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Fiber-reinforced green composites made from natural plant fibers are an increasingly popular sustainable alternative to conventional high-performance composite materials. Given the variety of natural fibers themselves, and the even larger variety of possible composites with specific fiber dosage, fiber orientation distribution, fiber length distribution, and fiber–matrix bond characteristics, micromechanics-based modeling is essential for characterizing the macroscopic response of these composites. Herein, an analytical multiscale micromechanics model for elastic homogenization is developed, capable of capturing the variety. The model features (i) a nanoscopic representation of the natural fibers to predict the fiber stiffness from the universal stiffness of the fiber constituents, mainly cellulose, (ii) a spring-interface model to quantify the compliance of the fiber–matrix bond, and (iii) the ability to model any (and any combination of) orientation distribution and aspect ratio distribution. Validation is performed by comparing the predicted stiffness to experimental results for as many as 73 composites available in the literature. Extensive sensitivity analyses quantify the composite stiffening upon increasing fiber volume fraction, fiber alignment, fiber length, and fiber–matrix interface stiffness, respectively. [ABSTRACT FROM AUTHOR]

Abstract Biocomposites are promising materials for traditional composites replacement in specific applications due to their interesting properties and sustainability. Although the composite components are manufactured near net shape, some machining operations, commonly drilling, are commonly required prior to mechanical joining of the components. Tool geometry, mainly the point angle of the drill, strongly affects the performance of the drilling process of composites in terms of machining induced damage. The aim of this work is analyzing the influence of the point angle of the drill on the damage generated during drilling of 100% biodegradable composite, using both numerical and experimental approaches. The novelty of the work relies on the lack of studies of drilling 100% biodegradable composites. The influence of the point angle on the thrust forces and hence in the machining induced damage was demonstrated. [ABSTRACT FROM AUTHOR]

The purpose of this article is to understand the influence of typical composite parameters (interfacial bond strength, surface-area and fibre mechanical properties) on the tensile properties of nonwoven composite materials. The materials investigated were flax, hemp and Poly-(propylene) (PP) and Maleic Anhydride-grafted PP (MAPP), which provide different configurations in terms of fibre mechanical properties, bundle individualization and fibre/matrix interface. Whereas hemp fibres exhibit poorer tensile properties and lower bundle individualization than flax fibres, their higher lignin content evaluated by FT-IR analysis improves the interfacial shear strength (IFSS) with PP and MAPP. However, the tight interface developed with hemp fibres has only a weak effect at the scale of composites. With low-IFSS systems such as plant fibres associated with polyolefin matrices, mechanical properties at the macroscale are governed by the fibre mechanical properties and bonding area rather than by the interfacial bond strength. [ABSTRACT FROM AUTHOR]

This work deals with fibrous biocomposites prepared by using nettle and poly(lactic acid) fibers and employing carding and compression-molding processes. The role of carding process in determining the tensile strength of the biocomposites was analyzed. The tensile, bending and impact properties of the biocomposites were found to increase initially with the increase of nettle fiber content till 50 wt% and decrease afterwards. The thermogravimetric analysis inferred that the thermal stability of the biocomposites increased with the increase of nettle fiber content. The dynamic mechanical analysis showed that the biocomposites exhibited high storage modulus, low loss modulus, and low damping factor. Further, the biocomposites exhibited excellent biodegradability and their biodegradability increased with the increase of nettle fiber content. Overall, the biocomposite prepared with equal weight proportion of nettle and poly(lactic acid) showed high potential for automotive dashboard panel application. [ABSTRACT FROM AUTHOR]

Natural fibers are not as rigid as glass or carbon fibers. During composites extrusion and injection molding, they tend to bend and twist in the polymeric matrix, thus resulting in fiber waviness and decreased mechanical properties of natural fiber composites. The most widely used models for the estimation of interfacial shear strength (IFSS) and elastic modulus, which consider the fiber aspect ratio and mechanical properties of the fiber and matrix, do not consider these important features. In order to account for fiber waviness, an effective fiber length is proposed in this paper. The undulation of the fibers is approximated with a sinusoidal arc along with a calculated new length. The proposed correction factor depends on the wavelength and amplitude of the wave approximating the fiber. To verify this method, blends of polylactic acid (PLA) and polycarbonate (PC) (prepared with and without an interchange reactions catalyst) with addition to various percentages of cellulosic fibers (5 wt%, 10 wt% and 15 wt%) have been prepared and characterized. It has been demonstrated that by considering the corrected length values, it is possible to predict the mechanical properties and the effective reinforcement attained in the composites by using the most widely used models. In particular, the prediction of the elastic modulus is slightly affected by this correction, whereas the calculation of IFSS is strongly dependent on it. [ABSTRACT FROM AUTHOR]

[Display omitted] Plastic pollution has become a global threat to humanity. Fortunately, humanity has always found ways of overcoming such threats through multipronged approaches. To overcome this current threat brought about by anthropogenic linear pattern of take-make-use-dispose of fossil-based plastics, an intentional approach of adopting biobased plastics which are renewable has taken shape. In this approach, governments, industry, and academia are at the forefront of making determined commitments to slow down the spiralling carbon footprint and aim at net zero carbon emissions by 2050. In this regard, PHAs which have a rich resume of desired properties to replace non-renewable fossil-based plastics are increasingly becoming popular. However, PHA production cost is still high compared with the fossil-based plastics and there exists properties performance gap because they are typically brittle, especially the short chain length PHAs (Scl-PHAs). Considerable efforts are geared towards tuning the mechanical properties as well as reducing the cost to meet the market requirements. The most authentic way of tackling these twin-challenges of reducing the cost of PHA products and their properties enhancement is the incorporation of fillers sourced from renewable sources, especially the plant biomass. In this comprehensive review, Scl-PHAs biopolymers are discussed, their modifications with plant biomass (natural fibres and components, agro-residues, and industrial residues) are elucidated. Moreover, their wide scope of applications, sustainability performance (biodegradation studies) and other viable end-of-life options are amply discussed. Finally, we draw conclusions and highlight future opportunities in this exciting bioplastic area. [ABSTRACT FROM AUTHOR]

In this paper, analytical and 3D numerical models are developed to investigate the mechanical behavior of sandwich pipe under internal pressure loading. The suggested models provide an exact solution for stresses, strains and displacement on the sandwich pipe, which is made of epoxy material for the core layer and reinforced materials with an alternate-ply for the skin layers. The aim of this analysis is to evaluate the potential applications of jute and pineapple leaf fiber (PALF) bio-fibers in order to replace glass synthetic fibers generally employed in sandwich pipes. In this subject, a failure analytical analysis was developed using TSAI-WU criterion. The results of stress, strain and displacement distribution through the thickness are presented for the analytical and numerical models. The comparison between the both models results show a very good agreement. In order to increase the rigidity of a biocomposite sandwich and reduce the gap compared with a synthetic sandwich, a gradual reinforcing of layer numbers was chosen, which permitted the best behavior. The ultimate pressure and safety factors obtained by increasing biocomposite layers are significant for composite transportation pressure pipelines, especially for sandwich pipe based on PALF/epoxy. • We aim at modeling a sandwich pipe under internal pressure loading using analytical and 3D numerical models for failure analysis. • The structure is a made of epoxy material for the core layer and reinforced materials with an alternate-ply for the skin layers. • Evaluate the potential applications of bio-fibers in order to replace synthetic fibers generally employed in sandwich pipes using TSAI-WU criterion. • Substituting synthetic fibers by bio-fibers yields a satisfactory result by increasing the number of layers. [ABSTRACT FROM AUTHOR]

A study of the impact behaviour and the post-impact residual strength of fully biodegradable composites is presented in this work. To this end, low-velocity impact tests and compressive residual strength tests were carried out on flax/PLA laminates. The results were compared with carbon/epoxy laminates, showing some important advantages in terms of absorbed energy and normalized residual strength. The reason was attributed to different energy absorption mechanisms; the main failure mode in flax/PLA laminates is fibre failure while residual strength of carbon/epoxy laminates is dominated by delaminations. [ABSTRACT FROM AUTHOR]

Composite materials based on renewable agricultural and biomass feedstocks are increasingly utilized as these products significantly offset the use of fossil fuels and reduce greenhouse gas emissions in comparison with conventional petroleum-based materials. However, the inclusion of natural fibers in polymers introduces several challenges, such as excess water absorption and poor thermal properties, which need to be overcome to produce materials with comparable properties to the conventional composite materials. Instead of using rather expensive chemical and physical modification methods to eliminate these aforementioned challenges, a new trend of utilizing waste, residues, and process by-products in natural fiber-polymer composites (NFPCs) as additives or reinforcements may bring considerable enhancements in the properties of NFPCs in a sustainable and resilient manner. In this paper, the effects of waste materials, residues or process by-products of multiple types on NFPCs are critically reviewed and their potential as NFPC constituents is evaluated. [ABSTRACT FROM AUTHOR]

The production of ligno-cellulosic biomass-based composites requires the development of new methodologies to evaluate the reinforcement potential of a given biomass, such as miscanthus studied in the work. Miscanthus stems from thirteen genotypes were broken into elongated fragments and mixed with polypropylene composites in an internal mixer. The aim is to find the best protocol able to discriminate miscanthus genotypes for their reinforcement capability. The following process parameters were optimized in order to maximize the reinforcement effect of the stem fragment filler: mixing parameters (mixing time, rotor speed and chamber temperature), temperature, fragment content, size and length distributions and coupling agent. The relationship between the process parameters and the mechanical properties of composites were analyzed to evaluate the influence of genotype on reinforcement performance, showing the robustness of the protocol in effectively discriminating genotypes according to their reinforcing capacity. [ABSTRACT FROM AUTHOR]

Biodegradable fiber-reinforced biocomposites from steam-exploded coconut fibers and polylactic acid (PLA) and polybutylene succinate (PBS) plastic were developed in this study. Biocomposite filaments and samples were produced using a commercial-scale screw extruder and a 3D printer, respectively. In-depth mechanical and thermal analyses were also performed. The results showed that the tensile strengths of PLA mixed with 3% coconut fiber (PLA97/F3) and 6% coconut fiber (PLA94/F6) decreased by approximately 22% and 23%, respectively, compared to the 64% reduction of that of the original PLA after four-week storage. The bending modulus of the PLA/fiber composite was better than that of the original PLA (21–29% higher), whereas a 5–8% improvement was observed for the PLA/PBS/fiber composites. The impact strengths of PLA97/F3 and PLA77/PBS20/F3 were approximately 8.5% and 7.4% higher than those of the original PLA and PLA/PBS, respectively. During the degradation test, both PLA97/F3 and PLA77/PBS20/F3 exhibited higher tensile strengths than the original materials. Finally, this research presents encouraging results for the production of biodegradable fiber-reinforced biocomposites that are applicable to 3D printing platforms. The final products can be used as replacement or aftermarket components of automobiles. • PLA, PBS, and steam-exploded coconut fiber were used for filament production. • The 3D-printed biocomposites were subjected to mechanical and thermal tests. • Coconut fiber is effective as a natural fiber reinforcement material. • The products have higher tensile strengths than original materials during degradation test. [ABSTRACT FROM AUTHOR]

Environmental awareness of the global waste problem has driven the development of new green composites made from either renewable or biodegradable materials. Among the variety of available green composites, natural composites based on poly-lactic acid (PLA) have shown noteworthy performance due to their short degradation time after disposal, good strength, and ease of processing by conventional methods. In particular, green composites manufactured with PLA matrix reinforced with Manicaria Saccifera fabric (MF) display mechanical properties that have shown to be very competitive compared with similar materials. In this study, the tensile properties of a green composite of PLA reinforced with MF are optimized by using a Taguchi method approach. The processing parameters, fabric chemical treatment parameters, compression molding parameters, and fiber content are analyzed simultaneously to yield the optimum biocomposite properties. The predicted optimum parameters are experimentally verified. Tensile tests and scanning electron microscope (SEM) analysis are used. Significant improvements on both the tensile strength (114.2%), and the elastic modulus (120.6%) of the biocomposite are achieved. [ABSTRACT FROM AUTHOR]

The clean and sustainable development of biomass resources has attracted tremendous attention to alleviate the increasingly serious energy depletion and environmental problems. Hence, it is urgently needed to design a green product through a cleaner production strategy to bridge the gap between materials and sustainability toward environmental protection and practicality. Herein, a bamboo fiber/polybutylene succinate (PBS) biocomposite that carries silver nanoparticles (AgNPs) with electromagnetic interference (EMI) shielding and antibacterial activity, as well as the performance of interface reinforcement, were prepared using a green, efficient, and scalable bionic strategy of PDA coupling with minimal environmental footprint. The proposed bamboo fiber/PBS biocomposites, which showed multifunctionality and environmental adaptability, revealed good antibacterial activity, where the average inhibition zone diameters against E. coli and S. aureus bacteria reached 5.37 ± 0.36 and 3.96 ± 0.74 mm, respectively. Simultaneously, gains in the EMI shielding effectiveness (∼29.72 dB) and mechanical properties (improved by 24.58% in tensile strength, 39.13% in tensile modulus, 14.60% in flexural strength, and 19.67% in flexural modulus) were realized. Overall, this work displays a novel pathway toward eco-friendly and multifunctional nature fiber/polymer composites for high-value utilization. A green and sustainable natural fiber-reinforced polybutylene succinate biocomposite carrying silver nanoparticles based on a clean, simple and bionic strategy was proposed for antibacterial application and electromagnetic interference shielding. [Display omitted] • An eco-friendly biocomposite was realized via a green and bionic strategy. • AgNPs were synthesized through a clean synthetic route. • Biocomposites exhibit a remarkable EMI shielding effectiveness. • Enhanced interfacial interaction was attained. • Biocomposites possess antibacterial performance towards E. coli and S. aureus. [ABSTRACT FROM AUTHOR]

This paper presents and analyzes the behavior of bumper beams made of PLA/flax composites subjected to low velocity impacts. The relevance of this material resides in the biodegradability of both fibers and matrix. Moreover, the after-impact behavior of this composite is excellent due to the absence of delamination. Impact tests have been performed using a drop weight tower within the range of impact energies 5 J ≤ E imp ≤ 73 J. The experimental setup enabled the measuring of impact velocity, residual velocity, load-time history and failure mode. Results show that damage generated during impact produces a significant reduction of residual stiffness but the residual strength is not affected by damage generated in the range of the applied impact energies considered. [ABSTRACT FROM AUTHOR]

The use of 100% biodegradable composites in the industry is increasing significantly over the years, mainly due to their excellent properties as well as to the growing ecologic concern. However, after their manufacture, the composite pieces do not always have the final shape, requiring subsequent processing operations, usually drilling and trimming. The performance of cutting processes on fully biodegradable composites are often limited by induced damage as fraying and delamination. This type of phenomena is related, among others, with the cutting parameters and geometries of the tool. Orthogonal cutting is a simplified process that could help in the understanding of damage mechanisms, it is a well-known technique in traditional composites but its use in biocomposites is an almost unexplored field. This work focuses on flax/PLA 100% biodegradable woven composites. The specimens have been manufactured with different angles of orientation, ranging from 0° to 60°, being subjected to orthogonal cutting in a special machine developed for that purpose that allows to develop cutting tests with linear displacement at high speeds. Damage extension, failure modes, and cutting forces are analyzed allowing the extraction of important experimental information. [ABSTRACT FROM AUTHOR]

This study investigates the evolution of hygromechanical properties of flax/PP nonwoven composites in a wide range of environmental Relative Humidity (RH) conditions from 10 to 98% RH. The influence of microstructure with various porosity content (Φ = 5, 30, 50%) on the mechanical and hygroscopic behaviours is studied and compared to glass/PP composites as a baseline. No significant changes in the moisture content and mechanical properties of glass-fibre reinforced composites are observed. For flax fibre nonwoven composites, the porosity greatly impacts the kinetic of sorption with moisture saturation varying from 9 h to 15 days with decreasing voids. Hygroscopic expansion is hardly modified by the porosity content while anisotropic expansion is always observed. Tensile behaviour and properties are slightly changed over a range of 10–75%RH but negatively impacted between 75% and 98% RH. Interestingly, unlike the tangent tensile modulus and strain at rupture of flax/PP composites, the yield strength exhibits a non-monotonic trend with an optimal value over 50% RH; compressive stresses at the fibre/matrix interface induced by flax fibres hygroexpansion are proposed to explain this trend. • Evolution of hygromechanical properties of flax/PP non-woven composites was investigated. • A large range of porosity (5, 30, 50%) and humidity (10–98%) was explored. • The kinetic sorption behaviour was greatly impacted by porosity content. • Tensile behaviour and properties are slightly changed over a range of 10–75%RH. [ABSTRACT FROM AUTHOR]