Composites Part C Open Access最新文献

The use of thermoplastic composites as a sustainable alternative to thermosets is gaining increasing popularity due to their improved recyclability at the end of life. The fatigue performance of glass fibre/acrylic, glass fibre/acrylic- polyphenylene ether, and glass fibre/epoxy specimens, under three distinct upper stress levels (R-ratio = 0.1; f = 5 Hz) was studied. S–N curves were established for these specimens both before and after immersing them for three months in seawater (temperature: 50 °C). The dry thermoplastic composites exhibited similar fatigue performance to the thermoset counterpart at higher stress levels, with thermosets showing greater endurance at lower stress levels. Interestingly, the aged specimens showed comparable fatigue endurance, with a slight advantage in favour of the thermoplastic composites and less variability in their data. This study offers important insights into the fatigue performance of thermoplastic composites, emphasising their potential as sustainable alternatives to conventional thermoset composites for various marine applications.

This research reports the results of implementation of composite materials and the complete redesign of a tipping silo semi-trailer. The conventional semi-trailer, used for comparison, was designed based on a Feldbinder commercial model, while the innovative one has the same overall dimensions but a new geometry, while maintaining the same performance in terms of deflection and safety factor. The research involves sizing and verification of the results obtained using finite element software (Solidworks Simulation®) with different loading conditions. The main result is that the optimised solution has the lowest weight, with a reduction of about 28 % considering the same equipment and accessories mounted on the two solutions. The last part of the research concerns an estimate of economic investment containing the return on the initial investment and the reduction in fuel consumption by comparing the two solutions. Considering that the vehicle always carries the maximum (payload = 27,500 kg) and the overall weight reduction of about 1800 kg, there is a reduction in fuel consumption for the proposed solution. The return on investment for the new solution occurs between three/four years depending on the number of kilometres driven annually. Finally, the purpose of this paper is to create an example of a procedure for reducing the carbon footprint and the fuel consumption of vehicles by replace and redesign entire mechanical components, in this case industrial vehicles, that would be useful to follow and replicate for any specific case study and increase the eco-sustainability of industrial manufacturers.

The quest for light weight hybrid polymer composites (HPC) has resulted into multiple materials and structural configurations for achieving high performance in automotive and aerospace applications. Incidentally, the past reported work has (in general) involved variable GSM while investigating reinforced fiber layers. The variable GSM may lead to a random response of each layer to the applied forces and thermal degradation, due to which attributing the role of various layers to results/properties is difficult to ascertain. This research employs a uniform/consistent approach with high GSM (400) based HPC with multiple stacking sequences of glass (G), carbon (C), and Kevlar (K) to investigate thermo-mechanical properties. The research first focuses on fabrication of eleven stacking sequences of hybrid combinations, followed by identification of an optimal sequence based on mechanical (tensile strength, flexural strength, charpy impact resistance) and thermogravimetric analysis (TGA) characterization. Additionally, scanning electron microscopy (SEM) for fracture mechanisms of hybrid composites showing fiber pull out, matrix crack, and delamination. Results show that the tertiary combination having 2 Glass, 5 Carbon and 5 Kevlar layers (G2C5K5) named H9 herein provides a good balance of tensile, flexural, impact resistance and thermal properties; its deviation from the best of each category is within approximately 5, 13.5, 9.9 and 10.9 % (for tensile, flexural, impact, TGA) respectively. The range of properties evaluated in this study is deemed suitable for lightweight aircraft structures.

A semi-analytical procedure is presented for predicting the complete flexural response of partially interacting steel–concrete composite beams up to failure. The governing equation of the Euler–Bernoulli beam theory is solved wherein concrete, steel and the shear connectors joining the concrete slab to the steel beam are assumed to have nonlinear stress-deformation relationships. The adopted constitutive relationship for the connectors allows for partial or full composite action. The solution is applicable to beams and one-way slabs subjected to concentrated or uniform load and/or their combination. The governing equation is numerically solved by satisfying the equilibrium and compatibility requirements along the member. For the reinforced concrete part of the composite beam, a nonlinear moment–curvature relationship is developed that accounts for concrete nonlinearity in compression and for cracking and tension-stiffening in tension as well as for steel reinforcement nonlinearity. The steel profile is assumed to have a bilinear elasto–plastic strain-hardening moment–curvature relationship. Comparison of the proposed model results with the corresponding experimental load–deflection curves and interfacial shear–slip curves of several beams tested by others shows good agreement. The relative simplicity, efficiency and easy application of the present solution make it possible to accurately predict the failure load, interfacial slip and full nonlinear response of partially interacting composite beams.

Recent earthquakes have highlighted the need to strengthen existing structures with substandard designs. NFRPs provide a sustainable, cost-effective alternative for strengthening, but accurately predicting their performance remains a challenge. This study investigates the use of machine learning algorithms for predicting the compressive strength concrete specimens confined with various NFRPs. Four algorithms were employed: decision tree, random forest, neural network, and gradient boosting regressor. A diverse dataset encompassing various geometries, material properties, and confinement configurations was used to train and evaluate the models. Gradient boosting regressor (GBR) achieved the highest performance, with an average R-squared value of 0.94 and low mean absolute error (MAE) and root mean squared error (RMSE) during training and k-fold cross-validation. Neural network and random forest also demonstrated satisfactory performance, with average R-squared values of 0.88 and 0.86, respectively, during cross-validation. These results suggest that machine learning holds promise for predicting the compressive strength of concrete confined with NFRPs. GBR offers the most accurate predictions, making it a valuable tool for engineers seeking to optimize the design and performance of strengthened structures using sustainable materials.

The purpose of this research was to develop “green” materials by combining poly(lactic acid) (PLA) with two agricultural by-products, namely flax seed meal (FSM) and rapeseed straw (RSS). The natural fillers (0–20 wt.%) were mixed with PLA through extrusion and then injection molded into specimens. The samples were analyzed for their thermal, morphological, mechanical, and physical features and biodegradability. Thermal properties and crystallinity were analyzed using Differential Scanning Calorimetry (DSC), while the morphology was investigated by Scanning Electron Microscopy (SEM). Mechanical properties were characterized through tensile, flexural, and impact measurements, while surface hardness was evaluated by Shore D tests. Water absorption and biodegradability of the samples were also examined. DSC measurements revealed a nucleating effect of both bio-fillers. Based on the tensile tests, major improvement in stiffness was found with the biocomposites having up to ∼16 % higher Young's modulus than neat PLA (2.5 GPa). It came, however, at the cost of tensile strength, which decreased from 56 to 51 MPa even in the presence of the lowest amount (2.5 wt.%) of FSM. Loss in strength was due to the limited adhesion between the components, as also supported by SEM images. The hardness slightly (1–2 %) improved in the presence of even 2.5 wt.% bio-filler and it remained at that level at higher filler loading as well. Laboratory-scale composting revealed that both fillers facilitated biodegradation with FSM being superior. In the presence of 10–20 wt.% FSM, the rate of decomposition was found to be twice as fast compared to neat PLA.

Polymers and their composites are now widely used in several industrial sectors, owing to their flexibility in developing customized products. The significant surge in plastic usage has led to a severe challenge in managing end-of-life plastic waste. Millions of tons of plastic waste produced annually mainly end up in landfills, leaking into the environment and posing severe threats to ecosystems. Innovative solutions to reuse/recycle/repurpose plastic waste are desired to address these global challenges. Therefore, in this study, a sustainable route to converting plastic waste into additive manufacturing (AM) feedstock is presented, where waste plastic bottles (mainly Polyethylene Terephthalate, PET) are recycled using an in-house 3D-printed filament extrusion system to produce filaments for fused filament fabrication (FFF) process. In addition to the recycled PET (rPET), virgin carbon fiber reinforced polyamide-6 (PA6-CF) polymer composites were also used to produce hybrid feedstock filaments. The rPET and rPET/PA6-CF composite filaments were extruded using an in-house filament extruder setup. The produced rPET-based filaments were characterized for their chemical and thermal properties. Subsequently, mechanical characterization was performed on 3D-printed specimens. The mechanical analysis revealed better tensile strength for rPET/PA6-CF than rPET; however, the rPET demonstrated better failure strain and young modulus, demonstrating their potential as viable materials for industrial and consumer applications. The outcomes of this study revealed promising results to promote sustainable production and consumption, complementing the circular economy practices with a straightforward production route to convert plastic waste into AM feedstock.

Omni first-ply-failure (FPF) envelopes are an elegant yet conservative approach to assess composite laminate failure on a global level. Omni envelopes can be found increasingly in recent publications. However, the development process of those envelopes shows a lack of clarity. At some point the illustration switches from a laminate-strain basis $({\varepsilon }_x,{\varepsilon }_y,{\gamma }_{xy})$ to the particular case of laminate principal-strain $({\varepsilon }_I,{\varepsilon }_{II})$ basis. The latter is elegant, as the principal-strain space can be easily plotted in 2D. This article presents two procedures to directly determine omni FPF envelopes and it clarifies the transfer to principal strains.

While the Tsai–Wu criterion is used in almost all available publications, the present article uses Cuntze’s failure mode concept (FMC). The article provides a simple example case, which demonstrates the application of omni envelopes in context of FEA based CFRP design.

Unidirectional long fiber reinforced polymers generally exhibit unfavorable abrupt and brittle failure under mechanical stresses without pre-warning which currently limits their use in safety critical applications. The lack of ductility of such composites can be overcome by interlayer hybridization where Low Strain (LS) material is sandwiched between High Strain (HS) material. This results in complex failure mechanisms, including multiple interacting damage modes, such as ply fragmentation and delamination. All-carbon unidirectional hybrid laminates with different layup sequences were designed and manufactured to study the pseudo-ductile behavior. An available analytical model was exploited to predict the damage scenarios of the laminates, both with stress-strain diagrams and damage mode maps. Tensile tests were carried out using different measurement and observation techniques including digital image correlation (DIC), embedded distributed fiber optic sensors (dFOS) and helicoidal X-ray computed tomography (CT). A finite element model was also developed to predict the damage mechanisms. Validated by experimental results, the numerical model was found to accurately predict the tensile damage modes and their evolution in the considered unidirectional thick ply all-carbon hybrid laminates.

Fluororubber (FKM) is an irreplaceable sealing material that plays a critical role in new energy vehicles, petrochemical and aerospace industries. Their broad applications arise from the excellent thermal stability and solvent resistance of fluororubber. Despite there are increasing number of reports on preparation methods, properties and characterization of FKM in literature, there is still a lack of a thorough and comprehensive review that summarizes these results. This paper provides an overview of FKM types, preparation methods, property testing and microscopic characterization, and attempts to give a comprehensive introduction to the vulcanization mechanism of FKM using ternary fluororubber. The mechanical mixing method was identified as the most versatile preparation method in the review, but it is susceptible to causing agglomeration of nanomaterials. Furthermore, different vulcanization systems and reinforcing fillers can be chosen based on the application direction of FKM. Carbon nanomaterials with high inherent strength have the best reinforcing effect on FKM, although they also exhibit the most significant self-agglomeration effect. This can be mitigated through synergistic use of fillers of multiple dimensions and interfacial modification in future research. Additionally, current challenges and future prospects for FKM nanocomposites are also discussed.