber-reinforced polymer (stiff) skins and elastomeric (soft) core. This bi-material configuration enhances their energy absorption capability while retaining stretching-dominated behavior. We investigate their mechanical properties through an analytical model and finite element simulations. Our results show that they achieve enhanced energy absorption approximately 2–2.8 times higher than their homogeneous counterparts while marginally compromising their stiffness and strength. When compared to previously reported materials, these materials achieve superior strength-energy absorption characteristics, making them an excellent candidate for stiff and strong, lightweight energy absorbing applications.
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Wood and lignocellulosic-based material components are explored in this review as functional additives and reinforcements in composites for extrusion-based additive manufacturing (AM) or 3D printing. ...The motivation for using these sustainable alternatives in 3D printing includes enhancing material properties of the resulting printed parts, while providing a green alternative to carbon or glass filled polymer matrices, all at reduced material costs. Previous review articles on this topic have focused only on introducing the use of natural fillers with material extrusion AM and discussion of their subsequent material properties. This review not only discusses the present state of materials extrusion AM using natural filler-based composites but will also fill in the knowledge gap regarding state-of-the-art applications of these materials. Emphasis will also be placed on addressing the challenges associated with 3D printing using these materials, including use with large-scale manufacturing, while providing insight to overcome these issues in the future.
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