Applied Composite Materials最新文献

Structural Health Monitoring (SHM) of composite structures necessitates developing robust and resilient sensors which operate in harsh environments with high degree of sensitivity, and are easily integrable in structural components. Electrospinning has been explored in the past for the fabrication of nanofibers whereas electrospraying has been exploited for the deposition of electrosprayed clusters. In this paper, a hybrid manufacturing technique is proposed for manufacturing nanofibrous webs from conductive polymer composite (CPC) solutions. The degree of shear thinning of the solutions is compared by rheological analysis, which shows that the solution with a 2% w/v is effective for electrospray, with a greater degree of shear thinning behavior than a 10% w/v solution. These webs gain their structural integrity and provide multiple sensing mechanisms when nano-sprayed clusters of the same CPC solution weld the fibers obtained through electrospinning together on a polycarbonate substrate. These laminates are then cut into strips and pasted on glass fiber-reinforced polymer (GFRP) composites for strain monitoring with an aim for SHM. Electrochemical impedance spectroscopy is used to characterize the sensing capability using the electrolyte/interface and surface reactions. The thermogravimetric analysis was conducted to study the suitable temperature range for the developed sensor. The measured gauge factor is 2.5. The sensor is tested up to 2000 cycles while the maximum linearity error and maximum hysteresis error of the sensor are calculated as 0.893 and 1.168. This proves the sensor’s effectiveness for quasistatic as well as dynamic loading scenarios. The fractographic analysis also shows that the sensors can follow various failure modes with the applied load.

Subsea oil and gas facilities in specific regions are affected by sand dune accumulation loads, requiring fully enclosed protective structures to ensure integrity. Steel protective structures are limited by their weight. Glass Fiber Reinforced Polymer (GFRP) offers a compelling alternative due to its low weight, high strength, and corrosion resistance. This study investigates the damage effects on GFRP protective structures caused by sand dune accumulation and hydrostatic pressure. The Puck criterion was used to predict matrix and fiber failure, while progressive damage analysis, implemented through the ABAQUS USDFLD subroutine, was employed to track damage evolution. The Finite Element Analysis (FEA) predicted flexural strength (756.34 MPa) closely matched experimental results (702.76 MPa), with a 7.62% error, confirming model accuracy. Under sand dune loads, hat-shaped stiffeners greatly improved stability. For stiffened structures, displacement increased from 77.25 mm to 556.01 mm as sand height rose from 4 m to 10 m. Damage progressed from matrix tensile failure at lower heights to matrix compression and fiber damage at higher loads. At a 400 m water depth (4 MPa), the hat-shaped stiffeners exhibited matrix tensile damage with a displacement of 12.85 mm. Doubling the bottom panel thickness reduced displacement by 60.17% to 5.12 mm.

The automotive energy-absorbing box can significantly reduce impact energy during accidental collisions, thereby protecting the lives of passengers and minimizing damage to the main components of the vehicle. However, it is often exposed to a hot and humid environment. Therefore, research on the ability of the automotive energy-absorbing box to resist thermal and humid erosion is necessary. This work investigates the crashworthiness of biomimetic composite thin-walled tubes under quasi-static axial crushing, focusing on the effect of hot water treatment. The thin-walled tubes, inspired by honeycomb structures, were manufactured using carbon fiber composites through a multi-cavity preform mold method. Three-point bending tests and interlaminar shear tests were carried out to identify the effect of hot water on the mechanical response of the unidirectional composites and the Lap-shear Strength between layers. Quasi-static crushing tests and CT scanning observation were conducted to characterize the mechanical behavior, crashworthiness mechanisms, and energy absorption capacity of the thin-walled tubes. Results indicate that, following hot water treatment, the flexural strength of the composite material decreased by 57.3%, while the Lap-shear Strength was reduced by 23.65% to 29.94%. Correspondingly, the crush performance of the biomimetic CFRP thin-walled tubes was reduced to varying extents: total energy absorption (EA) fell by 7.48%–39.16% and the initial peak force (F_ip) by 13.19%–30.21%. The crushing performance of thin-walled tubes with Geometric Structure C and 90° oriented carbon fibers is less affected by hot water treatment. Despite these reductions, all tubes retained a stable progressive crushing mode, and the energy absorption mechanism underwent significant changes compared to before hot water treatment. These findings provide valuable insights for designing durable and reliable composite structure for safety-critical applications in industries such as automotive and aerospace.

This study experimentally investigated the coupled impact-tension response of CFRP/Al Flat-Joggle-Flat (FJF) adhesive joints under 10 J, 20 J, and 30 J impact energies, and systematically elucidated the damage mechanisms and performance evolution of FJF joints. The key innovative findings are summarized as follows. A pronounced “impact surface effect” was discovered in dissimilar-material joints. When aluminium served as the impacted surface, the peak contact force increased by 10.5%, whereas impact on the CFRP preserved a significantly higher residual load-bearing capacity. The coupled influence of impact energy and impact surface on failure-mode transitions was quantitatively established for the first time. Under impact energies of 10 J and 20 J on the CFRP, failure was primarily characterized by delamination and fiber tearing; at 30 J, the dominant failure shifted to a mixed mode consisting of cohesive failure within the impact zone accompanied by approximately 51.9% fiber tearing in the non-impacted region. Impact on the aluminum alloy exhibited a consistent failure pattern across all energy levels, characterized by cohesive failure in the adhesive layer within the impact zone along with fiber tearing in non-impact regions. Moreover, continuous recordings during tensile failure were employed to reveal the initiation and propagation of damage. This work delivers the first quantitative experimental data and failure mechanism analysis for dissimilar FJF joints under impact-tension, guiding crashworthy design of rail-vehicle multi-material joints.

This paper is intended to investigate the half-thickness z-pin effect on balancing interlaminar improvement and intralaminar adverse impact of polyimide z-pin reinforced polymer composites. The z-pin pre-hole implanted (ZPI) process was employed to mitigate initial intralaminar damage. The experimental results indicate that z-pins with the different length can significantly improve the mode II fracture toughness (G_II) of specimens. And the reinforced effect of half-thickness z-pins is significantly better than that of full-thickness z-pins, which attribute to the larger bonded area between pulled-out z-pin and laminates. The propagation G_IIC of specimens with a bonded area of 305.36 mm² is increased by 524.63%. Compared with unpinned specimens, the flexural strength of specimens with half-thickness z-pins has a retention of 97%. Meanwhile, the plastic strain energy of specimens with half-thickness z-pins is twice as large than that of specimens with full-thickness z-pins. In short, half-thickness z-pins could achieve the desirous equilibrium of mechanical properties between the interlaminar and the intralaminar.

Carbon fiber reinforced polymer (CFRP) is widely used in aerospace due to its excellent mechanical properties, and the corresponding high-efficiency, high-strength joining techniques have become a key research focus. Among various factors influencing the failure mechanisms and residual life of CFRP joints, the actual service environment plays a crucial role. In this study, the damage formation and performance degradation of CFRP bolted joints under thermo-oxidative aging condition were investigated. Experimental results demonstrate that, even in the absence of external loads, a thermo-oxidative environment can lead to material internal damage within the jointed zone. The difference in the coefficients of thermal expansion between the fibers and matrix can also lead to the appearance of matrix damage and delamination at the entrance and exit of the joining holes. In addition, From the experimental results, it can be seen that thermo-oxidative ageing has a significant effect on the tensile load-bearing properties of the joining structure, and with the increase in ageing temperature up to 150℃, the load-bearing stiffness and strength of the joining structure decreases by up to 34.8% and 23.1%, respectively. These findings highlight the impact of thermo-oxidative aging on the integrity and performance of CFRP bolted joints, emphasizing the need to account for environmental degradation in the design and durability assessment of aerospace composite structures.

This study addresses the challenge of optimizing mechanical performance in aramid/carbon fiber hybrid-reinforced polymer (A/CFHRP) composites by investigating effects of hybrid ratio. Specimens with controlled aramid/carbon fiber ratios were fabricated via vacuum-assisted resin transfer molding (VARTM). The novelty lies in the integration of high-resolution in situ X-ray computed tomography (CT) tensile testing with three-dimensional (3D) damage analysis, enabling visualization of failure mechanisms under progressive loading. 3D reconstructions revealed intralaminar damage distribution patterns and crack propagation pathways. Low aramid content (26.7 wt%) exhibited brittle carbon fiber-dominated fracture with limited crack deflection. Excess aramid (80 wt%) induced ductile pull-out mechanisms but compromised strength. Additionally, in situ CT images show that carbon-aramid hybridization can improve stress transfer and energy dissipation. This study offers a key theoretical foundation for enhancing the performance of A/CFHRP composites and also broadens the application scope of in situ CT technology.

This study presents a comprehensive comparative analysis of tribological and thermal properties of PA-based composites, investigating PA66 reinforced with short glass fibers containing PTFE/silicone versus PA6 reinforced with glass beads in gear pairings. Durability lifetime tests were performed to analyze the tribological behavior of steel pinion and driven composite gear systems under controlled torque conditions at high, medium, and low loadings at room temperature to investigate load-failure mechanism correlations. DSC measurements were performed to research how glass transition temperature (T_g) and different crystallization behaviors impact lifetime performance. Abrasive wear on gear flanks was measured to evaluate the impact of glass reinforcements on friction properties. Thermal feedback regarding gear operation was obtained through infrared camera measurements of gear surface temperatures. Results demonstrate that thermal monitoring reveals temperature spikes exceeding 20 °C precede failure, with PA6 reinforced with glass beads exhibiting thermal runaway at high torques while PA66 with glass fibers and PTFE/silicone maintains steady-state thermal profiles. PA6 with glass beads demonstrates superior low-torque performance through isotropic reinforcement, whereas PA66 with glass fibers and PTFE/silicone provides consistent high-torque reliability via internal lubrication mechanisms.

This study investigates the damage effects and residual structural strength of Carbon Fiber Reinforced Polymer (CFRP) laminates under multi-factor coupled lightning strikes, combining numerical simulations and experimental methods. An electro-thermal-chemical coupling model was developed to simulate lightning damage under varying layup angles, lightning current peaks (7.6–100 kA), different thickness and grounding conditions. Experimental validation was conducted via a lightning current A-component generator and residual tensile strength tests. The results show that the damage area is directly proportional to the current size, showing rapid expansion at the peak value. When the current peak reaches 46 kA, the damage area reaches 2738.4 mm². The single ground will lead to the asymmetric damage of carbon fiber laminates, and the damage on the grounding side will increase by 53.5%, but the total area is similar to the two-side ground. The residual tensile strength of carbon fiber laminates decreased significantly with the increase of current. At the peak of 45 kA current, the residual tensile strength decreased by 39%. The simulation accurately predicted damage areas, aligning with experimental results. The linear fitting was performed on the residual intensity data with different current amplitudes, and the fitting index R² > 0.9. This article analyzes the correlation between conductive paths and damage characteristics, providing research references for optimizing lightning protection design.

In this paper, a finite element model based on continuum damage mechanics was developed to investigate the load transfer and damage progression mechanisms of ply-interleaved composite laminates subjected to tensile loading. Hashin criterion and a gradual degradation scheme were used to predict the intralaminar damage initiation and evolution, which were coded and integrated into the commercial finite element package ABAQUS/Explicit through a user-defined VUMAT material subroutine. Synchronously, an interface cohesive element was utilized to predict the interlaminar delamination damage. To verify the proposed model, quasi-static tensile tests were performed on specimens with different interruption distances. The results showed that with the increasing interruption distance, the failure load, failure displacement, and stiffness of the specimens decrease. A good agreement was achieved between the experimental and simulation results in terms of load-displacement response and damage morphology, validating the predictive capability of the model. Furthermore, the load transfer mechanism and damage evolution process of ply-interleaving composite laminates under tensile loading were clearly revealed. This work will pave the way for the engineering application of ply-interleaving composite structures.