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Purpose: To inves)gate the effect of irradia)on)me and zirconia thickness using low power Er,Cr:YSGG laser irradia)on (for debonding purposes) on the thermal changes and shear bond strength (SBS) of resin-bonded 3% mol yIrium oxide stabilized tetragonal zirconia polycrystal (3YTZP) specimens. Materials and Methods: 3Y-TZP slices of 0.5-, 2-, and 3-mm thick were used. The temperatures during laser irradia)on using single spot irradia)on at different)mes (30 seconds, 60 seconds, 90 seconds, and 120 seconds) and line scanning irradia)on from one spot to another at three different distances (2, 4, and 6 mm) were recorded. Single spot and line scanning irradia)on data were analyzed using three-way ANOVA (a = .05) and generalized linear mixed model, respec)vely. Nonirradiated (control) and irradiated resin-bonded 3Y-TZP specimens were shear tested, and the data were analyzed using two-way ANOVA (a = .05). Results: Under single spot irradia)on, the laser-induced temperature was higher through thin 3Y-TZP at any)me compared to thick 3Y-TZP. For the line scanning method, short distances (2 and 4 mm) resulted in a significant increase in temperature for 0.5-mm thick specimens. Laser irradia)on significantly decreased the SBS of the 0.5-mm group compared to the nonirradiated group. A_er irradia)on, the bond strength of the 2- and 3-mm thick 3Y-TZP was similar to the nonirradiated group. Conclusions: The temperature and bond strength of low-power laser irradiated 3Y-TZP specimens was affected by the specimen thickness but not by the irradia)on)me tested. Low-power laser irradia)on is an effec)ve debonding method for thin Y-TZP restora)ons. [ABSTRACT FROM AUTHOR]

We report on viscous adhesion measurements conducted in sphere-plane geometry between a rigid sphere and soft surfaces submerged in silicone oils. Increasing the surface compliance leads to a decrease in the adhesive strength due to elastohydrodynamic deformation of the soft surface during debonding. The force-displacement and fluid film thickness-time data are compared to an elastohydrodynamic model that incorporates the force measuring spring and finds good agreement between the model and data. We calculate the pressure distribution in the fluid and find that, in contrast to debonding from rigid surfaces, the pressure drop is non-monotonic and includes the presence of stagnation points within the fluid film when a soft surface is present. In addition, viscous adhesion in the presence of a soft surface leads to a debonding process that occurs via a peeling front (located at a stagnation point), even in the absence of solid–solid contact. As a result of mass conservation, the elastohydrodynamic deformation of the soft surface during detachment leads to surfaces that come closer as the surfaces are separated. During detachment, there is a region with fluid drainage between the centerpoint and the stagnation point, while there is fluid infusion further out. Understanding and harnessing the coupling between lubrication pressure, elasticity, and surface interactions provides material design strategies for applications such as adhesives, coatings, microsensors, and biomaterials. [ABSTRACT FROM AUTHOR]

Effects of incorporating carbon nanotubes (CNTs) and short carbon fibers (SCFs) into the polyvinyl chloride (PVC) foam core on the flexural behavior of sandwich beams are investigated. Upper and lower skins are made of laminated composites and an initial debonded interface among the upper skin and core is considered. The mechanical properties of the hybrid CNT/SCF/PVC core are determined employing micromechanical models. To inspect the flexural behavior of sandwich beams at macro-scale, end notched shear (ENS) test is simulated using the finite element method (FEM). The results indicate an increase in flexural stiffness in the presence of CNT and SCF. [ABSTRACT FROM AUTHOR]

An analytical solution based on the infinite layer theory of Novak and Biot's consolidation equation is developed in this study to evaluate the impact of local debonding occurring at the pile–soil interface. The potential functions are employed to decouple the differential equations that govern the soil deformations, while the dynamic resistances of soil are determined from the boundary conditions at the pile–soil interface in accordance with computational theory for mixed boundary problems. The Adomian decomposition method is introduced to obtain the dynamic impedances of pile. The effects of local debonding on the dynamic resistances of soil are investigated by comparing the results from the present solution with available schemes based on perfect contact assumption. The influences of pile–soil modulus ratio, exciting frequency, soil permeability, and slenderness ratio of pile while considering local debonding were then examined. The numerical results indicate that the local debonding occurring at the pile–soil interface dramatically weakened the lateral dynamic impedances of pile, and this trend was particularly pronounced at high frequency and small modulus ratio. Additionally, the local debonding phenomenon also imposes limitations on the implementation of the equivalent single‐phase solution in practical engineering applications. The presented solution theoretically demonstrates the significant impact of local debonding on the dynamic response of piles embedded in saturated soil and may provide insight into determining parameter values in empirical equations. [ABSTRACT FROM AUTHOR]

In this paper, a new micromechanical hysteresis loop constitutive model of C/SiC composites with different interphases was developed considering the probabilistic‐statistical matrix fragmentation process. The lengths of matrix fragmentation were divided into three types, that is, long matrix fragments (LMFs), medium matrix fragments (MMFs), and short matrix fragments (SMFs). The distributions of the LMFs, MMFs, and SMFs with increasing tensile stress were determined using the probabilistic‐stochastic model by assuming the two‐parameter matrix strength distribution. The micro stress field of the LMFs, MMFs, and SMFs upon unloading and reloading was obtained and adopted to determine the corresponding stress‐strain relations. The interaction of matrix fragmentation lengths, especially for the LMFs with large debonding energy (LDE) and SMFs, was considered in the closed‐form constitutive model and hysteresis‐based inverse tangent modulus (ITMs) damage parameter. Synergistic effects of the fiber volumes, peak stresses, and interface debonding energy on the interface damage state, mechanical hysteresis loops, and related ITMs with small debonding energy and LDE were also analyzed. Comparisons of the mechanical hysteresis loops using the new hysteresis models considering matrix stochastic fragmentation and hysteresis models considering constant matrix fragmentation were also discussed. Experimental cyclic tensile hysteresis loops and unloading/reloading ITMs of C/(PyC)/SiC and C/(PyC+SiC)/SiC composites with different interphase thickness (i.e., t = 300, 600, 1000, and 2000 nm) were predicted using the developed constitutive model. Evolution of the unloading/reloading interface slip ratio was analyzed for different tensile peak stresses. [ABSTRACT FROM AUTHOR]

This paper attempts to evaluate the influence of strain rate on the debonding stress of the spherical nanoparticles using a closed form solution. A coherent model to correlate a relationship between the debonding stress of polymer-based nanocomposites and the strain rate was developed. A representative volume element (RVE) containing a spherical nanoparticle, an interphase material, and a pure polymer phase was regarded. A relationship between the debonding stress and the applied strain rate, the material, and geometrical properties of the RVE's constituents was correlated. In addition to the strain rate, the role of some effective variables such as nanoparticles size, interphase thickness, and interphase stiffness on the debonding stress were investigated. To evaluate the model, three case studies based on the experimental studies performed on silica nanoparticles/epoxy, CaCO3 nanoparticles/high-density polyethylene (HDPE), silica nanoparticles/photopolymer nanocomposites were conducted. For the nano-silica/epoxy system, the results revealed that by enhancing the strain rate, the normalized debonding stress decreases. Additionally, under a certain strain rate, the normalized debonding stress enhances as much as the stiffness of interphase material increases and the nanoparticle size decreases. In the case of CaCO3/HDPE nanocomposites, it was observed that by increasing the size of nanoparticles, the normalized debonding stress was reduced significantly. For the nano-silica/photopolymer nanocomposites, it was found that the dependence of the normalized debonding stress on the strain rate is more remarkable for the thicker interphase region. The proposed model can be used to predict the mechanical properties of nanoparticles/polymer systems under high strain rate conditions. [ABSTRACT FROM AUTHOR]

Among several composite repair methods, single-sided bonded patch repair is a simple and time-effective method, but its post-repair tensile strength is usually low compared to that of double-sided repair and scarf repair. Despite the tensile loading, out-of-plane bending deformation is inevitable owing to the step-like load path and generates peel stress in the adhesive layer. This study proposes a variable stiffness (VS) patch that mitigates steep stiffness changes at the edge of the patch using a curvilinear fiber orientation and verifies its effectiveness in delaying patch debonding. The damage progress in the single-sided repaired quasi-isotropic CFRP laminate under tensile loading was predicted using three-dimensional finite element analysis with cohesive elements. Although patches debonded from one end in the loading direction, the VS patch with low stiffness near the end obtained a smaller out-of-plane deformation and a higher debonding onset strain than those of the standard quasi-isotropic patch. Furthermore, tensile tests of patch-repaired CFRP specimens demonstrated an increase in the debonding onset strain by the VS patch with a small variation. These results confirmed the effectiveness of the VS patch in the single-sided bonded repair of composite structures. [ABSTRACT FROM AUTHOR]

Featured Application: Rehabilitation of Oil and Gas Pipelines. The aging pipeline infrastructure around the world necessitates immediate rehabilitation. Internal replacement pipe (IRP) is a trenchless system offering a versatile and cost-effective solution across a variety of industries, including oil, natural gas, water, and wastewater. As a structural pipeline repair system, IRPs are subject to lateral deformation because of surface traffic loading. The present study evaluates the impact of adhesion between the host pipe and the IRP, with a focus on assessing the debonding effect on the behavior of the repair system under lateral deformation and bending. This was achieved using a comprehensive approach, including experimental, numerical, and analytical techniques. Varying levels of adhesive strength resulting from different methods of surface preparation were considered. The effectiveness of the IRP system on both discontinuous host pipes with various crack widths and continuous host pipes was also investigated. The results demonstrate that adhesive strength exerts a significant influence on the repair system, especially in the case of narrow circumferential cracks, while its impact on the continuous system is minimal. For optimal performance, it is essential to choose adhesives that possess sufficient shear strength while also accounting for the required debonding length. This approach ensures that minor discontinuities are effectively controlled, thereby enhancing the system′s fatigue life. The reliable determination of the maximum allowable shear strength for the adhesive or the debonding length can ensure that it does not negatively affect fatigue life. The findings presented in this study offer new insights into the development of trenchless repair techniques that can enhance system performance and extend service life. [ABSTRACT FROM AUTHOR]

Highlights Composite materials provide an alternative to conventional structural materials. Sandwich composites show high bending strength and superior strength‐to‐weight ratio. The major drawback in sandwich composites is debonding of skin from core, that causes failure of a component during the usage at different loads. To overcome this issue, the current work identifies a solution of introducing nylon screws (M6 × 32) to adhere firmly the skins consisting of glass fibers with PET (Polyethylene Terephthalate) core. The sandwich composites were fabricated by vacuum infusion process. Two flat sandwich composites were fabricated; one with nylon screws placed perpendicular to the skin and the other a plain sandwich composite. Mechanical characteristics of the specimens such as fracture toughness, flexural strength and shear strength were studied. Specimens with nylon screws showed 21.78% more fracture toughness compared to plain specimen. The presence of screws acts as hindrance to the propagation of cracks in the interfacial region resulting in the enhancement of debonding resistance of the specimens. Also, sandwich specimens with nylon screws exhibited 136% and 142% improvement in flexural and shear strength respectively when compared to plain sandwich specimens. The investigation of scanning electron microscope (SEM) images of tested specimens indicates strong interfacial bonding between skin and the core of specimens with nylon screws. Introduction of light‐weight nylon screws in z‐direction enhanced the bonding between face sheets and foam core. Sandwich composites with nylon screws exhibited superior bending and shear strength compared to plain specimens. Crack propagation in the interfacial region is restricted by the presence of nylon screws. Investigation of fractured specimens indicated a strong interfacial bonding in the specimens with screws. [ABSTRACT FROM AUTHOR]

Ceramic matrix composites (CMCs) have a wide range of applications in key areas, such as aerospace and defense, and to study the mechanical properties and damage mechanisms of fiber-reinforced CMCs under different tensile conditions. Firstly, an ultrasonic vibration tensile device was designed, based on stress superposition and softening effect, the ontological relationship of materials under ultrasonic vibration-assisted stretching was established to study the damage mechanism of materials under different vibration conditions. The results show that tensile damage has multiple damage mechanisms occurring, i.e., matrix multiple cracking, interfacial debonding, and fiber fracture, and is also the main cause of nonlinear characteristics. Under high-frequency alternating load, the tensile strength decreased by up to 32 MPa, and the strain at break increased by up to 0.24 %; the tensile damage mechanism changed, the interfacial strength of the fiber and matrix decreased, the fiber toughness increased significantly, and the fracture morphology became flatter. [ABSTRACT FROM AUTHOR]

Perylenediimide‐chitosan/γ‐poly (glutamic acid) microcapsules sizing (PDI‐CS/γ‐PGA) core–shell microcapsule is designed and used to establish a novel interphase in carbon fiber/epoxy (CF/EP) composite, and the interfacial property, as well as the damage self‐reporting of the composite, is compared with desized carbon fiber (CF‐desized)/EP and commercial carbon fiber (CF‐COM)/EP composite. The ruptured PDI‐CS/γ‐PGA microcapsule exhibits strong "turn‐on" green fluorescence from the released PDI upon mechanical stimuli. The anchoring of PDI‐CS/γ‐PGA microcapsule on carbon fiber with PDI‐CS/γ‐PGA microcapsules sizing (CF@PDI‐CS/γ‐PGA) surface results in increased chemical activity and roughness, exhibiting a weak green fluorescence signal instead of non‐fluorescence on CF‐desized and CF‐COM surface. The transverse fiber bundle tensile (TFBT) strength of CF@PDI‐CS/γ‐PGA composite is 80.97% and 31.09% higher than those of CF‐desized/EP and CF‐COM/EP composite, which is attributed to the mechanical interlocking and chemical bonding interaction between carbon fiber and epoxy matrix by introducing PDI‐CS/γ‐PGA microcapsule with spherular structure and active groups. After microdroplet testing, the strong "turn‐on" green fluorescence signal of the released PDI from the microcapsules is detected in the interfacial debonding regions, realizing the microscopic damage self‐reporting of CF@PDI‐CS/γ‐PGA composite. [ABSTRACT FROM AUTHOR]

Debonding regions can occur at the interface of aluminium/rigid polyurethane foam composite plates (ARCP) during manufacturing. To help improve the technological process of manufacture, it is essential to precisely locate these debonding regions. This paper proposed a method to image the debonding regions in the ARCP based on the A0 mode Lamb waves. To study the influence of overlap between the debonding region and the coil of the electromagnetic acoustic transducer (EMAT) on Lamb wave propagation, a three-dimensional finite element simulation model was developed. A positive linear relationship was obtained between the amplitude of the A0 mode and the overlap rate between the debonding region and the coil of the EMAT, which was verified through experiments. Based on such relationship, an imaging method was proposed. The imaging method consisted a horizontal scanning for the entire sample and vertical scanning for possible debonding regions determined from the horizontal scanning. The result of the imaging experiments can precisely reveal the size and position of the debonding regions, the maximum relative error of the centre position of the defect is 7.5% and the maximum relative deviation of the dimensions is 16.0%. This imaging method can serve as a reference for debonding imaging in composite plates. [ABSTRACT FROM AUTHOR]

The first phase of this study aimed to validate multi-scale approaches based on Representative Volume Elements (RVEs) for graphene–polyethylene nanocomposites. stress–strain curves of experimental results were compared with numerical homogenization results. The stress amplification obtained from these simulations was used to predict GNP aspect ratios, demonstrating good agreement with permeability results. After validation of the multiscale approach, this study investigates the adhesion between nanoparticles and matrix in anisotropic GNP-HDPE metamaterial nanocomposites, emphasizing the role of the carboxyl (COOH) functional group in improving adhesion. The RVE model is used to investigate the debonding initiation and progression in these anisotropic nanocomposites under tensile and shear loading. Results indicate a variance in debonding onset and growth depending on orientation relative to the GNP axis. In tensile loading, debonding initiates at higher strains along the GNP axis than perpendicularly. Under shear loading within an anisotropic distribution, debonding behaviour varies significantly between planes perpendicular and parallel to the GNP axis. GNP surfaces with fully debonded surfaces slightly exceed 0.6% perpendicular to the GNP axis but increase to over 10.5% parallel to it. [ABSTRACT FROM AUTHOR]

In this study, we address the challenge of hidden damages in FRP composites, such as delamination, matrix cracking, and fibre breakage resulting from transverse low-velocity impact (LVI)—damages often elusive on the surface. Our methodology operates at the meso-scale, depicting laminates as stacked homogenized plies incorporating interfaces. To capture the mechanical behaviour and damages, we extend an existing nonlinear mean-field debonding model (NMFDM), accommodating asymmetric matrix plasticity (AAMP), fibre–matrix interface debonding failure, and in-plane progressive failure. In a key enhancement, we introduce a strain rate term to the AAMP model, addressing strain rate effects associated with LVI loading. Additionally, we incorporate a novel strain-driven 3D failure criteria, offering a more precise assessment of progressive failure subjected to LVI loading. The interfaces between plies are modelled using surface-based cohesive behaviour to capture interaction phenomena. To validate the developed NMFDM, we conduct impact simulations at various energies on a UD composite laminate consisting of AS4/8552 carbon fibre and epoxy matrix. These simulations showcase the predictive capability and accuracy of the NMFDM in capturing the intricate behaviour and damage progression of UD composites subjected to LVI. [ABSTRACT FROM AUTHOR]

Background: Fiber-matrix debonding is a precursor for transverse cracking and several other types of damage in fiber composites. However, to date, there are limited experiment-based reports that study the fundamental mechanisms of fiber-matrix debonding. Objective: This work aims to uncover the governing mechanisms of fiber-matrix interface debonding by full-field measurements supplemented by numerical simulations. In particular, the application of a dual-vision image-based characterization approach on single glass macro fiber samples is discussed and proven useful in understanding the in-plane and out-of-plane debonding characteristics at the fiber-matrix interface. Methods: Full-field strain and displacement measurements based on digital image correlation are performed on model single-fiber composites. The use of a dual-vision system allows strain measurements in the vicinity of the fiber-matrix interface, also allowing for the identification of critical strain and stress values corresponding to the initiation and propagation of debonding damage. The experimental data are used to calibrate an inverse identification approach that outputs the shape of the debonded interface along the fiber length. Results: Full-field measurements allow for establishing correlations between local and global strain fields. Observation of debonding propagation along the fiber axis seems to be representative of the crack tunneling during the early stages of the failure process, i.e., when the crack tip is subjected to opening mode only. Conclusions: Side view measurements are useful as a first-order approximation of the debonding propagation velocity along the fiber axis but fail to provide accurate measurements for the debonding shape, esp. in areas where the crack is under a dominantly shear stress state. This issue can be resolved by full-field measurements coupled with computational simulations. [ABSTRACT FROM AUTHOR]

Background and Aims: One side effect of orthodontic treatment is microcrack formation during debonding process. Since the type of ligation may affect the applied debonding force, this study was conducted to investigate the effect of ligation method on the enamel microcrack formation following debonding of orthodontic brackets. Materials and Methods: The present study was an experimental in vitro study. 69 extracted human premolar teeth were divided into 3 groups with 23 teeth by a simple random method. A bracket was bonded on the buccal surface of the teeth, then the desired tooth was placed in a typodont where the rest of the teeth were mounted. Then, the arch wire was passively placed in the bracket slot. The samples were ligated by one of these three methods based on the study group: 1. Oring ligation 2. Tight ligation with a wire ligature for each tooth separately 3. Ligation of all arch teeth together, using a wire ligature. The buccal surfaces of the teeth were observed under a stereomicroscope and the length, location, and the number of microcracks were recorded before and after debonding process. In order to analyze the data, generalized estimating equation analysis was used. Results: In all three groups, a significant increase was observed in the average total length and number of enamel microcracks following the debonding process. (P<0.001 in all three groups), with no statistically significant difference between the three study groups. However, it was greater in group 2 than that of groups 3 and 1 respectively. In general, the number of new cracks was more in mid-buccal area followed by cervical and occlusal areas. Conclusion: The debonding process caused an increase in the average total length as well as the number of enamel microcracks. Type of ligation might affect the enamel microcrack formation so that in tight ligation group we had the greatest increase in the enamel damage especially in mid-buccal area of the tooth. Tight ligation method can cause more enamel cracks than O-ring ligation and full arch ligation methods. [ABSTRACT FROM AUTHOR]

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In order to reveal adsorption-regulation micromechanism and debonding micromechanism between wall surface and magnetorheological (MR) wall-climbing robot legs, an interparticle normal magnetic attraction (NMA) mechanics model was constructed based upon the magnetic-dipole theory. According to analysis of NMA mechanics, it was confirmed that the interparticle NMA could be intensified with enhancing magnetic-particle diameter but was weakened with ratio of adjacent magnetic-particles distance to magnetic-particle radius. It means that the adhesive capacity between MR wall-climbing robot legs and wall surface could be strengthened by increasing magnetic-particle size and decreasing interparticle distance. Furthermore, it was found that the NMA of the first particle in the magnetic chain was positively related to magnetic-particles number until the magnetic-particles number reached a critical value. Consequently, the adsorption ability between MR wall-climbing robot legs and wall surface could be effectively controlled by changing magnetic-particles number. Besides, the strongest NMA appeared at the middle of the magnetic chain. However, the weakest NMA locates at both ends of the magnetic chain. Thus, it could be concluded that the end of the magnetic chain would be separated from wall surface rather than fracture occurred in the middle of the magnetic chain when the MR wall-climbing robot legs divorced from wall surface. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effectiveness of different pain mitigation methods during orthodontic debonding and to evaluate pain sensitivity across various regions of the dentition. A total of 144 participants (50 males and 94 females) with metal brackets were randomly assigned to one of four groups: High-Frequency Vibration (V), Cotton Roll (CR), Elastomeric Wafer (EW), and Open Mouth group (OM). Pain levels were measured using the Visual Analog Scale (VAS) across different sextants of the dentition. The Kruskal-Wallis test and post hoc analyses were conducted to compare VAS scores between groups. The Mann-Whitney test was used to analyse sex-based differences. The V group, utilizing high-frequency vibration, had the lowest total VAS score, indicating superior pain relief compared to CR, EW, and OM groups. No significant difference was observed between the CR and EW groups. Median VAS scores were highest in the lower front sextant, followed by the upper front sextants, and lowest in the posterior regions, indicating greater pain sensitivity in the anterior regions during debonding. High-frequency vibration was the most effective method for reducing pain during orthodontic debonding, particularly in the anterior dental regions. Both CR and EW methods were also effective but to a lesser extent. These findings suggest that high-frequency vibration could significantly improve patient comfort during orthodontic procedures. Utilizing high-frequency vibration for orthodontic debonding can enhance patient comfort, especially in the more sensitive anterior dental regions, thereby potentially improving treatment compliance and experience. Trial registration: NCT05904587. [ABSTRACT FROM AUTHOR]

Debondable pressure‐sensitive adhesives (PSAs) promise access to recyclability in microelectronics in the transition toward a circular economy. Two PSAs were synthesized from a tetravalent thiol star‐polyester forming thiol‐catechol‐connectivities (TCC) with either the biorelated DiDopa‐bisquinone (BY*Q) or the fossil‐based bisquinone A (BQA). The PSAs enable debonding by oxidation of TCC‐catechols to quinones. The extent of debonding efficiency depends on the interaction modes, which are determined by the chemical structure differences of both TCC‐motifs. BY*Q‐TCC‐PSA debonds with exceptional loss of 99 % of its approx. 2 MPa shear strength in glass‐on‐glass junctions. For BQA‐TCC‐PSA, a debonding efficiency of only approx. 60 % was found, irrespective of its initial shear strength, which could be tuned up to approx. 7 MPa. The efficiency of debonding for BY*Q‐TCC‐PSA after TCC‐oxidation is linked to the loss of synergistic interactions without strongly affecting the bulk glue properties, outperforming the purely catechol‐based BQA‐analogue. [ABSTRACT FROM AUTHOR]

Auf dem Weg zur Kreislaufwirtschaft ermöglichen abschaltbare Haftklebstoffe (engl. pressure sensitive adhesives, PSA) Zugang zu Wiederverwertbarkeitsstrategien in der Mikroelektronik. Zwei PSAs wurden aus einem tetravalenten Thiol‐Sternpolyester synthetisiert, der Thiol‐Catechol‐Verknüpfungen (thiol‐catechol‐connectivity, TCC) mit dem biobasierten DiDopa‐Bischinon (BY*Q) oder dem fossilbasierten Bischinon A (BQA) bildet. Die PSAs ermöglichen das Entkleben durch Oxidation der TCC‐Catechole zu Chinonen. Die Ablösungseffizienz hängt von den Interaktionsmoden ab, die aus den unterschiedlichen chemischen Strukturen der beiden TCC‐Motive folgen. BY*Q‐TCC‐PSA zeigt beim Entkleben einen außergewöhnlichen Verlust von 99 % seiner ursprünglichen Scherfestigkeit von ca. 2 MPa in Glas‐auf‐Glas‐Verklebungen. Für BQA‐TCC‐PSA wurde ein Verlust der Scherfestigkeit von nur ca. 60 % festgestellt, unabhängig vom ursprünglichen Wert, der bis auf ca. 7 MPa eingestellt werden konnte. Die Effizienz der Ablösung von BY*Q‐TCC‐PSA nach der TCC‐Oxidation konnte mit dem Verlust synergetischer Wechselwirkungen in Verbindung gebracht werden. Dabei verändern sich die Eigenschaften des Bulk‐Klebstoffs weniger stark als im nur auf Catecholen basierenden BQA‐Analogon. [ABSTRACT FROM AUTHOR]

Geothermal wells are subjected to higher loads compared to conventional oil and gas wells due to the thermal cycles that occur during both production and non-production phases. These temperature variations can affect the cohesion of the cement within the formation and casing, creating micro-annuli channels that can ultimately compromise the integrity of the well. Therefore, this study employs an intensive finite element methodology to analyze the debonding criteria of casing–cement systems in geothermal wells by examining over 36 independent models. The wellbore cooling and heating processes were simulated using three cohesive zone models (CZM): Type I (tensile), Type II (shear), and mixed (Type I and II simultaneously). The analysis revealed that Type I debonding occurs first during cooling at a temperature of around 10 °C, while Type II is the primary failure mode during heating. Evaluations of interfacial bonding shear strength (IBSS) values indicated that the debonding of the cement would even occur at high IBSS values (3 and 4 MPa) at a differential temperature of 300 °C, while the other IBSS of 1 MPa withstands only 60 °C. However, achieving an IBSS of 4 MPa with current technology is highly unlikely. Therefore, geothermal well operation and construction must be modified to keep the differential temperature below the critical temperature at which the debonding of the cement initiates. The study also found that debonding during cooling happens at lower differential temperatures due to generally lower values for interfacial bonding tensile strength (IBTS), typically less than 1 MPa. The novelty of the study is that it provides new insights into how specific temperatures trigger different types of debonding, highlights that high IBSS values may not prevent debonding at high differential temperatures, and recommends operational adjustments to maintain temperatures below critical levels to enhance cement integrity. Additionally, this study reveals that debonding during cooling occurs at a lower differential temperature change due to the reduced value of the interfacial bonding tensile strength (IBTS). [ABSTRACT FROM AUTHOR]

This study utilized experimental research to investigate the efficiency of using normal aggregate concrete (NAC) or recycled aggregate concrete (RAC) as a new concrete layer for repairing projectile bullet damage to strengthening reinforced concrete (RC) beams. This study comprised the construction and testing of eight RC beams made of RAC and NAC. They are initially subjected to projectile bullets and after that tested with flexure load to evaluate the effect of using RAC and NAC that was investigated. The findings of test results demonstrate that the repaired specimens with RAC or NAC experienced a higher load capacity than the damaged control specimens. As such, this approach could potentially use to restore RAC or NAC beams were previously damaged by projectile bullets. In addition, the findings of this research indicate that the load capacity of the damaged RC beams that were previously repaired using the NAC layer was higher than the load capacity of the damaged RC beams that were repaired using the RAC layer. The load capacity enhanced significantly of (106%–118%) and (104%–113%), respectively, when NAC and RAC are utilized in repairs. Therefore, using either NAC or RAC concrete is more economical, environmentally friendly, and efficient than demolishing. [ABSTRACT FROM AUTHOR]

The purpose of this research is to solve the problem of debonding of polyacrylonitrile (PAN) fibers in asphalt to improve the property of asphalt materials. A simple layer-by-layer self-assembly method was employed, in which a chitosan (CS)/phytanic acid (PA) coating was first constructed on the fiber surface. This coating immobilized Fe3O4 nanoparticles on the fiber surface by electrostatic adsorption and coordination, resulting in a robust active surface to obtain Fe3O4-PA-CS-PAN fibers, which were used to laminate styrene–butadiene–styrene (SBS)-modified asphalt. Dynamic shear rheometer (DSR) tests confirmed that the Fe3O4-PA-CS-PAN fiber-modified asphalt possessed superior viscoelastic properties and rutting resistance. At 64 °C, the viscosity modulus (G′) and viscous modulus (G′′) of the 1.5% Fe3O4-PA-CS-PAN fiber-modified asphalt increased by 18.23% and 26.19%, respectively, compared with that of the same dosage of PAN fiber-modified asphalt. This can be ascribed to the effective enhancement of the bonding of the interface between the modified PAN fibers and the asphalt. This research contributes to the development and improvement of future road materials. [ABSTRACT FROM AUTHOR]

• A pulsed laser method is used to debond ethylenevinylacetate polymer from silicon. • The glass/polymer layer can be separated from silicon in solar photovoltaic cells. • Nanosecond pulses at 355 nm and 532 nm are more effective than 1064 nm. • Transient surface melting does not damage the silicon wafer or metallic contacts. • Pulsed laser debonding can be applied to silicon photovoltaic panel recycling. The active silicon cell of a solar photovoltaic (PV) panel is covered by an ethylenevinylacetate (EVA) adhesive and a protective top glass layer. Separating this glass-EVA layer from the underlying silicon represents a bottleneck for recycling PV panels. Previous work has shown that the EVA-Si bond can be weakened by applying a continuous source of heat to melt the EVA. In this paper, a new method using nanosecond laser pulses is demonstrated to induce transient melting selectively at the EVA-Si interface. This impulsive heating method can cleanly separate the glass-EVA layer from the silicon in both model and commercial multicrystalline PV panels. The dependence of this debonding on parameters like laser pulse fluence (laser pulse energy per area), wavelength, applied pressure, and scan speed were characterized. For model PV panels, the single-pulse laser fluences required for spontaneous separation of the assembly under the force of gravity, were 0.23, 0.32 and 0.78 J/cm2 for 355 nm, 532 nm and 1064 nm, respectively. The use of shorter wavelengths reduces the laser fluence needed for debonding, while higher fluences can compensate for faster laser beam scanning rates. Optical and electron microscopy images of the Si surfaces before and after laser irradiation show that the textured antireflection layer is destroyed but the silver metal grid remains intact. Preliminary experiments using 532 nm pulses showed that the laser debonding method could remove the glass-EVA layer from sections of decommissioned commercial PV panels, even when the top glass layer was densely cracked. [ABSTRACT FROM AUTHOR]

Warm-mix recycling technology has gained increasing adoption in practical engineering owing to its notable environmental and economic advantages. Nevertheless, the intricate interfacial mechanisms governing the interaction between asphalt and aggregate during the reprocessing process remain unclear. The objective of this study is to investigate the adhesion and debonding behaviors between warm-mix recycled asphalt and aggregates through the utilization of molecular dynamics simulation. Molecular models representing the asphalt-aggregate interface in four different states (virgin, long-term aged, recycled, and warm-mix recycled) were developed to assess the interaction effects between various asphalt binders and aggregates. The aggregation of asphalt components under both dry and humid conditions was evaluated using mean square displacement and molecular radial distribution function. Furthermore, the debonding behaviors of different asphalt-aggregate interfaces were analyzed by defining the adhesion energy. The findings indicate that aging enhances the aggregation behavior of the molecular structure while diminishing the contact area and molecular activity between the asphalt binder and aggregate. Although the compound regenerant fails to fully degrade the oxidation functional groups in aged asphalt, it effectively penetrates and fills the intermolecular aggregation spaces, thereby increasing the contact area and molecular activity between the asphalt and aggregate. The warm-mix regeneration process primarily enhances the activity of lightweight components to improve adhesion between the aged asphalt and aggregates. The present study provides a certain research basis for the microinterface mechanism between warm-mix recycled asphalt-aggregate. [ABSTRACT FROM AUTHOR]

To investigate the debonding process, an in-situ pullout experiment on an indented single polypropylene fiber was conducted using X-ray microtomography. This study utilized mechanically regularized global digital volume correlation (Reg-G-DVC) to measure the deformation fields of the fiber, matrix, and interfaces during interfacial debonding. Reg-G-DVC mitigates the impact of low contrast on measurement uncertainties, ensures the convergence of DVC calculations, and enables the element size to be reduced to improve the spatial resolution. The displacement jumps of the shared nodes between the fiber and the matrix were used to quantify interfacial debonding. The profiles of the normal and tangential components of the displacement jumps exhibited periodic features corresponding to the geometry of the indented fiber as it was pulled out. Additionally, the force–displacement curves displayed multi-peak fluctuations corresponding to the fiber geometry, thereby indicating that the periodic indentation of the fiber enhanced friction and the cohesive force between the fiber and the matrix during the pullout process. The displacement jumps along the fiber was maximum at the embedded initiation and decreased along the fiber toward the embedded end. The aforementioned research demonstrated the advantages of utilizing Reg-G-DVC in measuring displacement fields during interfacial debonding, which provides deformation data for identifying and validating interface models. [ABSTRACT FROM AUTHOR]

Performance and longevity of bridge structures are usually compromised by the use of expansion joints, which are prone to material deterioration and are costly to maintain. To address these drawbacks, partially continuous systems with link slabs are increasingly adopted. This study aims to provide a detailed understanding of the behavior of link slabs. A numerical model was developed using finite element analysis to simulate the behavior of the link slabs. The results of the model were compared to those of the analytical solution. The study also examined the effects of various parameters, including the Debonding Length Ratio (DLR) and the span length on link slab performance. The results indicate that the numerical model tends to overpredict the link-slab rotations when compared to the analytical solution. However, the moments in the link slab showed a decrease with increasing span length in the numerical analysis, contrary to the analytical solution which indicated an increase. In addition, higher DLRs resulted in reduced rotations and increased moments in the numerical model, whereas the analytical solution showed no effect on rotation and a decrease in moments with higher DLR. These results highlight the necessity of using detailed numerical models to accurately analyze and optimize the design of link slabs. [ABSTRACT FROM AUTHOR]

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To ensure a strong adhesive bond, most standards and adhesive manufacturers specify a maximum adhesive gap of 1 mm when bonding fiber reinforced composite structures. In manufacturing large components, such as joining two halves of wind turbine blades, meeting this gap tolerance specification is impractical; gaps larger than 10 mm are common in large adhesively bonded composite structures using state-of-the-art manufacturing techniques. Currently, there is a lack of fundamental understanding of the failure mechanics of adhesive gaps larger than 3 mm. To create such understanding, glass fiber – acrylic thermoplastic composite panels bonded using different epoxy adhesives within single-lap joint samples with adhesive thicknesses of 0.1 mm, 0.3 mm, 1 mm, 3 mm, 5 mm, and 10 mm were sheared to failure. A transition from cohesive to adhesive failure was observed to occur about 1 mm to 3 mm joint thicknesses. Plotting the shear stress normalized by the ratio of the joint width to thickness as a function of the joint thickness normalized by the joint length is shown to result in the ability to fit simple empirically derived models of the cohesive-to-adhesive failure transition, regardless of the adhesive. Furthermore, using these normalized variables, all the observed cohesively failed specimens collapse to a single master curve, as do the adhesively failed specimens. [ABSTRACT FROM AUTHOR]

The paper presents an analytical model to study the shear driven debonding of a composite cantilever beam subjected to a point load. The composite structure consists of two elastic beams connected by an interface layer, and the model uses cohesive zone models to simulate the degradation process at the joint. These cohesive zone models are characterized by non-continuous and linear softening in the relationship between shear stress and relative tangential displacement. The results are expressed using non-dimensional parameters, and the model yields quasi-static equilibrium paths that demonstrate snap-back responses in both force and displacement values. The significance of the research lies in its application to structural engineering, where composite materials are extensively used. The study emphasizes the critical role of the interface layer strength in maintaining the structural integrity of composites. The proposed model advances the understanding of debonding by introducing a constitutive relation for the interface that accounts for the step-wise change in mechanical properties. The governing equations for the cantilever beam are derived, considering the equilibrium of forces and moments, and the relative tangential displacement at the interface. The model delineates three stages of interface degradation: no relative slip, plastic deformation, and progressive debonding. The analytical solutions for each stage provide insights into the beam deflection, shear stress, and axial force distribution. This research contributes to the field by offering a more refined analytical approach to study debonding in composite beams, which is essential for improving the design and analysis of composite structures. [ABSTRACT FROM AUTHOR]

In this work, the Yb2Si2O7 interphase was prepared on SiC fibers using the sol–gel method. The influence of sol concentration on the morphology of the interphase was discussed. After heat treatment in argon at 1200°C for 1 h, the Yb2Si2O7 was grown in situ on the fiber surface, forming an interphase layer. Then, SiCf/Yb2Si2O7/SiC minicomposites were prepared by chemical vapor infiltration (CVI). The Yb2Si2O7 interphase exhibited no changes throughout the high‐temperature preparation process and maintained stability and compatibility with the fiber and matrix. The tensile strength of SiCf/Yb2Si2O7/SiC minicomposites with Yb2Si2O7 interphase was significantly higher than SiCf/SiC minicomposites without interphase. The crack deflection, interfacial debonding, and fiber pullout were observed in the tensile fracture of the SiCf/Yb2Si2O7/SiC minicomposites. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the clinical performance of two-wing–retained resin-bonded fixed dental prostheses (RBFDPs) after 5 years of clinical use with respect to technical and biologic complications, as well as survival and success rates. Materials and Methods: RBFDPs were fabricated from 3Y-TZP zirconia layered by hand (Lava Frame veneered with Lava Ceram; 3M ESPE) or metal (Remanium Star, Dentaurum; layered with Reflex, Wieland). The primary endpoints were debonding and fracture. The secondary endpoints (marginal integrity, marginal discoloration, abrasion of antagonist dentition, patient satisfaction, Gingival Index, and side effects) were evaluated at baseline and after 5 years. Survival and success rates were calculated using the KaplanMeier method. Log-rank test was used to compare the survival and success rates of the different materials. Results: The mean observation time was 6 years and 10 months. The estimated cumulative success rate after 5 years was 88.9% ± 10% for metal-supported and 33% ± 16% for all-ceramic two-wing RBFDPs. After conversion into one-wing RBFDPs, the survival rate was 100% in both groups. Debonding of one of the two wings was the major complication. One zirconia framework fracture occurred. Metal-based twowing RBFDPs showed a significantly higher success rate, but lower esthetic evaluation. Conclusion: Due to a reduction in technical complication rate and less invasiveness, one-wing RBFDPs should be preferred over two-wing RBFDPs whenever possible. [ABSTRACT FROM AUTHOR]

Introduction: When the traditional incremental technique is used for direct placement of composite resin in a deep occlusal cavity, each increment (2 mm or thicker) is individually cured where it undergoes hardening and shrinkage. As increments are bonded to all cavity walls, a constrained shrinkage develops in tooth, composite, and/or interfaces. In the first composite increment, this constrained shrinkage generates tensile stresses which are distributed in a nonuniform pattern within that increment, resulting in premature stressing of the dentin bond of the hybrid layer at the pulpal floor before it reaches full maturation. This premature stressing leads to initiation of interfacial debonding and propagation to form a microgap. This behavior is associated with persistent postoperative sensitivity and tooth pain, over the time, which subsequently results in restoration failure. Aims: This paper provides a comprehensive review on the first composite increment and its dependency on placement technique for the interaction behavior with the maturing dentin-adhesive bond at pulpal floors in deep occlusal cavities. Materials and Methods: The dental database was searched, and 59 articles were collected and included in this review, spanning the years from 1984 to 2023. Results and Discussion: Three biomimetic direct restorative techniques were reported in the literature for incrementally restoring large occlusal cavities. These techniques are the decoupling with time, the decoupling with fiber, and the decoupling with split-increment. They all aim at minimizing the generated shrinkage stresses in the first composite increment for protecting the developing dentin bond of the hybrid layer until it reaches full maturation and thus preventing the initiation and propagation of interfacial defects at pulpal floors of deep occlusal cavities. Finally, the restoration is completed by placing and curing successive increments of 1.5 mm each to fill the cavity; their number depends on the cavity depth. These increments can each be cured immediately following placement. Conclusions: In deep occlusal cavities, the interaction behavior between the first composite increment and the maturing dentin-adhesive bond at the pulpal floor depends on the technique used for the increment placement. This behavior is either favorable with the direct biomimetic techniques or unfavorable with the traditional incremental technique. With the direct biomimetic techniques, no premature shrinkage stressing of the dentin bond is induced at the pulpal floor. This prevents the initiation of interfacial debonding and propagation to form microgaps and results in the absence of postoperative sensitivity and persistent tooth pain.

Securing the structural safety of blades has become crucial, owing to the increasing size and weight of blades resulting from the recent development of large wind turbines. Composites are primarily used for blade manufacturing because of their high specific strength and specific stiffness. However, in composite blades, joints may experience fractures from the loads generated during wind turbine operation, leading to deformation caused by changes in structural stiffness. In this study, 7132 debonding damage data, classified by damage type, position, and size, were selected to predict debonding damage based on natural frequency. The change in the natural frequency caused by debonding damage was acquired through finite element (FE) modeling and modal analysis. Synchronization between the FE analysis model and manufactured blades was achieved through modal testing and data analysis. Finally, the relationship between debonding damage and the change in natural frequency was examined using artificial neural network techniques.

The fiber-reinforced polymer (FRP) strengthening of reinforced concrete (RC) elements with torsional deficiencies has not yet been extensively studied. Existing studies have primarily focused on rectangular RC beams. The few studies on L or T-shaped beams have used open-form retrofitting methods. However, premature debonding of the retrofitting from concrete surfaces often leads to detachment before achieving enhanced torsional capacity. This study introduces an innovative application of closed-form FRP retrofitting for RC T-beams against torsion. Two novel closed-form torsional upgrading methods were proposed and investigated through a comprehensive experimental program involving eight large-scale T-beams. One method employs FRP ropes embedded in transverse grooves near the surface, while the other combines U-shaped EB-FRP strips with FRP ropes. Additionally, two configurations were examined replicating scenarios where the upper part of the slab is accessible or inaccessible. The results demonstrate that the closed-form methods improve torsional strength by 9% to 25% and twist at failure by 92% to 536% compared to unstrengthened beams, with beams retrofitting through the slab exhibiting superior performance. Step-by-step technical guidelines of the proposed methods are presented to minimize construction defects and ensure effective implementation in real RC structures. [ABSTRACT FROM AUTHOR]

The present article proposes an hybrid equilibrium element (HEE) formulation for the prediction of cohesive fracture formation and propagation with the crack modelled by extrinsic interface embedded at element sides. The hybrid equilibrium element formulation can model high order (quadratic, cubic and quartic) stress fields which strongly satisfy homogeneous equilibrium equations, inter‐element and boundary equilibrium equations. The HEE can implicitly model both the initially rigid behaviour of an extrinsic interface and its debonding condition with separation displacement and softening. The extrinsic interface is embedded at the element sides and its behaviour is governed by means of the same degrees of freedom of HEE (generalized stresses), without any additional degree of freedom. The proposed extrinsic cohesive model is developed in the thermodynamic framework of damage mechanics. The proposed crack propagation criterion states that crack grows when the maximum principal stress reaches the tensile strength value, in a direction orthogonal to the principal stress direction. The crack is embedded at an element side and the mesh around crack tip is adapted, by rotation of the element sides, in order to have the interface aligned to the crack growth direction. Three classic two‐dimensional problems of fracture propagation are numerically reproduced and the results compared to the experimental data or to the other numerical results. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastic (CFRP) composites have been widely used in engineering. This paper investigates the effect of composite z-pin (polyimide fiber/epoxy resin) on flexural properties of skin/stringer composite structure with different z-pin densities and diameters. Compared with unpinned specimens, the peak loading and energy absorption of z-pinned specimens are increased by 98% and 9 times, respectively. Parameterized research indicates that the optimal z-pin density is 1.35%. And thin z-pins are beneficial to improve the peak loading and energy absorption, which attributes to more total contact area of z-pins. The statistical results present that z-pin pre-hole inserted (ZPI) process can significantly reduce initial damages of z-pinned specimens compared with Ultrasonically Assisted Z-fiber (UAZ) process. Specifically, the z-pin inclination angle is decreased by 60%, and the initial damages in eye-like zone are prominently reduced. The z-pin makes the specimen exhibit the quasi-brittle behavior under flexural loading by playing a bridging role, which makes the flexural properties of specimens prominently increased. In addition, the "snubbing effect" will enhance the bridging effect of z-pins, but it will lead to inter-fibers debonding, splitting, and shear failure of z-pins. [ABSTRACT FROM AUTHOR]

Highlights Glass fiber reinforced plastics (GFRPs) is a key material for the outer protecting layer of ships as well as for energy storage tanks. Its ballistic and blast resistance is closely related to the inclusion structure of its glass fiber and polyester matrix, however, the related detailed studies have not been reported. In this paper, ballistic shooting tests and finite element simulations are both employed to investigate the ballistic limit velocities (V50) of GFRPs and reveal the effects of glass fiber layers and the polyester matrix thickness on the V50. The results show that the V50 of GFRPs is essentially linearly related to the thickness of the target plate for a given number of glass fiber layers. An increase in the number of glass fiber layers enhances the overall V50 value of GFRPs, but the linear relationship with the thickness remains unchanged. The target plate with more layers of glass fiber interacts with the projectile for a longer time, resulting in the debonding of the fiber and the resin matrix. The resin around the crater loses its support and then produces irregular cracks. Based on energy conservation, a theoretical model for predicting the V50 of GFRPs with considering the effects of glass fiber and polyester matrix is proposed. After comparing the results of theoretical calculations with experimental and simulation data, the relationship equations between the key parameters (ballistic strength) in the model and the number of fiber layers and target plate thickness are finally given. These findings can provide support for the design of ballistic GFRPs. Ballistic velocity limit (V50) of glass fiber reinforced plastics (GFRPs) obtained by experiment and finite element simulation Tuning the V50 of GFRPs by designing the number of glass fiber and polyester thickness. Proposed a theoretical model for predicting the V50 of GFRPs. [ABSTRACT FROM AUTHOR]

Transitioning towards a circular economy, extensive research has focused on dynamic covalent bonds (DCBs) to pave the way for more sustainable materials. These bonds enable debonding and rebonding on demand, as well as facilitating end‐of‐life recycling. Acylhydrazone/hydrazone chemistry offers a material with high stability under neutral and basic conditions making it a promising candidate for materials research, though the material is susceptible to acid degradation. However, this degradation under acidic conditions can be exploited, making it widely applicable in self‐healing and biomedical fields, with potential for reprocessing and recycling. This review highlights studies exploring the reversibility of acylhydrazone/hydrazone bonds in various polymers, altering their properties, and utilizing them in applications such as self‐healing, reprocessing, and recycling. The review also focuses on how the mechanical properties are affected by the presence of dynamic linkages, and methods to improve the mechanical performance. [ABSTRACT FROM AUTHOR]

The need for ceramic composites is increasing over a vast range of industrial applications, including energy and nuclear technology (structural materials for fission and fusion applications); space (thermal shields) or chemical sectors. Current finite element (FE) models are not able to reproduce the aleatory nature of crack generation and propagation through materials and interfaces. To tackle the shortcomings of FE models, a nonlocal bond‐based peridynamics model implemented in the Abaqus FE code has been updated to reproduce the behavior of interfaces between ceramic materials. Two‐ and three‐dimensional simulations have been used to simulate three‐point bend tests for a range of ceramic composites and compared with experiments available in the literature. The model reproduced most of the experimental failure loads, as well as correctly reproducing the failure modes and crack patterns. In particular, the model was able to predict two mechanisms for interface failure, cohesive failure, in which the two materials separate exactly at the interface, and cohesive failure of the substrate, in which a thin layer of the weaker material remains attached to the stronger material and a crack propagates in the weaker material, rather than at the interface. Both failure modes are experimentally observed and still difficult to reproduce with currently available FE simulations. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced polymers (CFRP) present machining challenges due to inherent properties such as inhomogeneity and anisotropy, which make them vulnerable to damage during drilling. This study investigates the machining-induced damage caused by drilling CFRP composite laminates under dry and cryogenic conditions, considering the impact of cutting speeds, feed rates, and tool coatings on thrust force, delamination, and surface roughness. Acoustic emission (AE) measurements are also performed to investigate machining-induced damage at different stages of the machining process. The experimental results indicate that machining-induced damage is significantly reduced under cryogenic conditions compared to dry drilling. Specifically, under cryogenic conditions, the combination of high feed rates and cutting speeds led to a 13.2% reduction in the average delamination factor, a 10.5% improvement in surface roughness, and a 43.4% decrease in acoustic emission RMS. A scanning electron microscope (SEM) and a 3D surface profilometer were used to evaluate the machining-induced damage to the hole wall surface under dry and cryogenic conditions. The drilling damage patterns were identified through AE signals, with frequencies associated with matrix cracking, delamination, fiber/matrix debonding, and fiber breakage during the drilling of CFRP layers, primarily around 67 kHz, 170 kHz, and 280 kHz, respectively. [ABSTRACT FROM AUTHOR]

Strand debonding patterns and release (prestress transfer) practices can result in significant local stresses at prestressed girder ends, which are not accounted for in design. This article presents a numerical and analytic study of various single-webbed prestressed concrete girder shapes for which large amounts of prestressing are necessitated by the use of 0.7 in. (17.8 mm) diameter strands. Shapes with wide bottom flanges are shown to potentially exhibit large stresses that effectively pry, or peel, the portions of the flanges extending from the web away from the web. Such peeling stresses can be mostly mitigated by partially debonding strands in the recommended pattern from the outside in. Similarly, releasing or cutting strands in a uniform manner mitigates peeling stresses. While releasing all strands simultaneously is optimal, it is unlikely to be practical for large prestressed components. For conventional release operations, the results presented in this article indicate that a symmetrical top-down method would not result in significant peeling stress. Moreover, prestressed girder end region detailing requirements aimed at providing adequate flange confinement and strand anchorage at the ultimate limit would be adequate to control peeling stresses, including those resulting from the inadvertent use of a poor release sequence. [ABSTRACT FROM AUTHOR]

A novel experimental setup, utilizing 3D Digital Image Correlation (3D‐DIC), is employed to characterize the mechanical behaviour of composite solid propellant (CSP) under uniaxial compression at three displacement rates (1, 7, and 50 mm/min). At larger deformation, 3D‐DIC consistently shows smaller strains than nominal strain values, and this difference increases with deformation across all the displacement rates. Displacement rates significantly affect the non‐linear stress‐strain response of the CSPs. After the completion of the compression test, the specimen is unloaded, and the lengths of the unloaded specimens measured after 24 hour indicate a recovery of 90–94 % of the original length of the specimens. The recovered length increases with an increase in the displacement rate. Initially, Poisson's ratio is close to 0.5, and dilatation is zero, indicating an incompressible behaviour. However, both Poisson's ratio and dilatation increase with an increase in longitudinal strain, indicating a transition to compressible behaviour. Comparing the scanning electron microscope (SEM) micrographs of the virgin and compressive‐loaded samples, noticeable debonding is observed at the matrix‐particle interfaces. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Orthodontie Française is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Securing the structural safety of blades has become crucial, owing to the increasing size and weight of blades resulting from the recent development of large wind turbines. Composites are primarily used for blade manufacturing because of their high specific strength and specific stiffness. However, in composite blades, joints may experience fractures from the loads generated during wind turbine operation, leading to deformation caused by changes in structural stiffness. In this study, 7132 debonding damage data, classified by damage type, position, and size, were selected to predict debonding damage based on natural frequency. The change in the natural frequency caused by debonding damage was acquired through finite element (FE) modeling and modal analysis. Synchronization between the FE analysis model and manufactured blades was achieved through modal testing and data analysis. Finally, the relationship between debonding damage and the change in natural frequency was examined using artificial neural network techniques. [ABSTRACT FROM AUTHOR]

SiC particle-reinforced Al metal matrix (SiCp/Al) composites are more and more widely used in the aerospace field due to their excellent properties, and the realization of high-quality drilling of SiCp/Al composites has an important impact on improving the performance of parts. In this paper, ultrasonic elliptical vibration-assisted helical milling (UEVHM) is applied to the machining of SiCp/Al composites. Firstly, the kinematic analysis of UEVHM is carried out, and then the cutting force model is established, which takes into account the interaction between particles and the cutting edge, and calculates the crushing force, pressing force, and debonding force of the particles. Finally, the UEVHM tests are conducted to verify the accuracy of the model and to analyze the influence of process parameters on the cutting force. It was found that the radial and axial forces decreased by 34% and 39%, respectively, when the spindle speed was increased from 2000 r/min to 10,000 r/min; the radial and axial forces increased by 200% and 172%, respectively, when the pitch increased from 0.1 mm to 0.4 mm; and the radial and axial forces increased by 29% and 69%, respectively, when the rotational speed increased from 30 r/min to 70 r/min. The maximum error between the cutting force model and the experimental values is 19.06%, which has a good accuracy. The research content of this paper can provide some guidance for the high-quality hole-making of SiCp/Al composites. [ABSTRACT FROM AUTHOR]