Articoli di riviste: "Double Cantilever Beam (DCB) test"

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

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Alfred Franklin, V., T. Christopher e 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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Gourlie, A. D., G. N. Podolski e J. R. Fleet. "A Detailed Statistical Examination of the Double Cantilever Beam (DCB) Test". CORROSION 47, n. 9 (settembre 1991): 728–35. http://dx.doi.org/10.5006/1.3585859.

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LOO, SHANE ZHI YUAN, PUAY CHENG LEE, ZAN XUAN LIM, NATALIA YANTARA, TONG YAN TEE, CHER MING TAN e ZHONG CHEN. "INTERFACE FRACTURE TOUGHNESS ASSESSMENT OF SOLDER JOINTS USING DOUBLE CANTILEVER BEAM TEST". International Journal of Modern Physics B 24, n. 01n02 (20 gennaio 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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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, n. 10 (ottobre 2011): 1361–68. http://dx.doi.org/10.1016/j.compositesa.2011.05.019.

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Hlača, Ivan, Marin Grbac e Leo Škec. "Determining Fracture Resistance of Structural Adhesives in Mode-I Debonding Using Double Cantilever Beam Test". Zbornik radova 22, n. 1 (20 dicembre 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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Tawk, I., J. F. Ferrero, J. J. Barrau, E. Abdullah e M. Sudre. "Amultilayered Solid Element used to Model Composite Delamination". Advanced Composites Letters 19, n. 1 (gennaio 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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Shen, Yurong, Dongsheng Huang, Ying Hei Chui e Chunping Dai. "Fracture of Parallel Strand Bamboo Composite under Mode I Loading: DCB Test Investigation". Advances in Materials Science and Engineering 2019 (23 settembre 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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Gliszczynski, A., S. Samborski, N. Wiacek e J. Rzeczkowski. "Mode I Interlaminar Fracture of Glass/Epoxy Unidirectional Laminates. Part II: Numerical Analysis". Materials 12, n. 10 (16 maggio 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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Pavelko, Vitalijs. "Application of the Nonlinear Model of a Beam for Investigation of Interlaminar Fracture Toughness of Layered Composite". Key Engineering Materials 665 (settembre 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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Jiang, Xiao-Wei, Shijun Guo, Hao Li e 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, n. 4 (15 febbraio 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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Cañas, José, Luis Távara, Antonio Blázquez e Alejandro Estefani. "Overview of Gc Tests Used to Evaluate Composite–Composite Adhesive Joints". Journal of Multiscale Modelling 10, n. 03 (settembre 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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Nakamura, Kota, Yu Sekiguchi, Kazumasa Shimamoto, Keiji Houjou, Haruhisa Akiyama e 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, n. 2 (8 gennaio 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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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 e Fernando M. Judas. "Mode I fracture characterization of human bone using the DCB test". International Journal of Structural Integrity 6, n. 3 (8 giugno 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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Alfred Franklin, V., e 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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Abuobaid, A., D. Heider e 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, n. 4 (10 maggio 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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Zheng, Xi Tao, Lin Hu Gou, Shu Yun Han e Fan Yang. "Experimental and Numerical Study on the Mode I Delamination Toughness of Z-Pinned Composite Laminates". Key Engineering Materials 417-418 (ottobre 2009): 185–88. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.185.

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An experimental investigation was performed on mode I delamination of z-pinned double-cantilever-beams (DCB) and associate z-pin bridging mechanisms. Tests were performed with ten types of samples: (1) big-pin reinforced DCB (double-cantilever-beams) with three areal densities D=2.01%, 5.15%, 8.04%, respectively; (2) median-pin reinforced DCB with three areal densities D=0.85%, 2.17%, 3.40%; (3) small-pin reinforced DCB with three areal densities D=0.25%, 0.63%, 0.90% and (4) without pin reinforced DCB specimens. Delamination tests samples were prepared from unidirectional continuous carbon ﬁbre/epoxy prepreg (T300/TDE86), made into 3 mm thick unidirectional laminates with and without a block of Z-pins in the crack path. Fracture testing was carried out under Mode I (standard DCB test). Experiments have shown that increases in debond resistance and ultimate strength depend on the material, size, density, location of the pins and the mechanisms of pin deformation. A finite element (FE) model is developed to investigate mode I delamination toughness of z-pin reinforced composite laminates. The z-pin pullout process is simulated by the deformation of a set of non-linear springs. A critical crack opening displacement (COD) criterion is used to simulate crack growth in a DCB made of z-pinned laminates. The toughness of the structure is quantified by the energy release rate, which is calculated using the contour integral method. The FE model is verified for both unpinned and z-pinned laminates. Predicted loading forces from FE analysis are compared to available test data. Good agreement is achieved. The numerical results indicate that z-pins can greatly increase the mode I delamination toughness of the composite laminates.

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Zhao, Hong Ping, Robert Kwok Yiu Li e Xi Qiao Feng. "Experimental Investigation of Interlaminar Fracture Toughness of CFRP Composites with Different Stitching Patterns". Key Engineering Materials 297-300 (novembre 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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Kim, Y. C., H. K. Choi e J. U. Cho. "Experimental Study On Fracture Property Of Double Cantilever Beam Specimen With Aluminum Foam". Archives of Metallurgy and Materials 60, n. 2 (1 giugno 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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Terasaki, Nao, Yuki Fujio, Shin Horiuchi e 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 (settembre 2019): 102328. http://dx.doi.org/10.1016/j.ijadhadh.2019.01.022.

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Pavelko, Igor, e Vitalijs Pavelko. "The crack quasi-static growth and analysis of interlaminar crack resistance of layered composite". MATEC Web of Conferences 349 (2021): 01005. http://dx.doi.org/10.1051/matecconf/202134901005.

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Using the model of quasi-static crack growth and test result of the double cantilever beam (DCB) sample of layred carbon/epoxy composite, the general regularities of the interlaminar crack resistance of mode 1 were studied. The main attention was focused on the variability of crack resistance associated, on the one hand, with the continuity of the fracture process, and, on the other hand, with the non-homogeneity of the material structure, which causes local random deviations from the average characteristics of the material.The dissipation energy rate (total crack resistance) and crack resistance function (R-curve) were extracted from test results and their properties analyzed.

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Shifa, Madni, Fawad Tariq e Rasheed Ahmed Baloch. "Influence of Carbon Nanotubes on the Interlaminar Properties of Carbon Fiber Aluminum Metal Laminates". Key Engineering Materials 778 (settembre 2018): 100–110. http://dx.doi.org/10.4028/www.scientific.net/kem.778.100.

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The present research work describes the fabrication and interlaminar properties testing of carbon fiber aluminum metal laminates (CARALL). CARALL was fabricated through hand layup process followed by compression molding technique and interlaminar properties were assessed through double cantilever beam (DCB) test short beam and flexural test. Different treatments were performed on the surface of aluminum alloy and parameters were optimized to ensure good adhesion between metal sheet and carbon composite layer. Pull-off adhesion test was performed to gauge the adhesion strength of epoxy resin on aluminum alloy sheet. Effect of Multi-wall carbon nanotubes (MWCNTs) was also investigated on the interlaminar properties of CARALL. Treated surface of aluminum alloy sheet was examined under Optical and Field Emission Scanning Electron Microscopy (FE-SEM). Porous surface was evident on aluminum sample due to surface treatment which contributes towards better adhesion between epoxy resin and metal surface through mechanical interlocking and diffusion mechanism. FE-SEM and stereo microscopy was also performed on fractured DCB samples and underlying fracture mechanism was discussed. Test results demonstrated that addition of MWCNTs deteriorated the interlaminar properties of CARALL by weakening the interface between treated aluminum surface and carbon composite.

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Kali, Naresh, e 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, n. 1 (1 febbraio 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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Xie, Zong Hong, Xiang Li, Jian Zhao, Jie Hao, Yan Peng Sun e Xiao Dong Sui. "Study on the Mode I Interlaminar Fracture Toughness of Multi-Directional Composite Laminates". Advanced Materials Research 718-720 (luglio 2013): 186–90. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.186.

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The double cantilever beam (DCB) test method and the modified beam theory are adopted to investigate the Mode I interlaminar fracture toughness of multi-directional composite laminates. The test procedure was developed by using a stereoscopic microscope to observe the delamination front tip and a testing machine to record the displacement and load data. A dial indicator was used to eliminate the error due to initial clearance in the clamp. A modified beam theory and a compliance calibration method were used to calculate the interlaminar fracture toughness. The Mode I interlaminar fracture toughness of carbon fiber reinforced bismaleimide resin matrix (BMI) composite laminates with four different interface patterns ( 0/0, 45/-45, 0/-45 and 0/90, respectively) was obtained. The results show that the patterns of interface ply angles have an obvious influence on Mode I interlaminar fracture toughness of composite laminates.

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Mohan, J., A. Karač, Neal Murphy e Alojz Ivanković. "An Experimental and Numerical Investigation of the Mixed-Mode Fracture Toughness and Lap Shear Strength of Aerospace Grade Composite Joints". Key Engineering Materials 488-489 (settembre 2011): 549–52. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.549.

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In the present study, the mixed-mode fracture toughness of an adhesively bonded composite joint system was examined using a variety of linear elastic fracture mechanics (LEFM) based tests. These tests include the mode I double cantilever beam (DCB), mixed-mode asymmetrical DCB (ADCB) and mode II end load split (ELS) test. The joint system was also evaluated using the wide area lap shear (WALS) test that is often employed by the aerospace industry. While lap shear type tests are relatively simple to perform and post-process compared to their LEFM counterparts, the results can often be misleading and are greatly dependent on the overlap length, thickness of substrate and type of fillet. The experimental tests were also simulated using OpenFOAM, a finite volume based software package. Through this combined experimental-numerical approach, a greater understanding of the influence of the peel ply surface treatment and scrim cloth on the behaviour of the WALS test was achieved.

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Li, Yan, Yiu Wing Mai e Lin Ye. "Fracture Properties and Characteristics of Sisal Textile Reinforced Epoxy Composites". Key Engineering Materials 312 (giugno 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 e M. M. Stevanović. "Delamination Strain Energy Release Rate in Carbon Fiber/Epoxy Resin Composites". Materials Science Forum 555 (settembre 2007): 515–19. http://dx.doi.org/10.4028/www.scientific.net/msf.555.515.

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Abstract (sommario):

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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28

Zou, Guang Ping, Peng Fei Yang, Jie Lu e Yong Gui Li. "The Debond Fracture of Sandwich Plate with Corrugated Core Using Cohesive Zone Element". Key Engineering Materials 525-526 (novembre 2012): 117–20. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.117.

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Abstract (sommario):

In this paper, flatwise tensile test (FWT) and modified double cantilever beam (DCB) experiment were conducted to investigated the debond fracture of sandwich plate with corrugated core. In the experiment, the crack always stays at the face/core interfacial. Tensile bond strength of face core can be given from the flatwise tensile test and we can get the mode I fracture toughness GIC from DCB tests. It is found that the trends of curves change greatly at the beginning, with the propagation of crack, load against open displacement curves change smoothly. In order to simulate the face/core failure of sandwich plate with corrugated core, the cohesive element model is used. Tensile strength and strain energy release rate measured by the experiments presented in this paper are used in as parameters for simulation of the debond fracture. By comparing with the experiment results, the model can express the face/core failure of sandwich plate with corrugated core validly.

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29

Bittencourt, Mario, Alireza Akhavan-Safar, Diogo Santos, Sabine Wenig e Lucas F. M. Da Silva. "Fatigue Threshold Analysis of Adhesives: Displacement Control vs. Load Control Strategy". Journal on Mechanics of Solids 1, n. 1 (11 novembre 2022): 9–14. http://dx.doi.org/10.24840/2975-8262_001-001_001843.

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Abstract (sommario):

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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30

Coronado, Patricia, Pedro Camanho, Antonio Argüelles, Jaime Viña e Sara Sánchez. "Low Temperature and Resin Effects on the Mode I Interlaminar Fracture Toughness in Aeronautical Quality Polymer Composites". Proceedings 2, n. 23 (14 novembre 2018): 1478. http://dx.doi.org/10.3390/proceedings2231478.

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Abstract (sommario):

In the present research the fracture behavior in mode I under static loading of two aircraft quality composites materials has been analyzed at different test temperatures. The composites under study are made of the same unidirectional AS4 carbon fiber reinforcement and had different matrix of epoxy resin, one made of epoxy type 3501-6, and the other with epoxy type 8552 (modified to increase its toughness). Double cantilever beam (DCB) specimens were tested for different temperatures: 20 °C (room temperature), 0 °C, −30 °C and −60 °C, in order to simulate flight conditions. The results obtained from the static tests were analyzed using the Gompertz function.

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31

Xie, Honglei, Li Wan, Bo Wang, Haiping Pei, Weiqing Liu, Kong Yue e Lu Wang. "An Investigation on Mechanical Behavior of Tooth-Plate-Glass-Fiber Hybrid Sandwich Beams". Advances in Polymer Technology 2020 (12 febbraio 2020): 1–11. http://dx.doi.org/10.1155/2020/6346471.

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Abstract (sommario):

Tooth-plate-glass-fiber hybrid sandwich (TFS) is a type of sandwich composites fabricated by vacuum-assisted resin infusion process, in which glass fiber facesheets reinforced by metal plate are connected to foam core through tooth nails. Bending properties and interlaminar properties of TFS beams with various foam densities were investigated by flexural tests and DCB (double cantilever beam) tests. The test results showed that by increasing the foam core density from 35 kg/m3 to 150 kg/m3, the peak strength of TFS beams significantly increased by 168% to 258% compared with similar sandwich beams with fibrous composite facesheets. With the change of foam density and span length, the main failure modes are core shear and facesheet indentation beneath the loading roller. The interlaminar strain energy release rates of TFS specimens also increased by increasing the density of the foam. In addition, an analytical model was used to predict the ultimate bending strength of TFS beams, which were in good accordance with the experimental results.

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32

Kier, Zachary T., e Anthony M. Waas. "Determining effective interface fracture properties of 3D fiber reinforced foam core sandwich structures". Journal of Reinforced Plastics and Composites 37, n. 7 (15 gennaio 2018): 490–503. http://dx.doi.org/10.1177/0731684417753298.

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Abstract (sommario):

Foam core sandwich composites are finding a wider use in aerospace, automotive, and construction applications. These structures present unique challenges in terms of material failure and interaction and are sensitive to damage and imperfections introduced during manufacturing. An emerging class of 3D fiber reinforced foam core aims to replace monolithic foams used in sandwich structure cores particularly in demanding high-performance aerospace applications. This research is focused on investigating the development of testing methods capable of measuring the effective interface fracture properties between the facesheet and the core in 3D fiber reinforced foam cores. Double cantilever beam and end-notched flexure specimens are developed to evaluate the mode I and mode II fracture properties of a 3D fiber reinforced foam core. The design, development, and initial failure of a mode I interface fracture test for 3D fiber reinforced foam cores are presented. The digital image correlation results on the failed tests allowed for a different approach to be utilized in designing a new bonded double cantilever beam specimen for testing the mode I fracture of a 3D fiber reinforced foam core sandwich structure that resulted in a successful interface fracture test. The bonded DCB specimens exhibited relatively smooth crack propagation and produced GIc values similar to honeycomb sandwich structures and significantly higher than comparable foam structures.

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33

Wei, Zhen, Yu Tao Ju e Qing Chun Zhou. "Research on the Rate-Dependent Fracture Energy of Al/HTPB Adhesive Interface". Advanced Materials Research 834-836 (ottobre 2013): 670–75. http://dx.doi.org/10.4028/www.scientific.net/amr.834-836.670.

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Abstract (sommario):

The mode-I fracture of adhesive surface was studied by uniaxial tensile test of the double cantilever beam (DCB) adhesive joints which were made from aluminium sheet and Hydroxyl-terminated polybutadienec (HTPB). The load - displacement curves which characterize the response of the macroscopic fracture show a significant rate-dependent property, i.e. the peak load and corresponding displacement increase with the increase of the loading rates. The critical energy release rate has been defined in two waysnon-linear initiation point (NL) and the maximum load point based on the experimental curves, was gained by the corrected beam theory of fracture mechanics. In addition, the cohesive parameters-fracture energy was also decided by the inversion identification method. The fracture energy obtained numerical simulation is slightly greater than the value obtained by the corrected beam theory, but both results indicate the fracture energy of the adhesive interface also increases continuously with increasing loading rates.

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34

Wang, K. F., B. L. Wang e Y. Y. Fan. "Mode-I fracture analysis of micro-scale high-temperature superconductors via the double cantilever beam model and gradient elasticity theory". Modern Physics Letters B 34, n. 33 (13 agosto 2020): 2050376. http://dx.doi.org/10.1142/s0217984920503765.

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Abstract (sommario):

In this paper, fracture behavior of a micro-scale double cantilever beam (DCB) made of superconducting materials is investigated based on the strain gradient theory. Both zero-field cooling (ZFC) and field cooling (FC) magnetization processes are considered. The closed-form solutions of the energy release rates and stress intensity factors are obtained. For ZFC process, superconducting materials are easy to damage during the process of reducing magnetic field rather than increasing magnetic field. For FC process, applied magnetic field will impede superconductors to damage. Moreover, the normalized energy release rate predicted by classical beam theory is larger than that predicted by strain gradient theory. As the characteristic length increases, the normalized energy release rate decreases. The present model may be useful for designing experiments to test the fracture toughness of micro-scale high-temperature superconductors.

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35

Ribas, Maria, Henrique Oliveira, Alireza Akhavan-Safar, Ricardo Carbas, Eduardo Marques, Sabine Wenig e Lucas Silva. "Characterization of the mechanical properties of a polyurethane adhesive: Tensile strength and Fracture tests". Engineering Manufacturing Letters 2, n. 1 (11 ottobre 2024): 14–22. http://dx.doi.org/10.24840/2795-5168_002-001_2757.

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Abstract (sommario):

The aim of this paper is to study the response of a polyurethane-based adhesive when subjected to different loading conditions. To achieve this, double cantilever beam (DCB) and dogbone specimens were manufactured, and tensile strength, fracture and fatigue fracture tests were performed. The results of the tensile tests revealed a tensile strength of 14.5 MPa and an elastic modulus of 0.27 GPa for the studied polyurethane adhesive. The analysis of the fatigue tests showed that fatigue crack growth starts to stabilize after 20% of the test is done, and that the adhesive used is more suitable for static loading conditions than for cyclic loading conditions, since the value of the average , 0.2 N/mm, is much lower than the value of the average , 4 N/mm.

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36

Wang, Can, e Hao Ran Chen. "Interfacial Creep Fracture Behavior of Foam Core Sandwich Composites with Different Resin". Materials Science Forum 813 (marzo 2015): 127–32. http://dx.doi.org/10.4028/www.scientific.net/msf.813.127.

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Abstract (sommario):

Interfacial creep fracture behavior of sandwich composites consisting of E-glass/ unsaturated polyester (UPE) resin and E-glass/vinyl ester (VE) resin facings over PMI foam core has been experimentally investigated. Digital image correlation (DIC) method was employed in the double cantilever beam (DCB) test to measure the creep displacement field surrounding the crack tip. Crack opening displacements (COD) at various creep time were extracted from the creep displacement field and mode I stress intensity factors were determined using the small region COD-based linear extrapolation method. Significant increments of COD and nominal stress intensity factor are found in specimen with UPE resin and specimen with VE resin after 24 hours creep test. It is also found that specimen with UPE resin has a better interfacial creep fracture resistance than that of specimen with VE resin.

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37

Shindo, Y., K. Horiguchi, R. Wang e H. Kudo. "Double Cantilever Beam Measurement and Finite Element Analysis of Cryogenic Mode I Interlaminar Fracture Toughness of Glass-Cloth/Epoxy Laminates". Journal of Engineering Materials and Technology 123, n. 2 (16 novembre 2000): 191–97. http://dx.doi.org/10.1115/1.1345527.

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Abstract (sommario):

An experimental and analytical investigation in cryogenic Mode I interlaminar fracture behavior and toughness of SL-E woven glass-epoxy laminates was conducted. Double cantilever beam (DCB) tests were performed at room temperature (R.T.), liquid nitrogen temperature (77 K), and liquid helium temperature (4 K) to evaluate the effect of temperature and geometrical variations on the interlaminar fracture toughness. The fracture surfaces were examined by scanning electron microscopy to verify the fracture mechanisms. A finite element model was used to perform the delamination crack analysis. Critical load levels and the geometric and material properties of the test specimens were input data for the analysis which evaluated the Mode I energy release rate at the onset of delamination crack propagation. The results of the finite element analysis are utilized to supplement the experimental data.

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38

Kopietz, Mark, Fatih Bilgin, Sergiy Grishchuk e Bernd Wetzel. "Fiber/Matrix Adhesion in Glass Fiber Reinforced Inorganic-Organic Polyurea/Polysilicate Resins". Key Engineering Materials 742 (luglio 2017): 9–16. http://dx.doi.org/10.4028/www.scientific.net/kem.742.9.

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Abstract (sommario):

In this work newly developed phosphate-free polyurea/polysilicate resins (denoted as 2P) were explored and compared to market established 3P Resins® regarding their fiber/matrix adhesion with coupling agents introduced for further property improvement. Fiber/matrix adhesion was determined by macro mechanical test, i.e. interlaminar shear strength (ILSS), double-cantilever beam (DCB), Charpy impact, and tensile tests.It was demonstrated that 2P resins containing epoxidized linseed oil (ELO) replacing unfavorable organic phosphate esters in 3P Resins® as phase transfer agents nearly reach similar adhesion properties between fiber and matrix compared to established 3P Resins®. Additionally, some coupling agents were found to increase the ILSS by up to 26 %, the energy release rate by up to 7 %, the Charpy impact strength by up to 18 %, and the tensile modulus by up to 11 %.

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39

Barile, Claudia, Caterina Casavola e Alberto Cazzato. "Acoustic Emissions in 3D Printed Parts under Mode I Delamination Test". Materials 11, n. 9 (18 settembre 2018): 1760. http://dx.doi.org/10.3390/ma11091760.

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Abstract (sommario):

This paper applies an innovative approach based on the acoustic emission technique to monitor the delamination process of 3D parts. Fused deposition modelling (FDM) is currently one of the most widespread techniques for additive manufacturing of a solid object from a computer model. Fundamentally, this process is based on a layer-by-layer deposition of a fused filament. The FDM technique has evolved to the point where it can now be proposed, not only as a prototyping technique, but also as one applicable to direct manufacturing. Nonetheless, a deeper comprehension of mechanical behavior and its dependence on process parameters must include the determination of material properties as a function of the service load. In this work, the effects of extrusion temperature on inter-layer cohesion are studied using a method employing a double cantilever beam (DCB). The ASTM D5528 standard was used to determine the delamination energy, GI. In addition, the acoustic emission technique was employed to follow the delamination process during testing. Finally, a Charge-Coupled Device (CCD) camera and a calibrated grid was employed to evaluate crack propagation during testing.

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40

Kelkar, Ajit D., Ram Mohan, Ronnie Bolick e Sachin Shendokar. "Effect of Electrospun Fibers on the Interlaminar Properties of Woven Composites". Advanced Materials Research 47-50 (giugno 2008): 1031–34. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.1031.

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Abstract (sommario):

Failure by delamination of composite laminates due to low velocity impact damages is critical because of the subsurface nature of delamination. Traditional methods such as stitching and Zpinning, while improving interlaminar properties in woven composites, lead to a reduction of the inplane properties. To alleviate these problems, use of Tetra Ethyl Orthosilicate (TEOS) nano fibers manufactured using electrospinning technique in fiber Glass-Epon composite laminates is investigated for their potential to improve the interlaminar properties. Electrospun coated fiber glass woven mats are impregnated with epoxy resin using Heated-Vaccum Assisted Resin Transfer Moulding (H-VARTM) process. The interlaminar properties of the nano engineered hybrid composites obtained using ASTM Double Cantilever Beam (DCB) tests and short beam shear tests are compared with those without the presence of electrospun fiber layers, to study their influence. The short beam shear tests revealed a 20% improvement due to presence of TEOS interlaminar electrospun nanofibers. It is also noteworthy that fibers cured at different temperature levels had variation in performance as observed in MSBS test results.

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41

Nicoli, Edoardo, David A. Dillard, Charles E. Frazier e Audrey Zink-Sharp. "Characterization of mixed-mode I/II fracture properties of adhesively bonded yellow-poplar by a dual actuator test frame instrument". Holzforschung 66, n. 5 (1 luglio 2012): 623–31. http://dx.doi.org/10.1515/hf-2011-0171.

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Abstract (sommario):

Abstract Experimental results for the fracture behavior under mixed-mode in-plane loading conditions of adhesively bonded wood specimens are reported. The material systems considered involved yellow-poplar (Liriodendron tulipifera), a hardwood of the Magnoliaceae family, as adherends bonded with two different adhesives, a moisture-cure polyurethane (PU) and a phenol/resorcinol/formaldehyde (PRF) resin. A dual actuator test frame permitted fine scanning of fracture behavior over a full range of mixed-mode I/II levels for double cantilever beam (DCB) geometry specimens. These tests showed that, in the considered material systems, the critical strain energy release rate, c, tends to increase as the mode-mixity of the loading increases. In particular, the increase is steeper in proximity to pure mode II loading for the PRF bonded specimens. The experimental values of c obtained were fairly scattered, as is common when testing wood systems. This variability is due in part to the natural variability of wood but also to other factors such as the orientation of the grain in the bonded beams and variations of bondline thickness. In particular, measurements of adhesive layer thickness were performed. This analysis was implemented with microscopic examination of samples cut from untested DCB specimens, where the bondline had not been disrupted by the test. Although the wood parts were power planed prior to bonding, rather large variations of the adhesive layer thickness were observed: on the order of 1–100 μm for specimens bonded with the PU resin and 10–50 μm for specimens bonded with the PRF resin, which showed somewhat more consistent fracture behavior.

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42

Giusti, Ruggero, e Giovanni Lucchetta. "Cohesive Zone Modeling of the Interface Fracture in Full-Thermoplastic Hybrid Composites for Lightweight Application". Polymers 15, n. 22 (19 novembre 2023): 4459. http://dx.doi.org/10.3390/polym15224459.

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Abstract (sommario):

With the increasing demand for lightweight and high-performance materials in the automotive and aerospace industries, full-thermoplastic hybrid composites have emerged as a pivotal solution, offering enhanced mechanical properties and design flexibility. This work aims to numerically model the fracture strength in full-thermoplastic hybrid composites made by forming and overmolding organosheets. The mode I fracture was investigated by modeling the behavior of T-joint specimens under a tensile test following the cohesive zone modeling (CZM) approach. The sample was designed to replicate the connection between the laminate and the overmolded part. Double cantilever beam (DCB) specimens were manufactured with organosheets and tested to mode I opening to determine the interlaminar fracture toughness. The fracture toughness out of the mode I test with DCB specimens was used to define the CZM parameters that describe the traction-separation law. Later, due to the particular geometry of the T-join specimens that under tensile load work close to pure mode I, the cohesive parameters were determined by inverse analysis, i.e., calibrating the theoretical models to match experimental results. The fracture resistance T-joint specimens appeared dependent on the fiber-bridging phenomenon during the delamination. In particular, the presence of fiber-bridging visible from the experimental results has been replicated by virtual analyses, and it is observed that it leads to a higher energy value before the interface’s complete breakage. Moreover, a correspondence between the mode I fracture toughness of the DCB specimen and T-joint specimens was observed.

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43

Schmidt, Jakob, Marcus Klingenhöfer, Jörg Kaufmann, Holger Cebulla e Lothar Kroll. "Characterization of the interlaminar fracture toughness of unidirectional thermoplastic composites". Technologies for Lightweight Structures (TLS) 5, n. 1 (24 marzo 2022): 77–85. http://dx.doi.org/10.21935/tls.v5i1.157.

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Abstract (sommario):

In this study, the critical energy release rate in mode I (G1c) for thermoplastic composites made of carbon fiber (CF) and glass fiber (GF) with a polyamide 6 (PA6) matrix is investigated. Double cantilever beam (DCB) was used as the specimen for the mode I test, and the ASTM D 5528-13 was chosen as standard. Moreover, different methodological approaches were applied by comparing different data reduction schemes from the ASTM D 5528-13 and further analytic approaches from the literature. In addition to the conducted experiments, a numerical model of the DCB test is developed and the virtual crack closure technique (VCCT) is performed on the numerical model to determine G1c for PA6-CF and PA6-GF. For the interlaminar fracture toughness G1c a value of 2.87 mJ/mm2 was determined for PA6-GF and a value of 2.16 mJ/mm2 for PA6-CF, which indicate that the use of PA6 as matrix in a composite structure leads to good resistance to damage. A comparison of the different methodological approaches showed a good agreement between the analytical approaches from the literature and the ASTM D 5528-13. In contrast, the values generated for G1c by the VCCT method were significantly higher than those of the other methods.

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Kobayashi, Kenji, Tomohiko Omura e Masakatsu Ueda. "Effect of Testing Temperature on Sulfide Stress Cracking of Low Alloy Steel". Corrosion 74, n. 6 (9 gennaio 2018): 603–12. http://dx.doi.org/10.5006/2605.

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Abstract (sommario):

In this study, effects of environmental temperature on susceptibility to sulfide stress cracking (SSC)—a type of hydrogen embrittlement (HE) occurring in sour environments—of low alloy steels were investigated from the perspective of hydrogen entry, absorption, and accumulation. SSC susceptibility was evaluated using a double cantilever beam (DCB) test and a four-point bend (4PB) test in sour environments at several testing temperatures. 4PB test specimens included notched and un-notched specimens to investigate influences of stress concentration and local stress. In the case of evaluation methods using specimens with high-stress concentration area, a decrease in testing temperature from room temperature to 4°C significantly increased SSC susceptibility. Hydrogen entry and absorption behaviors were also evaluated at several testing temperatures using a hydrogen permeation test. The hydrogen concentration at the plastic deformed area increased remarkably with decreasing testing temperature. It is considered that the influence of testing temperature is due to hydrogen concentration at the stress concentration area with plastic deformation. In a low temperature condition, the degree of hydrogen accumulation at the crack tip areas of a DCB specimen or crack initiation site of a 4PB specimen could be higher than that in a higher temperature condition. When steels are applied to low temperature conditions with H2S, a prior material evaluation reproducing both environmental temperature and actual stress condition is needed.

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Ahn, Jae Seok, Kwang Sung Woo e Dong Woo Lee. "Delamination Analysis of Carbon Fiber-Reinforced PEEK Using Coarse Mesh". Advanced Materials Research 538-541 (giugno 2012): 1624–29. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.1624.

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Abstract (sommario):

The simulation of the delamination process in composite structures made from carbon fiber-reinforced polyetheretherketone (PEEK) is quite complex and requires advanced finite element modeling techniques. Failure analysis tools must be able to predict initiation, size and propagation of delamination process. The objective of the paper is to present modeling technique which is able to predict a delamination in a double-cantilever-beam (DCB) test. The approach is to use a fracture mechanics criterion, but to avoid the complex moving mesh technique. The modeling technique using coarse mesh adopts higher-order approximation (p-level=8) based on Lobatto shape functions. For fracture analysis, also, virtual crack closure technique (VCCT) is considered. Using moving nodal modes, the delamination analysis is implemented and then the performance of present analysis is demonstrated by comparing with the results of references.

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Khaledi, Kavan, Stephan Wulfinghoff e Stefanie Reese. "Finite Element Modeling of Bond Formation in Cold Roll Bonding Processes". Key Engineering Materials 767 (aprile 2018): 323–30. http://dx.doi.org/10.4028/www.scientific.net/kem.767.323.

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Abstract (sommario):

The paper aims to present a finite element model for the bond strength evolution in cold roll bonding processes. To accomplish this, first, the micro-mechanisms taking place along the cold welded joint interfaces are explained. Then, based on the microscopic description of cold welding processes, a bonding interface model is employed to describe the bond formation between the rolled metallic layers. The obtained bond strength is calculated based on the governing parameters of the bonding such as the degree of plastic deformation and the surface cleanness. The numerical simulation given in this paper includes the modelling of joining during cold roll bonding followed by the debonding process in Double Cantilever Beam (DCB) peeling test. Finally, the effects of two important factors on the bond formation, i.e. (1) the degree of plastic deformation and (2) the surface cleanness, are numerically investigated.

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47

Silva, Filipe G. A., Jose Xavier, Fábio A. M. Pereira, José J. L. Morais, Nuno Dourado e Marcelo F. S. F. Moura. "Determination of cohesive laws in wood bonded joints under mode I loading using the DCB test". Holzforschung 67, n. 8 (1 dicembre 2013): 913–22. http://dx.doi.org/10.1515/hf-2013-0012.

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Abstract (sommario):

Abstract The cohesive laws (CLs) have been investigated by means of direct and inverse methods concerning wood bonded joints under pure mode I. The experimental results were obtained by tests with double cantilever beam. The direct method is based on the differentiation of the relation between strain energy release rate and crack opening displacement at the crack tip. An equivalent crack method was used to evaluate the strain energy release rate in the course of the test without monitoring the crack length, which is difficult to observe exactly. The crack opening displacement was determined by postprocessing local displacements measured by digital image correlation. The inverse method requires a previous assumption of the CL shape, and as such, a trilinear law with bilinear softening relationship was selected. The cohesive parameters were identified by an optimization procedure involving a developed genetic algorithm. The idea is to minimize an objective function that quantifies the difference between the experimental and the numerical load-displacement curves resulting from the application of a given law. A validation procedure was performed based on a numerical analysis with finite elements. Both methods in focus provided good agreement with the experimental data. It was observed that CLs adopted by the inverse method are consistent with the ones obtained with the direct method.

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48

Li, Wei, Yinghonglin Liu, Peng Jiang, Fuping Guo e Jiahao Cheng. "Study on Delamination Damage of CFRP Laminates Based on Acoustic Emission and Micro Visualization". Materials 15, n. 4 (16 febbraio 2022): 1483. http://dx.doi.org/10.3390/ma15041483.

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Abstract (sommario):

This study investigated the mechanism of delamination damage in the double cantilever beam (DCB) standard test by the use of the strain energy release rate. The curve of the strain energy release rate was verified by the Rise Angle (RA) method. For this purpose, 24-layer carbon fiber/epoxy multidirectional laminates with interface orientations of 0°, 30°, 45°, and 60° were fabricated according to the standard ASTM D5528(13). In the course of this test, acoustic emission (AE) was used for real-time monitoring, and combined with micro visualization, the damage mechanism of composite multidirectional laminates was studied at multiple scales. Combining the AE detection results with micro visualization, it is found that the AE parameters and the damage to multidirectional laminates could realize a one-to-one correspondence. Through the study of the variation of the RA value, load, and strain energy release rate with the crack length, it is proved that the AE parameters can effectively characterize the initiation of delamination damage.

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49

Gomez, A., e C. Berggreen. "Cohesive zone modelling to predict crack growth under fatigue loading". IOP Conference Series: Materials Science and Engineering 1293, n. 1 (1 novembre 2023): 012012. http://dx.doi.org/10.1088/1757-899x/1293/1/012012.

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Abstract (sommario):

Abstract This manuscript presents the partial results in the development of numerical models based on Cohesive Zone Modelling to analyse quasi-static and fatigue crack propagation in adhesive interfaces. This work applied to adhesive interface between fibre laminates and structural epoxy adhesive of a wind turbine blade 3rd shear-web connection to the trailing edge panels. Fracture characterization experiments using the Double Cantilever Beam with Unequal Bending Moments (DCB-UBM) specimen are performed, and results are used to determine different modelling parameters, such as the mixed-mode cohesive laws and fatigue damage parameters for cohesive crack propagation. The developed numerical model is compared and validated against sub-component testing on two different scale levels, using a Modified Tear Test (MTT) specimen geometry with simplified geometry and loading, and a more complex geometry sub-component specimen with a simplified Shear Web Disbond Test (SBDT). The work is carried out as part of the CORTIR-II project, funded by the Danish Ministry of Energy.

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Zhao, Qi, Dong Zhao e Jian Zhao. "Thermodynamic Approach for the Identification of Instability in the Wood Using Acoustic Emission Technology". Forests 11, n. 5 (10 maggio 2020): 534. http://dx.doi.org/10.3390/f11050534.

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Abstract (sommario):

In order to monitor the crack growth of the wood material better and reduce failure risks, this paper studied the attenuation characteristics of acoustic emission signals in wood through pencil lead breaking (PLB) tests, in the aim of estimating the true amplitude value of the acoustic emission source signal. The tensile test of the double cantilever beam (DCB) specimens was used to simulate the crack tip growth within wood material, monitoring acoustic activity and location of crack tips within wood material using acoustic emission technology and digital image correlation (DIC). Results showed that the attenuation degree of acoustic emission signals increased exponentially as the propagation distance increased, and the relationship between relative amplitude attenuation rate and the propagation distance of the acoustic emission signal was established by the regression method, which provides the input parameters for the establishment of the crack instability prediction model in the next step. Based on a thermodynamic approach, a theoretical model for predicting crack instability was established, and the model was verified by DCB tests. The model uses acoustic emission parameters as the basis for judging whether the crack is instable. It provides theoretical support for the application of acoustic emission technology in wood health monitoring.

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