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We developed a method to evaluate the failure rate (FR) for the cylindrical part of a composite high-pressure hydrogen vessel with arbitrary dimensions, number of layers, and stacking sequences by giving the mean and standard deviation of the fiber strength development rate and the stiffness reduction rate under various damage types. The FR is the rate at which the residual strength of a vessel is below the maximum service pressure (125%NWP). Assuming a case in which the vessel is designed with the damage-tolerance design, the FR was calculated for the case of all-layer matrix cracking (assuming beginning-of-life) and fiber failure in two layers in addition to the matrix cracking (assuming the most severe damage that is tolerable during service). The observations demonstrate the importance of improving the probability of detection for non-destructive testing in ensuring the safety of damage-tolerance-designed vessels after fiber failure. The mean strength of the fibers mainly affected the mean residual strength of the composite high-pressure hydrogen vessels when the dimensions and stacking sequence remained unchanged. [ABSTRACT FROM AUTHOR]

This paper focuses on the mechanical response and viscoelastic properties of double‐blade composite stiffened structure (DCSS) under low‐velocity impact (LVI). Firstly, the impact resistance and viscoelastic behavior of the DCSS are revealed by LVI testing at four different locations using the same initial velocity. Next, the damage morphologies at the impact locations are observed with ultrasonic A‐ and C‐scan equipment and optical microscopy. At last, the DCSS containing impact damage is implemented for axial compression and the strain values of the DCSS surface are obtained using a strain testing system to reveal its residual properties and buckling behavior. The results show that there are significant differences in the impact damage modes at the four different locations. The maximum impact resistance is observed at location D, while location A has the opposite. The DCSS has a certain viscoelastic behavior at LVI and conforms to an exponential decay model. Moreover, position B presents interface debonding damage due to stiffness discontinuities at the flange and skin bonding and severely weakens the load carrying performance of the DCSS. Highlights: The impact resistance of different positions is analyzed by LVI experimental results.Viscoelastic properties exist at different impact locations and obey the exponential decay model.Impact damage alters the buckling load and residual strength of the DCSS.The damage mechanism of the triangular zone is revealed by damage morphology. [ABSTRACT FROM AUTHOR]

AbstractThe copper mesh provides effective lightning strike protection for composite structures, while its efficiency can be compromised in scarf-repaired composite structures. In this study, after verified by test results, a numerical analysis procedure was employed to predict the lightning ablation damage and residual bending performances of scarf-repaired composite laminates with copper mesh protection. Initially, the ablation damage and bending damage mechanisms of good repaired and poor repaired composite laminates were analyzed. Then, the impact of lightning strike attachment position and repair design parameters including overlap length and thickness of adhesive layer on the lighting protection performances was investigated. The results indicate that ablation damage of composite and adhesive materials near the repair area significantly compromises structural integrity and reduces the bending strength. The predominant bending failure mode of scarf-repaired woven composite laminates after lightning strike is fiber failure in warp direction, accompanied by small areas of matrix failure and delamination failure. The reestablishment level of the electrical path varies with overlap length and thickness of adhesive layer, subsequently affecting the ablation damage area and depth. This study can provide a reference for the design and process control of scarf-repair in copper mesh protected composite structures. [ABSTRACT FROM AUTHOR]

To evaluate the residual strength of the ship after explosion, the Explosion Smith Method (ESM) is proposed. The innovation of the ESM lies in two aspects: firstly, based on the Baker shock wave and quasi-static pressure model, Jones critical velocity model, propose a method for assessing the range of explosion damage of cabin and validated through referenced experiments. Secondly, proposes the strain-stress relationship of the deformation element. To verify the feasibility of the ESM and study the influence of TNT location and mass, 16 simulations and EMS calculations were conducted. The results showed that the residual strength is most impacted when the TNT in top deck. For side cabin, the explosion products discharged and impact reduced. The trend of the ESM and simulation were consistent, but the result of ESM was more severe. The reason that strain-stress relationship of the deformation element more stringent, resulting in the ESM smaller than the simulation. However, as the TNT increases the error decreases. In the future, more research can be conducted on the deformed structures to enhance the accuracy of the ESM. [ABSTRACT FROM AUTHOR]

The all-CFRP sandwich structure with ultralight honeycomb is designed and manufactured by stretching process. Two scenarios, including global and local impact, are considered to reveal the characteristics of impact resistance. The effects of different impact energies and core densities on energy absorption and failure mechanism are thoroughly discussed. Meanwhile, the post-impact residual compressive strength is carried out to evaluate the influence of impact on structural strength and stability. The results show that under the global impact, the impact resistance is related to core density, and the energy absorption is mainly from honeycomb core. While under the local impact, as the impact energy increases, the failure mechanism of the structure changes from core crushing to penetration. The research provides a guidance for low-velocity impact performance and structural optimization design of sandwich structures. [ABSTRACT FROM AUTHOR]

An enhanced nonlinear fatigue damage cumulative model proposed is based on the strength degradation characteristics of composites, aiming to investigate damage progression under fatigue loading. Building upon this foundation, given the assumption of a linear correlation between fatigue cumulative damage and stress level, a methodology is presented for extrapolating the damage curve of untested stress levels from that of tested stress levels. The model substantiates its reliability by validating against experimental data from several distinct material types. The reliability of the model has been validated using experimental data from multiple groups of materials. The experimental results indicate that the model can effectively reflect the fatigue damage development characteristics of composite materials. Simultaneously, the predicted stress levels derived from the proposed methodology show lesser deviation from the fitted data. Finally, a life prediction method founded on the proposed model is introduced, validated for its high prediction accuracy through experimentation. Highlights: An enhanced fatigue damage model of composites is established.A novel residual strength model for composites has been established.Present a methodology for calculating the stress level damage curve.The fatigue life prediction method of the proposed model is developed. [ABSTRACT FROM AUTHOR]

Epoxy resin as a thermoset polymer is vulnerable to creep loading even at room temperature due to its viscoelastic nature. This study investigated the effect of reinforcing epoxy resin with different functionalized multi-walled carbon nanotubes (MWCNT) contents on the creep response and post-creep residual tensile properties of nanocomposites. The creep tests were performed on the nanocomposite specimens containing different filler contents and the neat epoxy specimen at 40°C under a constant load level of 200 N. It was found that the nanocomposites containing 0.3 wt% MWCNTs experienced 29.6%, 69.1%, and 74.1% decreases in the elastic strain, creep strain, and steady-state creep strain rate, respectively, compared to the neat epoxy. Furthermore, the tensile strength and stiffness of the neat epoxy and nanocomposite specimens were evaluated before and after a partial creep test (at a load level of 200 N for 150 min) by conducting tensile tests. The nanocomposites containing 0.3 wt% MWCNTs demonstrated considerable improvements of 35.9%, 41.2%, 27.9%, and 28.1% in strength, residual strength, stiffness, and residual stiffness, respectively, compared to the neat epoxy. Furthermore, scanning electron microscopy assessment was utilized to investigate the fracture surfaces of the nanocomposite specimens. [ABSTRACT FROM AUTHOR]

Due to its simple design and cost-effectiveness, Bromhead ring shear apparatus is widely used to assess the drained residual strength through various testing procedures such as single stage, preshearing, and multistage. However, when compared to back-calculated case histories, values obtained through these testing procedures were found to be higher due to wall friction. To address this, Stark and Vettel (Geotech Test J 15:24–32, 1992) have introduced the "Flush testing procedure" which involves adding remolded soil to the specimen and reconsolidate it, in order to minimize the wall friction. Although the procedure yielded satisfactory results, it is more time-consuming. This paper presents a comparison between a proposed preconsolidated presheared flush (P.P.F) and flush testing procedures. The test results showed that this procedure has successfully minimized the effect of wall friction, providing values lower than those obtained using the flush procedure in shorter time. [ABSTRACT FROM AUTHOR]

This study investigates the repair of damaged curved glass/epoxy composite laminates through various adhesive reinforcements and adhesively bonded external patches. The experimental procedures involve fabricating laminates, conducting four-point bending tests, quasi-static indentation tests, and optimizing damaged areas. Results demonstrate the influence of repairs on curved beam strength and interlaminar tensile strength. Adhesive repairs with chopped fiber reinforcement outperform plain epoxy and particle fiber-reinforced repairs, preserving 51.28% of curved beam strength. Adhesively bonded external patches, both single and double, with chopped fiber reinforcement exhibit significant strength recovery 72.08% and 80.78% compared to virgin samples. The study emphasizes the effectiveness of adhesively bonded external patches, particularly those with chopped glass fiber reinforcement, in enhancing curved beam strength and interlaminar tensile strength. This research provides valuable insights for repairing angled structures, such as those in airplane components, showcasing potential applications of these techniques for structural maintenance. HIGHLIGHTS: Investigated adhesive reinforcements and bonded external patches for curved composites. Laminates fabricated, tested for bending, indentation, and optimized in damaged region Chopped fiber adhesive repairs preserve significant 51.28% strength. Adhesively bonded patches exhibit 72.08% and 80.78% strength recovery. [ABSTRACT FROM AUTHOR]

This study deals with the compressive performance of cold-formed steel semi-oval hollow section (CFS-SOHS) stub columns after exposure to a standard fire. An experimental program was carried out on 17 CFS-SOHS stub columns after four different fire exposure temperatures, namely 300°C, 550°C, 750°C, and 900°C. Details of post-fire test specimens, material properties, stub column test arrangements, and results are described and discussed in this paper. A finite-element model was established and then validated by the experimental compressive performance in terms of ultimate strength, load-end shortening response, and failure mode. Parametric analyses were then performed on 160 post-fire CFS-SOHS stub column specimens to furnish more numerical data. The acquired experimental and numerical compressive strengths were compared against the design predictions by the direct strength method (DSM) initially calibrated for open sections, and the modified DSM initially proposed for CFS-SOHS without fire. A reliability analysis was performed. Comparisons show that the modified DSM offers accurate and reliable post-fire residual resistance predictions for CFS-SOHS stub columns after exposure to the standard fire. [ABSTRACT FROM AUTHOR]

This research investigates reinforced concrete beams with three groups of Glass Fiber Reinforced Polymer (GFRP) bar, Sand-blasted Glass Fiber Reinforced Polymer (SGFRP) bar and steel bar with concrete containing recycled materials with different concrete mix design before and after applying elevated temperature. The concrete mix designs include replacing glass powder and micro-silica with a part of concrete cement and replacing waste crumb rubber and glass crumb with a part of fine and coarse concrete aggregate. The beams were subjected to high temperature up to 600 °C in an electric furnace, and then subjected to the flexural strength test. The results showed that applying elevated temperature to beams reinforced with composite bars caused a sharp drop in flexural strength. The beam exposed to high temperature containing glass powder, coarse rubber and micro-silica had 2.2 times more flexural strength than the reference beam exposed to high temperature, and the beam not exposed to high temperature in this mix had 36% more flexural strength and 54% more ductility than the reference beam that was not exposed to high temperature. The beam with SGFRP bar with sand coating showed higher flexural strength after applying elevated temperature than the beam with GFRP bar with normal surface. In general, the replacement of recycled materials in the concrete improved the performance of the beams against elevated temperature compared to the beams with normal concrete. [ABSTRACT FROM AUTHOR]

If the temperature and environment effects on the oxidation of SiC fibers have been extensively documented, the impact of external stresses (stress‐oxidation coupling effect) remains questioned. Therefore, interrupted static fatigue tests were conducted on filaments. Surviving specimens (>60%) were subsequently tensile tested and fracture surfaces recovered for analysis. The external stress was found to have no impact on the oxidation regime (linear or parabolic) nor on its rate, which is comparable to literature data. As long as the slow crack growth (SCG) incubates (negligible growth rate), the oxidation was shown to govern the embrittlement. Fracture surface analysis revealed tensile residual stresses, attributed to a wedge effect when specimens were unloaded. Rare tests (<2%) were interrupted while the crack had significantly grown highlighting the successive crack fronts. Sources of residual stresses and differences between fiber types (flaw position inducing a bias on lifetime prediction) are discussed. In these circumstances, a coupling effect between the oxidation embrittlement and the SCG could be assumed for moderate stress levels, which is pertinent for most of ceramic matrix composite applications. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department 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.)

In this study, an extended finite element method (XFEM)-based numerical analysis procedure is developed as part of a framework for assessing damage slow growth behaviors of an adhesively bonded composite joint. This CFRP-CFRP single strap joint is stabilized with an aluminium honeycomb subjected to static compression through four-point bending. The adhesively bonded patch has a 140 mm overlap length centered on its 440 mm parent structure. The residual strengths are determined using an adhesive element failure criterion and a failure index based on energy release rate for disbonded and delaminated joints. XFEM is utilized to introduce pre-initiated cracks of various lengths and to calculate the energy release rates for each of four failure scenarios. Mesh convergence studies are conducted to acquire appropriate element sizes at crack tip. Additionally, multiple numerical benchmark models to experimental and numerical literatures are devised to validate individual components of the proposed finite element model. Results of the energy release rates for joints with cracks starting at the gap region suggest that a mixed-mode fracture occurs. At small crack lengths, mode-I is relatively low, and mode-II is high. As the crack length increases, mode-I increases, and mode-II gradually decreases. The energy release rates for joints with cracks starting in the taper end show that only a mode-II fracture exists. Finally, slow growth damage could be identified in each of the four damage scenarios. Joints with cracks initiated from the taper end exhibit substantially longer periods of slow growth damage when compared to joints with cracks initiated from the gap region. [ABSTRACT FROM AUTHOR]

The present study investigated the behavior of concrete‐filled steel tubes (CFST) and concrete‐filled double‐skin steel tubes (CFDST) of square and rectangular shapes after exposure to elevated temperatures. The infill concrete was prepared with granulated blast furnace slag (GBS) as fine aggregate, and no natural fine aggregate was used. A total of 20 CFST and CFDST specimens of both square and rectangular shapes were prepared. The specimens were heated at 200, 400, 600, and 800°C temperatures for 2 h and allowed to cool inside the furnace after heating. Axial load was applied to the specimens to check their behavior after exposure to fire. The reduction in the load‐carrying capacity was insignificant for the specimens heated at 200, 400, and 600°C for both square and rectangular CFST and CFDST conditions. The decrease in load‐carrying capacity was slightly higher in the case of CFDST specimens compared to CFST specimens. A three‐dimensional finite element model using ABAQUS software was proposed for predicting the behavior of the tested specimens. The proposed model could predict the behavior of both unheated and heated specimens with acceptable accuracy. [ABSTRACT FROM AUTHOR]

In the foundry industry, casting sand cores require high and low peak and residual strengths, respectively, to achieve comprehensive optimal mechanical performance. The peak and residual strengths of sand cores are positively related, highlighting the criticality of balancing them. Thus, an innovative approach comprising the incorporation of anionic surfactants into the silicate binder was introduced to balance both factors. Additionally, the investigation of the effects of the anionic surfactants on the physical properties of the silicate binder, including its colloidal stability, surface tension and adhesion, revealed that four different anionic surfactants reduced the surface tension and adhesion of the silicate binders and reduced the residual strength of the silicate-bonded sand cores. Among them, 0.10 wt% lauryl ether phosphate reduced the surface tension and adhesion of the adhesive by 49.64 and 112 mN/m, respectively, and reduced the residual strength of the sand core by 0.035 MPa. However, increasing the dosage did not further reduce the residual strength of the sand core, although it continued to reduce its peak strength. Therefore, during silicate binder modification with anionic surfactants, the dosage of the anionic surfactant must be kept at ≤0.10 wt%, as this dosage exerted the most comprehensive optimal modification effect, which was attributable to the adsorption of anionic polymers onto the surface of the silicate aggregates. This adsorption weakened the network structure of the silicate aggregates and imparted the sand cores with appropriate mechanical properties during casting. [ABSTRACT FROM AUTHOR]

A four-point flexure after impact test method has been developed to assess the damage tolerance of sandwich structures under flexural loading. This test method, recently standardized as standard practice ASTM D8388 by ASTM International, is designed for use with sandwich specimens that have been impact damaged per ASTM D7766. The test method utilizes a four-point flexure fixture to test specimens using the methodology from ASTM D7249, along with modifications specified in the practice. The sandwich configurations investigated consisted of carbon/epoxy facesheets with a Nomex® honeycomb core. Mechanical testing was conducted to evaluate the proposed specimen design, fixturing, and test procedure. Finite element analysis was used to finalize the specimen sizing. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department 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.)

ObjectivesIn this paper, an orthogonal braided glass fiber composite sandwich panel with a PVC foam core and dimensions of 150 mm×100 mm×26 mm is selected as the research object in order to study the impact mechanical properties of composite sandwich panels. The dynamic response and residual compressive strength of the panel under single-point low-velocity impact are then analyzed.MethodsFirst, a series of drop hammer impact tests are conducted to study the failure mode, impact force-displacement response and energy absorption characteristics of the panel under different impact energies. Next, quasi-static compression experiments are conducted to investigate the maximum compression load capacity and residual compressive strength under impact damage.ResultsThere are significant differences in the failure modes and impact force-displacement characteristics of the sandwich panel under different impact energies. The core mainly absorbs impact energy through compression deformation. As the impact energy increases, the maximal impact force, dent depth and absorbed energy of panel gradually increase, while the maximum compression load capacity and residual strength decrease after impact. The damage degree of the impacted composite sandwich panel determines its residual compressive strength. ConclusionThe findings of this study can provide valuable references for the impact resistance design of naval ship structures.

Silicon carbide fiber-reinforced silicon carbide ceramic matrix composites（SiCf/SiC） used in aero-engines are damaged or even failed due to the oxidation and corrosion by high-temperature and high-speed combustion gases. In this work，the gas generation device was used to simulate the complex gas environment in the aircraft engine，and the aviation kerosene mixed with liquid oxygen fuel in a certain proportion was ignited to form a high-temperature and high-speed combustion gas to assess the material. The oxidation test for 10 h and thermal shock test for 1000 cycles in combustion gas environment at 1200 ℃ were conducted on SiCf/SiC composites respectively. And the protective effect of environmental barrier coating（EBC）on SiCf/SiC composites was investigated. Uniaxial tensile tests were conducted on SiCf/SiC composites and SiCf/SiC-EBC composites after combustion gas environment assessment，and their fracture and cross-section micro-morphologies were observed by scanning electron microscopy. The results show that no significant oxidation of fibers and interphases is found in SiCf/SiC composites and SiCf/SiC-EBC composites after oxidation for 10 h in combustion gas environment，and their uniaxial tensile strength decreases by less than 2%. After 1000 thermal shock cycles in combustion gas environment，multiple micro-cracks are formed and oxidative corrosion of the interfacial layer occurs inside the SiCf/SiC composites，and the uniaxial tensile strength decreases by 41.3%. The EBC coating can effectively protect the SiCf/SiC composites from oxidation and corrosion of high-temperature gas，and the uniaxial tensile strength of SiCf/SiC-EBC composites decreases by 16.6% after 1000 thermal shock cycles.

Purposes Bird impact resistance has always been one of the important testing factors for aircraft airworthiness. In order to explore the bird impact resistance performance of civil aircraft nose side panel, three methods of rivet failure ratio assessment, energy method, and residual bearing capacity assessment are used to evaluate. Methods The effectiveness of the numerical model was verified by simulating the bird impact behavior of three types of side wall panels by using PAM-CRASH software, and the reliability of the above method was evaluated according to the bird impact failure of the three test specimens. Findings The research results indicate that the lower the proportion of rivet failures, the better the bird impact resistance of the structure; When the proportion of rivet energy absorption increases and the proportion of skin energy absorption decreases, the anti-bird-collision performance of the structure is improved; Among the above methods, the residual bearing capacity evaluation method can realize quantitative analysis of the bird impact resistance performance. The lower the damage factor value, the better the bird impact resistance performance of the side wall panel. Conclusions By summarizing the applicability and limitations of the bird impact performance evaluation method for side wall panels, this work provides valuable reference for the safety design and research and development of later civil aircraft.

The interactions between soil-structure are largely governed by the shear strength at the soil-structure interface, particularly in situations involving large displacements, known as shear residual strength. This latter can be influenced by a range of factors, including normal stress, physical properties, surface roughness, wall friction. The main objective of this study is to investigate clogging related to surface roughness form, in addition to wall friction arises from consolidation. In order to investigate the impact of wall friction, experiments involving ring shear tests were carried out on kaolin. Four different consolidation durations were employed to induce varying settlements of the upper platen, while three distinct testing procedures, including single stage, multistage, and preshearing, were utilized. Additionally, different levels of surface roughness were incorporated to investigate the effect of clogging. The test results obtained from various testing procedures indicate that employing a single stage procedure with zero consolidation time is the most suitable approach for mitigating the influence of wall friction. For clogging effect, is dependent on the materials used, namely, the kaolin and the mixture, as well as, the interfaces involved.

During the drilling process of large displacement wells, due to the high horizontal-vertical ratio, the movement of the drill string underground is complex, resulting in severe wear on the casing wall and a reduction in casing strength, greatly affecting subsequent drilling and production operations. A casing wear efficiency model based on energy transfer was applied. The segmented method was used to determine the lateral force on the pipe string, and the crescent-shaped wear of the casing was analyzed. Based on the API (American Petroleum Institute) minimum wall thickness method, the crescent-shaped casing wear was simplified, and a method for predicting casing wear and calculating residual strength was established. Using this model, calculations were performed on a large displacement well in the South China Sea. The results show that lateral force is the main factor affecting casing wear, and reverse circulation drilling has a significantly greater effect on casing wear than normal drilling. The most severely worn section of the entire wellbore is the section with the greatest dogleg severity, where the risk of casing failure is highest, making it the critical section for implementing anti-wear measures. After the completion of the four-stage operation in this well, the depth of casing wear at the location of the maximum dogleg severity is 1.15 mm, and the casing strength has decreased to 58. 24% of its original strength, but still meets strength requirements. The research outcome provides a basis and reference for the prevention and control of casing wear in highdisplacement wells in the South China Sea. [ABSTRACT FROM AUTHOR]

In order to study the influence of slip structure on the mechanical behavior and residual strength of casing, parameters such as support force and friction force between slips and casing were derived based on the interaction relationship between slips and casing. Tensile tests were conducted on casing materials in this paper, and the working process of anchoring casing with single and double slips was simulated. The influence of indentation depth on the residual strength of casing was analyzed. The results show that the deformation of the casing is relatively severe when the single slip sealing force reaches 120 kN. According to the law of residual strength curve, there is a turning point where the stress concentration factor tends to be gentle, and the corresponding indentation depth value at this point increases with the increase in casing diameter. Single slips were unable to effectively bite into P110 and P125 casings, and the bite did not achieve the effect of setting the casing. However, when double slips were used to anchor the casing, the inner wall of the casing had deeper indentation, and the double slips could firmly seat the casing. These results indicate that replacing single slips with double slips can effectively achieve the setting effect. [ABSTRACT FROM AUTHOR]

Understanding the deformation and damage behaviors of soft rocks under temperatures and water–rock interactions is crucial for designing rock engineering structures and for assessing geotechnical disasters. Hence, the physical–mechanical characteristics and damage mechanisms of silty mudstone under heating and water-cooling cycles were determined by a series of laboratory tests. The results indicate that heating and water-cooling treatments prompt crack development within silty mudstone, observable through volume augmentation along with reductions in mass, density, and P-wave velocity. The interconnections between the decrease of mechanical properties such as elastic modulus, cohesion, and internal friction angle of silty mudstone and the factors including temperatures and cycle number are explicitly established. The deterioration of the physical–mechanical properties of silty mudstone primarily arises from the thermal expansion, dehydration, and hydrolysis of mineral constituents. Furthermore, a new damage constitutive model for silty mudstone considering temperature and the number of heating and water-cooling cycles is established based on lognormal distribution and the Mohr–Coulomb criterion. Additionally, the model parameters S0 and F0 characterize the homogeneity and average strength, enabling a quantitative assessment of the damage degree of rocks. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department 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.)

Fiber-reinforced polymer (FRP) wraps of reinforced concrete columns might be vulnerable to accidental damage or vandalism. This study aims to develop a simple empirical tool that is based on experimental results to aid in the condition assessment and establish the reduced axial strength ratio (P/Po) of short columns that are loaded at small eccentricities. A total of 47 cylinders, 152 mm in diameter (D), were wrapped with carbon–FRP sheets of 1–3 layers [i.e., producing confinement effectiveness (fcc′/fc′) of 2.3–4.0] and were then subjected to a vertical cut of length (x) that varied from 0.20D to 0.61D at midheight. The loading eccentricity (e) varied from zero to 0.1D. The cut location around the perimeter, for the angle (θ) that was measured from the point of extreme compression, was varied from 0° to 180°. The jacket cuts affect eccentrically loaded cylinders more severely than concentrically loaded ones. As e increased from zero to 0.1D, P/Po reduced from 1.0 to 0.81 for intact samples and from 0.56 to 0.40 for samples with jacket cut. As the cut location traveled around the circumference starting from extreme compression (θ = 0°), less strength reduction was observed where P/Po increased, and at θ = 180° it even exceeded P/Po at zero eccentricity. This suggests a reduction in eccentricity due to a shift in the cross-sectional centroid due to the disturbed confinement on one side. Design models that account for e/D, θ, x/D, and inclined cuts have been developed and calibrated for cylinders of up to 22 slenderness ratio. In addition, a design example is presented. [ABSTRACT FROM AUTHOR]

Corrosion-induced defects, extensive and unavoidable in marine structures, pose significant threats to structural integrity and safety. This study aims to assess mechanical response and investigate the failure mechanism of composite-repaired circular hollow section (CHS) steel tubes. A feasibility analysis is conducted through verifying the axial compression performance of a uniformly corroded tube and an Aramid fiber-reinforced polymer (AFRP) strengthened perfect tube. Subsequently, mechanical responses of the corroded and AFRP-repaired tubes are studied, accompanied by parametric studies to comprehensively evaluate the influence of corrosion region, and the depths and densities of corrosion pits. Consequently, critical damage modes of the AFRP patches are explored using a user-defined material subroutine developed based on Hashin failure and Yeh delamination damage criteria. Numerical predictions indicate that composite patches improve the structural residual strength, but not necessarily enhance the structural ductility under diverse failure patterns. In addition, AFRP patches contribute to improving the overall structural load-bearing capacity by alleviating local buckling or regional collapse. Moreover, fiber compression damage emerges as the dominant mode. Premature failure of putty agent initiates stress concentration, intensifies subcritical damage, aggravates critical damage, and expedites final failure. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials 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 enable the long-term use of existing wooden structures, appropriately evaluating the extent of damage of the biodeterioration of structural performance, including members and joint systems, is necessary. To give one example, accurately estimating the single shear strength performance of nail and screw joints with decay is crucial. Therefore, this study proposes a method to model this by dividing wood into multiple layers with different strength performance, considering the grade of deterioration in a cross-section of decayed wood. The model was used to differentiate the sound layer and three decayed layers (multilayer) according to the extent of the damage. The estimated values, which were produced using the proposed model, were compared to the single shear strength of screw and nail joints with decay using two species of wood, namely Abies sachalinensis (Todomatsu) and Cryptomeria japonica (Sugi). The results point to a good fit between the average value of the experimental results and the estimated values of the proposed model. Compared with the existing (single-layer) model, the proposed model improved the accuracy of estimating the strength of wood undergoing early deterioration and therefore was considered usable. [ABSTRACT FROM AUTHOR]

Compressive performances of composite structures can be significantly decreased due to the lightning strike damage, so the structures with lightning frighten must be considered lightning protection design. In this study, compressive experiments after lightning strikes were conducted on non‐protected, 12‐layer interlaminar carbon nanotube film (CNF) protected, and traditional surface silver coating (TSSC)‐protected composite laminates. A numerical analysis procedure was established, incorporating a lightning strike ablation damage simulation (LSADS) module and compressive residual strength calculation (CRSC) module. The procedure's effectiveness was verified by the experiment results. Based on this procedure, the compressive performances and the possible failure mechanism of laminates after lightning strikes were analyzed. The results show that the laminates with TSSC protection and 12‐layer interlaminar CNF protection can increase compressive residual strength compared with non‐protected laminates. The predominant compressive damages of the laminates after lightning strikes are fiber‐matrix shear damage and fiber fracture damage. Optimized one‐layer interlaminar CNF protection with a thickness of 0.36 mm can increase the laminate compressive strength but decrease the structural weight. This study offers a reference and basis for the lightning strike protection design of composite structures. Highlights: CNF in lightning strike protection of composite structures.Compressive failure mechanism of composite laminates after lightning strikes.A numerical procedure to evaluate lightning damage and compressive performances.Design of interlaminar CNF protection. [ABSTRACT FROM AUTHOR]

Understanding the damage behaviors and mechanisms of soft rocks affected by rock‒water interactions is crucial for designing civil engineering structures and assessing geotechnical hazards. In this study, the physico-mechanical properties of silty mudstone subjected to wetting-dewatering cycles were investigated by P-wave velocity, three-dimensional scanning, and triaxial tests. The micro-mechanisms induced by rock‒water interactions were revealed using microscopic testing. The results indicate that mass, P-wave velocity, elastic modulus, peak strength, and cohesion of silty mudstone decrease with increasing wetting-dewatering cycles, while the internal friction angle follows a normal distribution. Wetting-dewatering cycles enhance the interface roughness of silty mudstone and reduce the plasticity index, leading to increased sliding friction. Continuous cycles exacerbate crack development and accumulation, weakening interlocking action and affecting energy dissipation. The dissipated energy rate serves as an indicator for crack stress thresholds, including crack closure, crack initiation, and crack damage stresses. The deterioration of silty mudstone strength primarily results from hydration-swelling softening and adsorption-fracturing driven by rock‒water interactions. Furthermore, a new constitutive model considering residual strength and nonlinear deformation characteristics was developed, effectively capturing the damage behaviors of silty mudstone under rock‒water interactions. The proposed model is also applicable to other types of rocks exhibiting similar damage mechanisms. [ABSTRACT FROM AUTHOR]

A compression after impact test method has been developed to assess the damage tolerance of sandwich structures under edgewise compressive loading. This test method, recently standardized as ASTM D8287, was designed to test specimens that have been impact damaged per ASTM D7766. The fixture design utilizes end loading with top and bottom edge supports to prevent end-brooming and out-of-plane rotation. Additionally, knife edge side supports provide out-of-plane restraint to buckling, similar to the existing laminate edgewise compression after impact test fixture. The sandwich configurations investigated were constructed from glass/epoxy and carbon/epoxy facesheets with a Nomex honeycomb core. Mechanical testing was conducted to evaluate the proposed specimen design, fixturing, and test procedure. Finite element analysis was used to verify the strain gage placement and damage size limits. [ABSTRACT FROM AUTHOR]

The investigation of fatigue behavior typically involves time‐consuming tests, leading some researchers to explore methodologies based on self‐heating tests to reduce the process. For composite materials, the conventional approach involves piecewise linear approximations of the self‐heating curve and the stress transition between the first and second regimes is arbitrarily associated with a fatigue lifetime equal to 106 cycles. This paper proposes a novel methodology to address these simplifications. First, a non‐linear viscoelastic model is used to describe the self‐heating curve. Based on the mechanisms established in the literature, a link is proposed between the dissipation and the fatigue limit. The load leading to a significant contribution of non‐linear mechanisms is associated with an infinite life time. It allows the identification of an S– N curve and prediction of fatigue behavior through a minimal number of tests. The comparison with fatigue results is satisfactory. Highlights: A link is proposed between dissipation and fatigue.Modeling of the dissipation in laminated composites subjected to cyclic loadings.A criterion is proposed to identify the fatigue limit based on the dissipation.A S– N curve is identified and extrapolated up to high cycles fatigue. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the mechanical properties and structural behaviors of reinforced concrete (RC) beams with various corrosion levels. For this purpose, six RC beams were subjected to accelerated corrosion tests, with three pairs corresponding to 1-month, 2-month, and 3-month corrosion degrees. After corrosion tests, the corroded reinforcing bars and concrete were tested to measure the mechanical properties of the materials, such as reinforcement strength, concrete strength, reinforcement diameter reduction, and rebar weight loss. Additionally, the three corroded RC beams with three levels of corrosion were subjected to bending tests to determine their remaining structural capacity and failure patterns. Furthermore, Atena software was used to perform a series of numerical finite element methods to verify the experiment results, which indicated that a good agreement of structural behaviors was observed between the experiment and FEM analysis. FEM analysis is successful when the error of maximum force between experiment and simulation is less than 3% and the error of displacement at maximum load between simulation and experiment is less than 1.8%. The results showed that the load–defection relationships and crack patterns of corroded RC beams were significantly influenced by corrosion level. In addition, predicting the dangerous cross-section of steel structures will support maintenance work to reduce risks for the project. [ABSTRACT FROM AUTHOR]

Building demolition produces construction waste in large amounts and this waste impose environmental problems. The use of recycled coarse aggregate obtained from demolished concrete will reduce environmental problems, landfill space and also saves natural aggregate sources. Though the use of recycled materials from construction is in practice, addition of recycled concrete aggregate reduces compressive strength, increases porosity and possesses poor ductile property. Addition of steel fibres can significantly improve the mechanical properties. In this study, the influence of steel fiber on the mechanical behavior of concrete made of different percentages of recycled concrete aggregate is evaluated. Water cement ratios of 0.3 and 0.4 were considered. Steel fiber volume fraction was varied from 0%, 0.5%, 0.75% and 1%. The results of compressive strength, split tensile strength, flexural strength, flexural toughness and residual strength factor are evaluated for varied percentages of recycled concrete aggregate and steel fiber contents. Results showed that with increase in steel fibers content there is improvement in compressive strength, split tensile strength, flexural strength, flexural toughness and residual strength factor of concrete made of recycled concrete aggregates. Addition of steel fiber improves the mechanical property of concrete by making it a ductile material. Natural coarse aggregates can be replaced with RCA up to 60% along with steel fibers and it is possible to achieve strength equal to that of normal concrete. The recommended optimum percentage of steel fibers is 0.75%. The models developed in this study could be used for the prediction of mechanical properties of concrete under unreinforced and fibre reinforced conditions. [ABSTRACT FROM AUTHOR]

The occurrence and development of a landslide is a gradual process of destruction, causing huge losses to people's lives and property. The shear strength of the shear zone gradually decreases to the residual state during the sliding process but it can recover to a certain extent during a relatively stable period. In a landslide, more than one slide usually occurs; however, after the first slide stops, it can enter a dormant period. The sliding surface can then experience a self-healing strength recovery phenomenon; this self-healing phenomenon has a significant impact on the reactivation of the landslide. Relevant studies have shown that the strength of the sliding surface is slightly greater than the residual strength when a landslide is reactivated; however, the explanations provided by these studies have not been sufficiently systematic. In this study, focusing on the undisturbed slide zone soil of the Huaipa landslide in Sanmenxia City, the "shear–pause–shear–pause–shear" test scheme is adopted. The soil is subjected to 3 h, 6 h, 12 h, 24 h, and 72 h healing shear tests, and combined with the SEM microstructure characteristics of the shear surface, to explore the internal mechanism of self-healing. The results show that the landslide soil exhibits strong self-healing strength recovery characteristics; however, these strength recovery characteristics decrease rapidly after experiencing a very small displacement. The strength recovery was strongly correlated with the vertical stress and healing time. With increasing vertical stress, the strength recovery value of the soil increases. Under low pressure, the strength recovery is small, and under high pressure, the strength recovery is obvious. With increasing healing time, the strength recovery increases; however, the increase in the amplitude diminishes and ultimately approaches zero with increasing healing time. A "healing phenomenon" occurs in the shear surface of slide zone soil after a short period of time. A shear strength value greater than the residual strength can be used to check the landslide design, which can effectively reduce costs. [ABSTRACT FROM AUTHOR]

The results of an experimental work to explore the effect of elevated temperatures on load resistance of reinforced concrete beams with glass fiber-reinforced polymers (GFRP) bars are reported in this paper. Twenty beams with cross-sectional dimensions of (120 x 200 x 1600 mm) were designed. Two specimens were evaluated at room temperature as reference beams, while the remaining eighteen were treated to high temperatures (200, 400, 600, and 800 °C) for 30, 60, and 90 minutes before being subjected to a similarly increased four-point load-up to the failure. The influence of raised temperature on load-deflection relationships as the failure modes for tested beams was examined and compared to a control beam. Compression failure is the most frequent failure mechanism in all the analyzed GFRP beams before and after exposure to high temperatures, according to the experimental test data. However, as the temperature and exposure time increased, the failure mode shifted from compression to balance and tensile failure. The beam heating was done under elastic loading, making these results unique. After 60 minutes of exposure to temperatures of 200, 400, 600, and 800 ⁰C, the residual loading capacity of heated beams was reduced by 13%, 17.39%, 32.6%, and 41.3%, respectively, compared to the control beam.

Objective Bedding deep cutting slopes containing weak interlayers are commonly found in slope engineering, whose stability is influenced by two key factors: The strength of the sliding zone soil and the reserved thickness of the base (the distance from the base of an excavated slope to the weak interlayer). Methods In this research, taking the K42 cutting slope of the Yang-Xuan Expressway as an example, the evolution process of slope deformation was analyzed, especially the characteristics of basal heave deformation. The properties of the deep sliding zone soil in the slope were revealed by ring shear tests, which are suitable for studying the shear strength of soil that has experienced large shear displacements. Moreover, the residual strength parameters of the saturated sliding zone soil were applied to analyze the reserved thickness of the base. Results The results show that sliding zone soils exhibit obvious strain softening characteristics, which become more evident as the normal stress decreases. As the soil shear strength transitions from peak strength to residual strength, both the cohesion force and internal friction angle decrease, with the cohesion force decreasing to a greater extent than the internal friction angle. The residual cohesion force of sliding zone soil varies slightly with the shear rate, while the relationship between the residual internal friction angle and shear rate varies as a logarithmic function. When the shear rate is less than 2 mm/min, the residual shear strength parameter of sliding zone soil is more sensitive to the shear rate and vice versa. Conclusion Furthermore, according to the regression equations of the critical states of slope stability, the reserved thickness of the base under different slope rates was divided into four zones: A (extremely unstable zone), B (unstable zone), C (basically stable zone) and D (stable zone), and based on this, the criterion and early warning model of the reserved thickness of the base for slope excavation were established.

The room temperature tensile properties and elevated temperature tensile properties of peak aged Al-Cu-Mg-Ag hub forgings after different heat exposure temperatures and heat exposure time were tested，and the thermal stabilities of the forgings at different temperatures were compared and analyzed. The results show that Al-Cu-Mg-Ag forgings exhibit good thermal stability. After exposure at 150 ℃ for 1 to 100 h，there were no significant changes in room temperature tensile properties and elevated temperature tensile properties. Short time heat exposure at 150-200 ℃ for 1 h does not reduce the overall performance，but the strength of Al-Cu-Mg-Ag forgings decreases with the increase of heat exposure temperature and the extension of heat exposure time. After 100 h of exposure at 200 ℃ and 250 ℃，the room temperature yield strength remains 61.1% and 37.2 %，and the room temperature tensile strength remains 77.8% and 60.8%，the elevated temperature yield strength remains 61.6% and 42.8%，and the elevated temperature tensile strength remains 67.5% and 47.6%，respectively. The main precipitates of Al-Cu-Mg-Ag forgings are Ω phase and θ′ phase. Under the experimental conditions of Kt=1 and R=0.1，the room temperature fatigue limit after 200 ℃/10 h heat exposure is 278 MPa，which is 10.6% lower than the fatigue limit of 311 MPa before heat exposure.