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This paper presents a feasibility study on damage size quantification throughout the damage expansion procedure using the integral differential method based on the developed frequency response function (FRF) programme. A designed pattern of piezoelectric Micro Fibre Composite (MFC) transducers was integrated with three composite panels for a real time monitoring testing by swept sine vibration input signals under three varied frequency bandwidths ranged from 10 to 1 kHz, 1k-3 kHz and 3k-5 kHz, respectively. The composite panels under pristine stage without any impact damages were tested and documented as a cross-reference for subsequent quantification estimation. The damages were introduced around transducers array, and its expansion process is equivalently simulated by a repetitive impact test procedure. A modified damage index, difference of response (DoR), was derived through integral differential method to assess the FRF outcome change of damaged composite plate relative to the pristine state. Combined with damage geometrical dimensions measured by thermography imaging technology, a quantification formula is derived reversely through numerical analysis, which showed a segmentation linear relation between the DoR and damage size governed by the power and logarithmic functions. The damages under different severity subjected to an additional composite plate were successfully quantified by the segmentation formula, which validate the feasibility of quantification with DoR. [Display omitted] [ABSTRACT FROM AUTHOR]

Piezoelectric Internet of Things (IoT) sensors with energy-harvesting capabilities, which can convert mechanical energy into electrical energy, promote battery-less systems. Such sensors can harness the vibration generated by spacecraft and other moving objects, eliminating the need for external power sources or battery replacements, thereby improving the autonomy and reliability of the system. This study investigates the features of a novel piezoelectric vibration energy harvester (PVEH) that comprises a carbon fiber-reinforced polymer (CFRP) electrode. The CFRP electrode provides outstanding electrical conductivity (7190 S/m) and enhances the mechanical characteristics of the energy collector, thereby ensuring a steady electrical energy yield during resonance. The piezoelectric composite consists of potassium sodium niobate (KNN) nanoparticles mixed with epoxy resin. Results show that when the KNN content is about 30 vol%, the piezoelectric properties of d 33 and d 31 are 15.21 pC/N and − 5.68 pC/N, respectively. Under an applied displacement of 0.05 mm, the CFRP-reinforced PVEH (C-PVEH) provides an impressive output energy volume density of 89.61 μW/cm3, which is capable of lighting LED bulbs with ease. Notably, this technology shows great application potential for powering wireless communication systems, indicating a remarkable advancement in the field of self-powered IoT sensors. This study provides valuable insights into the potential application of this groundbreaking technology. [Display omitted] • This article presents a novel PVEH based on CFRP enhancement, which can convert mechanical energy into electrical energy. • The PVEH comprises a piezoelectric composite layer consisting of KNN nanoparticles mixed with epoxy resin, with optimal KNN content of about 30 vol%. • The CFRP electrode provides outstanding electrical conductivity and enhances the mechanical characteristics of the energy collector, ensuring a steady electrical energy yield during resonance. • The C-PVEH delivers a remarkable output energy volume density of 89.61 μW/cm3, indicating its capability to light LED bulbs with ease and great application potential for powering wireless communication systems. [ABSTRACT FROM AUTHOR]

This paper presents a study on the Mode I fracture behavior and crack monitoring of bonded carbon fiber reinforced polymer (CFRP) composite joints with carbon nanotube (CNT)-based polymer adhesive layer. Bonded joints were fabricated using woven carbon/epoxy composite substrates and CNT-based epoxy adhesives. Mode I fracture tests were carried out with double cantilever beam (DCB) bonded joint specimens, and the dependence of the critical energy release rate at the onset of crack growth, i.e., fracture toughness, on the nanotube content in the adhesive layer and the adhesive layer thickness was examined. The electrical resistance of the bonded joint specimens was monitored during the tests. An analytical model based on the electrical conduction mechanism of CNT-based polymers was also employed to describe the electrical resistance change due to crack propagation in the bonded joint specimens, and a good correlation was obtained between the predicted and measured results. The electrical resistance change is found to result in quantitative assessment of crack length based on resistance measurement. It is demonstrated that the bonded CFRP composite joints with CNT-based polymer adhesive layer have improved fracture properties together with crack sensing capability. [ABSTRACT FROM AUTHOR]

This paper deals with the cryogenic dynamic fatigue behavior of cracked piezoelectric ceramics under electric fields analytically and experimentally. The crack was created normal to the poling direction. Constant load-rate testing was conducted, using three-point bending technique, with the single-edge precracked-beam (SEPB) specimens at room temperature and liquid nitrogen temperature (77 K). The effects of electric fields and loading-rate on the fracture load were examined. Plain strain finite element analysis (FEA) was also performed, and the energy release rate for the permeable crack model was calculated to discuss the effects of loading-rate and temperature on the critical energy release rate. [ABSTRACT FROM AUTHOR]

This paper investigates the through-thickness tensile behavior of woven glass fiber reinforced polymer (GFRP) composite laminates at cryogenic temperatures. Tensile tests were carried out with cross specimens at room temperature and liquid nitrogen temperature (77 K), and the through-thickness elastic and strength properties of the woven GFRP laminates were evaluated. The failure characteristics of the woven GFRP laminates were also studied by optical and laser scanning microscopy observations. A three-dimensional finite element analysis was performed to calculate the stress distributions in the cross specimens, and the failure conditions of the specimens were examined. It is found that the cross specimen is suitable for the cryogenic through-thickness tensile characterization of laminated composite materials. In addition, the through-thickness Young's modulus of the woven GFRP composite laminates is dominated by the properties of the matrix polymer in the given temperature, while the tensile strength is characterized by both, the fiber to matrix interface energy and the cohesion energy of the matrix polymer. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes an experimental and analytical study on the dynamic fatigue behavior of cracked piezoelectric ceramics under AC electric fields. Constant load-rate testing was conducted in three-point bending with the single-edge precracked-beam specimens. The crack was created normal to the poling direction. The effects of AC electric fields and loading-rate on the fracture load were examined. A phenomenological model of domain wall motion was also used in finite element computation, and the energy release rate for the permeable crack model was calculated. The effect of AC electric fields on the critical energy release rate was then examined. The results suggest that (1) the fracture load of PZT ceramics decreases as the load-rate decreases; (2) an overall decrease in the fracture load occurs when testing under AC electric fields; and (3) the critical energy release rate is not very affected by the AC electric fields. [Copyright &y& Elsevier]

Abstract: We examine the nonlinear electromechanical response of piezoelectric mirrors driven by PZT thick films in a combined numerical and experimental investigation. First, some electromechanical tests were performed to measure the response (displacement versus load, displacement versus electric field) of the PZT thick films on elastic layers. A finite element analysis was then employed to determine the material properties in the PZT thick films using measured data. Next, the mirror tilt angle and electromechanical field concentrations due to electrodes in piezoelectric mirrors under electric fields were analyzed by introducing a model for polarization switching in local areas, and a nonlinear behavior was discussed in detail. The mirrors consisted of four fully or partially poled PZT unimorphs. Test results on the mirror tilt angle versus electric field, which verify the model, were also presented. [Copyright &y& Elsevier]

Abstract: This paper examines the nonlinear electromechanical response of 1-3 piezoelectric/polymer composites. The piezocomposites contain square or circular piezoelectric rods in an epoxy matrix. Experiments were conducted to measure the displacement versus electric field curves, using the device specimen of the 1-3 piezocomposites. Three dimensional finite element analysis was also carried out to study the electromechanical fields in the 1-3 piezocomposites by introducing a model for polarization switching. Comparison was then made between simulation and experiment. [Copyright &y& Elsevier]

Abstract: The objective of this work is to investigate the interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates loaded in a mixed-mode bending (MMB) apparatus at cryogenic temperatures. The finite element analysis (FEA) is used to determine the mixed-mode interlaminar fracture toughness of MMB specimen at room temperature (RT), liquid nitrogen temperature (77K) and liquid helium temperature (4K). A FEA coupled with damage is also employed to study the damage distributions within the MMB specimen and to examine the effect of damage on the mixed-mode energy release rate. The technique presented can be efficiently used for characterization of mixed-mode interlaminar fracture and damage behavior of woven laminate specimens at cryogenic temperatures. [Copyright &y& Elsevier]

Abstract: This paper describes an experimental and analytical study on the static fatigue behavior of piezoelectric ceramics under electromechanical loading. Static fatigue tests were carried out in three-point bending with the single-edge precracked-beam specimens. The crack was created perpendicular to the poling direction. Time-to-failure under different mechanical loads and dc electric fields were obtained from the experiment. Microscopic examination of the fracture surface of the piezoelectric ceramics was performed as well. A finite element analysis was also made, and the applied energy release rate for the permeable crack model was calculated. The effect of applied dc electric fields on the energy release rate versus lifetime curve is examined. The most important conclusion we reach is that the lifetimes for the piezoelectric specimens under a positive electric field are much shorter than the failure times of specimens under a negative electric field for the same mechanical load level. [Copyright &y& Elsevier]

Abstract: The electromechanical field concentrations due to circular electrode at the interface of piezoelectric disk composites have been discussed. This paper consists of two parts. In the first part, the problem of an internal electrode embedded at the interface of two dissimilar semi-infinite piezoelectric solids was formulated by means of Hankel transforms, and the solution was solved exactly. In the second part, finite element analysis was carried out to study electromechanical response in piezoelectric disk composites containing a circular electrode at the interface by introducing a model for polarization switching in local areas of field concentrations. A nonlinear behavior induced by localized polarization switching was observed between the strain and the voltage applied to the electrode. [Copyright &y& Elsevier]

Abstract: The theory of ferromagnetic elastic materials of multidomain structure is applied to develop a crack growth rate equation of a finite crack in a soft ferromagnetic material under mode I tensile loading and uniform magnetic field. The plane strain and plane stress problems are considered. Dugdale’s assumption regarding the plastic zone in metals is applied to estimate the effect of yield around the crack tip. The accumulated plastic displacement criterion is used for developing a solution for the crack growth rate. Numerical values of crack growth rate are obtained for a soft ferromagnetic strip with a single-edge crack and the results are displayed graphically. Crack growth rate tests are also conducted on nickel–iron soft magnetic materials with a single-edge cracked plate specimen geometry in the bore of a superconducting magnet, and a comparison is made between numerical results and experimental data. [Copyright &y& Elsevier]

Abstract: We investigate the nonlinear bending behavior of piezoelectric laminated actuators as a function of the amplitude and frequency of large electric fields both analytically and experimentally. Laminated beam theory is expanded to allow for the cantilever piezoelectric/metal/piezoelectric actuator, and the effects of alternating current (ac) electric fields on the tip deflection are analyzed. A simple phenomenological model of a vibrating domain wall in electric fields is used, and the macroscopic actuator response is predicted. A nonlinear three-dimensional finite element analysis is also employed. Experimental results are presented to validate the predictions using bimorph-type bending actuators made with thin soft lead zirconate titanate (PZT) layers and a thin metal sheet. Calculations show reasonable agreement with the experimental data, and support a role for domain wall motion in the nonlinear material response of the soft PZT under ac electric fields. [Copyright &y& Elsevier]

Abstract: The static electromechanical displacement and polarization switching properties of piezoelectric laminated actuators under three point bending have been investigated theoretically, numerically and experimentally. A laminated beam theory is expanded to allow for piezoelectric/metal/piezoelectric actuator, and the effects of electromechanical loading on the displacements of the actuators are analyzed. A nonlinear three-dimensional finite element procedure which allows to compute the polarization switching behavior is also proposed. Three point bending tests are used to validate the numerical predictions, using laminated actuators made with thin soft lead zirconate titanate (PZT) piezoelectric layers and a thin metal sheet, and comparison is made between numerical results and experimental data. [Copyright &y& Elsevier]

Abstract: The theory of linear piezoelectricity is applied to solve the plane strain electroelastic problem of a central active piezoelectric transformer in presence of a crack located normal to the interfaces. The ends of the crack are situated at equal distances away from the interfaces. The problem of an infinite central active piezoelectric transformer is formulated by means of integral transforms and reduced to the solution of a system of Fredholm integral equations of the second kind. Numerical calculations are carried out, and the fracture mechanics parameters such as stress intensity factor, energy release rate and energy density factor based on both permeable and impermeable crack models are shown graphically and compared. [Copyright &y& Elsevier]

This paper developed smart composite structures with screen-printed piezoelectric composite energy harvesters. P(VDF-TrFE) based composites with BaTiO 3 particles of different concentrations were deposited via screen printing and studied regarding surface morphology, crystalline structure, piezoelectric, dielectric and mechanical properties. It was identified that P(VDF-TrFE) with 5 wt% BaTiO 3 addition exhibited the best piezoelectric property. Even with a monotonic reduction in the β phase crystallisation as the BaTiO 3 concentration was increased, a 5 wt% inclusion of BaTiO 3 led to the rise of d 33 from −28.63 pC/N to −33.90 pC/N. This was attributed to the enhanced interfacial polarisation and the stress concentration induced by the addition of the ceramic particles. Subsequently, the printed piezoelectric composites were co-cured with glass fibre reinforced composites (GFRPs) and carbon fibre reinforced composites (CFRPs). The assembled harvesters were tested under both sinusoidal excitation and real industrial vibration. It was found that the smart composites with 5 wt% BaTiO 3 always manifested the best energy harvesting performance. For the optimised generator, maximum power of 2 μW and 1.5 μW could be obtained when using GFRPs and CFRPs as substrates under 1 g peak-peak sinusoidal excitation, respectively. The harvested energy could be used to power a commercial accelerometer with the help of a power management system. When exciting the GFRP-based energy harvester with an optimised printed piezoelectric generator at 7 g p-p acceleration, the power harvested was sufficient to maintain the operation of the accelerometer for 0.34 s. [ABSTRACT FROM AUTHOR]

With the recent increase in the adoption of silk in structural and medical applications, ensuring the long-term structural integrity of silk has become crucial. Previously, we successfully enhanced the static performance of silk by incorporating cellulose nanofibers (CNFs). This result is consistent with the common knowledge that nanofillers, such as CNFs, can alter the fatigue properties of materials. In this study, we evaluated the impact of CNFs on the fatigue performance of silk by comparing CNF-reinforced silk with regular silk. The tensile strength, Young's modulus, and toughness of the silk yarns were measured before and after cyclic loading. The evolutions of the properties between the silk types were recorded and compared. In addition, the friction coefficients of silk were measured using the Capstan method to assess the contribution of interfiber abrasion to the observed enhancement. The results showed that the CNFs significantly enhanced the fatigue performance of silk, with a notable 80.5 % increase in toughness observed after cyclic loading. Further, the friction properties of the different silk types were similar, eliminating friction as a cause of the resulting enhancement. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper developed a multifunctional composite sandwich structure with optimised design on topological cores. As the main concern, full composite sandwich structures were manufactured with carbon fibre reinforced polymer (CFRP) facesheets and designed cores. Three-point bending tests have been performed to assess the mechanical performance of designed cellular sandwich structures. To evaluate the energy harvesting performance, the piezoelectric transducer was integrated at the interface between the upper facesheet and core, with both sinusoidal base excitation input and acceleration measured from real cruising aircraft and vehicle. It has been found that the sandwich with conventional honeycomb core has demonstrated the best mechanical performance, assessed under the bending tests. In terms of energy harvesting performance, sandwich with re-entrant honeycomb manifested approximately 20% higher RMS voltage output than sandwiches with conventional honeycomb and chiral structure core, evaluated both numerically and experimentally. The resistance sweep tests further suggested that the power output from sandwich with re-entrant honeycomb core was twice as large as that from sandwiches with conventional honeycomb and chiral structure cores, under optimal external resistance and sinusoidal base excitation. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the cryogenic flexural fatigue and electrical resistance responses of CNT-based composites. [•] Cooling from room temperature to 77K causes an increase in the fatigue resistance. [•] The composite fatigue performance is affected by the nanotube content. [•] The electrical resistance-based sensing method was successfully applied. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we characterize the cryogenic mechanical response of nonwoven polyester/epoxy composites for high temperature superconducting devices. The test specimens were produced from the composite cylindrical components, and tension, compression and flexure tests were performed at room temperature and liquid nitrogen temperature (77K) to evaluate the elastic and strength properties of the composites. The failure characteristics of the composites were examined by microscopic observations of failed specimens. The temperature dependence and anisotropy of the composite properties were discussed. [Copyright &y& Elsevier]

Abstract: This paper reports the cryogenic interlaminar shear properties of composite insulation systems for the superconducting magnet coils in the International Thermonuclear Experimental Reactor (ITER). Short beam shear tests were performed at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K) on three insulation systems consisting of woven glass fiber reinforced plastic (GFRP) composites with different polymer resins and polyimide films, and the dependence of their apparent interlaminar shear strength on the temperature and the polymer resins was discussed. A detailed observation of failed specimens was made to verify the failure mechanisms. Insulation systems subjected to gamma irradiation at room temperature were also considered, and the effect of irradiation on the cryogenic interlaminar shear properties was examined. [Copyright &y& Elsevier]

Abstract: The purpose of this research is to characterize the cryogenic delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates subjected to Mode II fatigue loading. Mode II fatigue delamination tests were performed at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K) using the four-point bend end-notched flexure (4ENF) test method, and the delamination growth rate data for the woven GFRP laminates were obtained. The energy release rate range was determined by the finite element method. Microscopic examinations of the specimen sections and fracture surfaces were also carried out. The present results are discussed to obtain an understanding of the fatigue delamination growth mechanisms in the woven GFRP laminates under Mode II loading at cryogenic temperatures. [Copyright &y& Elsevier]

Abstract: This paper investigates the cryogenic fatigue delamination behavior of glass fiber reinforced polymer woven laminates under Mode III loading. Fatigue delamination tests were conducted using split cantilever beam specimens at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K). A finite element analysis was also employed to calculate the energy release rate. The temperature dependence of the fatigue delamination growth rate vs. energy release rate range is discussed. Fracture surfaces were examined by scanning electron microscopy to identify the delamination mechanisms under fatigue loading. The important conclusion we reach is that the Mode III fatigue delamination growth rates of woven laminates at cryogenic temperatures are lower than that at room temperature. [Copyright &y& Elsevier]

[Display omitted] • The functionally graded piezoelectric composites (FGPC) for energy-harvesting were manufactured successfully by a novel method. • The figure of merit which represents the efficiency of power generation in the 33 mode of FGPC is up to 72 times larger than homogenous composites. • The FGPC has the ability to collect energy from the typing process, with the maximum average output voltage of 120 mV. • In the 31 bending vibration mode, FGPC possesses a relatively high-power generation efficiency of up to 107 nW cm−3. The power supply to the sensors becomes increasingly critical as the Internet of Things (IoT) evolves. Hence, our goal is to transform ambient environmental energy in our daily lives into electrical energy and then give power to IoT sensors. In this work, we developed and manufactured functionally-graded piezocomposite using poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] and barium titanate (BaTiO 3 , BTO) particles. Functionally graded materials offer better specific strength, toughness, and fatigue resistance than homogeneous composite materials, making them appropriate for energy-harvesting. Spin coating and hot-pressing methods were used to create BTO/P(VDF-TrFE) composites with varying BTO particle fractions and structures. After determining the optimal spin coating and hot-pressing conditions, the composites were polarized using the corona poling technique. The structure and properties of the composites were determined by scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction. Then the piezoelectric characteristics were tested, and impact and vibration energy production tests were devised and carried out. This research provides a feasible manufacturing method for functionally graded piezocomposites and investigates the material energy-harvesting potential. Meanwhile, guidance is offered for the construction of functionally graded piezoelectric composites structures for use in various types of energy-harvesting applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies the effect of magnetic fields on the fracture toughness in nickel iron soft ferromagnetic materials. Tensile tests were conducted on single-edge cracked plate specimens in the bore of a superconducting magnet at room temperature, and the critical load was determined. The magnetoelastic analysis of a soft ferromagnetic strip with a single-edge crack was also performed, and the magnetic stress intensity factor was calculated. Based on the magnetic stress intensity factor, the fracture toughness was then obtained. [Copyright &y& Elsevier]

Abstract: The cryogenic fatigue delamination behavior of glass fiber reinforced polymer woven laminates under Mode I loading has been investigated experimentally and numerically. Fatigue delamination tests were conducted using double cantilever beam specimens at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K). Fracture surface examination using scanning electron microscopy revealed delamination mechanisms under fatigue loading. A finite element analysis was also employed to calculate the J-integral range and damage distributions. The effects of temperature and loading condition on the fatigue delamination growth rates were discussed. [Copyright &y& Elsevier]

Abstract: This paper describes an experimental and analytical study on fracture and damage behavior of GFRP woven laminates at cryogenic temperatures. CT (compact tension) tests were carried out at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K) to evaluate the critical values of the fracture mechanics parameters. During the CT tests, AE (acoustic emission) method was implemented. AE signals can identify the critical load at which gross failure occurs. A FEA (finite element analysis) was also applied to calculate the fracture mechanics parameters. The failure criteria (Hoffman criterion and maximum strain criterion) or the damage variable based on the continuum damage mechanics was incorporated into the model to interpret the experimental measurements and to study the damage distributions within the specimen. Several methods of calculating J-integral are discussed. [Copyright &y& Elsevier]

Abstract: This paper describes an experimental and analytical study on the cryogenic fatigue behavior of glass fiber reinforced polymer woven laminates under Mode I loading. Fatigue crack growth rate tests were performed using compact tension specimens at room temperature, liquid nitrogen temperature (77 K), and liquid helium temperature (4 K). The fracture surfaces were also examined by scanning electron microscopy to correlate with the fatigue properties. A finite element method coupled with fatigue damage was adopted for the extensional analysis. The effects of temperature and loading condition on the fatigue crack growth rates are examined. [Copyright &y& Elsevier]

This paper examines the thermo-mechanical behavior of cracked G-11 woven glass/epoxy laminates with temperature-dependent material properties under tension at cryogenic temperatures. Three-dimensional finite elements are employed to model the architecture of the two-layer woven laminates. It is assumed that the cracks are confined to individual fiber bundles oriented transverse to the tensile load direction and span the thickness of the fiber bundles. The effects of residual thermal stresses caused by differences in the coefficients of thermal expansion of the composite constituents, and cracks on the mechanical behavior of two-layer G-11 woven laminates at cryogenic temperatures are explored. Numerical results for Young''s modulus, Poisson''s ratio, and stress distributions and concentrations are obtained and discussed in detail. [Copyright &y& Elsevier]

We deal with the thermal–mechanical response of multi-layered G-11 woven glass/epoxy laminates with cracks and temperature-dependent properties under tension at liquid helium temperature (4 K). The composite material is assumed to be in generalized plane strain. Cracks are located in the fill fiber bundles and are assumed to span the width of the fill fiber bundles. Finite element model is used to study the influence of residual thermal stresses on the mechanical behavior of multi-layered woven laminates with cracks. Numerical calculations are carried out, and the Young''s modulus and stress distributions near the crack tip are shown graphically. [Copyright &y& Elsevier]

Highlights • Lower fracture strength of Terfenol-D in the presence of a magnetic field. • Prediction of Terfenol-D fracture loads by means of three different criteria. • Prediction of fracture initiation loci using three different criteria. • Higher accuracy of SED approach compared to the PM and UMTS criterion. Abstract The mechanical properties of Terfenol-D, a giant magnetostrictive material used in applications such as actuators and sensors, have been barely studied, in particular in the presence of notches. Thus, the aim of this work is to fill this gap present in literature. Three point bending tests have been carried out on U-notched specimens with a notch radius of 0.15 mm. The load has been applied at different distances from the midpoint in order to obtain different combinations of mode I and mode II, with the fraction of mode I always being predominant. The results show that higher contributions of the mode II lead to higher fracture loads. In addition, the data experimentally obtained have then been compared with the predictions provided by three different failure criteria, i.e. the strain energy density (SED) approach, the U-maximum tangential stress (UMTS) criterion and the theory of critical distances (TCD) method. Finally, the fracture initiation angles obtained experimentally have been compared with those proposed by the three approaches, and their weaknesses and strengths have been reported. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) composites integrated with sensors have received attention because the composite material can transmit information about the structural condition during operation. This study investigated the crack self-sensing capability of GFRP composites with magnetostrictive Fe–Co fibers under mixed-mode bending. The mixed-mode bending (MMB) test was performed using GFRP composites with a certain number of Fe–Co fibers introduced. Three different mixed-mode I/II ratios for MMB tests were selected and tested. The self-sensing capability of crack propagation was discussed by measuring the magnetic flux density induced by the inverse magnetostrictive effect using Hall probes. The GFRP composites with Fe–Co fibers fabricated in this study are a promising monitoring technology for non-contact sensing. [Display omitted] [ABSTRACT FROM AUTHOR]

• As deposited sputtered thin films stress can be designed. • Amorphous FeSiB thin films have magnetic properties stress-dependent. • Permeabilities are larger for the tensile stress region than in the compressive stress region. • Stress is reducing the permeabilities of the thin films. • Amorphous FeSiB thin films can be candidates for Stress Impedance sensing systems. This study aimed to understand the magnetic behavior of amorphous Fe–Si–B thin films in the presence of residual stress. Residual stress appeared in the thin films during the sputtering process, which was controlled by changing the Ar flow rate during sputtering. Consequently, some thin films developed compressive stress and others developed tensile stress. The residual stress generated in the films ranged from –100 to 400 MPa. The magnetization curves of the samples were measured to extract their magnetic parameters, namely, the magnetic permeability, coercive field, and saturation magnetization. For the films of thickness 500 nm, the relative permeability was higher under tensile stress (µ r ∼ 1000) than under compressive stress (µ r ∼ 100). A transition between the high and low permeability values occurred for residual stress in the range 0–100 MPa. The relative permeability decreased from 1100 to 800 as the tensile stress increased from 0 to 400 MPa. In addition, the relative permeability decreased from 150 to 100 as the compressive stress increased from 0 to –100 MPa. Moreover, a transcritical state was observed in the samples under compressive stress. For the films of thickness 200 nm, the tensile stress lowered the relative permeability from 800 to 400; however, the compressive stress did not change the permeability significantly. [ABSTRACT FROM AUTHOR]

Composite materials, such as carbon fiber-reinforced polymer (CFRP), glass fiber reinforced polymer, and fiber-reinforced metal matrix, have considerable application potential in the aerospace industry as structural components require remarkable mechanical properties such as high strength, high elasticity, and lightweight. Structural health monitoring (SHM) is required to ensure the safe use of these structural components during service. Magnetostrictive materials can convert mechanical energy into magnetic energy, and are considered desirable candidates to be used in SHM sensors owing to their large magnetostriction, long life, and low cost. In this study, we developed the composite materials comprising CFRPs with embedded Fe–Co wires and evaluated their magnetic and magnetostrictive characteristics using the vibrating sample magnetometer and strain gauge, respectively. Furthermore, the magnetostriction was analyzed using the nonlinear constitutive equations for magnetostrictive materials. It was shown that the largest piezomagnetic constant of 0.281 × 10−9 m/A is obtained for the CFRP with Fe–Co wires of 0.05 mm diameter. Microstructural observation of the Fe–Co wires with different diameters was performed to investigate the differences in grain structure and residual strain because the diameter of the Fe–Co wire affects the magnetostrictive response. Finally, the magnetostrictive characteristic was measured at high temperatures. The piezomagnetic constant at 373 K was about the same as the value obtained at room temperature. These results will contribute to developing the high-performance CFRP/Fe–Co wire composites that can be used in SHM sensors operating in high-temperature environments. [Display omitted] • A CFRP/Fe–Co wire composites exhibiting a magnetostrictive response was developed. • The nonlinear piezomagnetic coefficients of CFRP with Fe–Co wires were obtained. • The effect of the wire drawing process on the magnetostrictive characteristics was clarified using Fe–Co wires. • This composite material has a potential to monitor damage in CFRP at high temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the cryogenic mixed-mode II/III fatigue delamination growth in woven laminates. [•] The resistance to fatigue delamination growth at cryogenic temperatures is higher than that at room temperature. [•] The fracture surfaces show the presence of matrix hackles. [•] The inclined hackles are identified with the mixed-mode II/III delamination growth. [ABSTRACT FROM AUTHOR]