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Regenerative biomaterials play a crucial role in the success of maxillofacial reconstructive procedures. Yet today, limited options are available when choosing polymeric biomaterials to treat critical size bony defects. Further, there is a requirement for 3D printable regenerative biomaterials to fabricate customized structures confined to the defect site. We present here a 3D printable composite formulation consisting of polycaprolactone (PCL) and silk fibroin microfibers and have established a robust protocol for fabricating customized 3D structures of complex geometry with the composite. The 3D printed composite scaffolds demonstrated higher compressive modulus than 3D printed scaffolds of PCL alone. Furthermore, the compressive modulus of PCL

There is an enormous demand for bone graft biomaterials to treat developmental and acquired bony defects arising from infections, trauma, tumor, and other conditions. Polycaprolactone (PCL) has been extensively utilized for bone tissue engineering but limited cellular interaction and tissue integration are the primary concerns. PCL-based composites with different biomaterials have been attempted to improve the mechanical and biological response. Interestingly, a few studies have tried to blend PCL with aqueous silk fibroin solution, but the structures prepared with the blend were mechanically weak due to phase mismatch. As a result, silk microparticle-based PCL composites have been prepared, but the microfibers-reinforced composites could be superior to them due to significant fiber-matrix interaction. This study aims at developing a unique composite by incorporating 100-150 μm long (aspect ratio; 8:1-5:1) silk-fibroin microfibers into the PCL matrix for superior biological and mechanical properties. Two silk variants were used, that is, Bombyx mori and a wild variant, Antheraea mylitta, reported to have cell recognizable Arginine-Glycine-Aspartic acid (RGD) sequences. A. mylitta silk fibroin microfibers were produced, and composites were made with PCL for the first time. The morphological, tensile, thermal, biodegradation, and biological properties of the composites were evaluated. Importantly, we tried to optimize the silk concentration within the composite to strike a balance among the cellular response, biodegradation, and mechanical strength of the composites. The results indicate that the PCL-silk fibroin microfiber composite could be an efficient biomaterial for bone tissue engineering.

Composite filament materials with embedded sensors are increasing in demand to create 3D printed hierarchical sensor structures in a cost-effective and scalable way for the development of wearable and geometry-conforming sensing devices. Traditional methods of encapsulating sensors with polymers are implemented through techniques such as adhesive bonding and potting. For microelectronic device encapsulation, the plastic moulding technologies are employed. However, final products from these methods have geometry constraints and are not easily customizable. This paper presents a methodology of fabrication of polymer filaments embedded with 550-µm radio-frequency identification (RFID) chip using extrusion process for 3D Printing applications. The fabricated filament (3 mm diameter) is manufactured with a 1.5 mm extrusion nozzle specifically designed for this process and controlled by an RFID reader. The RFID sensor filaments produced by this extrusion encapsulation technique were successfully used to produce objects on an existing Fused Deposition Modelling (FDM) 3D printing machine. Such filaments and printed devices are wireless, battery-less, flexible, customizable, and repairable, and hence are advantageous in new sensor applications including the internet of things (IoT). The 3D printed objects produced via this process will have the ability to sense the environment and communicate with reader devices due to their unique embedded RFID codes. This development will subsequently open new avenues for meeting the growth in IoT demands forecast as a pillar of industry 4.0.

This paper presents a novel 3D-printable polymer-based liquid antenna for radio frequency identification (RFID) in the ultrahigh-frequency (UHF) band. Fused deposition modelling, the most widespread and inexpensive 3D printing technique, is used for printing a substrate including polypropylene (PP) and acrylonitrile butadiene styrene (ABS). An ALN-9762-WRW type RFID tag containing a meander metal antenna is modified and printed with microfluidic channels in the substrate. As an ionic liquid, a saltwater dilution is injected into the microfluidic channels designed via a computer-aided design program. A fabricated hybrid liquid antenna is tested using a 200mW UHF RFID reader with the ISO 18000-6C EPC Gen2 protocol. The sensitivity to liquid antenna radiation is measured at distances of 20–900 mm by varying saltwater dilution’s salinity and conductivity between 0 and 12000 ppm and 0-20000μS, respectively. Besides saltwater, an essential oil, peppermint oil (C62H108O7), is also used for liquid antenna. The absorption, refraction, reflection, and scattering characteristics of the polymer substratum are explored in the estimation method. The essential oil produces a buffer area in the 3D layers, which can change the polarization of the antenna. The designed and fabricated 3D-printed hybrid liquid antenna can be utilized in embedded systems suitable for chemical or biological sensing within perpetual systems such as blood or oil circuits.

To produce plastic parts of high geometrical quality and dimensional stability through injection moulding process there are several key variables that must be considered. These include processing parameters such as packing time, cooling time, packing pressure, melt temperature, mould temperature and the intrinsic melt flow characteristics of polymeric materials used to produce the part. The challenge of producing high quality part is further compounded if the input polymer material is of reclaimed waste streams with inherent inconsistency in their nature. In this work, significant number of simulation-based studies are conducted using Autodesk Moldflow software to delineate the contributing issues pertinent to the part quality and achieve topological optimization by reducing critical parameters of shrinkage and warpage while ensuring overall cycle time viable for industrial production rates. Key simulation variables were obtained through experimental characterization of flow and thermal properties of the recycled olefin plastics. Different gate locations were simulated, and the best gate locations were selected for a two-gate system. These gates were provided with gate valve controllers for controlling the polymer flow to create cascaded injection moulding scenarios. Such scenarios were iterated with the objective of reducing the pressure required for cavity filling and thereby reducing the clamp force required. Optimized melt and mold temperatures of 245 °C, 20 °C were used for all the simulations performed. The result obtained from the most optimized simulation showed an average cycle time of 10.42 secs, volumetric shrinkage of 5.08%, warpage of 1.05 mm and clamp force of 79.81 tonne would be required to produce a part of 200 mm*100 mm*1.5 mm dimensions. Following a cascaded injection setup, it was shown that the clamp force could be reduced by 60.57%.

Attributable to complex structural characteristics, the 3-D hierarchical structures possess different failure modes as compared to the traditional laminate structures, resulting in improved impact resistance properties. In this work, a comprehensive study of ballistic performance of 3-D woven and 3-D knitted structures has been undertaken and suitability of these structures for various applications on the basis of their geometrical distinctiveness has also been described. Different material systems have been investigated which are considered to be suitable for ballistic applications. Ballistic testing has been performed on leading 3-D hierarchical structures woven/knitted by polyamides (aramid, PA-6) and ultra-high-molecular-weight-polyethylene (UHMWPE) filaments to study their failure mechanisms against 30. Cal FMJ projectiles. The experimentation has been performed utilizing light-gas gun apparatus, under the instructions provided by internationally known standard NIJ-0101.06. Furthermore, appropriate sabot design has been scrutinized which is crucial to the whole experimental procedure, as sabots hold the projectile into the gas gun barrel and plays the key role in keeping the projectile straight and maintaining its velocity. Damage patterns were found to be different in knitted and woven structures; as knitted structures showed smaller damage affected region as compared to woven preforms.

Permeation is a combination of diffusion and sorption phenomena. The extent of permeation (gas/vapor/liquid) through a composite polymer material is a function of several factors including the comp...

The present study aims to design high performance functionalized lignin-epoxy composites. In this work, the triethylammonium hydrogen sulphate ionic liquid (IL) was introduced onto the surface of lignin micro/nanoparticles while it was extracted from biomass, to prepare a highly functional and reinforcing IL-Lignin filler in an epoxy matrix. A bio-composite of IL-Lignin epoxy was prepared from IL-Lignin and a fast curing epoxy pre-polymer hardened with an anhydride-based curing agent using a simple one-step method. The thermal degradation mechanisms and the influence of the IL-Lignin on the thermal stability and cure kinetics of IL-Lignin epoxy networks have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fourier Transformation Infrared spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analysis confirm that the ammonium-based IL coupled with lignin is an effective promoter for crosslinking of the epoxy pre-polymer resulting in higher and faster degrees of conversion. Nuclear magnetic resonance spectroscopy reveals the characteristics of IL extracted lignin. Using atomic force microscopy (AFM) and dynamic light scattering (DLS), topographical features of the IL-Lignin surfaces and particle size of lignin at nanoscale were investigated and supporting evidence inferred underpinning the improved mechanical properties. The addition of 2 wt% IL-Lignin yielded an 80% increase in flexural strength (99.10 MPa), a 57% increase in flexural modulus (2.84 GPa), a 52% increase in tensile strength (40.90 MPa) and a 23% increase in toughness (86.08 kJ/m3), compared to the neat epoxy matrix. There was, however, a softening effect on the glass transition temperature due to the addition of IL-Lignin. This particular system of composite matrix is prone to controlled breakdown at the end of its lifecycle even after post cure due to biodegradable lignin linkages.

Cellulose nanocrystals (CNC) are a class of nanoscale biopolymers produced from cellulose sources. CNC materials have gained growing interests which can be attributed to their excellent properties such as excellent biocompatibility, good mechanical properties and high aspect ratio whilst also being an inexpensive material that can be produced from green and renewable sources. Due to the abundant hydroxyl functional groups, the surface of CNC materials are ready to be tuned and functionalized via chemical reactions allowing for many different applications, such as being a reinforcing agent to be incorporated into a hydrophobic polymer matrix. In this review paper,we firstly introduce the general methods for producing CNC from different sources. Different strategies used for surface modification ofCNCare then discussed. Finally, the recent progress on the applications of CNC and CNC composite materials are described in detail.

The ionic polymer metal composite (IPMC) actuator is a kind of soft actuator that can work for underwater applications. However, IPMC actuator control suffers from high nonlinearity due to the existence of inherent creep and hysteresis phenomena. Furthermore, for underwater applications, they are highly exposed to parametric uncertainties and external disturbances due to the inherent characteristics and working environment. Those factors significantly affect the positioning accuracy and reliability of IPMC actuators. Hence, feedback control techniques are vital in the control of IPMC actuators for suppressing the system uncertainty and external disturbance. In this paper, for the first time an adaptive full-order recursive terminal sliding-mode (AFORTSM) controller is proposed for the IPMC actuator to enhance the positioning accuracy and robustness against parametric uncertainties and external disturbances. The proposed controller incorporates an adaptive algorithm with terminal sliding mode method to release the need for any prerequisite bound of the disturbance. In addition, stability analysis proves that it can guarantee the tracking error to converge to zero in finite time in the presence of uncertainty and disturbance. Experiments are carried out on the IPMC actuator to verify the practical effectiveness of the AFORTSM controller in comparison with a conventional nonsingular terminal sliding mode (NTSM) controller in terms of smaller tracking error and faster disturbance rejection.

Two Australian native wooden sources (Acacia Mangium and Eucalyptus Globulus) derived pulps were explored as raw feed stocks to prepare the valuable nanomaterial of cellulose nanocrystals (CNC). After bleaching and acid hydrolysis, cellulose nanocrystals were successfully produced with high yields of approximately 60% for both kraft pulps. According to the characterization of SEM and AFM, the as prepared CNC had a rod like structure with the length and diameter in the range of 200~1000 nm and 10~100 nm, respectively based on the initial wooden source. XRD confirmed the crystalline structure of the resulting CNC. Further characterisation by TGA showed that the chemical treatment of the wood pulp had impact upon the thermal stability, evidenced by a lower onset temperature of the thermal decomposition of CNC.

Graphene has become an important research focus in many current fields of science including composite manufacturing. Developmental work in the field of graphene‐enhanced composites has revealed several functional and structural characteristics that promise great benefits for their use in a broad range of applications. There has been much interest in the production of multiscale high‐performance, lightweight, yet robust, multifunctional graphene‐enhanced fiber‐reinforced polymer (gFRP) composites. Although there are many reports that document performance enhancement in materials through the inclusion of graphene nanomaterials into a matrix, or its integration onto the reinforcing fiber component, only a few graphene‐based products have actually made the transition to the marketplace. The primary focus of this work concerns the structural gFRPs and discussion on the corresponding manufacturing methodologies for the effective incorporation of graphene into these systems. Another important aspect of this work is to present recent results and highlight the excellent functional and structural properties of the resulting gFRP materials with a view to their future applications. Development of clear standards for the assessment of graphene material properties, improvement of existing materials and scalable manufacturing technologies, and specific regulations concerning human health and environmental safety are key factors to accelerate the successful commercialization of gFRPs., This work considers the key approaches for the introduction of graphene nanomaterials into fiber‐reinforced polymer composites so‐called nanoaugmentation and nanoengineering methods to produce multiscale smart composites. The ultimate goal of this work is to facilitate the faster industrial adoption of graphene products by filling current barriers that the technology faces, including supply chain challenges, lack of safety and standardization regulations, as well as the research gaps.

Unlike stochastic foams, 3D printed lattice structures can be created with a tailored microstructure to achieve the desired global mechanical properties. In this study, quasi-static energy absorption of six polymeric lattice structures of different unit cell topologies and deformation behaviours but with identical relative density are investigated. For the first time, a recently developed powerful 3D printing technology, namely Multi Jet Fusion (MJF), is utilized to produce high quality and performance lattices. Nonlinear finite element analysis (FEA) is used to analyse their compressive response and energy-absorbing characteristics. To validate the FEA results, experimental compression tests are performed on two types of lattices. The results of this investigation showed that the global energy absorption of lattices can be improved through controlling and manipulating their micro-topology. It is found that the lattice structures with bending-dominated deformation have low stiffness and strength but provide good energy absorption capability. The stretch and buckling dominated structures are shown to be stiffer and stronger but have low energy absorption performance. The findings of this research identify high performing unit cell geometries that can be used for energy absorption application of lattice structures in the development of advanced 3D printed structures that are superior to stochastic foams. Keywords: Lattice structure, Cell topology, 3D printing, Multi Jet Fusion, Finite element analysis, Energy absorption

Parallel robots feature several favourable properties, including the potential for high acceleration and accuracy. However, in order to minimise cycle times and optimise the usage of factory space, industrial applications commonly include multiple closely mounted robots, working on the same or closely located objects. As parallel robots generally suffer from a limited workspace-to-footprint ratio, attempting to utilise parallel robots for such applications typically leads to issues with mechanical interference. This paper investigates the feasibility of dividing a planar workspace into several smaller areas, each of them serviced by a dedicated planar parallel mechanism. Applications where this arrangement could be beneficial include 2D manufacturing operations, such as water jet cutting and laser cutting. Additionally, the proposed arrangement could be extended by actuating either the work object fixture or the entire array of mechanisms in one additional degree of freedom. The resulting architecture could be beneficial for 3D manufacturing operations, such as additive or subtractive manufacturing. The presented analysis studies the limitations of such architectures in terms of mechanical interference and achievable kinematic performance. Solutions to reduce mechanical interference are introduced and screw-theory-based indices are employed to evaluate the achievable kinematic performance.

This paper is investigating a more environment-friendly type of alkali-activated materials so-called boroaluminosilicate geopolymer (BASG). The microstructural and thermal behaviour of boroaluminosilicate geopolymers is studied using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) respectively. The chemical bonds forming the geopolymeric network as well as the reaction of the matrix at the elevated temperatures up to 600 °C are investigated. Different combinations of sodium silicate, sodium hydroxide solution and borax are utilised to activate fly ash. The effect of boron ions, from the alkaline solution, on forming geopolymer gel is the main idea of the study. FTIR spectroscopy shows that not only boron ions have an undeniable influence on the formation of geopolymer compounds but also the change in the content of sodium silicate has a significant role in the gel homogeneity of geopolymer products. The existence of certain peaks relating to boron compounds is an evidence to the formation of the BASG binder. These peaks vary as the composition of the activator is changed. In addition, TGA results reveal that the water molecules embedded within the matrix could be one of the main reasons for changes in the mechanical characteristics. Loss of water at the temperatures above 200 °C has a similar pattern as of the strength development of the samples. It maintains the significant role of water molecules in the geopolymer structure.

Due to its superior electronic, thermal, and mechanical properties, graphene is considered to be the most promising candidate for constructing energy storage and conversion devices. One important way to exploit the potential of graphene is to create graphene composites with other functional materials. Graphene-based hybrid composites (GHCs) have been fabricated by incorporating inorganic and/or organic species into graphene through covalent and/or noncovalent interactions. Different methods of fabrication resulted in different properties of GHCs. So far, GHCs have found wide applications in various sectors. In this article, recent progress and achievements in the preparation of two- and three-dimensional GHCs are reviewed, followed by detailed discussions on their physical, chemical, and mechanical properties. The article then focuses on the detailed applications of GHCs in energy storage and conversion devices.

Process modelling and simulation for composites manufacturing have advanced remarkably lately, evolving from just an assistive design tool to playing a pivotal role in the optimisation of Liquid Composite Moulding (LCM) processes. In particular, to improve the mould filling stage, the placement optimisation of resin injection gates and air vents on the mould design has received great research attention due to their substantial influence on the manufacturing efficiency and product quality. When optimisation algorithms are introduced into predictive numerical simulations to assist mould design, the notion of simulation-based optimisation is formed. This review provides a comprehensive literature compilation on the state-of-the-art of simulation-based optimisation of gates and vents configuration for LCM processes, focusing on the optimisation algorithms adopted and their respective search strategies. The search performance, solution optimality and application suitability of each algorithm with respect to different moulding scenarios are discussed to provide helpful guidelines for future optimisation studies.

With advances in 3D printing technology, now honeycomb structures can be made with virtually unlimited unit cell geometries and cell arrangements giving a wide range of possible mechanical properties. However, studies on such structures have been mainly limited to the hexagonal honeycombs with little work done on other cell geometries. This paper investigates the effect of unit cell geometry on the in-plane compressive response and energy absorption behaviour of honeycombs using full-scale non-linear numerical simulations. Nine types of honeycombs are designed from different unit cell shapes, but having the same relative density. Finite element analysis is used to simulate the honeycombs’ behaviour under uniaxial compression loading. The results showed that unit cell geometry and cell arrangement affect the honeycombs’ compressive response significantly and provide different energy absorption characteristics. This comparison study shows that the honeycombs in which the deformation mode is dominated by bending of cell edges present a lower stiffness (effective modulus) and compressive strength, but a smoother plateau stress. The honeycombs having their deformation mode dominated by plastic buckling present a higher stiffness with less stable and undulated plateau stress. The results of this study provide more understanding in predicting the global behaviour of honeycomb structures and their energy absorption characteristic through their micro-topology. The effect of cell shape and its arrangement on the selection of honeycombs for energy absorption application is discussed and a methodology is proposed to balance the energy absorption with maximum transmitted stress, which is crucial for energy-absorbing design of structures.

Honeycomb structures have been widely used for impact protection and energy absorption applications. However, studies on such structures have been mainly limited to metallic honeycombs with little research done on polymeric honeycomb structures. The purpose of this paper is to study the in-plane static compressive crushing behaviour and energy absorption capacity of 3D printed polymeric honeycomb structures of different unit cell thicknesses. Uniaxial quasi-static compression tests were performed on hexagonal honeycomb structures of varying wall thicknesses printed in Nylon 12 by fused deposition modelling 3D printing. Numerical simulations using ABAQUS/Explicit finite element analysis software were performed to determine the compressive behaviour of the same honeycomb structures. Gibson and Ashby’s analytical model was also used to determine the theoretical plateau stresses of the honeycombs. The experimental compressive behaviour, plateau stress and energy absorption capacity of the honeycombs w...

The use of Molecular Dynamics (MD) simulations for predicting subtle structural, thermomechanical and related characteristics of lignocellulosic systems is studied. A historical perspective and the current state of the art are discussed. The use of parameterised MD force fields, scaling up simulations via high performance computing and intrinsic molecular mechanisms influencing the mechanical, thermal and chemical characteristics of lignocellulosic systems and how these can be predicted and modelled using MD is shown. Individual discussions on the MD simulations of the lignin, cellulose, lignin-carbohydrate complex (LCC) and how MD can elucidate the role of water on the surface and microstructural characteristics of these lignocellulosic systems is shown. In addition, the use of MD for unearthing molecular mechanisms behind lignin-enzyme interactions during precipitation processes and the deforming/structure weakening brought about by cellulosic interactions in some lignocellulosic systems is both predicted and quantified. MD results from relatively smaller systems comprised of several hundred to a few thousand atoms and massive multi-million atom systems are both discussed. The versatility and effectiveness of MD based on its ability to provide viable predictions from both smaller and massive starting systems is presented in detail.

In fused deposition modeling (FDM) additive manufacturing process, it is often difficult to determine the actual levels of process parameters in order to achieve the best dynamic mechanical properties of FDM manufactured part. This is mainly due to the large number of FDM parameters and a high degree of interaction between the parameters affecting such properties. This requires a large number of experiments to be determined. This paper presents a study on the influence of six FDM process parameters (layer thickness, air gap, raster angle, build orientation, road width, and number of contours) on the dynamic mechanical properties of the FDM manufactured parts using the fraction factorial design. The most influential parameters were statistically obtained through the analysis of variance (ANOVA) technique, and the results indicate that the layer thickness, the air gap, and the number of contours have the largest impact on dynamic mechanical properties. The optimal parameters for maximum dynamic mechanical properties were found to be layer thickness of 0.3302 mm, air gap of 0.00 mm, raster angle of 0.0°, build orientation of 0.0°, road width of 0.4572 mm, and 10 contours. Finally, a confirmation experiment was performed using optimized levels of process parameters, which showed good fit with the estimated values.

Fused Deposition Modelling (FDM) has attained its reputation due to the capability of rapidly fabricating prototypes from concept design to real parts in shorter time and lower cost than traditional manufacturing processes. This study sheds light on the dynamic mechanical properties of Polyphenylsulfone (PPSF) material fabricated by FDM additive manufacturing process considering the effect of its various process parameters. Three major FDM process parameters are considered in this study, namely, raster angle, raster width and build style. Dynamic Mechanical Analysis is carried out with sweeping temperature at three different fixed frequencies, e.g., 1 Hz, 50 Hz and 100 Hz. Taguchi method is employed for the optimization of process parameters towards achieving better damping properties. Experimental results such as maximum storage modulus, maximum loss modulus, peak of Tan Delta and maximum complex viscosity are captured and the effects of process parameters on these damping properties of PPSF samples are investigated.