Search Results (10)

The agricultural sector faces growing pressure to enhance productivity and sustainability, prompting innovation in machinery design. Traditional materials such as steel still dominate but are a cause of increased weight, soil compaction, increased fuel consumption, and corrosion. Composite materials—and, more specifically, fiber-reinforced polymers (FRPs)—offer appealing alternatives due to their high specific strength and stiffness, corrosion resistance, and design flexibility. Meanwhile, increasing environmental awareness has triggered interest in biocomposites, which contain natural fibers (e.g., flax, hemp, straw) and/or bio-based resins (e.g., PLA, biopolyesters), aligned with circular economy principles. This review offers a comprehensive overview of synthetic composites and biocomposites for agricultural machinery and equipment (AME). It briefly presents their fundamental constituents—fibers, matrices, and fillers—and recapitulates relevant mechanical and environmental properties. Key manufacturing processes such as hand lay-up, compression molding, resin transfer molding (RTM), pultrusion, and injection molding are discussed in terms of their applicability, benefits, and limits for the manufacture of AME. Current applications in tractors, sprayers, harvesters, and planters are covered in the article, with advantages such as lightweighting, corrosion resistance, flexibility and sustainability. Challenges are also reviewed, including the cost, repairability of damage, and end-of-life (EoL) issues for composites and the moisture sensitivity, performance variation, and standardization for biocomposites. Finally, principal research needs are outlined, including material development, long-term performance testing, sustainable and scalable production, recycling, and the development of industry-specific standards. This synthesis is a practical guide for researchers, engineers, and manufacturers who want to introduce innovative material solutions for more efficient, longer lasting, and more sustainable agricultural machinery. Full article

The use of bio-based and biodegradable matrix materials in fiber-reinforced polymers (FRPs) is an approach to reduce the consumption of fossil resources and the amount of polymer waste. This study aims to assess the influence of the process parameters on the resulting mechanical properties of extruded bio-based and biodegradable continuous fiber-reinforced thermoplastics (CFRTPs) in the form of sheets. Therefore, the impregnation temperature during the production of PLA/flax fiber composites is varied between 220 °C and 280 °C, and the consolidation pressure, between 50 bar and 90 bar. A design of experiments approach is used. Fiber contents of 28.8% to 34.8% and void contents of 6.8% to 15.5% are determined for the composites by optical measurements. To assess the mechanical properties, tensile tests are performed. Using the evaluation software Minitab, a strong negative influence of the consolidation pressure on the tensile modulus and the tensile strength is observed. Increasing the pressure from 50 bar to 90 bar results in a reduction in the tensile modulus of 50.7% and a reduction in the tensile strength of 54.8%, respectively. It is assumed that this is due to fibers being damaged by the external force exerted onto the materials during the consolidation process in the calender. The influence of the impregnation temperature on the mechanical properties cannot be verified. Full article

Bio-based resins, obtained from renewable raw materials, are a more sustainable alternative to oil-based resins for fiber-reinforced polymer (FRP) composites. The incorporation of lignin in those resins has the potential to enhance their performance. This paper presents results of an experimental study about the effects of Lignoboost lignin incorporation on a partially bio-based vinyl ester (VE) resin. Two resins were prepared—without (reference) and with lignin addition (4% by weight) to its main chain—and their chemical, thermophysical, and mechanical properties were compared using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile and shear tests. Results suggest that the addition of lignin to the base resin resulted in a copolymer of increased heterogeneity and higher molecular weight, incorporating stiff and complex aromatic structures in the polymer chain. While requiring high-temperature curing, the VE–lignin copolymer presented improvements of 27% in tensile strength, 4% in shear strength, and increased glass transition temperature by about 8 °C, thus confirming the potential of this natural biopolymer for FRP composite applications. Full article

This paper presents a numerical study to evaluate the fire resistance of concrete beams and slabs incorporating natural fiber-reinforced polymers (FRP). A validated finite element model was applied to carry out a series of numerical studies on fire-exposed reinforced concrete (RC) beams and slabs strengthened with conventional and bio-based FRP composites. The model calculates the temperature-dependent moment–curvature relationship for various segments of the member at each time step, which are then used to calculate the moment capacity and deflection of the member. The variables in the beams and slabs include different strengthening techniques (externally bonded FRP and near-surface mounted FRP), different fiber composites, and fire insulation schemes (uninsulated and insulated). The results from the study indicate that the bio-based FRP-strengthened RC members undergo a faster degradation in moment capacity and also experience higher deflections under fire exposure. This leads to a lower fire resistance in RC members with bio-based FRP composites compared to beams and slabs with conventional FRP-strengthened concrete members. The addition of fire insulation to the bio-based FRP-strengthened members can enhance their fire performance and help achieve the required fire resistance ratings for use in building applications. In this study, the NSM CFRP-strengthened RC beams were found to have a fire resistance of 3 h without any fire insulation; however, the bio-based FRP-strengthened beams required a layer of vermiculite–gypsum-based fire insulation material (of about 25 mm) to achieve similar fire resistance. Full article

Recent research trends focus on developing bio-based (derived from agricultural byproducts) fiber-reinforced polymer (FRP) composites for structural applications. Fire resistance is one of the key issues that need to be addressed for the use of these FRP materials in buildings. The thermal and mechanical properties of the constituent materials essentially determine the fire performance (and the fire resistance rating) of a structural member, and these properties vary with temperature. Further, the properties of composite materials such as the FRP are highly influenced by the composition and type of fibers and matrix, and these thermo-mechanical properties also vary significantly with temperature. Due to this variation, the fire resistance of FRP materials (both conventional and bio-based) poses a major concern for use in buildings. Currently, very few standardized test procedures are available for evaluating the high-temperature material properties of FRP composites. In this paper, a review of testing protocols and procedures for undertaking tests on FRP materials at various elevated temperatures for evaluating their properties is carried out. Recommendations are provided on the most suitable test methods, specimen conditions, testing regime, and other issues associated with testing at elevated temperatures. In addition, the applicability of the proposed test methods is illustrated through a case study on conventional FRP specimens. Further, the applicability of the recommended test procedures for measuring high-temperature properties of bio-based FRP composites is highlighted. Full article

This research investigates the effectiveness of bio-sourced flax fiber-reinforced polymer in comparison with a traditional system based on carbon fiber-reinforced epoxy polymer in order to confine recycled aggregate concretes. The experimental investigation was conducted on two series of concrete including three mixtures with 30%, 50%, and 100% of recycled aggregates and a reference concrete made with natural aggregates. The concrete mixtures were intended for a frost environment where an air-entraining agent was added to the mixture of the second series to achieve 4% air content. The first part of the present work is experimental and aimed to characterize the compressive performance of confined materials. The results indicated that bio-sourced composites are efficient in strengthening recycled aggregates concrete, especially the air-entrained one. It was also found that the compressive strength and the strain enhancement obtained from FRP confinement are little affected by the replacement ratio. The second part was dedicated to the analytical modeling of mechanical properties and stress–strain curves under compression. With the most adequate ultimate strength and strain prediction relationships, the full behavior of FRP-confined concrete can be predicted using the model developed by Ghorbel et al. to account for the presence of recycled aggregates in concrete mixtures. Full article

In this work, Adenine is proposed, for the first time, as a cross-linker for epoxy resins. Adenine is an amino-substituted purine with heterocyclic aromatic structure showing both proton donors, and hydrogen bonding ability. DSC studies show that adenine is able to positively cross-link a biobased DGEBA-like commercial epoxy precursor with good thermal performance and a reaction mechanism based on a ¹H NMR investigation has been proposed. The use of such a formulation to produce composite with recycled short carbon fibers (and virgin ones for the sake of comparison), as well as jute and linen natural fibers as sustainable reinforcements, leads to materials with high compaction and fiber content. The curing cycle was optimized for both carbon fiber and natural fiber reinforced materials, with the aim to achieve the better final properties. All composites produced display good thermal and mechanical properties with glass transition in the range of HT resins (T_g > 150 °C, E’ =26 GPa) for the carbon fiber-based composites. The natural fiber-based composites display slightly lower performance that is nonetheless good compared with standard composite performance (T_g about 115–120 °C, E’ = 7–9 GPa). The present results thus pave the way to the application of adenine as hardener system for composites production. Full article

Fiber Reinforced Polymers (FRPs) are increasingly popular building materials, mainly because of their high strength to weight ratio. Despite these beneficial properties, these composites are often fabricated in standardized mass production. This research aims to eliminate costly molds in order to simplify the fabrication and allow for a higher degree of customization. Complex three-dimensional shapes were instead achieved by a flat reinforcement, which was resin infused and curved folded into a spatial object before hardening. Structural stability was gained through geometries with closed cross-sections. To enable this, the resource-saving additive fabrication technique of tailored fiber placement (TFP) was chosen. This method allowed for precise fibers’ deposition, making a programmed anisotropic behavior of the material possible. Principles regarding the fiber placement were transferred from a biological role-model. Five functional stools were produced as demonstrators to prove the functionality and advantages of the explained system. Partially bio-based materials were applied to fabricate the stool models of natural fiber-reinforced polymer composites (NFRP). A parametric design tool for the global design and fiber layout generation was developed. As a result, varieties of customized components can be produced without increasing the design and manufacturing effort. Full article

The proven effectiveness of highway crossing infrastructure to mitigate wildlife-vehicle collisions with large animals has made it a preferred method for increasing motorist and animal safety along road networks around the world. The crossing structures also provide safe passage for small- and medium-sized wildlife. Current methods to build these structures use concrete and steel, which often result in high costs due to the long duration of construction and the heavy machinery required to assemble the materials. Recently, engineers and architects are finding new applications of fiber-reinforced polymer (FRP) composites, due to their high strength-to-weight ratio and low life-cycle costs. This material is better suited to withstand environmental elements and the static and dynamic loads required of wildlife infrastructure. Although carbon and glass fibers along with new synthetic resins are most commonly used, current research suggests an increasing incorporation and use of bio-based and recycled materials. Since FRP bridges are corrosion resistant and hold their structural properties over time, owners of the bridge can benefit by reducing costly and time-consuming maintenance over its lifetime. Adapting FRP bridges for use as wildlife crossing structures can contribute to the long-term goals of improving motorist and passenger safety, conserving wildlife and increasing cost efficiency, while at the same time reducing plastics in landfills. Full article

A method to modify polymers is that of introducing fibers in a matrix to produce a fiber-reinforced polymer (FRP). Consequently, the aim of this work was to study the compatibility effect of four coupling agents on wool FRP properties, using poly(lactic acid) plasticized with maleinized linseed oil as polymer matrix. The content of wool assessed was 1 phr. The compatibilizers were (3-(2-aminoethylamino)propyl)-trimethoxysilane, trimethoxy (2-(7-oxabicyclo (4.1.0)hept-3-yl) ethyl) silane, tris(2-methoxyethoxy)(vinyl) silane and titanium (IV) (triethanolaminate)isopropoxide. Initially, wool was modified with coupling agents in an acetone/water (50/50) solution. Mechanical properties were evaluated by tensile and flexural properties, hardness by Shore D measurement and impact resistance by Charpy’s energy. Differential scanning calorimetry, dynamic thermo-mechanical analysis, and thermogravimetric analysis were conducted to evaluate the interaction among components and the effect of the coupling agents on the thermal properties of the original material. Color, wettability and scanning electron microscopy were used to describe physical and microstructural properties. Modification of fibers allows achieving improved mechanical properties and changes the thermal properties of the FRPs slightly. Coupling agent treatment helps to formulate PLA–MLO and sheep wool materials and to improve their performance, thereby creating a broader spectrum of applications for PLA maintaining the bio-based character of the material. Full article