Applied Composite Materials最新文献

Using fibre reinforced polymer (FRP) to confine reinforced concrete columns is a commonly employed method for strengthening in civil engineering. Columns are essential load-bearing elements, and their failure can result in a disastrous collapse of the structure. The aim of this study is to address a deficiency in the current body of knowledge by conducting a comprehensive examination of the application of carbon fibre-reinforced polymer (CFRP) and aramid fibre-reinforced polymer (AFRP) composite as a material for retrofitting. This study investigates the influence of the quantity of CFRP layers and the incorporation of aramid fibres as retrofitting elements on improving blast resistance. Experimental results presented by Yan et al. (2020) consisting of 12 columns with varying thicknesses and strengthening were validated using the finite element tool LS DYNA. The numerical modelling results showed that using CFRP reinforcement improved the ability to withstand damage, leading to a decrease in residual displacement. Verified numerical models are utilised to conduct parametric analysis on the impact of aramid fibre reinforcement polymer (AFRP) on mid-plane displacement and internal energy absorption. The results suggested that AFRP exhibit greater resistance to blast loads as compared to CFRP.

In this paper, we use numerical modeling to predict the effective electrical conductivity of Carbon-Black/Ultra-High-Molecular-Weight-Polyethylene (CB/UHMWPE) nanocomposites. The models are based on the microstructure observed in X-ray microcomputed tomography (μCT) scans. For the examined range of carbon black weight fraction, the scans demonstrate conductive CB particles to be agglomerated around the UHMWPE granules, creating CB-containing layers surrounding the granules and forming electrically conductive network. First, the generalized effective medium (GEM) method is considered as an analytical tool to predict the overall conductivity based on the volume fraction of conductive inclusions. The applicability of this method for the observed microstructure with conductive layers is discussed. Then, an alternative two-stage approach based on a combination of numerical and analytical modeling is proposed. Finite element models of representative volume elements (RVEs), incorporating the CB-containing layers, are developed. It is shown that the GEM parameters of the CB-layers can be determined by the comparison of the numerical modeling results with the experimental measurements of the overall composite conductivity.

This study examines the influence of yarn breakage, specifically the number of layers and their location, on the low-velocity impact response and post-impact compression performance of 3D woven composites. Specimens with yarn breakage on either the upper or lower surface were impacted at two different energy levels. Damage evaluation was conducted using C-scan, μ-CT, and DIC methods. The results indicate that yarn breakage on the lower surface (tension zone) leads to notable reductions in initial stiffness (up to 40.2%) and peak load (up to 33.4%), with a clear threshold effect when two or more layers are broken. This condition also resulted in significantly expanded damage area (up to 94.3% increase). In contrast, breakage on the upper surface (compression zone) mainly increased energy absorption (up to 84.4%) and permanent displacement (up to 65%) under high-energy impact. Additionally, compression-after-impact strength was approximately 11% lower for specimens with yarn breakage on the lower surface, where failure was governed by a damage network initiated by the yarn breakage. These findings provide concrete design guidelines for avoiding critical strength reduction and optimizing damage tolerance in composite structures containing yarn breakage defects, particularly for aerospace applications where impact resistance is crucial.

Honeycomb structures are widely used in buffering, protective systems, and impact-related applications due to their lightweight, high strength, and excellent energy absorption capabilities. However, conventional honeycomb designs often suffer from limited load-bearing capacity, single-stage collapse behavior, and insufficient energy absorption efficiency, making them inadequate for high-performance energy-absorbing systems. To address these limitations, this study proposes a novel Framed Diamond-Star Honeycomb (FDSH) structure with a dual-plateau response. The mechanical performance and energy absorption characteristics of the proposed structure were systematically investigated through quasi-static compression experiments and finite element simulations. The effects of key geometric parameters, including cell angles and wall thickness, were also analyzed. The results show that the FDSH structure exhibits a distinct dual-plateau behavior during compression and achieves significant improvements in specific energy absorption—by approximately 238.18% and 161.97%—compared to traditional star-shaped honeycombs (SSH) and re-entrant hexagonal honeycombs (REH), respectively. Furthermore, parametric studies confirm that geometric parameters have a significant influence on plateau stability and energy absorption performance.

Compared to conventional honeycomb structures with a positive Poisson’s ratio, negative Poisson’s ratio (NPR) structures exhibit greater densification strain under impact, enabling more efficient energy absorption. Based on this principle, a novel cuttlebone-inspired multi-circular arc core (MCAC) structure is proposed, exhibiting NPR behavior and an enhanced energy absorption (EA) capacity. Furthermore, multilevel designs (2-level, 4-level, and 6-level) were developed based on the MCAC unit to explore hierarchical structural advantages. The results demonstrate that the proposed MCAC honeycomb achieves a 30% higher stress plateau and a 36.6% increase in EA compared to a conventional star-shaped honeycomb of equal size, with a notable improvement in in-plane performance. Under a 1 J impact load, EA increases by 11.12% as core levels increase from 2 to 6; however, this trend reverses at higher impact energies. Parametric studies reveal that the large arc centroid angle θ_R significantly influences EA, yielding a 7.05% improvement in the 6-level design. These findings suggest that the MCAC design offers a promising solution for vehicle energy-absorbing box (EAB) applications.

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.