Search Results (143)

To enhance the low-frequency vibration suppression capability of cantilever beams, a magnetically tunable piezoelectric cantilever beam structure (MTPCBS) is proposed in this paper. A magnetic spring with negative stiffness (NSMS) is fixed at the free end of a cantilever beam, forming a quasi-zero-stiffness structure. Meanwhile, a macro-fiber composite (MFC) patch is bonded near the root of the beam to implement active skyhook damping control for active vibration control. A theoretical model of the cantilever beam, NSMS, and MFC is established, and the displacement transmissibility of the MTPCBS is derived. The influences of the magnet distance of the NSMS and the control gain of the controller are investigated via simulation. Experimental results indicate that compared to the single beam, the effective vibration isolation frequency of the proposed MTPCBS shifts from 15.3 Hz to 4.6 Hz. When subjected to random vibration excitation ranging from 1 to 80 Hz, the root mean square (RMS) value of vibration decreases from 0.03 g to 1.77 × 10⁻³ g, with the vibration attenuation rate improving from −50% to 91%. The proposed MTPCBS and active–passive vibration control method for cantilever beams significantly enhances low-frequency vibration suppression capabilities, providing a feasible strategy for achieving broadband vibration suppression. Full article

As demanded by the rapid development of wearable electronics, flexible pressure sensors have attracted more and more attention worldwide. However, the performance of pressure sensors based on the piezoelectric effect has not been qualified for practical application. In this work, we designed and prepared PVDF/BTO fibers by an electrospinning approach and constructed pressure sensors for various human motion detection purposes. The performance is dramatically enhanced due to the high piezoelectric coefficient of BTO nanoparticles and the utilization of PVDF matrix with a high β content. The optimized pressure sensor presents a high power density of 27.5 nW cm⁻² at 10 N load stress and remains stable even after 3000 cycles. For human action application, the maximum output voltage is up to 20 V. The optimum β content of the PVDF matrix is up to 72.9%, which in turn contributes to the high energy-harvesting capability of the designed composites. The prepared PVDF/BTO composites show benign capability for sensing various human actions. This work shapes a new strategy for high-performance pressure sensors based on piezoelectric composites. Full article

This study investigates the machining challenges of fiber-reinforced composite materials (FRCMs), focusing on carbon fiber-reinforced polymer (CFRP) plates, which exhibit high abrasiveness, delamination tendency, and accelerated tool wear. Two solid carbide helical end mills, designed for composite machining, were evaluated through helical interpolation drilling. Acoustic emission signals were continuously acquired via a piezoelectric sensor during standardized cycles, and tool wear was assessed using confocal microscopy and a digital altimeter. Signal processing played a central role, combining energy-based metrics and damage indices to identify the onset of wear and early delamination, enhancing the understanding of tool degradation and improving machining reliability. Full article

Composite engine fan blades are critical aircraft engine components, and their failure can compromise the safe and reliable operation of the entire aircraft. To enhance aircraft availability and safety within a condition-based maintenance framework, effective methods are needed to identify damage and monitor the blades’ condition throughout manufacturing and operation. This paper presents a unique experimental framework for real-time monitoring of composite engine blades utilizing state-of-the-art structural health monitoring (SHM) technologies, discussing the associated benefits and challenges. A case study is conducted on a representative Foreign Object Damage (FOD) panel, a substructure of a LEAP (Leading Edge Aviation Propulsion) engine fan blade, which is a curved, 3D-woven Carbon Fiber Reinforced Polymer (CFRP) panel with a secondary bonded steel leading edge. The loading scheme involves incrementally increasing, cyclic 4-point bending (loading–unloading) to induce controlled damage growth, simulating in-operation conditions and allowing evaluation of flexural properties before and after degradation. External damage, simulating foreign object impact common during flight, is introduced using a drop tower apparatus either before or during testing. The panel’s condition is monitored in-situ and in real time by two types of SHM sensors: screen-printed piezoelectric sensors for guided ultrasonic wave propagation studies and surface-bonded Fiber Bragg Grating (FBG) strain sensors. Experiments are conducted until panel collapse, and degradation is quantified by the reduction in initial stiffness, derived from the experimental load-displacement curves. This paper aims to demonstrate this unique experimental setup and the resulting SHM data, highlighting both the potential and challenges of this SHM framework for monitoring complex composite structures, while an attempt is made at correlating SHM data with structural degradation. Full article

One of the tasks of the FutureWings project, funded by the European Commission within the 7th framework, was to numerically validate the mechanical behavior of a wing whose deflections had to be controlled via a suitable distribution of piezoelectric patches. Starting from a reference geometry (a NACA 0012 airfoil), wing profiles were implemented and analyzed using the fluid–structure interaction analysis technique. The wing section was designed with a morphing profile in which both the front and rear parts self-deform via piezoelectric patches that serve actuators glued to the skin of the profile. A Macro Fiber Composite (MFC) was used as the piezoelectric actuator. Aeroelastic analyses were performed at low Mach numbers under the sea-level flight condition. Analysis of the technical solution was based on an examination of the aerodynamic coefficients and polar curves of the profile, as the control voltage of the patches can vary. The results were compared with those available in the literature. As a preliminary step, this work contributes to examining the current technical possibilities of this technology relating to the application of piezoelectric patches as actuators in the field of aerostructures. Full article

Most existing carbon fiber composite materials are formed by high-temperature molding of multiple layers of fiber cloth. During the manufacturing and usage processes, materials are prone to defects such as voids, delamination, and inclusions, which seriously threaten their service life and safety performance. Ultrasonic testing is currently a widely adopted method for detecting defects in carbon fiber composite materials. However, existing narrow-pulse ultrasonic transducers often have to sacrifice emission energy to achieve narrow-pulse emission, which results in their limited ability to penetrate thicker carbon fiber composite materials. To address this issue, this paper proposes the design of a focused laminated transducer. By stacking and bonding lead titanate piezoelectric wafers and using a concave lens made of organic glass to focus ultrasonic waves, the emission sound intensity of the ultrasonic transducer is enhanced. The simulation results show that the designed focused double-stack transducer has a directivity gain that is 4.49 dB higher than that of the traditional single-piezoelectric-wafer transducer. The transducer fabricated based on this design has successfully achieved effective detection of internal defects in carbon fiber composite materials. Full article

(1) Background: Structural Health Monitoring Systems (SHMSs) can reduce maintenance costs and aircraft downtime. However, their economic impact remains underexplored, particularly in cost–benefit terms. (2) Methods: This study conducted a targeted literature review on all the existing studies consisting of seventeen economic analyses of SHMS applications. Key features—such as SHMS type, structural material, vehicle type, integration stage, and cost elements—were classified to identify prevailing trends and gaps. (3) Results: The analysis revealed a predominance of piezoelectric-based SHMS applied to metallic fixed-wing aircraft, with limited attention to composite structures and e-VTOLs. Most studies focused on maintenance phase impacts, overlooking integration costs during manufacturing. Potential benefits like operational life extension, prognostic capabilities, and safety margin reduction were rarely explored, while critical drawbacks such as detection performance, reliability, and power consumption were underrepresented. Maintenance and fuel costs were the most frequently considered economic drivers; downtime costs were often neglected. (4) Conclusions: Although the majority of reviewed studies suggest a positive economic impact from SHMS implementation, significant gaps remain. Future research should address SHMS reliability, integration during early design stages, and applications to emerging aircraft like e-VTOLs to fully realize SHMS economic advantages. Full article

Background/Objectives: Polymeric monoaxial nanofibers are gaining prominence due to their numerous applications, particularly in functional scenarios such as wound management. The study successfully developed and built a special-purpose vessel and device for fabricating polymeric nanofibers. Fabrication of composite scaffolds from piezoelectric poly(vinylidenefluoride-trifluoroethylene) copolymer (PVDF-TrFE) nanofibers encapsulated with myrrh extract was investigated. Methods: The gyrospun nanofibers were characterized using SEM, EDX, FTIR, XRD, and TGA to assess the properties of the composite materials. The study also investigated the release profile of myrrh extract from the nanofibers, demonstrating its potential for sustained drug delivery. The composite’s antimicrobial properties were evaluated using the disc diffusion method against various pathogenic microbes, showcasing their effectiveness. Results: It was found that an 18% (w/v) PVDF-TrFE concentration produces the best fiber mats compared to 20% and 25%, resulting in an average fiber diameter of 411 nm. Myrrh extract was added in varying amounts (10%, 15%, and 20%), with the best average fiber diameter identified at 10%, measuring 436 nm. The results indicated that the composite nanofibers were uniform, bead-free, and aligned without myrrh. The study observed a cumulative release of 79.66% myrrh over 72 h. The release profile showed an initial burst release of 46.85% within the first six hours, followed by a sustained release phase. Encapsulation efficiency was 89.8%, with a drug loading efficiency of 30%. Antibacterial activity peaked at 20% myrrh extract. S. mutans was the most sensitive pathogen to myrrh extract. Conclusions: Due to the piezoelectric effect of PVDF-TrFE and the significant antibacterial activity of myrrh, the prepared biohybrid nanofibers will open new avenues toward tissue engineering and wound healing applications. Full article

This paper focuses on the mathematical and numerical modeling of a non-classical macro fiber composite (MFC) piezoelectric transducer, MFC-P2, integrated with an aluminum cantilever beam for energy harvesting applications. It seeks to harness the transverse vibration energy in the environment to power small electronic devices, such as wireless sensors, where conventional power sources are inconvenient. The P2-type macro fiber composites (MFC-P2) are specifically designed for transverse energy harvesting applications. They offer high electric source capacitance and improved electric charge generation due to the strain developed perpendicularly to the voltage produced. The system is modeled analytically using Euler–Bernoulli beam theory and piezoelectric constitutive equations, capturing the electromechanical coupling in the d31 mode. Numerical simulations are conducted using COMSOL Multiphysics 6.29 to reduce the complexity of the mathematical model and analyze the effects of material properties, geometric configurations, and excitation conditions. The theoretical model is based on the transverse vibrations of a cantilevered beam using Euler–Bernoulli theory. The natural frequencies and mode shapes for the first four are determined. Depending on these, the resonance frequency, voltage, and power outputs are evaluated across a 12 kΩ resistive load. The results demonstrate that the energy harvester effectively operates near its fundamental resonant frequency of 10.78 Hz, achieving the highest output voltage of approximately 0.1952 V and a maximum power output of 0.0031 mW. The generated power is sufficient to drive ultra-low-power devices, validating the viability of MFC-based cantilever structures for autonomous energy harvesting systems. The application of piezoelectric phenomena and obtaining electrical energy from mechanical vibrations can be powerful solutions in such systems. The application of piezoelectric phenomena to convert mechanical vibrations into electrical energy presents a promising solution for self-powered mechatronic systems, enabling energy autonomy in embedded sensors, as well as being used for structural health monitoring applications. Full article

A bistable effect on a laminate structure with a piezoelectric patch was tested to harvest kinetic energy. The composite bistable plate was prepared in the autoclave with two different orientations of the glass fibers. The dynamic tests were performed on the universal testing machine using cyclic vertical compression excitation. During the tests, the bottom edge of the plate was clamped firmly while its upper edge was attached with some clearance to enable sliding. In such a configuration, the friction force between the plate and upper clamp element is responsible for the plate excitation. Simultaneously, the plate has enough space to change the shape between the two equilibria. During the harmonic excitation of the testing machine operating mode, a piezoelectric element was placed on the bistable plate and its voltage and normalized power outputs were evaluated. The experiments were repeated with additional mass distribution, which influenced the natural frequency of the plate. Full article

Piezoelectric materials, due to their ability to generate an electric charge in response to mechanical deformation, are becoming increasingly attractive in the engineering of bone and neural tissues. This manuscript reports the effects of the addition of nanohydroxyapatite (nHA), introduction of gold nanoparticles (AuNPs) via sonochemical coating, and collector rotation speed on the formation of electroactive phases and biological properties in electrospun nanofiber scaffolds consisting of poly(vinylidene fluoride) (PVDF). FTIR, WAXS, DSC, and SEM results indicate that introduction of nHA increases the content of electroactive phases and fiber alignment. The collector rotational speed increases not only the fiber alignment but also the content of electroactive phases in PVDF and PVDF/nHA fibers. Increased fiber orientation and introduction of each of additives resulted in increased SFE and water uptake. In vitro tests conducted on MG-63 and hiPSC-NSC cells showed increased adhesion and cell proliferation. The results indicate that PVDF-based composites with nHA and AuNPs are promising candidates for the development of advanced scaffolds for bone and neural tissue engineering applications, combining electrical functionality and biological activity to support tissue regeneration. Full article

Ligament tears can strongly influence an individual’s daily life and ability to engage in physical activities. It is essential to develop artificial scaffolds for ligament repairs in order to effectively restore damaged ligaments. In this experiment, the objective was to evaluate fibrous membranes as scaffolds for ligament repair. These membranes were created through electrospinning using piezoelectric polyvinylidene fluoride (PVDF) composites, which contained 1 wt.% and 3 wt.% of copper-impregnated nanohydroxyapatite (Cu-nHA). The proposed electrospun membrane would feature an aligned fiber structure achieved through high-speed roller stretching, which mimics the properties of biomimetic ligaments. Nanoparticles of Cu-nHA had been composited into PVDF to enhance the pirzoelectric β-phase of the PVDF crystallines. The study assessed the physicochemical properties, antibacterial activity, and biocompatibility of the membranes in vitro. A microstructure analysis revealed that the composite membrane exhibited a bionic structure with aligned fibers resembling human ligaments. The piezoelectric performance of the experimental group containing 3 wt.% Cu-nHA was significantly improved to 25.02 ± 0.68 V/g·m⁻² compared with that of the pure PVDF group at 18.98 ± 1.18 V/g·m⁻². Further enhancement in piezoelectric performance by 31.8% was achieved by manipulating the semicrystalline structures. Antibacterial and cytotoxicity tests showed that the composite membrane inherited the antibacterial properties of Cu-nHA nanoparticles without causing cytotoxic reactions. Tensile tests revealed that the membrane’s flexibility of strain was adequate for use as artificial scaffolds for ligaments. In particular, the mechanical properties of the two experimental groups containing Cu-nHA were significantly enhanced compared with those of the pure PVDF group. The favorable piezoelectric and flexible properties are highly beneficial for ligament tissue regeneration. This study successfully developed PVDF/Cu-nHA piezoelectric fibers for a biocompatible, unidirectional piezoelectric membrane with potential applications as ligament repair scaffolds. Full article

The use of electrospun carbon nanofibers (ECNs) has been the focus of considerable interest due to their potential implementation in sensing. These ECNs have unique structural and morphological features such as high surface area-to-volume ratio, cross-linked pore structure, and good conductivity, making them well suited for sensing applications. Electrospinning technology, in which polymer solutions or melts are electrostatically deposited, enables the production of high-performance nanofibers with tailored properties, including fiber diameter, porosity, and composition. This controllability enables the use of ECNs to optimize sensing applications, resulting in improved sensor performance and sensitivity. While carbon nanofiber mats have potential for sensor applications, several challenges remain to improve selectivity, sensitivity, stability and scalability. Sensor technologies play a critical role in the global sharing of environmental data, facilitating collaboration to address transboundary pollution issues and fostering international cooperation to find solutions to common environmental challenges. The use of carbon nanofibers for the detection of air pollutants offers a variety of possibilities for industrial applications in different sectors, ranging from healthcare to materials science. For example, optical, piezoelectric and resistive ECNs sensors effectively monitor particulate matter, while chemoresistive and catalytic ECNs sensors are particularly good at detecting gaseous pollutants. For heavy metals, electrochemical ECNF sensors offer accurate and reliable detection. This brief review provides in-sights into the latest developments and findings in the fabrication, properties and applications of ECNs in the field of sensing. The efficient utilization of these resources holds significant potential for meeting the evolving needs of sensing technologies in various fields, with a particular focus on air pollutant detection. Full article

Damage in composite laminates evolves through complex interactions of different failure modes, influenced by load type, environment, and initial damage, such as from transverse impact. This paper investigates damage growth in cross-ply polymeric matrix laminates under tensile load, focusing on three primary failure modes: transverse matrix cracks, delaminations, and fiber breaks in the primary loadbearing 0-degree laminae. Acoustic emission (AE) techniques can monitor and quantify damage in real time, provided the signals from these failure modes can be distinguished. However, directly observing crack growth and related AE signals is challenging, making numerical simulations a useful alternative. AE signals generated by the three failure modes were simulated using modified step impulses of appropriate durations based on incremental crack growth. Linear elastic finite element analysis (FEA) was applied to model the AE signal propagating as Lamb waves. Experimental attenuation data were used to modify the simulated AE waveforms by designing arbitrary magnitude response filters. The propagating waves can be detected as surface displacements or surface strains depending upon the type of sensor employed. This paper presents the signals corresponding to surface strains measured by surface-bonded piezoelectric sensors. Fiber break events showed higher-order Lamb wave modes with frequencies over 2 MHz, while matrix cracks primarily exhibited the fundamental S₀ and A₀ modes with frequencies ranging up to 650 kHz, with delaminations having a dominant A₀ mode and frequency content less than 250 kHz. The amplitude and frequency content of signals from these failure modes are seen to change significantly with source–sensor distance, hence requiring an array of dense sensors to acquire the signals effectively. Furthermore, the reasonable correlation between the simulated waveforms and experimental acoustic emission signals obtained during quasi-static tensile test highlights the effectiveness of FEA in accurately modeling these failure modes in composite materials. Full article

Macro Fiber Composites (MFCs) exhibit significant potential in active control applications. These include vibration control for unmanned aerial vehicle wings and helicopter rotors. However, the high-voltage drive requirements of MFCs present challenges. The miniaturization of the controller is a mandatory condition in order not to affect the overall space utilization. Thus, this paper presents a specialized miniaturized high-voltage control system designed specifically for MFC actuators. The proposed system employs a mixed analog-digital modulation method (ADM). This method precisely regulates a discontinuous conduction mode flyback switch-mode power supply operating in current mode. The system achieves an adjustable high-voltage output range of -500 V to 1500 V. The mixed control system consists of several components. These include a switching power supply, a voltage divider circuit, a bleeder circuit, and a digital controller. Additionally, this high-voltage control system integrates with a Simulink software environment. The system is compact and lightweight. It also features high load capacity, high power, and excellent dynamic response. Moreover, it offers real-time control capabilities. Experimental validation on a high-aspect-ratio wing demonstrates that this control system achieves a vibration reduction effect of 65%. The miniaturized control system provides a valuable research base for vibration control studies. Full article