Artykuły w czasopismach: „Essai Double Cantilever Beam (DCB)”

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Alfred Franklin, V., T. Christopher i B. Nageswara Rao. "Influence of Root Rotation on Delamination Fracture Toughness of Composites". International Journal of Aerospace Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/829698.

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Large deviations have been observed while analysing composite double cantilever beam (DCB) specimens assuming each cracked half as a simple cantilever beam. This paper examines the effect of rotational spring stiffness(K)on the critical fracture energy(GIC)considering nonzero slope at the crack-tip of the DCB specimen by modelling each cracked half as the spring-hinged cantilever beam. The critical load estimates of DCB specimens fromGICare found to be in good agreement with in-house and existing test results of different composite material systems.

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Chen, T., C. M. Harvey, S. Wang i V. V. Silberschmidt. "Analytical corrections for double-cantilever beam tests". International Journal of Fracture 229, nr 2 (czerwiec 2021): 269–76. http://dx.doi.org/10.1007/s10704-021-00556-5.

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AbstractDouble-cantilever beams (DCBs) are widely used to study mode-I fracture behavior and to measure mode-I fracture toughness under quasi-static loads. Recently, the authors have developed analytical solutions for DCBs under dynamic loads with consideration of structural vibration and wave propagation. There are two methods of beam-theory-based data reduction to determine the energy release rate: (i) using an effective built-in boundary condition at the crack tip, and (ii) employing an elastic foundation to model the uncracked interface of the DCB. In this letter, analytical corrections for a crack-tip rotation of DCBs under quasi-static and dynamic loads are presented, afforded by combining both these data-reduction methods and the authors’ recent analytical solutions for each. Convenient and easy-to-use analytical corrections for DCB tests are obtained, which avoid the complexity and difficulty of the elastic foundation approach, and the need for multiple experimental measurements of DCB compliance and crack length. The corrections are, to the best of the authors’ knowledge, completely new. Verification cases based on numerical simulation are presented to demonstrate the utility of the corrections.

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Sponseller, David L., i Thomas E. Sponseller. "The Double Cantilever Beam (DCB) Test at Forty". BHM Berg- und Hüttenmännische Monatshefte 161, nr 1 (styczeń 2016): 19–26. http://dx.doi.org/10.1007/s00501-016-0449-7.

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Colonel, L., A. Calvez, F. Fournel, V. Larrey, S. Moreau, F. Mazen i F. Rieutord. "Double cantilever beam bonding energy measurement using confocal IR microscopy". Journal of Applied Physics 132, nr 21 (7.12.2022): 215106. http://dx.doi.org/10.1063/5.0114668.

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A new technique is assessed in order to measure, at the wafer scale, direct bonding energies. It is derived from the standard Double Cantilever Beam (DCB) method and uses interferometry in confocal IR laser source microscopy to measure crack openings. Such a bonding energy measurement protocol has better accuracy compared to other techniques. This is due to a better confocal microscopy resolution and the high intensity of the laser source. The elastic energy stored in bent wafers is obtained by measuring the beam curvature. DCB deformation models are discussed from the short-range crack opening theory to long distance beam-bending theories. Comparison is made between models, experimental results, and FEM simulations. Finally, the bonding energy error during standard measurements is estimated.

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Budzik, Michal K., i Henrik M. Jensen. "Evaluation of Defects in Adhesive Joint by Double Cantilever Beam Experiment". Key Engineering Materials 665 (wrzesień 2015): 101–4. http://dx.doi.org/10.4028/www.scientific.net/kem.665.101.

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We analyzed effects of interface/adhesive defects during fracture mechanical Mode I Double Cantilever Beam (DCB) tests of an adhesive joint. Two aluminium slabs were bonded using structural epoxy adhesive. A DCB experiment under static loading was conducted to estimate the critical fracture energy. During the ‘steady-state’ fracture we noted oscillating, random fluctuation in the force vs. displacement curve, and thus in the fracture energy. This is associated to the local variation of properties within the bondline and the interfaces. A simple model is derived to quantify the probable density of flaws observed experimentally.

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Wang, K. F., Y. Q. Wang, B. L. Wang i L. Zheng. "A double cantilever beam incorporating cohesive crack modeling for superconductors". Modern Physics Letters B 34, nr 15 (30.03.2020): 2050166. http://dx.doi.org/10.1142/s0217984920501663.

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In this paper, a double cantilever beam (DCB) specimen incorporating cohesive crack is developed for superconductors which have potential applications in high temperature superconducting cables in space solar power station. The cohesive interface is introduced along the crack front of the DCB model under electromagnetic force. The load-separation relation (i.e. the crack opening displacement) is used as the fracture mechanics parameter and the corresponding curves during fracture process are obtained and verified by the finite element numerical method. Results show that the presence of tensile electromagnetic force makes crack propagate easily. Superconductors with small cracks have good adaptability to the oscillation of magnetic fields while that with large cracks are easier to fracture during the descent of the magnetic field. In addition, the ductility ratio of the cohesive interface can significantly increase the fracture strength. The length of fracture zone decreases as the crack length increases.

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Dahlan, Hendery, Meifal Rusli, Mulyadi Bur i Rika Ampuh Hadiguna. "Kaji Teoritis Pengaruh Variasi Letak Retak Terhadap Perambatan Retak Dengan Pendekatan Double Cantilever Beam (DCB)". Jurnal Inovasi Rekayasa Mekanikal dan Termal 1, nr 2 (29.12.2023): 20–26. http://dx.doi.org/10.25077/inomet.1.2.20-26.2023.

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One of the causes of structural failure is the presence of defects in the form of cracks that appear during the manufacturing or usage process of the structure. The propagation of cracks in the structure greatly depends on the value of the energy released rate possessed by the defective structure. Therefore, it is necessary to calculate the energy released rate of a structure that has a crack. One simple approach is the double cantilever beam (DCB) method. The DCB approach is derived from the change in strain energy with respect to the change in crack length. In this study, variations in crack length and crack location will be analyzed using the DCB approach and compared with the Finite Element Method (FEM) approach. It can be concluded that the calculation of strain energy can be performed using the cantilever beam approach, where the results do not significantly differ from the FEM calculations. Additionally, the strain energy is heavily influenced by the length of the beam, as longer beams result in a significant increase in strain energy (cubic relationship). The value of Energy Released Rate (ERR) is highly influenced by the crack length; a longer initial crack length leads to a quadratic increase in the Energy Released Rate (ERR). Furthermore, the value of Energy Released Rate (ERR) is also affected by the crack location; the closer the crack is to the surface of the beam, the higher the Energy Released Rate (ERR) will be.

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Gourlie, A. D., G. N. Podolski i J. R. Fleet. "A Detailed Statistical Examination of the Double Cantilever Beam (DCB) Test". CORROSION 47, nr 9 (wrzesień 1991): 728–35. http://dx.doi.org/10.5006/1.3585859.

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Li, Rongzhi, Lin Ye i Yiu-Wing Mai. "Interlaminar Fracture of Stitched GFRP Laminates". Advanced Composites Letters 5, nr 1 (styczeń 1996): 096369359600500. http://dx.doi.org/10.1177/096369359600500101.

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The mode I interlaminar fracture of Kevlar thread stitched GFRP laminates has been studied using double-cantilever-beam (DCB) tests. It was found that stitching density and patterns influence interlaminar fracture performance of composites mainly through the different failure mechanisms of stitch threads during crack propagation.

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Balendran, B. "On the Double Cantilever Beam Specimen for Mode-I Interface Delamination". Journal of Applied Mechanics 61, nr 2 (1.06.1994): 471–73. http://dx.doi.org/10.1115/1.2901470.

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A compliance model is presented for a DCB specimen for mode-I interface delamination. The undelaminated part of the specimen is modeled by using Reissner’s mixed variational principle from which the rotation of the cross-section at the tip of the crack and the shear stress at the interface are evaluated. The results for a homogeneous beam with midplane crack are deduced and shown to be in better agreement with the experimental and finite element results than any of the existing models.

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Christopoulos, G. C., i S. A. Paipetis. "Interlaminar Fatigue Crack Propagation in Mode I of Carbon Fiber/PEEK Composites". Advanced Composites Letters 2, nr 1 (styczeń 1993): 096369359300200. http://dx.doi.org/10.1177/096369359300200101.

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A study of the mode I interlaminar fracture toughness of a unidirectional carbon fibre reinforced thermoplastic matrix composite has been made using Double Cantilever Beam, DCB, specimens. Delamination growth per fatigue cycle, da/dN, was related with the maximum applied cyclic strain energy release rate, GIMAX, using a power law.

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Tawk, I., J. F. Ferrero, J. J. Barrau, E. Abdullah i M. Sudre. "Amultilayered Solid Element used to Model Composite Delamination". Advanced Composites Letters 19, nr 1 (styczeń 2010): 096369351001900. http://dx.doi.org/10.1177/096369351001900103.

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This paper focuses on the latest development of a solid hexahedron element for composite delamination analysis. The 8-node solid is derived from a 20-node hexahedron. It is transformed into two physical independent 4-node shell elements according to the propagation of delamination process within the element. This transformation is driven by a transfer and damage laws that are defined by calibrating the element with a FE modeling for a double cantilever beam (DCB) test. According to the position of the crack in the element, one parameter defines the degradation of the transverse properties at the Gauss point as well as the transfer of the volume element towards the bi-plate formulation. A sensitivity study of the element is presented. A global-local finite element approach coupled with the traditional virtual crack closure technique (VCCT) method allows to calculate the energy release rates and to control the propagation of cracking in the element. This method is validated by comparison between conventional FE models and experimental tests [DCB, and end load split (ELS)]. Experimental asymmetric double cantilever beam (ADCB) test is carried out and modelled using the developed element. The numerical simulation properly correlates with the experimental results.

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LOO, SHANE ZHI YUAN, PUAY CHENG LEE, ZAN XUAN LIM, NATALIA YANTARA, TONG YAN TEE, CHER MING TAN i ZHONG CHEN. "INTERFACE FRACTURE TOUGHNESS ASSESSMENT OF SOLDER JOINTS USING DOUBLE CANTILEVER BEAM TEST". International Journal of Modern Physics B 24, nr 01n02 (20.01.2010): 164–74. http://dx.doi.org/10.1142/s0217979210064095.

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In the current work, a test scheme to evaluate solder joint interface fracture toughness using double cantilever beam (DCB) test has been successfully demonstrated. The obtained results, in terms of critical energy release rate, predict the joint failure based on the principle of fracture mechanics. The results can be used as a materials property in the reliability design of various types of solder-ball joined packages. DCB specimens made of 99.9 wt% copper were selected in the current work. Eutectic Sn -37 Pb and lead-free Sn -3.5 Ag -0.5 Cu solders were used to join two pieces of the copper beams with controlled solder thickness. The test record showed steady propagation of the crack along the solder / copper interface, which verifies the viability of such a testing scheme. Interface fracture toughness for as-joined, extensively-reflowed and thermally aged samples has been measured. Both the reflow treatment and the thermal aging lead to degradation of the solder joint fracture resistance. Reflow treatment was more damaging as it induces much faster interface reaction. Fractographic analysis established that the fracture has a mixed micromechanism of dimple and cleavage. The dimples are formed as a result of the separation between the hard intermetallic compound (IMC) particles and the soft solder material, while the cleavage is formed by the brittle split of the IMCs. When the IMC thickness is increased due to extended interface reaction, the proportion of IMC cleavage failure increases, and this was reflected in the decrease of the critical energy release rate.

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Hlača, Ivan, Marin Grbac i Leo Škec. "Determining Fracture Resistance of Structural Adhesives in Mode-I Debonding Using Double Cantilever Beam Test". Zbornik radova 22, nr 1 (20.12.2019): 59–74. http://dx.doi.org/10.32762/zr.22.1.4.

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Double cantilever beam (DCB) test is the most commonly used test for determining the fracture resistance of structural adhesive joints in mode-I debonding. Test specimens are composed of two equal plates that are glued together, and then exposed to the opening load causing crack propagation along the bonded surface. During the experiment, loadline displacement, applied force and crack length are measured continuously. Using these data, the fracture toughness of the adhesive can be computed by the procedure given in the relevant ISO standard (BS ISO 25217:2009). The calculations are based on simple beam theory and linear elastic fracture mechanics (LEFM) equations. In this paper, we will present the standard method for performing a DCB test and the method for data processing required to obtain the adhesive fracture toughness, i.e. the critical energy release rate. Experiments are performed for SikaPower® 4720 adhesive, applied with controlled thickness between the aluminium plates (adherends). After the curing period recommended by the adhesive manufacturer, DCB specimens with piano hinges are loaded by a tensile-testing machine. Loading is applied in the displacement-control mode because when the crack starts to propagate, the applied load drops. Using the optical measurement system GOM Aramis, complete displacement field is recorded during the experiment. Displacement field is then used to obtain the actual load-line displacement of the adherends (different than the one recorded on the tensile-testing machine grips) and the position of the crack tip. After syncing the measurements from different devices, fracture toughness for the adhesive is determined and a statistical analysis performed.

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Pavelko, Vitalijs. "Application of the Nonlinear Model of a Beam for Investigation of Interlaminar Fracture Toughness of Layered Composite". Key Engineering Materials 665 (wrzesień 2015): 273–76. http://dx.doi.org/10.4028/www.scientific.net/kem.665.273.

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Earlier presented the geometrically nonlinear model of a flexible beam (cylindrical bending of a plate) was used for analysis of post-buckling behavior of the layered composite with delamination at compression. In this paper the model is used for more details nonlinear analysis of double cantilever beam (DCB) that used in standard test for determination of the interlaminar fracture toughness composites with delamination-type damage. The main advantage of the model is a precise description of the curved axis of the beam (plate) without linearization or other higher order approximations. The exact solution of bending differential equation finally can be expressed in terms of the incomplete elliptic integrals of the first and second kind. The model describes only geometrically nonlinear effect of DCB arms bending (global effect) and should be combined with the procedure of effective delamination extension to correct DCB arms rotation at delamination front (local effect). First of all the nonlinear model can serve as a tool to estimate the possible error due the geometrical nonlinearity in comparison with linear solution. On the other hand, this model can be effectively used to determine interlaminar fracture toughness using DCB samples at large deflections. Validation of the model is made using data of standard tests of glass/epoxy DCB samples.

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Mohamed Ben Ali, Amina, Salah Bouziane i Hamoudi Bouzerd. "Computation of mode I strain energy release rate of symmetrical and asymmetrical sandwich structures using mixed finite element". Frattura ed Integrità Strutturale 15, nr 56 (28.03.2021): 229–39. http://dx.doi.org/10.3221/igf-esis.56.19.

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The use of composite materials is on the rise in different engineering fields, the main advantage of these materials for the aerospace industry is their low weight for excellent mechanical qualities. The analysis of failure modes, such as delamination, of these materials has received great attention from researchers. This paper proposes a method to evaluate the mode I Strain Energy Release Rate (SERR) of sandwich structures. This method associated a two-dimensional mixed finite element with virtual crack extension technique for the analysis of interfacial delamination of sandwich beams. A symmetrical Double Cantilever Beam (DCB) and asymmetrical Double Cantilever Beam (UDCB) have been analyzed in this study. The comparison of the results obtained by this method and those found in the literature shows efficiency and good precision for the calculation of Strain Energy Release Rate (SERR).

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Li, Yuan, Naoki Hori, Masahiro Arai, Hisao Fukunaga i Ning Hu. "Investigation on Interlaminar Mechanical Properties of Hybrid CFRP/VGCF Laminates". Advanced Materials Research 79-82 (sierpień 2009): 1759–62. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.1759.

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In order to improve the interlaminar mechanical properties of CFRP laminate, hybrid CFRP/VGCF laminates have been fabricated by newly-developed powder method. The critical load at crack growth Pc and fracture toughness GIC have been found to be increased with VGCF interlayer through double cantilever beam (DCB) tests. Fracture surfaces of DCB specimens have also been observed to interpret this improvement mechanism. Moreover, numerical simulations using finite element method (FEM) with cohesive elements have been carried out to analyze the delamination propagation. The numerically obtained interlaminar tensile strength of hybrid CFRP/VGCF laminates has also been verified to be higher than that of base CFRP laminates.

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de Morais, A. B. "A new fibre bridging based analysis of the Double Cantilever Beam (DCB) test". Composites Part A: Applied Science and Manufacturing 42, nr 10 (październik 2011): 1361–68. http://dx.doi.org/10.1016/j.compositesa.2011.05.019.

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Gliszczynski, A., S. Samborski, N. Wiacek i J. Rzeczkowski. "Mode I Interlaminar Fracture of Glass/Epoxy Unidirectional Laminates. Part II: Numerical Analysis". Materials 12, nr 10 (16.05.2019): 1604. http://dx.doi.org/10.3390/ma12101604.

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The paper deals with numerical analysis of double cantilever beam (DCB) predefined to Mode I Interlaminar Fracture Tests of GRFP unidirectional laminates. The numerical analyses were performed in the ANSYS® program based on the finite element. In geometrically nonlinear analysis, two algorithms, responsible for initiation and propagation of delamination front, were applied: Virtual Crack Closure Technique (VCCT) and Cohesive zone method (CZM). Due to the unidirectional arrangement of layers of the laminate, the problem of DCB test was solved with the use of one- and three-dimensional models with the implementation of linear interface element and contact element. The present study highlights the limitations of existing formulae used to reliably reflect the behavior of DCB. The use of three-dimensional models allowed confirming the curved shape of the delamination front observed in experimental studies. The application of the VCCT in the three-dimensional model led to an underestimation of the global response (force–opening displacement curve) recorded during numerical DCB test.

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Aalami, MR, i TN Chakherlou. "Investigating the effects of loading system on the fracture behavior of DCB specimens considering T-stress". Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 235, nr 12 (4.10.2021): 2654–65. http://dx.doi.org/10.1177/14644207211030963.

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Double cantilever beam specimen is a standard specimen for assessment of mode I failure and separation in adhesively bonded joints and also composite materials. Among the several load introduction systems, the piano hinges and end loading blocks are more common. It has been accepted that the fracture toughness results of the two cases are different, but the effect of the loading system on the load-displacement data and fracture mechanisms is not entirely known yet. Therefore, in this study, the two loading concepts are compared both by precise finite element simulations and experimental tests. The adhesive layer is modeled with its own material properties, and the failure of adhesive is investigated by known LEFM procedures. The results reveal that the load block makes the double cantilever beam specimen stiffer and exhibit more non-linear behavior. Moreover, double cantilever beam with the load block system fails in higher loads and lower crack opening displacements compared with the same specimen loaded by the hinges. To study the effect of loading arrangement in more details and including the softening phase, cohesive zone model was utilized. A correction for strain energy release rate based on the parameter T was proposed, and the role of the T-stress on the traction-separation law of the cohesive zone model and the load-displacement behavior were investigated. It was concluded that the T-stress as a crack tip constraint parameter can successfully justify the difference between the two cases. Applying the correction to the traction-separation law of CZM proves the validity of proposed correction in justifying the experimental results.

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Aalami, MR, i TN Chakherlou. "Investigating the effects of loading system on the fracture behavior of DCB specimens considering T-stress". Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 235, nr 12 (4.10.2021): 2654–65. http://dx.doi.org/10.1177/14644207211030963.

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Double cantilever beam specimen is a standard specimen for assessment of mode I failure and separation in adhesively bonded joints and also composite materials. Among the several load introduction systems, the piano hinges and end loading blocks are more common. It has been accepted that the fracture toughness results of the two cases are different, but the effect of the loading system on the load-displacement data and fracture mechanisms is not entirely known yet. Therefore, in this study, the two loading concepts are compared both by precise finite element simulations and experimental tests. The adhesive layer is modeled with its own material properties, and the failure of adhesive is investigated by known LEFM procedures. The results reveal that the load block makes the double cantilever beam specimen stiffer and exhibit more non-linear behavior. Moreover, double cantilever beam with the load block system fails in higher loads and lower crack opening displacements compared with the same specimen loaded by the hinges. To study the effect of loading arrangement in more details and including the softening phase, cohesive zone model was utilized. A correction for strain energy release rate based on the parameter T was proposed, and the role of the T-stress on the traction-separation law of the cohesive zone model and the load-displacement behavior were investigated. It was concluded that the T-stress as a crack tip constraint parameter can successfully justify the difference between the two cases. Applying the correction to the traction-separation law of CZM proves the validity of proposed correction in justifying the experimental results.

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Wang, Guijun, Yanqing Wu, Yuxiang Wang, Fenglei Huang i Tao Wang. "Experimental study of propellant/liner interface fracture characteristics". Journal of Physics: Conference Series 2891, nr 2 (1.12.2024): 022010. https://doi.org/10.1088/1742-6596/2891/2/022010.

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Abstract The propellant/liner interface debonding is one of the main failure modes affecting the structural integrity of solid rocket motors. In order to study the mechanical properties of the propellant/liner interface, the Double-Cantilever Beam (DCB) specimen of the propellant/liner interface was improved. Based on the propellant/liner interface DCB specimens, tensile tests at different temperatures and loading rates were carried out. Based on the digital image correlation(DIC) method, the strain field of the whole DCB specimen and the propellant part was analyzed respectively. Meanwhile, the fracture morphology of DCB specimen was analysed. The results show that the improved specimen can effectively characterize the properties of the propellant/liner interface. The propellant/liner interface shows obvious temperature and strain rate dependence, and the effect of temperature on the propellant/liner interface performance is more significant than that of loading rate. The deformation at the propellant/liner interface of the DCB specimen can reach about 50%, and the interface fracture mode of propellant/liner is cohesive fracture.

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Ramadas, Chennamsetti, Avinash Hood, Krishnan Balasubramaniam i Makarand Joshi. "Ultrasonic Lamb Wave Based Crack Growth Prediction for Estimation of Strain Energy Release Rate". Advanced Materials Research 585 (listopad 2012): 24–28. http://dx.doi.org/10.4028/www.scientific.net/amr.585.24.

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A technique is proposed to predict crack growth for the estimation of Strain Energy Release Rate (SERR) of Double Cantilever Beam (DCB) bi-metallic specimen, employing ultrasonic Lamb waves. Techniques based on the Time-of-Flight (ToF) of the Turning Lamb Mode (TLM) and Direct Lamb Mode (DLM) explored to determine the crack growth. Sensitivity analysis revealed that the Lamb mode with low velocity is more sensitive to crack growth than that of the high velocity Lamb mode.

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Jiang, Xiao-Wei, Shijun Guo, Hao Li i Hai Wang. "Peridynamic Modeling of Mode-I Delamination Growth in Double Cantilever Composite Beam Test: A Two-Dimensional Modeling Using Revised Energy-Based Failure Criteria". Applied Sciences 9, nr 4 (15.02.2019): 656. http://dx.doi.org/10.3390/app9040656.

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This study presents a two-dimensional ordinary state-based peridynamic (OSB PD) modeling of mode-I delamination growth in a double cantilever composite beam (DCB) test using revised energy-based failure criteria. The two-dimensional OSB PD composite model for DCB modeling is obtained by reformulating the previous OSB PD lamina model in x–z direction. The revised energy-based failure criteria are derived following the approach of establishing the relationship between critical bond breakage work and energy release rate. Loading increment convergence analysis and grid spacing influence study are conducted to investigate the reliability of the present modeling. The peridynamic (PD) modeling load–displacement curve and delamination growth process are then quantitatively compared with experimental results obtained from standard tests of composite DCB samples, which show good agreement between the modeling results and experimental results. The PD modeling delamination growth process damage contours are also illustrated. Finally, the influence of the revised energy-based failure criteria is investigated. The results show that the revised energy-based failure criteria improve the accuracy of the PD delamination modeling of DCB test significantly.

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Nakamura, Kota, Yu Sekiguchi, Kazumasa Shimamoto, Keiji Houjou, Haruhisa Akiyama i Chiaki Sato. "Creep Crack Growth Behavior during Hot Water Immersion of an Epoxy Adhesive Using a Spring-Loaded Double Cantilever Beam Test Method". Materials 16, nr 2 (8.01.2023): 607. http://dx.doi.org/10.3390/ma16020607.

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Double cantilever beam (DCB) tests were conducted by immersing the specimens in temperature-controlled water while applying a creep load using a spring. By introducing a data reduction scheme to the spring-loaded DCB test method, it was confirmed that only a single parameter measurement was sufficient to calculate the energy release rate (ERR). Aluminum alloy substrates bonded with an epoxy adhesive were used, and DCB tests were performed by changing the initial load values, spring constants, and immersion temperatures for two types of surface treatment. The initial applied load and spring constant had no effect on the ERR threshold. In contrast, the threshold decreased with the increasing immersion temperature, but even in the worst case, it was 15% of the critical ERR in the static tests. Using the creep crack growth relationship, it was revealed that there were three phases of creep immersion crack growth in the adhesive joints, and each phase was affected by the temperature. The spring-loaded DCB test method has great potential for investigating the combined effects of creep, moisture, and temperature, and this study has demonstrated the validity of the test method. The long-term durability of adhesive joints becomes increasingly important, and this test method is expected to become widespread.

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Burlayenko, Vyacheslav N., Tomasz Sadowski i Daniel Pietras. "Influence of Dynamic Loading on Fracture Behaviour of DCB Sandwich Specimen". ITM Web of Conferences 29 (2019): 02003. http://dx.doi.org/10.1051/itmconf/20192902003.

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Numerical simulations of dynamic fracture behaviour of a double cantilever sandwich beam subjected to uneven bending moments in plane conditions are carried out using the dynamic finite element analyses with the ABAQUSTM code. The strain energy release rate was evaluated by means of the finite element model developed within the two-dimensional (2-D) linear elastodynamic theory. This demonstrates the capability and the reliability of the finite element modelling as an extremely useful numerical tool for solving dynamic fracture mechanics problems. Also, the dynamic behaviour of fracture parameters and interface crack progression is discussed.

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Cañas, José, Luis Távara, Antonio Blázquez i Alejandro Estefani. "Overview of Gc Tests Used to Evaluate Composite–Composite Adhesive Joints". Journal of Multiscale Modelling 10, nr 03 (wrzesień 2019): 1842002. http://dx.doi.org/10.1142/s1756973718420027.

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The quality of composite–composite bonded joints is a very important issue for industries, especially for the aerospace sector. A deficient joint may stop the manufacturing process and its repairing may include very high costs. Nowadays, the quality of the joint is obtained by means of interlaminar fracture toughness tests, estimating the [Formula: see text] value (Energy Release Rate used to produce crack propagation) over coupons with (theoretically) the same conditions as those included in an actual part. Usually, [Formula: see text] is obtained by means of a Double Cantilever Beam (DCB) test. Although DCB is the reference test, it may present some drawbacks when a non-symmetrical coupon is used and when the adherents stiffness is low. An alternative to DCB is the Climbing Drum Peel (CDP) test which is able to address some of the DCB drawbacks. Nevertheless, both tests need the use of a universal testing machine, then they cannot be done in situ. In the present investigation, DCB and CDP main characteristics are analyzed and a new device, called Horizontal Drum Peel (HDP), which includes the advantages of previous tests and the possibility to perform the test over an actual part is presented.

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Wan, Li, Wei Qing Liu i Hai Fang. "Mechanical Behavior of Composite Column Reinforced Paulownia Wood Sandwich". Advanced Materials Research 168-170 (grudzień 2010): 2049–54. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.2049.

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Paulownia wood was drilled with some glass fibers fulfilled in the holes, which could be the core of the sandwich structures. In the manufacture processing, the fibers and resins left in the holes formed composite columns and merged with the facesheets. These could enhance the mechanical behavior of paulownia wood sandwich structures. Double cantilever beam(DCB) tests and bending analysis with finite element method were carried out. The improvement from the composite columns gave little contribution to bending behavior, but significant contribution to interfacial properties.

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Kim, Y. C., H. K. Choi i J. U. Cho. "Experimental Study On Fracture Property Of Double Cantilever Beam Specimen With Aluminum Foam". Archives of Metallurgy and Materials 60, nr 2 (1.06.2015): 1151–54. http://dx.doi.org/10.1515/amm-2015-0087.

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Abstract This study aims to investigate double cantilever beam specimen with aluminum foam bonded by spray adhesive to investigate the fracture strength of the adhesive joint experimentally. The fracture energy at opening mode is calculated by the formulae of British Engineering Standard (BS 7991) and International Standard (ISO 11343). For the static experiment, four types of specimens with the heights (h) of 25 mm, 30 mm, 35 mm and 40 mm are manufactured and the experimental results are compared with each other. As the height becomes greater, the fracture energy becomes higher. After the length of crack reaches 150 mm, the fracture energy of the specimen (h=35 mm) is greater than that of the specimen (h=40 mm). Fatigue test is also performed with DCB test specimen. As the height decreases, the fracture energy becomes higher. By the result obtained from this study, aluminum foam with adhesive joint can be applied to actual composite structure and its fracture property can possibly be anticipated.

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Shen, Yurong, Dongsheng Huang, Ying Hei Chui i Chunping Dai. "Fracture of Parallel Strand Bamboo Composite under Mode I Loading: DCB Test Investigation". Advances in Materials Science and Engineering 2019 (23.09.2019): 1–10. http://dx.doi.org/10.1155/2019/7657234.

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This paper describes the experimental studies on Mode I fracture of parallel strand bamboo (PSB) by the double cantilever beam (DCB) test. R-curves based on the elementary beam theory and specimen compliance are proposed in order to overcome the difficulties to monitor the crack propagation during experiments. The results demonstrate that the energy release rate (ERR) is influenced by the specimen geometry, i.e., the specimen width and initial crack length. The ERR at the plateau level is similar for the range of the analyzed widths (B = 20, 40, and 60 mm), while it decreases with width increasing up to 80 mm and 100 mm. The energy release rate for PSB specimens would verge to a stable value with the width increasing up to a specific value, while the value of the energy release rate will be influenced by the initial crack length. Consequently, the DCB tests also show that the obtained R-curve in this study is not a material property.

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Zhao, Hong Ping, Robert Kwok Yiu Li i Xi Qiao Feng. "Experimental Investigation of Interlaminar Fracture Toughness of CFRP Composites with Different Stitching Patterns". Key Engineering Materials 297-300 (listopad 2005): 189–94. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.189.

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Through-thickness stitching is one of the most effective techniques to improve the delamination resistance of composite laminates. The effects of two different stitching patterns on the mode-I interlaminar fracture toughness of unidirectional carbon fiber reinforced plastics (CFRP) are examined experimentally in the present paper by using the double cantilever beam (DCB) test method. It is found that the zigzag stitching pattern results in a better toughening effect than the straight line pattern, and that the stitching density also has a considerable influence on the mode-I fracture toughness.

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32

Alfred Franklin, V., i T. Christopher. "Fracture Energy Estimation of DCB Specimens Made of Glass/Epoxy: An Experimental Study". Advances in Materials Science and Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/412601.

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This paper examines critical load and corresponding displacement of double cantilever beam (DCB) composite specimens made of glass/epoxy of three different layups. Experiments were conducted on these laminates, and the fracture energy,GIc, was evaluated considering the root rotation at the crack tip. The present model requires the applied load-displacement history and crack extension to estimate fracture energy. Reduction schemes based on cubic and power law are also proposed to determine Young’s modulus and energy release rate and found good agreement with the published and test results.

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Yoshihara, Hiroshi, i Kyohei Nobusue. "Mode I and Mode II fracture toughness of densified Sitka spruce fabricated in an airtight atmosphere with high-temperature steam". Holzforschung 62, nr 1 (1.01.2008): 82–85. http://dx.doi.org/10.1515/hf.2008.012.

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Abstract Mode I and Mode II initiation fracture toughness was examined by DCB (double cantilever beam) and 3ENF (three-point bend end notched flexure) tests on specimens of compressed Sitka spruce. The compressed wood was fabricated by varying the compression ratio, and the effectiveness of the compression treatment was examined in view of improving the fracture mechanics properties. In both cases, the fracture toughness did not show a significant increase after the compression treatment. Thus, it would be necessary to develop a new compression treatment method to improve the fracture mechanics properties.

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Abuobaid, A., D. Heider i S. Yarlagadda. "A time-domain reflectometry method for automated measurement of crack propagation in composites during mode I DCB testing under cold, hot, and hot/wet conditions". Journal of Thermoplastic Composite Materials 32, nr 4 (10.05.2018): 558–73. http://dx.doi.org/10.1177/0892705718772873.

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This article describes an automated method for the measurement of crack initiation and propagation in composite materials during modeI double cantilever beam (DCB) testing under different environmental conditions. The method uses the time-domain reflectometry (TDR)-DCB system, which transmits a high-frequency pulse through a transmission line integrated within the composite test coupon and measures impedance discontinuities generated due to the presence of a crack. Using this system, real-time crack propagation in the specimen can be monitored, and the critical fracture toughness parameters ( GIC) can be calculated in a variety of environmental conditions. TDR-DCB test method was used for the measurement of GIC for dry and wet (water-saturated) DCB samples made from E-glass fiber/vinyl ester composites under dry conditions (room temperature (RT) at 94°C) and wet conditions (RT at 60°C). For all test conditions, TDR signals showed that crack initiation and propagation was the dominant mechanism in identifying impedance changes in the material. Changes in dielectric properties of the specimen due to the test conditions, whether from water uptake, temperature, or a combination of the two, did not significantly affect signal quality.

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35

Rajendran, Thamilarasu S., Mahzan Johar, Shukur Abu Hassan i King Jye Wong. "Mode I and Mode II Delamination of Flax/Epoxy Composite Laminate". MATEC Web of Conferences 202 (2018): 01002. http://dx.doi.org/10.1051/matecconf/201820201002.

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In recent decades, natural fibres are getting their attention as reinforcement in composite materials. This is because natural fibres are environmental friendly. However, delamination is commonly recognised as one of the earliest failures in composite laminates. The objective of the present work is to investigate mode I and mode II delamination behaviour of flax fabrics reinforced epoxy composite. The delamination characterisation was carried out using double cantilever beam (DCB) and three point end notched flexure (ENF) tests. The fracture toughness were calculated using experimental calibration method (ECM). Results showed that the average fracture toughness was 485 N/m and 962 N/m, respectively. Finally, through scanning electron micrographs, it was observed that the ply/ply debonding and fibre/matrix debonding were the major fracture mechanisms in DCB specimen. As for ENF specimen, shear fracture dominated the energy dissipation process.

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Waas, Victor D., Mas Irfan P. Hidayat i Lukman Noerochim. "Finite Element Simulation of Delamination in Carbon Fiber/Epoxy Laminate Using Cohesive Zone Model: Effect of Meshing Variation". Materials Science Forum 964 (lipiec 2019): 257–62. http://dx.doi.org/10.4028/www.scientific.net/msf.964.257.

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Delamination or interlaminar fracture often occurs in composite laminate due to several factors such as high interlaminar stress, stress concentration, impact stress as well as imperfections in manufacturing processes. In this study, finite element (FE) simulation of mode I delamination in double cantilever beam (DCB) specimen of carbon fiber/epoxy laminate HTA/6376C is investigated using cohesive zone model (CZM). 3D geometry of DCB specimen is developed in ANSYS Mechanical software and 8-node interface elements with bi-linear formulation are employed to connect the upper and lower parts of DCB. Effect of variation of number of elements on the laminate critical force is particularly examined. The mesh variation includes coarse, fine, and finest mesh. Simulation results show that the finest mesh needs to be employed to produce an accurate assessment of laminate critical force, which is compared with the one obtained from exact solution. This study hence addresses suitable number of elements as a reference to be used for 3D simulation of delamination progress in the composite laminate, which is less explored in existing studies of delamination of composites so far.

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37

Skoczylas, Jakub, Sylwester Samborski i Mariusz Kłonica. "Acoustic emission as a valuable technique used for monitoring polymer failures". Studia Universitatis Babeș-Bolyai Engineering 66, nr 1 (9.11.2021): 34–44. http://dx.doi.org/10.24193/subbeng.2021.1.4.

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In the paper, acoustic emission (AE) system was presented as a method that can be used to monitor polymer material failures. Samples fabricated of two aluminum profiles bonded together with a thick layer of cured epoxy resin were subjected to fracture tests. Epidian 53 epoxy resin cured with Z1 curing agent as well as Epidian 5 epoxy resin cured with PAC curing agent were selected as adhesives. Acoustic emission parameters were acquired during Double Cantilever Beam (DCB) tests. The frequencies of elastic waves released during failure were then analyzed using both Fast Fourier Transformation (FFT) and Wavelet Transformation (WT) for the two materials.

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38

Li, Yan, Yiu Wing Mai i Lin Ye. "Fracture Properties and Characteristics of Sisal Textile Reinforced Epoxy Composites". Key Engineering Materials 312 (czerwiec 2006): 167–72. http://dx.doi.org/10.4028/www.scientific.net/kem.312.167.

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In this paper, double cantilever beam (DCB) and end notch flexural (ENF) tests were performed to study mode I and mode II interlaminar fracture toughness of sisal textile reinforced epoxy composites. Two kinds of fiber surface treatment methods were used to improve the interfacial bonding properties between sisal fiber and the epoxy resin. Effect of fiber surface treatments on mode I and mode II fracture toughness was analyzed with the aid of microobservation and single fiber pull-out test. It was concluded that proper fiber surface treatment could improve the fracture properties of this kind of Eco-composite.

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Gordić, M. V., I. M. Djordjević, D. R. Sekulić, Z. S. Petrović i M. M. Stevanović. "Delamination Strain Energy Release Rate in Carbon Fiber/Epoxy Resin Composites". Materials Science Forum 555 (wrzesień 2007): 515–19. http://dx.doi.org/10.4028/www.scientific.net/msf.555.515.

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The paper reports on an experimental study of the Mode I interlaminar fracture of unidirectional carbon fibers/epoxy resin composites. Mode I delamination strain energy release rate GIC was determined in double cantilever beam (DCB) test, before and after gamma irradiation at various doses. Glass transition temperature, Tg of epoxy matrix was determined from dynamic mechanical measurements. The delamination surfaces of tested coupons were observed by scanning electron microscopy. The variations in GIC values were correlated with irradiation doses, Tg values and the features of delamination microfractographs, as well as with the variation under irradiation of matrix or fibre/matrix dominated mechanical properties.

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40

Terasaki, Nao, Yuki Fujio, Shin Horiuchi i Haruhisa Akiyama. "Mechanoluminescent studies of failure line on double cantilever beam (DCB) and tapered-DCB (TDCB) test with similar and dissimilar material joints". International Journal of Adhesion and Adhesives 93 (wrzesień 2019): 102328. http://dx.doi.org/10.1016/j.ijadhadh.2019.01.022.

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Nguyen, Dang Du, TaeGyeong Lim, Soomook Lim i Ji Won Suk. "Interlayer Separation in Graphene Paper Comprising Electrochemically Exfoliated Graphene". Nanomaterials 11, nr 4 (29.03.2021): 865. http://dx.doi.org/10.3390/nano11040865.

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The emergence of graphene paper comprising well-stacked graphene flakes has promoted the application of graphene-based materials in diverse fields such as energy storage devices, membrane desalination, and actuators. The fundamental properties of graphene paper such as mechanical, electrical, and thermal properties are critical to the design and fabrication of paper-based devices. In this study, the interlayer interactions in graphene paper were investigated by double cantilever beam (DCB) fracture tests. Graphene papers fabricated by flow-directed stacking of electrochemically exfoliated few-layer graphene flakes were mechanically separated into two parts, which generated force-displacement responses of the DCB sample. The analysis based on fracture mechanics revealed that the interlayer separation energy of the graphene paper was 9.83 ± 0.06 J/m2. The results provided a fundamental understanding of the interfacial properties of graphene papers, which will be useful for developing paper-based devices with mechanical integrity.

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Kali, Naresh, i Srikanth Korla. "Numerical Studies on Mode I Delamination and its Effect on the Vibrational Characteristics in Fibre Metal Laminates". IOP Conference Series: Materials Science and Engineering 1225, nr 1 (1.02.2022): 012039. http://dx.doi.org/10.1088/1757-899x/1225/1/012039.

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Abstract Fibre metal laminates (FMLs) afford the notable advances over ongoing composite materials for aerospace and automotive applications due to their low weight and outstanding mechanical properties. Nevertheless, FMLs are prone to damages during manufacturing and loading conditions. Double cantilever beam (DCB) and vibration test are the commonly used tools to assess fracture energy values and the level of damage influence on the material properties respectively. Therefore, this paper aims at correlating the numerical validation of mode I delamination with already published experimental data by Y.Pan et.al and study the influence of delamination under free vibration analysis of Magnesium (Mg AZ31) alloy based fibre metal laminates. For the presented model, the numerical values showed good acceptance with the experimental values of DCB test. It was also further observed that there is significant reduction in natural frequency due to delamination in the fibre metal laminates.

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Tserpes, Konstantinos. "Numerical evaluation of crack stopping mechanisms in composite bonded joints due to corrugation and bolts". MATEC Web of Conferences 304 (2019): 01003. http://dx.doi.org/10.1051/matecconf/201930401003.

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In this paper, the crack stopping mechanisms in corrugated composite bonded joints and hybrid bonded/bolted joints were evaluated numerically using the cohesive zone modeling approach. For the study, the DCB (double-cantilever beam) and the CLS (crack-lap shear) specimens were modelled. The first two specimens were subjected to static loads and the latter both to static and fatigue loads. The analysis was performed using the LS-DYNA explicit FE code. Fatigue crack growth simulation was performed using an in-house developed user-defined subroutine (UMAT). The numerical results reveal a crack stopping in the corrugated DCB, no crack stopping in the corrugated CLS and a reduction of crack growth rate in the bonded/bolted CLS for both static and fatigue loads. The methods and the findings of the present study can be used for the design of crack stopping features in adhesively bonded primary composite aircraft structures.

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TODOROVIĆ, MARIJA, MATHIEU KOETSIER, NAĐA SIMOVIĆ, IVAN GLIŠOVIĆ i MARKO PAVLOVIĆ. "DETERMINATION OF MODE I FRACTURE PROPERTIES OF EUROPEAN SPRUCE". Wood Research 68, nr 2 (26.04.2023): 334–47. http://dx.doi.org/10.37763/wr.1336-4561/68.2.334347.

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In this paper an efficient procedure for obtaining a cohesive law for Mode I timber fracture (crack opening), based on the Double Cantilever Beam (DCB) tests is given. DCB tests were performed on ten European spruce specimens in order to determine the energy release rate vs crack length (R curves). Two crucial parameters - crack length during the experiment and the crack tip opening displacement were obtained using 2D Digital Image Correlation (DIC) technique. In order to determine accurate fracture resistance (R curve), procedure which includes calculating cumulative released energy was employed. The cohesive law for Mode I fracture of wood was obtained by differentiation of the strain energy release rate as a function of the crack tip opening displacement. This cohesive law is further implemented in the successful numerical modelling of failure modes in large-scale end-notched glulam beams which were experimentally tested in four-point bending configuration.

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Choi, S. R., i J. A. Salem. "Fracture toughness of PMMA as measured with indentation cracks". Journal of Materials Research 8, nr 12 (grudzień 1993): 3210–17. http://dx.doi.org/10.1557/jmr.1993.3210.

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Fracture toughness of polymethyl methacrylate (PMMA) was evaluated with indentation cracks. The cracks were developed by indenting in a liquid acetone environment, as suggested by previous researchers. Due to the inconsistency in crack configurations with varying indentation loads and to the negligible residual stress from indentation, the application of the indentation strength method was limited in evaluating fracture toughness of PMMA. The semielliptical crack approximation, however, particularly at a low indentation load of 9.8 N, resulted in reasonable agreement with the value determined by three conventional fracture toughness testings using the compact tension (CT), double cantilever beam (DCB), and single edge notched beam (SENB) specimens. Measurements at other indentation load typically were in poor agreement with conventional methods due to poorly developed crack configurations.

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46

Hoa, S. V., S. Lin i J. R. Chen. "Hygrothermal Effect on Mode II Interlaminar Fracture Toughness of a Carbon/Polyphenylene Sulfide Laminate". Journal of Reinforced Plastics and Composites 11, nr 1 (styczeń 1992): 3–31. http://dx.doi.org/10.1177/073168449201100102.

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By using a double cantilever beam (DCB) specimen, the hygrothermal effect on Mode II (in-plane shear loading) interlaminar fracture toughness of a carbon/polyphenylene sulfide (PPS) unidirectional laminate was investigated. The critical strain energy release rates, Gnc, of the carbon/PPS laminate during crack propagation under Mode II loading for various temperature/relative humidity conditions were obtained both by linear beam theory and by the area method. It was found that the critical strain energy release rate of the carbon/PPS laminate increases with both moisture content and temperature. Fracture of the carbon/PPS laminate was characterized primarily by micro-cracking at low temperature/low moisture content and by matrix softening and fiber bridging at high temperature/high moisture content.

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Bittencourt, Mario, Alireza Akhavan-Safar, Diogo Santos, Sabine Wenig i Lucas F. M. Da Silva. "Fatigue Threshold Analysis of Adhesives: Displacement Control vs. Load Control Strategy". Journal on Mechanics of Solids 1, nr 1 (11.11.2022): 9–14. http://dx.doi.org/10.24840/2975-8262_001-001_001843.

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The aim of this paper is to study the response of a two-part polyurethane-resin adhesive under quasi-static and fatigue loading conditions, to compare load control and displacement control approaches for the mode I fatigue threshold analysis of the tested material. To achieve this, double cantilever beam (DCB) joints were manufactured and tested. For the post-processing of the raw data, a compliance-based beam method was used. Out of this analysis, R curves and Paris law curves were obtained. Both approaches showed a similar Paris law slope meaning a low sensibility of the crack growth rate between them. As the displacement control load decreases gradually during the test, it can give more precise threshold energy than the load control technique.

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Googarchin, Hamed Saeidi, Mohammad Hassan Shojaeefard, Mohammad Reza Gheibi i Zohreh Sarvi. "A novel cohesive zone model to simulate ductile adhesives in automotive structure metallic joints". International Journal of Computational Physics Series 1, nr 1 (6.03.2018): 301–8. http://dx.doi.org/10.29167/a1i1p301-308.

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In recent years, increasing utilize of the adhesively bonded joints due to its prominent features in distribution of the stress in bonded area and bonding dissimilar material has led to developing its computational aspects to provide more reliable response. In this regard, cohesive zone model (CZM) as an effective method to simulate bondline is introduced. The crucial aspect of this method is the determination of the relation between traction and separation in fracture process zone (FPZ). In fact, the traction-separation law (TSL) is a material model which must be properly obtained and applied to the adhesive bondline. According to the literature, mechanical response of the adhesive joints in most cases (especially in ductile and semi-brittle adhesives) is depended on the TSL curve shape. In this study, a novel CZM is developed to simulate double cantilever beam (DCB) adhesive joint. The main advantageous this new model is considering non-linear behavior of ductile adhesives in elastic region. DCB coupons fabricated by means of Al 6061 adherends and Araldite 2015 adhesive. After direct extraction of the TSL and obtaining cohesive parameters of the new model, numerical simulation of the DCB is conducted. Finally, sensitivity analysis of cohesive parameters and effect of initial crack length on the DCB response is investigated.

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Silva, F. G. A., M. F. S. F. de Moura, N. Dourado, F. A. M. Pereira, J. J. L. Morais, M. I. R. Dias, Paulo J. Lourenço i Fernando M. Judas. "Mode I fracture characterization of human bone using the DCB test". International Journal of Structural Integrity 6, nr 3 (8.06.2015): 355–66. http://dx.doi.org/10.1108/ijsi-05-2014-0023.

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Purpose – Fracture characterization of human cortical bone under pure mode I loading was performed in this work. The purpose of this paper is to validate the proposed test and procedure concerning fracture characterization of human cortical bone under pure mode I loading. Design/methodology/approach – A miniaturized version of the double cantilever beam (DCB) test was used for the experimental tests. A data reduction scheme based on crack equivalent concept and Timoshenko beam theory is proposed to overcome difficulties inherent to crack length monitoring during the test. The application of the method propitiates an easy determination of the Resistance-curves (R-curves) that allow to define the fracture energy under mode I loading from the plateau region. The average value of fracture energy was subsequently used in a numerical analysis with element method involving cohesive zone modelling. Findings – The excellent agreement obtained reveals that the proposed test and associated methodology is quite effective concerning fracture characterization of human cortical bone under pure mode I loading. Originality/value – A miniaturized version of traditional DCB test was proposed for cortical human bone fracture characterization under mode I loading owing to size restrictions imposed by human femur. In fact, DCB specimen propitiates a longer length for self-similar crack propagation without undertaking spurious effects. As a consequence, a R-curve was obtained allowing an adequate characterization of cortical bone fracture under mode I loading.

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Luo, Ming, Zhong-Hua Zhang, Yao-Heng Liu i Mou-Cheng Li. "Effect of Titanium and Boron Microalloying on Sulfide Stress Cracking in C110 Casing Steel". Materials 13, nr 24 (15.12.2020): 5713. http://dx.doi.org/10.3390/ma13245713.

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The effect of Ti and B microalloying on the hardenability, prior austenite grain size (PAGS), mechanical properties, and sulfide stress cracking (SSC) of C110 grade steel was studied by Jominy testing, static tensile testing, an optical microscope (OM), scanning electron microscopy (SEM) and double cantilever beam (DCB) testing. The results show that the addition of 0.015% Ti and 0.002% B into a medium-carbon Fe-Cr-Mo-Nb-V steel increased the hardenability and refined the PAGS and quenched martensite packets, and the size of carbides was reduced. It is believed that these behaviors are responsible for the improvement in the threshold stress intensity factor KISSC.

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