Composites Part C Open Access最新文献

In this article, a method is proposed for modifying the Takagi-Sugeno-Kang (TSK) fuzzy model, which enables the incorporation of incomplete data into the modeling process, extracting valuable information from it. The proposed methodology can prove advantageous in scenarios where experimental data are limited, and the exclusion of incomplete data is not feasible. In order to evaluate the proposed method, experimental data on reinforced concrete (RC) columns strengthened using Near-Surface Mounted (NSM) Fiber-Reinforced Polymer (FRP) bars with (hybrid) or without FRP jackets were collected from the existing literature. Since the mentioned strengthening methods are relatively new and are recommended for cases with eccentric loading or slender columns, the number of conducted tests is limited. Subsequently, fuzzy models were constructed using the conventional and the proposed modified methods. The comparison of the results of the two modeling methods demonstrated a higher accuracy of the proposed approach compared to the conventional one. Furthermore, parametric study of strengthening factors was performed, assessing their influence on capacity. It was found that increasing the axial rigidity of NSM FRP first increases the capacity and then decreases it. Additionally, increasing the confinement-related parameter leads to an increase in the capacity of the strengthened columns.

This paper presents a thorough investigation concerning low-velocity impact load assessments and three-point bending tests conducted on reinforced concrete (RC) beams. These beams were strengthened using two separated methods CFRP sheets or GFRP rods through the Near Surface Mounted (NSM) strengthening technique. The impact load was generated by releasing a 150-kg steel projectile from a height of 100 cm. Additionally, the numerical analysis using Finite Element Analysis (FEA) was performed for further investigations. The current study assesses the influence of NSM reinforcement and loading types on the failure mechanism of the retrofitted beams. Both the impact resistance and the flexural capacities of the RC beams show substantial enhancements due to the integration of FRP reinforcement. However, concerning equivalent axial FRP reinforcement stiffness, GFRP rods exhibited notably more significant improvements in the flexural strength of RC beams compared to CFRP strips. The load-carrying capacity of the GFRP rod-retrofitted specimen increased by 24.71 % under the flexural progressive loading, while that of the retrofitted specimen with CFRP strips increased by 15.26 %. Similarly, regarding impact loads, RC beams retrofitted with NSM-GFRP rods have demonstrated superior performance compared to their NSM-CFRP reinforced counterparts. Under impact loading, the maximum mid-span deflection of the strengthened RC beams with GFRP rod and CFRP strips decreased by 40.01 % and 23.36 %, respectively. Furthermore, the failure mode of the NSM-retrofitted specimens was changed from flexural dominant failure to a combined flexural-shear failure in comparison to the reference beams. In the case of impact loading, although the FRP retrofitted beams experienced less damage under the same number of impact loads, the cracking patterns of the tested specimens were shown similar.

This work investigates composites from renewable resources that exhibit high flexibility. The effect of three different weft-knitted structures on the tensile properties, flexural properties, tear resistance and puncture impact properties is analyzed in combination with two different flexible matrix materials. Furthermore, the potential of the knitted structures in flexible composites is compared to a woven fabric and comprehensively discussed. The tear resistance and the total absorbed energy in puncture impact tests were unaffected by the matrix material. Among the knitted structures, the highest tensile strength, tear resistance and impact properties were achieved with the interlock structure, whereas the double jersey with tuck stitch structure resulted in the lowest flexural modulus. However, a much higher tensile strength was achieved with the woven fabric, at the expense of a higher flexural modulus. Overall, knitted structures proved promising to be used in bio-based flexible composites for applications requiring high flexibility without the need for high tensile strength.

This study verified the possibility of using waste material from the food industry (black tea) as functional filler of rotomolded biobased high-density polyethylene-based composites. As part of the experimental work, the influence of the materials preparation, i.e., dry blending versus twin-screw extrusion, on the effectiveness of the stabilizing antioxidant effect of the black tea was analyzed. The aim of the work was to verify whether, despite the initial degradation of the structure of the lignocellulosic filler, it would be possible to keep its antioxidant capacity and the stabilizing effect on the polyethylene matrix. The research showed that the filler allowed to stabilize the polymeric matrix during the rotomolding process, despite the appearance of numerous defects in the form of pores and a reduction in mechanical properties, more significant for composites prepared by dry blending, obtaining elastic modulus drops of about 50 %. Furthermore, the pre-processing step by melt mixing results in a significant improvement of the composite's thermo-oxidation stability, with increases in the oxidation induction time (OIT), from 25 min for the HDPE to over 70 min for composites with 5 % black tea, and improved rheological behavior, preventing the crosslinking of the matrix, indicative of its thermo-oxidative degradation. The tea brewing process caused the decrease of antioxidant activity of the filler; however, it did not significantly affect the antioxidant behavior, maintaining its influence on the polymeric matrix when the material is prepared via twin-screw compounding, which was proved to provide better stability, increasing OIT by approximately 20 min later when compared to dry blending.

Recent advancements in fiber reinforced additive manufacturing leverage the piezoresistivity of continuous carbon fibers. This effect enables the fabrication of structural components with inherent piezoresistive properties suitable for load measurement or structural monitoring. These are achieved without necessitating additional manufacturing or assembly procedures. However, there remain unexplored variables within the domain of continuous fiber-reinforced additive manufacturing. Crucially, the roles of fiber curvature radii and sensing fiber bundle counts have yet to be comprehensively addressed. Additionally, the compression-sensitive nature of printed carbon fiber-reinforced specimens remains a largely unexplored research area. To address these gaps, this study presents experimental analyses on tensile and three-point flexural specimens incorporating sensing carbon fiber strands. All specimens were fabricated with three distinct curvature radii. For the tensile specimens, the number of layers was also varied. Sensing fiber bundles were embedded on both tensile and compression sides of the flexural specimens. Mechanical testing revealed a linear-elastic behavior in the specimens. It was observed that carbon fibers supported the majority of the load, leading to brittle fractures. The resistance measurements showed a dependence on both the number of sensing layers and the radius of curvature, and exhibited a slight decreasing trend in the cyclic tests. Compared with the sensors subjected to tensile stress, the sensors embedded on the compression side showed a lower gauge factor.

Fiber-reinforced composite materials, exemplified by CFRP, offer the possibility of achieving lightweight, high-stiffness, and high-strength structures by continuously and evenly distributing fibers. While topology and orientation optimization methods have been developed for anisotropic materials in the past, there remains a gap in design methods that consider manufacturability, especially for continuous fiber materials. In this study, we propose a design method that takes into account manufacturability, focusing on the aspects of continuity and uniformity in fiber-reinforced composite optimum design. Specifically, we introduce a two-stage optimization approach. In the first stage, we conduct concurrent optimization of topology and fiber orientation. We utilize a level-set function to represent topological configuration, while for orientation, we introduce a “double angle vector”, which enables us to consider fiber properties such as angular periodicity. These design variables are updated by solving partial differential equations based on reaction–diffusion equations. In the second stage, leveraging the optimal orientations obtained in the first stage, we optimize the path-line generation for the manufacture of continuous fiber materials. We introduce a scalar function representing path lines and formulate an optimization problem to ensure that the path lines are both evenly spaced and continuous. The update of design variables in this state is also achieved via solving the partial differential equation. Through the development of this two-stage optimization method, we aim to create an optimal structure with manufacturable continuous fiber materials, incorporating both the topology and fiber orientation that satisfy the requirements of continuity and uniformity.

Despite the extensive research on renewable resources (RR) and their potential applications in composite materials and sandwich structures, there remains a significant dearth of life cycle assessment (LCA) studies that comprehensively evaluate the efficacy of RR in mitigating environmental impacts (EI). To bridge this gap, the present study aims to investigate twelve different designs of sandwich panels, specifically referred to as Fibre Metal Laminates (FML). These FML combine aluminium skins (2024-T3 and 1200-H14), polymer matrices (Epoxy, Polyester, and Castor oil Bio-PU), natural fibres (Sisal, Coir, and Cynodon spp.), surface treatments for aluminium skins (sanding, NaOH, and Washprimer), and treatments for natural fibres (Ground, NaOH-treatment and untreated). A cradle-to-gate LCA is conducted, and the inventories are modelled using the OpenLCA 1.6.3 and ecoinvent 3.9 cut-off regionalized database. EI are evaluated in twelve categories, including climate change, fossil and nuclear energy use, freshwater (acidification, ecotoxicity and eutrophication), human toxicity (cancer and non-cancer), mineral resources use, ozone layer depletion, particulate matter formation, photochemical oxidant formation, and terrestrial acidification. Impact World+ method for Latin America version 1.251 is employed to calculate EI. Nine Eco-efficiency indicators and trade-off analyses are evaluated to gain insights into design decision outcomes. Among the various panels considered, FML12, manufactured with aluminium alloy 1200-H14 treated only with sanding, castor oil biopolymer and untreated coir fibres, present the most consistent eco-efficiency indicators. The reference scenario considers the average characteristics of FML (both environmental and mechanical) for trade-off analysis. Despite the fifty percent chance of better performance, FML12 is the only panel that shows higher mechanical performance and lower EI compared to the reference scenario. The importance of this article lies in the novel results obtained using the proposed eco-efficiency indicators, which can be expanded in further studies on the topic.

Carbon nanotube (CNT) reinforced hybrid polymer composites offer multi-functional and sustainable materials due to fascinating mechanical, electrical and thermal properties. However, many studies reported the impact of CNTs orientation and synergistically enhanced properties of hybrid polymer composites but only a few review literatures are published. This review provides a comprehensive overview of published research by addressing CNT classification, preparation methods, mechanical, thermal, and electrical properties, and potential applications, as due to high strength, high young's modulus, higher thermal and electrical conductivity these nano-dimensional hybrid composites find many applications in aerospace, automotive, electronics, energy storage, sensors, electromagnetic interference (EMI) shielding, engineering, and biomedical fields.

The main goal of this research is to design a very big crawler crane adopting composite material to lightweight the machine itself and compare its performance with the one made of classical structural steel. The research starts by sizing the main boom, assuming three different materials: steel, aluminium alloy and composite material. Many load conditions were involved and different criteria were assumed; there are stress safety factors, stiffness, dynamic performance (modal) and buckling phenomenon which is a very important parameter. Then other innovative load conditions were applied to the crane boom: moving load and time-varying wind speed to study the mechanical behaviour of the new solutions. The last step involves the design of additional elements: counter boom, counterweight, ropes, etc., and evaluating the final weight of the entire machine designed with innovative materials. In particular, the weight of the machine in steel configuration is about 5715 kN while this value reduces to 4670 kN and 3830 kN respectively for aluminum and composite material configurations. In other words, for the composite material solution, the final weight is about 67 % of the same machine built with steel, this value decreases to 34 % if only the main boom is evaluated.

The properties of organic fibre-based hybrid materials are influenced by a variety of factors and even minor changes in these variables can outcome in substantial discrepancies in strength. In this regard, the current study aims to optimise various influencing parameters such as weight percentage, alkaline treatment concentration, and fabrication parameters (compression moulding pressure, and temperature), with the goal of enhancing the overall strength of the composite. Calotropis gigantea-stem and Prosopis juliflora-bark fibres were used in varying weight percentages to create epoxy-based hybrid composites. After fabrication the mechanical characterisation like tensile, flexural, and impact properties of the composites were tested. Taguchi experimental design was applied, and the results were analysed using a hybrid Taguchi-grey relational investigation method. It was observed that a combination of 20 wt.% Calotropis gigantea/20 wt.% Prosopis juliflora/6 % NaOH pretreatment/100 °C temperature with 14 MPa pressure and had the most desirable mechanical properties in the fabricated composites. Calotropis gigantea ranks first in enhancing the composite strength, followed by Prosopis Juliflora, NaOH pretreatment%, compression moulding temperature and pressure. This work highlights the significant role of Calotropis gigantea and Prosopis Juliflora fibres in enhancing composite strength and provides valuable insights for future research in the field of hybrid composite development.