Additive Manufacturing: A Novel Method for Developing an Acoustic Panel made of Natural Fiber Reinforced Composite with Enhanced Mechanical and Acoustical Properties

Natural fibers and their composites are being widely used in almost all the applications in this modern era. However, the properties of natural fibers have to be enhanced in order to compete with synthetic fibers. This review paper opens up additive manufacturing, as a novel method for developing an acoustic panel using natural fiber composites with enhanced mechanical and acoustical properties. This approach will help to replace synthetic-based acoustic absorbers with biodegradable composite panels in acoustic applications. This review also covers, poly(lactic acid) as a polymer matrix and its advantages, the available variety of natural fibers as reinforcement in terms of mechanical and acoustical properties. The natural fiber-based filaments used in additive manufacturing and acoustic panels made from the available natural fibers are also elaborated here. This review shows the importance of additive manufacturing and its application to develop novel acoustic panels made of agricultural waste

Composites and foams based on polylactic acid (PLA)

Cette étude est destinée à la production et à la caractérisation des composites d'acide polylactique (PLA) et des fibres naturelles (lin, poudre de bois). Le moussage du PLA et ses composites ont également été étudiés afin d'évaluer les effets des conditions de moulage par injection et du renfort sur les propriétés finales de ces matériaux. Dans la première partie, les composites constitués de PLA et des fibres de lin ont été produits par extrusion suivit par un moulage en injection. L'effet de la variation du taux de charge (15, 25 et 40% en poids) sur les caractéristiques morphologique, mécanique, thermique et rhéologique des composites a été évalué. Dans la deuxième étape, la poudre de bois (WF) a été choisie pour renforcer le PLA. La préparation des composites de PLA et WF a été effectuée comme dans la première partie et une série complète de caractérisations morphologique, mécanique, thermique et l'analyse mécanique dynamique ont été effectués afin d'obtenir une évaluation complète de l'effet du taux de charge (15, 25 et 40% en poids) sur les propriétés du PLA. Finalement, la troisième partie de cette étude porte sur les composites de PLA et de renfort naturel afin de produire des composites moussés. Ces mousses ont été réalisées à l'aide d'un agent moussant exothermique (azodicarbonamide) via le moulage par injection, suite à un mélange du PLA et de fibres naturelles. Dans ce cas, la charge d'injection (quantité de matière injectée dans le moule: 31, 33, 36, 38 et 43% de la capacité de la presse à injection) et la concentration en poudre de bois (15, 25 et 40% en poids) ont été variées. La caractérisation des propriétés mécanique et thermique a été effectuée et les résultats ont démontré que les renforts naturels étudiés (lin et poudre de bois) permettaient d'améliorer les propriétés mécaniques des composites, notamment le module de flexion et la résistance au choc du polymère (PLA). En outre, la formation de la mousse était également efficace pour le PLA vierge et ses composites car les masses volumiques ont été significativement réduites.This study reports on the production and characterization of natural fiber reinforced polylactic acid (PLA) composites. Foaming PLA and its composites was also undertaken to investigate the effect of injection molding conditions (shot size) and natural fiber (flax and wood flour) content on the final properties of the final products. In the first part, PLA was mixed with flax fiber via extrusion and further processed by injection molding to manufacture the final parts. The effect of flax fiber content (15, 25, and 40% wt.) on the morphological, mechanical, thermal, and rheological properties of the composites was evaluated. In the second step, wood flour (WF) was selected to reinforce PLA. Compounding of PLA and WF was carried out in a twin-screw extruder followed by injection molding to obtain the test specimens. A complete series of morphological, mechanical, thermal, and dynamic mechanical analysis was performed to get a complete evaluation of WF addition (15, 25, and 40% wt.) on the properties. Finally, the last step studied PLA composites with natural fibers for the purpose of foaming. Foaming was carried out using an exothermic foaming agent (azodicarbonamide) via injection molding. Injection foaming proceeded after mixing PLA and natural fibers by extrusion. In this case, the shot size (amount of material injected into the mold: 31, 33, 36, 38, and 43% of the machine capacity) and reinforcement content (15, 25, and 40% wt.) were varied. The characterization included mechanical and thermal properties. The results showed that both flax and wood flour led to increased mechanical properties including flexural modulus and impact strength. Moreover, foaming was also effective for neat PLA and PLA composites, i.e. the overall density of the parts was significantly reduced

Current Progress in Biopolymer-Based Bionanocomposites and Hybrid Materials

In recent years, the development of biopolymers based on constituents obtained from natural resources has been gaining considerable attention. The utilization of biopolymers to engineer advanced bionanocomposites and hybrid materials is the focus of increasing scientific activity, explained by growing environmental concerns and interest in the novel features and multiple functionalities of these macromolecules.In this Special Issue, we aim to present the current state of the art in research pertaining to biopolymer-based bionanocomposites and hybrid materials, and their advanced applications. Contributions on the processing of biopolymers and bionanocomposites, the use of diverse biopolymer sources such as polysaccharides, the reinforcement of nanosized materials with biopolymers, and applications of these biopolymers, bionanocomposites, and biohybrid materials will constitute the backbone of this Special Issue

Additive Manufacturing of Bio and Synthetic Polymers

Additive manufacturing technology offers the ability to produce personalized products with lower development costs, shorter lead times, less energy consumed during manufacturing and less material waste. It can be used to manufacture complex parts and enables manufacturers to reduce their inventory, make products on-demand, create smaller and localized manufacturing environments, and even reduce supply chains. Additive manufacturing (AM), also known as fabricating three-dimensional (3D) and four-dimensional (4D) components, refers to processes that allow for the direct fabrication of physical products from computer-aided design (CAD) models through the repetitious deposition of material layers. Compared with traditional manufacturing processes, AM allows the production of customized parts from bio- and synthetic polymers without the need for molds or machining typical for conventional formative and subtractive fabrication.In this Special Issue, we aimed to capture the cutting-edge state-of-the-art research pertaining to advancing the additive manufacturing of polymeric materials. The topic themes include advanced polymeric material development, processing parameter optimization, characterization techniques, structure–property relationships, process modelling, etc., specifically for AM

Development of antibacterial hemp hurd/poly(lactic acid) biocomposite for food packaging

Contemporary research in food packaging is being progressively focused on the development of biodegradable food packaging from biobased materials for exploring alternatives to traditional, non-biodegradable petroleum based plastics. Consequently, bioplastics are increasingly gaining attention in the food packaging industry because of their potential of biodegradability and versatility in processing. The utilization of bioplastics however is limited because of their inherent shortcomings in thermal and mechanical stability. Recently, bioderived fillers and plant fibres are being extensively used to address the thermo-mechanical stability and to lower the overall material cost in comparison to the baseline bioplastics. Incorporation of biobased fillers and functional nanoparticles to bioplastics not only offers functionality but also enhances the cost-to-performance ratio of the biocomposites. To that end, this study focused on the development of cost effective, biodegradable, and functional food packaging material. Poly(lactic acid) has been used in food packaging to replace conventional petroleum based plastics, because it possesses higher mechanical properties, greater versatility in process selection and it is deemed safe for use in food contact. However, apart from the high cost, a major shortcoming of poly(lactic acid) is a slow crystallization, and hence often requiring an added nucleating agent. The addition of low cost biobased filler to poly(lactic acid) not only lowers the overall material cost but also accelerates crystallization kinetics acting as a nucleating agent. Industrial hemp hurd is explored as a biobased filler with poly(lactic acid) for biocomposites to lower material cost and to address environmental concerns associated with plastic recycling. However, a major concern for the combination of biobased fillers with polymer matrices to produce biocomposites is the weak fibre-matrix interfacial bonding. In recent years, several forms of glycidyl methacrylate-grafted polyolefins have been prepared through reactive extrusion or solution copolymerization to address this issue. The glycidyl methacrylate grafted copolymer is a potential compatibilizing agent for reducing the interfacial incompatibility in biocomposites. Hence, development of functional biocomposites for food packaging with poly(lactic acid) as bioplastic matrix, hemp hurd as biobased filler and glycidyl methacrylate as compatibilizer was the goal of this study. Accordingly, a biocomposite was developed using extrusion and injection moulding utilizing hemp hurd and poly(lactic acid) with properties comparable to poly(lactic acid) with grafting based interfacial compatibilization. Interfacial compatibility between poly(lactic acid) and hemp hurd increased with grafted glycidyl methacrylate in comparison to the noncompatibilized control, as corroborated by scanning electron microscopy fractography. The mechanical properties showed increases in the glycidyl methacrylate-grafted hemp hurd/poly(lactic acid) biocomposite, retaining 94% of the neat polymer strength, with increases in crystallinity at 20% (w/w) loading of hemp hurd. The impact strength data demonstrated that the addition of GMA possesses the potential of improving physical and mechanical properties of HH/PLA composites. The onset of thermal decomposition of the biocomposites obtained through TGA was marginally lower than that of neat PLA. The antibacterial property of hemp hurd is anecdotally reported, but not systematically investigated and reported. In this study, the antibacterial activity of hemp hurd against Escherichia coli was investigated. The antibacterial activity of hemp hurd inhibiting the growth of E. coli was significant. To further increase the antibacterial efficacy of hemp hurd, silver nanoparticles was encapsulated into hemp hurd that exhibited high effectiveness. The silver nanoparticles were synthesized into the hemp hurd using a proprietary method developed in collaboration with Ecofibre Pty Ltd. The inclusion of glycidyl methacrylate further assisted in elastic moduli and strength increase at 10–30 wt. % fraction of silver nanoparticle-loaded hemp hurd in poly(lactic acid), with 20 wt. % hemp hurd-filled biocomposite exhibiting the highest range of properties within the biocomposites investigated. Effective antibacterial activity was achieved with distinct decreases of 85% and 89% in bacterial growth at 0.025 wt. % and 0.05 wt. % loading of silver nanoparticle in the biocomposite. The biocomposites also maintained a safe level of heavy metal migration at 0.20–3.08 mg/kg which meets the European Union (EU) legislation (2002/72/EC), substantially lower than the permitted value of 60 mg/kg. Overall, the properties of these developed biocomposites demonstrated discernible potential in development of food packaging applications. Cost-benefit analysis was performed to assess the viability in commercial manufacturing for producing rigid food packaging. The biocomposite sensitivity and financial analyses provided data on the degree and magnitude of uncertainties related to investment to afford better product design, and establish the potential of PLA-industrial hemp biocomposites for food packaging applications. The findings of this study could create a platform upon which packaging designers, food scientists and engineers could initiate to employ biobased materials in their food packaging solutions

PLA composites reinforced with flax and jute fibers—A review of recent trends, processing parameters and mechanical properties

Multiple environmental concerns such as garbage generation, accumulation in disposal systems and recyclability are powerful drivers for the use of many biodegradable materials. Due to the new uses and requests of plastic users, the consumption of biopolymers is increasing day by day. Polylactic Acid (PLA) being one of the most promising biopolymers and researched extensively, it is emerging as a substitute for petroleum-based polymers. Similarly, owing to both environmental and economic benefits, as well as to their technical features, natural fibers are arising as likely replacements to synthetic fibers to reinforce composites for numerous products. This work reviews the current state of the art of PLA compounds reinforced with two of the high strength natural fibers for this application: flax and jute. Flax fibers are the most valuable bast-type fibers and jute is a widely available plant at an economic price across the entire Asian continent. The physical and chemical treatments of the fibers and the production processing of the green composites are exposed before reporting the main achievements of these materials for structural applications. Detailed information is summarized to understand the advances throughout the last decade and to settle the basis of the next generation of flax/jute reinforced PLA composites (200 Maximum).Thanks to the team members of Fibrenamics and Department of Mechanical Engineering, University of Minho, Azurém Campus, Portugal. FCT—Fundação para a Ciência e Tecnologia within the R&D Unit MEtRICs Project Scope UIDB/00319/2020 and R&D Unit 2C2T

Obtaining Properties of Polymeric Filaments for 3D Printing from Dinizia Excelsa Ducke Fiber and Copper Nanoparticles

With many existing contagious diseases, SARS-CoV-2 exemplifies the dangers of emerging infectious diseases, potentially leading to severe acute respiratory syndrome (SARS). In March 2020, the World Health Organization (WHO) declared COVID-19 a pandemic in response to the rapid increase in infections globally. This situation not only highlighted the vulnerability of populations to dangerous pathogens but also underscored the persistent challenges faced by the public health community in preventing and controlling contagious diseases. Furthermore, it led to excessive use of plastics that harm the environment, such as 70% alcohol due to its low cost and ease of use, which increased the use of plastic packaging and its improper disposal. There are studies on bioplastics reinforced with plant fibers, showing good mechanical properties, and using polymer nanocomposites with metal oxide nanoparticles, such as copper, where their incorporation can achieve optical, electronic, mechanical, and antimicrobial enhancements through the filament extrusion process. Therefore, the matrix is not only a support for the nanoparticles but can also improve antibacterial performance and expand the applications of this material to meet different requirements. The objective of this study is to produce, through extrusion, antimicrobial bioplastic filaments (PLA, plant fiber, and copper nanoparticles) for use in 3D printing and evaluate their tensile mechanical properties, Optical Morphology (OM), and Scanning Electron Morphology (SEM). The filaments produced with a plant fiber particle size of 140 µm exhibited superior quality and better mechanical performance, with tensile strengths of 33.63 and 23.83 MPa and elastic moduli of 2.69 and 5.45 GPa compared to those with a particle size of 30 µm

Renewable Biocomposite Properties and their Applications

Recently, with increasing environmental awareness and expanding global waste problems, eco-friendly biofillers have been recognized as a promising alternative to inorganic fillers in the reinforcement of thermoplastic and biodegradable plastics. Therefore, many industries are seeking more eco-friendly materials that will decrease the level of environmental contamination and economic cost. Bacteria cellulose, rice straw, rice husk, natural fiber, lignocellulose, cellulose, and paper sludge are renewable resources owing many beneficial properties; these materials were used to manufacture composite products such as sound absorbing wooden construction materials, interior of bathrooms, wood decks, window frames, decorative trim, automotive panels, and industrial and consumer applications. This chapter elucidates the different renewable biocomposite properties and their applications

Manufacturing, characterization and modelling of biodegradable composite materials

In the recent decades, there has been a high rise in the development of renewable materials due to awareness in environmental care. Part of the research in such materials has focused on the development of biodegradable composites using natural fibres as reinforcement of 'green' plastics. The use of biocomposites means a major reduction in the environmental impact of industrial components after their life cycle, thus, the development of tools for design with biocomposites could mean a breakthrough for its implementation in the industry. In this thesis, the basis for the development of tools for modelling the mechanical behavior of biocomposites have been arise for first time through the development of a constitutive model based on the simulation of the mechanical behaviour through rheological elements. The seven model parameters have been adjusted by quasi-static tensile tests, while the model has been successfully validated by tensile tests at different strain rates. The constitutive model has proved to be valid for composites reinforced with cotton, flax and jute, allowing a greater understanding of the behaviour of those biocomposites, as the fact that the viscoplastic behaviour is mainly produced by fibres behaviour. The existence of a constitutive model for biocomposites opens the doors to its application in structural components of responsibility greatly reducing design costs. Four different biocomposites were chosen to test the versatility of the constitutive model. Biodegradable PLA composites were manufactured by compression moulding combining two types of PLA as matrix and three natural fibres (flax, cotton and jute) as reinforcement. Moreover, the ACC’s were manufactured by solving the surface cellulose of the fibres, which after a regeneration process forms the composite matrix. Thus, four different biocomposites were successfully manufactured in this thesis. The parameters influencing the PLA based biocomposites manufacturing process (temperature, pressure, number of layers, type of fibre and matrix type) have been optimized to obtain a material with a strength greater than 100 MPa, indicating their potential application for replacing traditional composites, especially glass fibre composites. This could mean a large increase in the use of biocomposites in industrial applications such as automotive or aviation. However, it has been observed that biocomposites presents a viscoplastic behaviour with permanent deformations, which is far from the linear elastic behaviour until failure of traditional composites. This has motivated the development of computational tools for biocomposites to predict their behaviour under dynamic conditions such as impacts or machining. Impact test in drop tower were conducted in flax/PLA biocomposites, revealing a high energy absorption, above the absorbed by carbon fibre composites in the range of energies analysed. The main failure mode was fibre failure, while delaminations were not found. Due to this differences in failure modes, the normalized residual strength observed in biocomposites was higher than that reported in carbon fibre reinforced composites. Two different Finite Element Models were developed. First, a linear elastic model was used to reproduce the impact behaviour of ACC plates. Second, a model considering the influence of strain rate on the plastic behaviour of biocomposites was implemented to reproduce the impact behaviour of flax/PLA biodegradable composites. Finally, the different mechanisms of damage induced in drilling had been studied. For this, the damage induced under different cutting speeds, advances and drill geometries was analysed, noting that in this case delaminations were neither found as failure mode, revealing a good cohesion between fibre and matrix. Is also detachable the damage reduction with increasing drill feed rate, which is a novelty that can reduce the processing times of these materials in the industry. These machining tests are the basis for the application of a numerical model based on the constitutive model defined in this work.En las últimas décadas se ha producido un gran auge en el desarrollo de materiales renovables debido a la concienciación en el cuidado del medio ambiente. Parte de la investigación en dichos materiales se ha focalizado en el desarrollo de materiales compuestos biodegradables, empleando fibras naturales como refuerzo de plásticos ‘verdes’. El uso de los biocomposites puede suponer una gran reducción en el impacto ambiental de componentes industriales tras su ciclo de vida, por lo que el desarrollo de herramientas para el diseño con biocomposites significaría un gran avance para su implementación en la industria. En el presente trabajo se han planteado por primera vez las bases para el desarrollo de herramientas para el modelizado de los biocomposites desarrollando un modelo constitutivo que los defina, basándose dicho modelo en la simulación de su comportamiento mecánico por medio de elementos reológicos. Los siete parámetros del modelo han sido ajustados mediante ensayos a tracción cuasi-estáticos, mientras que la validación de los mismos se ha realizado con éxito por medio de ensayos de tracción a distintas velocidades de deformación. El modelo constitutivo ha demostrado ser válido para biocomposites reforzados con algodón, lino y yute, permitiendo una mayor comprensión del comportamiento de los biocomposites, tal como el hecho de que los comportamientos viscoplásticos tienen origen en las fibras y no en la matriz. La existencia de un modelo constitutivo para biocomposites abre las puertas a su aplicación en componentes de responsabilidad estructural reduciendo enormemente los costes de diseño. Se han fabricado distintos materiales para comprobar la versatilidad del modelo constitutivo. Los materiales compuestos biodegradables de PLA se han fabricado mediante modelizado por compresión en caliente, empleando dos tipos de PLA y tres fibras naturales (lino, algodón y yute). Por otro lado, los ACC han sido fabricados mediante la disolución de la celulosa superficial de las fibras, que tras una regeneración conforma la matriz del compuesto. Por lo tanto, se han fabricado con éxito cuatro biocomposites diferentes en el marco de la tesis. Los parámetros que influyen en el proceso de fabricación de los compuestos de PLA (temperatura, presión, número de capas, tipo de fibra y tipo de matriz) han sido optimizados para la obtención de un material con una resistencia superior a los 100 MPa, lo que revela su potencial aplicación para la sustitución de los materiales compuestos tradicionales, especialmente los compuestos de fibra de vidrio. Esto hace prever un gran incremento en su uso en aplicaciones industriales tales como la automoción o la aviación. Sin embargo, también se ha podido observar que los biocomposites presentan un comportamiento viscoso con deformaciones permanentes, lo que dista del comportamiento elástico lineal hasta rotura de los materiales compuestos tradicionales. Esto ha motivado el desarrollo de herramientas de cálculo para los biocomposites para la predicción de su comportamiento en condiciones dinámicas tales como impactos o mecanizados. Se han realizado ensayos de impactos en torre de caída en compuestos de lino/PLA, lo que ha revelado una gran absorción de energía de los mismos, superior a la absorbida por compuestos de fibra de carbono en el rango de energías analizado. El principal modo de fallo localizado en los biocomposites es la rotura de fibras, mientras que no se han encontrado delaminaciones. Debido a esta diferencia en los modos de fallo la resistencia residual normalizada es mayor en biocomposites que en compuestos de fibra de carbono estudiados. Se han desarrollado dos modelos de elementos finitos. En primer lugar, se han reproducido impactos en placas de ACC por medio de un modelo elástico lineal. En segundo lugar, se ha desarrollado un modelo que tiene en cuenta la influencia de la velocidad de deformación en el comportamiento plástico de los biocomposites, el cual fue implementado para reproducir el comportamiento ante impactos de compuestos de lino/PLA. Por último, se han estudiado los distintos mecanismos de daño inducidos en el taladrado de compuestos de PLA. Para ello, se ha estudiado el daño ante distintas velocidades de corte, avances y geometrías de broca, destacando que en este caso tampoco se han localizado delaminaciones como modo de fallo, revelando una buena cohesión entre fibra y matriz. También cabe destacar que se ha determinado una reducción del daño con el incremento de la velocidad de avance, lo que supone una novedad que puede reducir los tiempos de procesado de estos materiales en la industria. Estos ensayos son la base para la aplicación de un modelo numérico basado en el modelo constitutivo definido en este trabajo.Author gratefully acknowledge the support of Spanish Ministry of Economy under the project DPI2013-43994-R and the Carlos III of Madrid University for the financial support during the last three years.Programa Oficial de Doctorado en Ingeniería Mecánica y de Organización IndustrialPresidente: José Fernández Sáez.- Secretario: Eugenio Giner Maravilla.- Vocal: Samuel Charca Maman