Applied Composite Materials最新文献

The use of ceramic matrix composite (CMC) in blades is crucial for improving aero-engine performance. However, designing complex fiber architectures while considering manufacturing constraints poses significant challenges for blade design and evaluation. Manufacturing constraints specifically refer to fiber continuity constraints and fiber path curvature constraints. Here, a cross-scale design methodology and a static strength evaluation system for CMC blades were established and subsequently applied to the design of shrouded blades. The cross-scale design method adequately considered the variety and differences in fiber-architecture molding methods. Weaving parameters were optimized through a cost-effective, simulation-driven design. The blade performance and structural integrity were balanced under manufacturing constraints. The developed static strength evaluation system was used to compare the performance of different designs through simulation analysis and critical tests. No defect was found in the CMC blade prototypes after holding a load for 2 min at 1.15 times their maximum rotational speed. This demonstrated sufficient static strength and confirmed the effectiveness of the design methodology and evaluation system.

Achieving robust low-resistance electrical contact with carbon fibres embedded in polymeric matrices is a challenge, and different electrode fabrication methods mostly post-curing the composite have been examined in the literature. This paper investigates the use of metallic foils co-cured on the top surface of carbon fibre reinforced polymer (CFRP) composites to form stable electrodes. The effects of different electrode materials and their geometric variations on the interface resistance (IR) between CFRP and electrodes are studied experimentally. Finite element (FE) analysis is used to estimate the spread resistance (SR), providing a reliable measure of IR for various electrode–CFRP configurations. Copper is found to be the optimal electrode material and has a low IR per unit electrode area ranging from 2.5 × 10⁻⁴ Ωmm⁻² to 1 × 10⁻³ Ωmm⁻² independent of geometric parameters. Pull-off tests demonstrate that the co-cured electrodes exhibit acceptable mechanical bonding with the composite layer. Compared to other electrode fabrication methods, the co-curing technique is significantly easier, less invasive and more cost-effective, as it eliminates the need to alter or induce surface damage in CFRP specimens.

Graphical Abstract

Co-cured metal foils simplify electrode fabrication in CFRP and achieves stable, low interface resistance

In this study, an integrated composite antenna structure was designed and fabricated to investigate its behavior under low-velocity impacts with energy levels ranging from 10 J to 100 J. The specimens were positioned and supported in accordance with ASTM D7136 standards, while post-impact compression tests followed ASTM D7137 protocols. Numerical models were developed using ABAQUS finite element (FE) software to validate experimental results, including impact response curves, damage morphologies, and compression failure modes. Both experimental and simulation results demonstrated strong agreement, confirming the accuracy of the constitutive model. Additionally, electromagnetic performance evaluations through experiments and simulations verified the structural integrity and functional reliability of the antenna under varying impact conditions.

Metal matrix composite (MMC) sheets with well-dispersed reinforcements can be continuously produced using the accumulative roll-bonding (ARB) method. However, carbon fibers (CFs), an ideal reinforcement for MMCs, have not been extensively utilized due to the poor wettability of carbon/aluminum system. This study addresses this issue by modifying the fiber surface with copper (Cu) coating and applying this new reinforcement to Aluminum matrix composites (AMCs) produced via the ARB method. The results demonstrate that copper coated CFs (Cu-CFs) were well-dispersed throughout the matrix with appropriate ARB cycles. The surface treatment improved the spatial uniformity of the reinforcement, enhanced interfacial bonding, and refined the matrix grains. Consequently, the Cu-CF/Al composites exhibited the highest tensile strength (187.8 MPa) compared to composites reinforced with uncoated CFs (131.9 MPa) and monolithic Al without CFs (122.7 MPa). These findings suggest that combining ARB with electroless copper coating holds broad prospects in materials engineering, providing a valuable area of study for enhancing composite material performance.

This work aims to assess the potential of commercially available PA 6,6 nanofibrous mats when incorporated to large scale filament winding process. The conventional wet winding process was employed on a specially designed flat mandrel to manufacture uni-directional composite laminates. A49-12 K carbon fibers and cryogenic-compatible CTD 7.1 epoxy resin was employed. The winding process was temporarily paused at the mid-plane thickness to introduce a pre-crack using a 12 μm non-adherent film and to place PA66 nanofibers with an aerial weight of 3 g/m². The winding process then resumed. Laminate curing was performed in an autoclave oven for 3 h at 80^oC under nitrogen environment. Flat wound laminates were then cut into end notched flexure (ENF) test samples in accordance with ASTM D7905/D7905M-19. ENF tests were performed at room temperature (RT) and cryogenic conditions in a liquid nitrogen bath. Test results suggested that mode II strain energy (G_IIc) of interlayered laminates were 35% higher than the one of neat laminates when tested at room temperature. On the contrary, addition of polymeric nanofibrous interlayers reduced G_IIc by 40% in cryogenic conditions. Fractographic analysis suggested that the improvement at RT was primarily due to (i) toughening at the resin rich pockets inherent by the tow-undulation effect in wet winding (ii) crack deflection in irregular tow-tow interfaces. The reduction in G_IIc was attributed to synchrony of several factors, namely dominance of fiber/matrix debonding due to thermal contraction at fiber/resin interfaces, elevated brittleness of the polymeric nanofibers and pre-mature cracking due to nanofiber/resin debonding.

In this paper, an architecture-based approach is proposed to enhance the quasi-static crushing behaviour of trigger-free composite energy-absorbing structures. To validate the proposed methodology, specimens with an inner diameter of 32 mm and a wall thickness of ~ 1 mm were manufactured and tested under axial quasi-static compression (20 mm/min) using a filament winding technique. Two sets of samples were fabricated by including an external CFRP mesh to enhance the hoop strength and promote progressive crushing. By comparing the test results with those of the base material, a remarkable influence of the outer layer on the crash performance (> 50% of the SEA) was registered, despite a negligible increase in weight. Furthermore, since geometric modifications (e.g., edge chamfering) were unnecessary to achieve progressive crushing because of the contribution of the outer mesh, this approach can be further explored to simplify the manufacturing process of energy-absorbing structures.

Curing is a reaction leading to a hardened material in mixtures of two or more components known as themosetting polymers. The specific choice of components allows to regulate the speed of reaction. In some applications, fast kinetics are chosen to achieve a fully hardened product within seconds. Yet in other applications, where the mixture is cast in larger volumes, a slower curing rate is needed to allow the cast or mold process to be completed before significant hardening has been occurred. Specifically in the latter case, such a reaction is of importance to model accurately; yet an interplay of several mechanisms makes it challenging to predict the correct model to be used in curing. Such a polymer comprising multiple components has been analyzed by listing different models available. Based on them, a phenomenological model is proposed that resembles a slowly reacting thermosetting polymer. An inverse analysis approach is developed for acquiring a fit representing the data with a good agreement.

The methods and approaches used for composite repairs depend on the sector of industry, and exhibit both common elements and distinctions. Here we consider the repair methods used in four exemplary applications: marine, wind, automotive, and aerospace. Repairs are often overlooked as a means of imparting greater sustainability to composite products, but they are generally the least costly route for doing so. Approaching each industry from a common repairs perspective, the similarities are highlighted while the different approaches are compared. The problems associated with current approaches are examined, along with active research methods for each application. Areas for potential to increase efficiency of repairs through automation and introduction of new materials are identified. The review of repair methods is intended to stimulate new approaches and opportunities to transfer the approaches and practices employed across industries.

Carbon Fiber Reinforced Plastic (CFRP) is particularly suitable for replacing metal materials in the safety lap bars of amusement rides due to its excellent mechanical properties and lightweight nature. To ensure the safety and dependability of the CFRP lap bar, the mechanical characteristics of the lap bar were investigated through a combination of experimental and simulation methods, and the damage behavior is analyzed using acoustic emission (AE) and X-ray micro-computed tomography (micro-CT). Simulation results revealed that the maximum principal stress of the tubular element and lap bar arm was 132.27 MPa, located at the profile alteration point beneath the lap bar arm. The damage behavior of the lap bars was investigated through an analysis of the AE signals generated during the five experimental stages. With the increase in load, a large number of signals with frequencies exceeding 300 kHz appeared, indicating irreversible damage such as fiber pull-out and matrix cracking. In addition, the number of AE signals captured by Sensor 3 corresponding to the bent portion of the lap bar arm exceeded 6,000, representing the largest proportion and indicating that the damage in this area is relatively intensive. Furthermore, the internal damage morphology was reconstructed using micro-CT. The observed damage was primarily caused by interlayer damage. The failure of the CFRP lap bar is attributable to the cumulative effect of multiple damage modes, validating the reliability of the damage mode characterized by AE signals. Eventually, the damage evolution mechanism of the CFRP lap bar was clarified, providing a basis for design optimization and service evaluation.

Over-molded composites are produced by injecting short fiber composites over continuous fiber-reinforced composite inserts through an injection molding process. These composites are suitable for load bearing structural applications because of their high specific strength, stiffness, lightweight nature, and the ability to form complex structures through simple manufacturing processes. However, their performance is highly dependent on the interface adhesion between the short and continuous fiber-reinforced composite inserts. This study investigates the effect of preheating on the load bearing capacity of over-molded composites under tensile and flexural loads using experimental and numerical approaches. The damage mechanism of the over-molded composites is characterized using Hashin and cohesive zone failure criteria within ABAQUS/Explicit to capture the failure mechanisms. The experimental results revealed that preheated over-molded composites demonstrated a significant increase in tensile and flexural properties compared to non-preheated composites. For the non-preheated specimens, the primary failure mechanisms were interfacial debonding, insert delamination, and short fiber composite failure. Conversely, in the preheated specimens, both short and continuous fibers experienced simultaneous damage, owing to the strong cohesive bond formed by preheating. The predicted numerical results align well with the experimental results in terms of load-displacement behavior, strength, and damage morphologies, suggesting that the numerical simulation is a valuable tool for assessing the performance of over-molded composites.