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1
Ellison, Andrew, e Hyonny Kim. "Shadowed delamination area estimation in ultrasonic C-scans of impacted composites validated by X-ray CT". Journal of Composite Materials 54, n.º 4 (27 de julho de 2019): 549–61. http://dx.doi.org/10.1177/0021998319865311.
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Although ultrasonic pulse-echo C-scanning is a mature non-destructive evaluation technique for imaging internal damage in composite structures, a major impediment of obtaining a full characterization of the internal damage state is delamination shadowing effects. Specifically, shadowing refers to regions of interest that are behind other delamination planes or discontinuities with respect to the scanning surface. The delamination planes block ultrasonic wave transmission and the regions of interest are thus hidden (i.e. shadowed) from the scan. A methodology has been developed to expand ultrasonic scan data of impacted composites by utilizing damage morphology information that is well established in the composite impact research community, such as matrix cracks bounding delaminations, to estimate shadowed delamination information and matrix cracking. First, impacted flat composite plates were C-scanned by pulse-echo ultrasonic and the results were segmented by depth of damage to establish interface-by-interface delamination information. These delaminations were then fit by bounding lines representing the fiber/matrix crack directions defined by the orientations of plies adjacent to each interface to estimate the shadowed portion of the delamination results. The area inside this boundary was added to the original ultrasonic delamination area to create an estimation of the full delamination state at each shadowed interface. Additionally, because this extension method is based on the interactions between delaminations and matrix cracking, this extension method provides an approximation of the matrix cracking of adjacent plies. Results were compared with X-ray computed tomography scans to assess the effectiveness of the extension method.
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Toscano, Cinzia, Aniello Riccio, FrancescoPaolo Camerlingo e Carosena Meola. "On the use of lock-in thermography to monitor delamination growth in composite panels under compression". Science and Engineering of Composite Materials 21, n.º 4 (1 de setembro de 2014): 485–92. http://dx.doi.org/10.1515/secm-2013-0156.
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AbstractThe success of composites in automotive, aerospace, and naval applications is mainly related to their aptitude to be tailored to obtain a final product that perfectly fulfills the design requirements. However, during both manufacturing processes and maintenance, some flaws, like delaminations (which may escape simple visual inspection), may be induced in composite structures. The presence of delaminations is of major concern for the load-carrying capability of carbon fiber-reinforced polymer panels. Indeed, delaminations can strongly affect the structural strength and may grow under in-service loads, leading sometimes to catastrophic failures. The aim of this work is to explore the use of lock-in thermography for the monitoring of delamination propagation in composite structures when subjected to generic multiaxial loading conditions. A stiffened composite panel with an embedded skin delamination subjected to compressive loading was taken as a benchmark to assess experimentally the effectiveness of lock-in thermography for monitoring the delamination propagation in situ during the compressive mechanical test. The delamination size as a function of the applied load, observed by lock-in thermography during the execution of the compressive test, was used to validate the results of preliminary numerical computations.
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Mahieddine, Ali, e Mohammed Ouali. "Analysis of Delaminated Composite Plates". Advanced Materials Research 686 (abril de 2013): 104–8. http://dx.doi.org/10.4028/www.scientific.net/amr.686.104.
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A mathematical model for plates with partially delaminated layers is presented to investigate their behavior. In this formulation account is taken of lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. The region without delamination is modeled to carry constant peel and shear stresses; while the region with delamination is modeled by assuming that there is no peel and shear stress transfer between the top and bottom layers. Numerical results of the present model are presented and its performance is evaluated for static problems. Laminated beams and plates are often used as primary load-carrying structures. However, the mechanical properties of composite materials may degrade severely in the presence of damage. One of the common types of damage modes in laminated composites is delamination. The presence of delamination is one of the most prevalent life-limiting failure modes in laminated composite structures. Many researchers had been studying the effect of delamination. Wee and Boay [1] developed an analytical model to predict the critical load of a delaminated composite laminated beam. Lee et al. [2] investigated the buckling behavior of the beam plate with multiple delaminations under compression. Kapania and Wolfe [3] examined the buckling behavior of a beam plate with two delaminations of equal length. Wang et al. [4] improved the analytical solution by including the coupling between the flexural and axial vibrations of the delaminated sub-laminates. Lee et al. [5] studied a composite beam with arbitrary lateral and longitudinal multiple delamination. Finite-element methods have been developed using the layerwise theory by Kim et al. [6]. Tan and Tong [7] developed a dynamic analytical model for the identification of delamination embedded in a laminated composite beam. To investigate the effects of delamination of a plate layers, a finite-element model is developed. Both displacement continuity and force equilibrium conditions are imposed between the regions with and without delamination. The accuracy of the approach is verified by comparing results with previously published data.
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Hajikhani, Milad, Amir Refahi Oskouei, Mehdi Ahmadi Najaf Abadi, Amir Sharifi e Mohammad Heidari. "Progressive Fracture Evaluation in Composite Materials by Acoustic Emission Technique". Key Engineering Materials 465 (janeiro de 2011): 535–38. http://dx.doi.org/10.4028/www.scientific.net/kem.465.535.
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Glass/polyester and glass/epoxy laminated composites widely used in structures and have very near properties. These composite laminates have poor inter-laminar fracture resistance and suffer extensive damage by delamination cracking when subjected to out of plane loading and hence are vulnerable to delamination. The presence of delamination in the composite material may reduce the overall stiffness. Structural design and nondestructive test techniques have evolved as increased emphasis has been placed on the durability and damage tolerance of these materials. There are several methods used to investigate damages of composite materials. Acoustic emission is one of these. In this work the effect of delamination propagation on acoustic emission (AE) events in glass/polyester and glass/epoxy composites is obtained also Fracture surface examinations were conducted using a scanning electron microscope (SEM) and results in these two common composites compared. Consequently, revealed that the AE technique is a practicable and effective tool for identifying and separating kinds of cracks in these composites.
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Chang, Fu-Kuo, e Zafer Kutlu. "Delamination Effects on Composite Shells". Journal of Engineering Materials and Technology 112, n.º 3 (1 de julho de 1990): 336–40. http://dx.doi.org/10.1115/1.2903334.
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An analytical investigation was performed to study the effect of delamination on the response of cylindrical composite shells subjected to external loadings. It was of particular interest to determine the buckling load and the post-buckling behavior of externally pressurized cylindrical composite shells containing delaminations. An analytical model was developed that consists of a structural analysis for calculating the global deformations of the structures and a fracture analysis for determining the delamination growth in the structures. A nonlinear finite element code based on the updated Lagrangian formulation was developed for the model. Based on the results of calculations, it was found that delamination can significantly affect the buckling load and response of cylindrical composite shells subjected to externally pressurized loadings, depending upon the initial length and location of the delamination, ply orientation and laminate curvature. The calculated strain energy release rate at the crack tips indicates that delamination growth occurs in the wake of buckling due to Mode II shear fracture.
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Brunner, Andreas J., René Alderliesten e John-Alan Pascoe. "In-Service Delaminations in FRP Structures under Operational Loading Conditions: Are Current Fracture Testing and Analysis on Coupons Sufficient for Capturing the Essential Effects for Reliable Predictions?" Materials 16, n.º 1 (27 de dezembro de 2022): 248. http://dx.doi.org/10.3390/ma16010248.
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Quasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and 20%. However, differences in the size and possibly the shape, but also in the fibre lay-up, between test coupons and components or structures raise additional questions: Is G from a coupon test a suitable parameter for describing the behaviour of delaminations in composite structures? Can planar, two-dimensional, delamination propagation in composite plates or shells be properly predicted from essentially one-dimensional propagation in coupons? How does fibre bridging in unidirectionally reinforced test coupons relate to delamination propagation in multidirectional lay-ups of components and structures? How can multiple, localised delaminations—often created by impact in composite structures—and their interaction under service loads with constant or variable amplitudes be accounted for? Does planar delamination propagation depend on laminate thickness, thickness variation or the overall shape of the structure? How does exposure to different, variable service environments affect delamination initiation and propagation? Is the microscopic and mesoscopic morphology of FRP composite structures sufficiently understood for accurate predictive modelling and simulation of delamination behaviour? This contribution will examine selected issues and discuss the consequences for test development and analysis. The discussion indicates that current coupon testing and analysis are unlikely to provide the data for reliable long-term predictions of delamination behaviour in FRP composite structures. The attempts to make the building block design methodology for composite structures more efficient via combinations of experiments and related modelling look promising, but models require input data with low scatter and, even more importantly, insight into the physics of the microscopic damage processes yielding delamination initiation and propagation.
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Subba Rao, V. V., Godavarthi Yeswanth Kiran Kumar e Sansanka Pentapalli. "Reduction of AWJ Induced Delaminations by Impregnated Nanoclay GFRP Composites". Materials Science Forum 969 (agosto de 2019): 284–90. http://dx.doi.org/10.4028/www.scientific.net/msf.969.284.
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Composite materials are extensively used in various applications like space, aircraft, and automobile sector because of superior physical and mechanical properties even though they are costly. In recent technological innovations, using Montmorillonite (Nanoclay) to reinforce polymer-based composites has raised attention to academic and industrial sectors since small addition could enhance Mechanical properties thereby decreasing failures like delaminations. In present research work, the effect of AWJ machining parameters on delaminations of glass fibre reinforced epoxy composite is investigated. The Main objective is determining delamination factor and reduce delaminations which is major failure in laminates. This paper investigates on effects of impregnated Nanoclay epoxy in Bi-directional GFRP where previous research has been made only in changing the parameters for reduction of delaminations. The samples were machined using AWJ, delamination factors are measured using image-J software and SEM analysis for comparing micrographs. Finally with increase in nano clay weight fraction, delaminations are checked.
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Wei, Z., L. H. Yam e L. Cheng. "Delamination Assessment of Multilayer Composite Plates Using Model-based Neural Networks". Journal of Vibration and Control 11, n.º 5 (maio de 2005): 607–25. http://dx.doi.org/10.1177/1077546305052317.
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A procedure for damage detection in multilayer composites is described using model-based neural networks and vibration response measurement. The appropriate finite element model is established to generate the training data of neural networks. Internal delaminations with different sizes and locations are considered as the particular damage scenarios in multilayer composite plates. The damage-induced energy variation of response signal is investigated, and the mechanism of mode-dependent energy dissipation of composite plates due to delamination is revealed. In order to obtain the structural dynamic response of the samples, impulse forced vibration testing is conducted using a piezoelectric patch actuator and an accelerometer. To enhance the sensitivity of damage features in the vibrating plate, the damage-induced energy variation of the response signal decomposed by wavelet packets is used as the input data of backward propagation neural networks for the prediction of delamination size and location. The test results show that the proposed method is effective for the assessment of delamination status in composites.
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Marshall, I. H. "Delamination Buckling of Composite Materials". Composite Structures 13, n.º 3 (janeiro de 1989): 235–36. http://dx.doi.org/10.1016/0263-8223(89)90007-x.
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Sreekanth, T. G., M. Senthilkumar e S. Manikanta Reddy. "Natural Frequency based delamination estimation in GFRP beams using RSM and ANN". Frattura ed Integrità Strutturale 16, n.º 61 (19 de junho de 2022): 487–95. http://dx.doi.org/10.3221/igf-esis.61.32.
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The importance of delamination detection can be understood from aircraft components like Vertical Stabilizer, which is subjected to heavy vibration during the flight movement and it may lead to delamination and finally even flight crash can happen because of that. Any solid structure's vibration behaviour discloses specific dynamic characteristics and property parameters of that structure. This research investigates the detection of delamination in composites using a method based on vibration signals. The composite material's flexural stiffness and strength are reduced as a result of delaminations, and vibration properties such as natural frequency responses are altered. In inverse problems involving vibration response, the response signals such as natural frequencies are utilized to find the location and magnitude of delaminations. For different delaminated beams with varying position and size, inverse approaches such as Response Surface Methodology (RSM) and Artificial Neural Network (ANN) are utilized to address the inverse problem, which aids in the prediction of delamination size and location.
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Muc, Aleksander. "Buckling of Composite Structures with Delaminations—Laminates and Functionally Graded Materials". Applied Sciences 12, n.º 22 (10 de novembro de 2022): 11408. http://dx.doi.org/10.3390/app122211408.
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In the present paper, buckling problems of constructions with single delamination are examined. Structures were made of unidirectional laminates and functionally graded materials (FGM). Two types of delaminations (closed and opened) were both investigated in experiments both in rectangular plates and axi-symmetric shells. The first part of the work is devoted to the formulation of contact problems (embedded, closed delaminations) with the aid of various functional inequalities. Then, computational models are discussed. To study the influence of the variable material configuration of FGMs, the fourth-order plate/shell relations were adopted. Finally, three particular problems examined are the buckling of flat rectangular plates, spherical shells, and compressed rectangular plates with elliptical delaminations. The experiments were conducted using imperfection sensitivity analysis and post-buckling non-linear analysis. The results demonstrate that the unsymmetric configurations of FGM structures lead to the reduction of buckling loads for structures with delaminations. For FG structures, those effects are described by the simple coefficient. Linear fracture mechanics were employed to distinguish the form of unilateral boundary problems (closed or opened). In the first case, the stable variations of the strain energy release rate GI with the delamination length variations were observed, whereas in the second case the unstable variations were observed.
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János, Líska, e Kodácsy János. "Drilling of Glass Fibre Reinforced Plastic". Advanced Materials Research 472-475 (fevereiro de 2012): 958–61. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.958.
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Nowadays composite materials are used in many industrial areas. The main application of these is the aircraft industry. Problematic points with machining of composite materials are tool wear, tool life, delamination and temperature during machining of polymer composite materials. Paper focuses on investigation of delamination at drilling of glass fibre reinforced composites. Experiments were planned on the base so called design of experiment - DOE. We observed the evolution of delamination at investigations, when we combined 4 different variables (vc, fz, tool, cooling system). We investigated the evolution of force relations, torques, dimensional and shape accuracy, considering on delamination. We processed results statistically, for processing we used software MINITAB and MATLAB. We summarized results in tables and graphs.
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Tian, Xinpeng, Dong Yao e Qun Li. "Thermal buckling response and fracture analysis for delaminated fiber reinforced composite plates under thermo-mechanical coupling". Journal of Composite Materials 52, n.º 27 (2 de maio de 2018): 3715–30. http://dx.doi.org/10.1177/0021998318769132.
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Fiber reinforced composites are often subjected to severe thermal-mechanical coupling loads. In order to predict the stiffness and strength of the designed composites, thermal buckling response of the delaminated fiber reinforced composite plates and fracture analysis along the delamination front under thermo-mechanical coupling are investigated based on the generalized layerwise plate theory. Delamination between individual layers is considered as discontinuities in the displacement field using Heaviside step functions in the finite element model of delaminated composite plates. Governing equations are derived using virtual work principle and fracture analysis is performed by calculation of the strain energy release rate along the delamination front by means of the virtual crack closure technique. The effect of laying angle, delamination size, and delamination position on the critical thermal buckling temperature of laminated composite plates are investigated. Numerical results reveal that the critical thermal buckling temperature is insensitive to the delamination size less than an ‘irrelevant size’ and then significantly decreases with the increase of delamination sizes. The inside delamination has a greater influence on the critical thermal buckling temperature than the outside delamination. The maximum values of strain energy release rate always occur in the ‘equivalent material direction’ when the delamination is located in the middle of composite plates, while it is determined by laying angle and delamination position together for non-middle plane delamination.
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Sudha J., A., B. Sampathkumar S. e C. Vijaya A. "AE Waveform Analysis of Delamination in GFRP Composite Materials during Drilling". International Journal of Engineering and Technology 1, n.º 1 (2009): 63–66. http://dx.doi.org/10.7763/ijet.2009.v1.11.
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Sabău, Emilia, Cristian Vilău, Paul Bere e Adrian Popescu. "Finite element simulation of delamination process in composite materials". MATEC Web of Conferences 299 (2019): 06003. http://dx.doi.org/10.1051/matecconf/201929906003.
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The delamination phenomenon is undesirable and constitutes a major problem. In this paper, a study of delamination for composite materials reinforced with unidirectional glass fibers in polyester matrix is analyzed. The composite plates were made using two manufacturing technologies, hand lay-up and compression hand lay-up process. The study found out the maximum value of the force where delamination occurs and the specific delamination resistance. Also, it’s done a finite element simulation of delamination process at polymeric composite materials under transverse loads. The propagation model ofdelamination was implemented in finite element ANSYS software. There are presented the used materials for samples, the manufacturing process, laboratory equipment and the experimental results.
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Sellitto, Andrea, Aniello Riccio, A. Russo, Antonio Garofano e Mauro Zarrelli. "Nanofillers’ Effects on Fracture Energy in Composite Aerospace Structures". Key Engineering Materials 827 (dezembro de 2019): 43–48. http://dx.doi.org/10.4028/www.scientific.net/kem.827.43.
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Composite materials damage behaviour is, nowadays, extensively investigated in the frame of aerospace research programmes. Among the several failure mechanisms which can affect composites, delamination can be considered as the most critical one, especially when combined to compressive loading conditions. In this context, nanofillers can represent an effective way to increase the composites fracture toughness with a consequent reduction of the delamination onset and evolution. Hence, in this paper, the toughening effect of the nanofillers on the delamination growth in composite material panels, subject to compressive load, has been numerically studied. A validated robust numerical procedure for the prediction of the delamination growth in composite materials panel, named SMXB and based on the VCCT-Fail release approach, has been used to perform numerical analyses by considering two different types of nanofillers. Reference material, without nanofillers insertion, has been used as benchmark in order to assess the capability of nanofillers to enhance the fracture toughness in composite laminates.
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Aveiga, David, e Marcelo L. Ribeiro. "A Delamination Propagation Model for Fiber Reinforced Laminated Composite Materials". Mathematical Problems in Engineering 2018 (19 de junho de 2018): 1–9. http://dx.doi.org/10.1155/2018/1861268.
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The employment of composite materials in the aerospace industry has been gradually considered due to the fundamental lightweight and strength characteristics that this type of materials has. The science material and technological progress reached matched perfectly with the requirements for high-performance materials in aircraft and aerospace structures; thus, the development of primary structure elements applying composite materials became something very convenient. It is extremely important to pay attention to the failure modes that influence composite materials performances, since these failures lead to a loss of stiffness and strength of the laminate. Delamination is a failure mode present in most of the damaged structures and can be ruinous, considering that the evolution of interlaminar defects can carry the structure to a total failure followed by its collapse. The present work aims at the development of a delamination propagation model to estimate a progressive interlaminar delamination failure in laminated composite materials and to allow the prediction of material’s degradation due to delamination phenomenon. Experimental data, available at literature, was considered to determine some model parameters, like the strain energy release rate, using GFRPs laminated composites. This new delamination propagation model was implemented as subroutines in FORTRAN language (UMAT-User Material Subroutine) with formulations based on the Fracture Mechanics and Continuum Damage Mechanics. Finally, the UMAT subroutine was complemented with an intralaminar model and compiled beside the commercial Finite Element (FE) software ABAQUS™.
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Karim, M. R., T. Kundu e C. S. Desai. "Detection of Delamination Cracks in Layered Fiber-Reinforced Composite Plates". Journal of Pressure Vessel Technology 111, n.º 2 (1 de maio de 1989): 165–71. http://dx.doi.org/10.1115/1.3265653.
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In this paper, the dynamic response of delamination cracks in a layered fiber-reinforced composite plate is analytically studied. The plate is subjected to an antiplane loading and its surface response is computed in absence as well as in presence of delaminatioin cracks. To what extent the surface response is influenced by the presence of internal delamination cracks is investigated here. This study is important for nondestructive evaluation of internal damage in composites due to delamination. The problem is formulated in terms of integral equations in frequency domain. These equations are then solved by expanding the unknown crack opening displacement in a complete set of Chebychev’s polynomials, whose coefficients are solved by satisfying the traction-free condition at the crack surface. The time histories are obtained numerically by inverting the spectra via Fast Fourier Transform (FFT) routine. The results show significant influence of delamination crack geometries on the surface response of the plate.
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Ramadhan, Redha Akbar, Muhamad Giri Suada e Hendri Syamsudin. "A FINITE ELEMENT ANALYSIS OF CRITICAL BUCKLING LOAD OF COMPOSITE PLATE AFTER LOW VELOCITY IMPACT". Jurnal Teknologi Dirgantara 18, n.º 2 (27 de dezembro de 2020): 195. http://dx.doi.org/10.30536/j.jtd.2020.v18.a3328.
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Composite is a material formed from two or more materials that macroscopically alloyed into one material. Nowadays, composite has been generally applied as lightweight structure of aircraft. This is due to the fact that composites having high strength-to-weight ratio. It means the composites have the capability to take on various loads, despite their lightweight property.Laminate composite is one type of composite that has been generally used in aircraft industries. This type of composite is susceptible to low-velocity impact induced damage. This type of damage can be happening in manufacture, operation, or even in maintenance. Low-velocity impact could cause delamination. Delamination happens when the plies of laminated composites separated at the interface of the plies. This type of damage is categorized as barely visible damage, means that the damage couldn’t be detected with visual inspection. Special method and tool would be needed to detect the damage. Delamination will decrease the strength of the laminated composite.Delamination can be predicted with numerical simulation analysis. With increasing capability of computer, it is possible to predict the delamination and buckling of laminated composite plate. This research presents the comparisons of buckling analysis results on laminated plate composite and damaged laminated plate composite. By the result of LVI simulation, it is shown that low velocity impact of 19.3 Joule causing 6398 mm2 C-Scan delamination area inside the laminated composite. The delamination causing structural instability that will affect buckling resistance of the plate. The result of analysis shows that the existence of delamination inside laminate composite will lower its critical buckling load up to 90% of undamaged laminate’s critical buckling load.Keywords : composite, laminate, delamination, buckling.
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Azuan, S. A. Syed, J. M. Juraidi e Wan Mansor Wan Muhamad. "Evaluation of Delamination in Drilling Rice Husk Reinforced Polyester Composites". Applied Mechanics and Materials 232 (novembro de 2012): 106–10. http://dx.doi.org/10.4028/www.scientific.net/amm.232.106.
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Delamination is recognized as one of the most critical defects that can result from the machining composites. Delamination has been a major form of failure in drilled composite materials due to the composites lack of strength in the drilling direction, which results in poor surface finish, reduction in bearing strength, reduction in structural integrity and ultimately poor performance of the composite. Currently, most of the major research reported delamination address specific of machining fiber glass, graphite fiber or carbon fiber reinforced polymer composites. It is not yet clear how different drilling parameters affect the machinability of natural fiber reinforced polymer composite materials and quality of drilled holes. This paper report the investigation in drilling holes on natural fibre reinforced polyester composites and evaluate its hole quality by measuring delamination. Three different type of drill: twist 118o drill, brad drill and end mill were used. Drilling process is carried out for three spindle speed (1500 rpm, 2000 rpm and 2500 rpm) and three feed rate (0.1 mm/rev, 0.15 mm/rev and 0.2 mm/rev). Brad drill experienced higher delamination values compared to twist and end mill. Increasing of feed rate and spindle speed also caused a relevant increase in the delamination values. It is found that Rice husk reinforced polyester composites delamination value is lower when compared to the glass fiber reinforced polymer.
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Tay, TE. "Characterization and analysis of delamination fracture in composites: An overview of developments from 1990 to 2001". Applied Mechanics Reviews 56, n.º 1 (1 de janeiro de 2003): 1–32. http://dx.doi.org/10.1115/1.1504848.
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Delamination is a major failure mode in laminated composites and has received much research attention. A huge amount of literature has been published on this subject, resulting in considerable improvement in our understanding of delamination behavior. A rather comprehensive review paper was published by Garg in 1988. That paper contains 136 references from 1971 to 1988, a period spanning roughly two decades. A more recent survey by Pagano and Schoeppner contains critical reviews of many selected papers, especially the pioneering works on delamination research. An overview of Russian and Soviet literature on this subject is also given by Bolotin. The present paper aims to review major developments in the analysis and characterization of buckling driven delamination from 1990 to the present. Its abridged version was presented in a plenary lecture at the 13th International Conference on Composite Materials, Beijing. Particular emphasis is placed on the application of fracture mechanics methods in the analysis of delamination. The question of the extent of fracture mechanics’ success in characterizing delamination, both in laboratory-based specimens and in more realistic structural composite components, is discussed. Some recent numerical formulations for efficient computational modeling and analysis of delaminations are also reviewed. This review lists 270 major works covering a period of about a decade, indicating that there is still considerable research interest and activity in this field.
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Wang, Xu, Yan Li He e Jing Yi Wang. "A Delamination Factor Prediction Model for Drilling of Composite Materials". Advanced Materials Research 601 (dezembro de 2012): 41–45. http://dx.doi.org/10.4028/www.scientific.net/amr.601.41.
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In this paper，according to the shell theory , model are developed to predict delamination damage in the drilling process. Finally, we will get theoretical delamination factor and complete the prediction of the delamination damage area. The known references didn’t find similar model of predicting delamination damage. Therefore, it is new method. With the drilling process experimental contrast，the model is more effective for the prediction of delamination of the carbon fiber composite materials.
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Patel, Kamal S., e G. D. Ramtekkar. "Analysis of interlaminar stress concentration in laminated structure - A review". IOP Conference Series: Earth and Environmental Science 982, n.º 1 (1 de março de 2022): 012080. http://dx.doi.org/10.1088/1755-1315/982/1/012080.
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Abstract Composite materials are popular in the specialised construction industry, whether aviation or car industry or civil structures. Laminated composite is one of the prevalent forms. Analysis and design of laminated composite is the focus of the study. To obtain a better design of the laminated composite, understanding its behaviour properly is very important. Delamination is the critical phenomenon in the laminated composite plates and shell, which causes the failure. Delamination studies can be categorised into two parts: the onset of delamination and the second is the failure progression. Interlaminar stresses are the cause of the onset and progression of delamination in the laminated composites. Therefore, determining interlaminar stress is essential to predict the onset and failure progression due to delamination accurately. This paper reviews the historical attempts of study the delamination. This work is divided into the theoretical assumption, failure model and then numerical studies. In the numerical studies section finite difference method, 2D finite element method, and 3D finite element method have been discussed. Some other methods of analysis and important achievements have also been discussed.
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Makeev, A., e E. Armanios. "A Geometrically Nonlinear Model for Laminated Composite Strips With Extension-Twist Coupling in the Presence of Delamination". Journal of Applied Mechanics 65, n.º 3 (1 de setembro de 1998): 685–93. http://dx.doi.org/10.1115/1.2789112.
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A geometrically nonlinear analysis for the extension-twist coupling in pretwisted laminated composite strips in the presence of delamination is developed. Closed-form solutions for strips with internal and edge delaminations are obtained. A parametric study is performed to investigate the influence of delamination length, material system, and stacking sequence on the extension-twist coupling in a class of hygrothermally stable laminates. The model predictions are in good agreement with test data. The results indicate that internal delamination has a negligible influence on the extension-twist coupling behavior while free-edge delamination could result in a significant drop in coupling.
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Bijjam, Ramgopal Reddy, Srinivas Chandanam, Govind Nandipati e Sneha H. Dhoria. "Optimization of Machining Parameters in Drilling of Glass/Hemp/Bamboo Fibres Based Hybrid Polymer Composites". Annales de Chimie - Science des Matériaux 46, n.º 3 (30 de junho de 2022): 127–33. http://dx.doi.org/10.18280/acsm.460303.
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Significance of composite materials is increasing enormously in the progress of modern science and technology. The composites can be transformed into suitable components with high precision by machining, which can be used for present day applications. Drilling is crucial operation that is often used in the assembly of composite parts to obtain finished product. But the drilling induced damage may affect the performance of the composite. The present work is focused on the impact of various parameters in drilling like feed rate, spindle speed and drill diameter on surface roughness and delamination of glass/hemp/bamboo fibers embedded polymer hybrid composites. The composite is prepared by hand layup method. The drilling on composite is done on a CNC drilling machine and the maximum diameter due to delamination is measured using profile projector. To optimize drilling parameters for the sake of reducing the surface roughness and delamination factor, Taguchi method applied. The measured results are analyzed using commercially available software package Minitab19. The analysis is carried out using ANOVA (Analysis of Variance). In order to obtain best optimal conditions GRA (Grey Relational Analysis) is adopted. The results show that among all important parameters, feed rate and drill diameter are more crucial for surface roughness, whereas delamination is impacted by feed rate and speed of spindle.
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Motamedi, Damoon, Mahdi Takaffoli e Abbas S. Milani. "Nonlinear XFEM Modeling of Mode II Delamination in PPS/Glass Unidirectional Composites with Uncertain Fracture Properties". Materials 13, n.º 16 (12 de agosto de 2020): 3548. http://dx.doi.org/10.3390/ma13163548.
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Initiation and propagation of cracks in composite materials can severely affect their global mechanical properties. Due to the lower strength of the interlaminar bonding compared to fibers and the matrix, delamination between plies is known to be one of the most common failure modes in these materials. It is therefore deemed necessary to gain more insight into this type of failure to guide the design of composite structures towards ensuring their robustness and reliability during service. In this work, delamination of interlaminar bonding in composite end-notched flexure (ENF) samples was modeled using a newly developed stochastic 3D extended finite element method (XFEM). The proposed numerical scheme, which also incorporates the cohesive zone model, was used to characterize the mode II delamination results obtained from ENF testing on polyphenylene sulfide (PPS)/glass unidirectional (UD) composites. The nonrepeatable material responses, often seen during fracture testing of UD composites, were well captured with the current numerical model, demonstrating its capacity to predict the stochastic fracture properties of composites under mode II loading conditions.
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Balaji, N. S., S. Jayabal, S. Kalyana Sundaram, S. Rajamuneeswaran e P. Suresh. "Delamination Analysis in Drilling of Coir-Polyester Composites Using Design of Experiments". Advanced Materials Research 984-985 (julho de 2014): 185–93. http://dx.doi.org/10.4028/www.scientific.net/amr.984-985.185.
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Drilling of fiber reinforced composite materials presents a plethora of questions to the engineers and scientists. A number of research endeavors have been made in the recent years to fully characterize the drilling process of fiber reinforced composite materials. The efforts have been made in the direction of optimization of the operating variables and conditions for minimizing the drilling induced damages. This paper presented the delamination analysis of drilled holes in coir fiber-reinforced polyester composites. The results indicated that the delamination factor in coir fiber-reinforced composites is lower comparing with glass fiber reinforced composites.
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Balasubramanian, M., e S. Madhu. "Evaluation of delamination damage in carbon epoxy composites under swirling abrasives made by modified internal threaded nozzle". Journal of Composite Materials 53, n.º 6 (8 de agosto de 2018): 819–33. http://dx.doi.org/10.1177/0021998318791340.
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Carbon fibre-reinforced polymer composites are finding increased applications in the field of automotive manufacture and aircraft industries due to their appreciative combination of high strength and low weight. The machining of these composites with economically viable and high part qualities requires enhancement in machining strategies. Delamination and surface roughness are the undesirable geometrical defects inherent in abrasive jet machining of layered polymer composites. This investigation focuses on the mechanism of delamination and surface roughness in abrasive jet machining of carbon fibre-reinforced polymer composite. The paper endeavors at the exploration of the viability of imparting swirling motion to SiC abrasive particles by presenting internal threads in the newly designed nozzle. In this research, a novel threaded nozzle was introduced in the abrasive jet machine for making holes on the carbon fiber-reinforced polymer composites with the objective of reducing the delamination and surface roughness. This is a distinctive attempt of its kind and this has brought down the delamination factor considerably and, as a consequence, surface roughness obtained was minimum. Holes were made on carbon fiber-reinforced polymer composite by abrasive jet machining with a modified nozzle with and without an internal thread. The influence of abrasive jet parameters on the delamination factor (bottom and top) and surface roughness (Ra) was investigated. Maximum pressure and minimum SOD cause decrease in delamination and surface roughness in carbon fiber-reinforced polymer composite composites.
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NAGASHIMA, TOSHIO, e HIROSHI SUEMASU. "STRESS ANALYSES OF COMPOSITE LAMINATE WITH DELAMINATION USING X-FEM". International Journal of Computational Methods 03, n.º 04 (dezembro de 2006): 521–43. http://dx.doi.org/10.1142/s0219876206001181.
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The extended finite element method (X-FEM) is applied to the stress analysis of composite laminates having interlaminar planar delamination. In X-FEM analysis, the geometry of such delaminations can be modeled independent of the finite elements. The domain form of the contour integral can be used to compute the energy release rate in conjunction with X-FEM. As numerical examples, three-dimensional analyses for DCB and ENF test specimens were performed by X-FEM with various enrichment nodes, and the obtained results were examined. In addition, a model of the no-friction-contact condition by X-FEM was proposed and applied to ENF test analysis. Moreover, eigenvalue buckling analyses of a CFRP plate with delamination were performed by X-FEM as a practical example related to Compression After Impact (CAI) problems of composite materials. The numerical results show that X-FEM is an effective method for analyzing stress in composite laminates with delamination.
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Sun, Shi Yong, Zi Bin Yan e Rui Yang. "Numerical Study on the Delamination Onset in Drilling Composite Materials". Advanced Materials Research 472-475 (fevereiro de 2012): 2256–59. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.2256.
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The theoretical analysis and numerical study focused on the delamination onset of composites in drilling are presented. An analytical model considering the form of loads distribution is built. The formulas based on the fracture mechanics theory are given for predicting the critical drilling force of delamination onset. A finite element model is used to simulate the process of interfacial crack growth between layers. The interface elements are employed to account for delamination based on cohesive zone model. Some numerical results are given for verifying the validity of the distribution loading model and discussing the delamination onset and growth in drilling composites.
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Sellitto, Andrea, R. Borrelli, Francesco Caputo, Aniello Riccio e Francesco Scaramuzzino. "Application of the Mesh Superposition Technique to the Study of Delaminations in Composites Thin Plates". Key Engineering Materials 525-526 (novembro de 2012): 533–36. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.533.
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Laminated composite structures are increasingly finding more applications in various fields thanks to their lower weight if compared with other materials of the same strength. Nevertheless, composites thin plates show a critical behavior in terms of damage propagation mechanisms when subjected to (low velocity) impact. Indeed they tend to produce delaminations which can be hardly detected by optical inspections and can affect the global load carrying capability, leading to a premature structural collapse. The aim of this paper is to assess the capabilities of the Davies-Zhang approach (introduced in 1994 and aimed to the estimation of both the delamination initiation impact load and the size of the impact induced delaminations) by using a multiscale FE model based on the mesh superposition technique. Indeed the impact area has been modeled layer-wise with an element per layer while the rest of the structure has been modeled at laminate level by layered elements by means of a homogenization approach for the determination of the equivalent laminate material properties. The impact induced delamination area has been determined by adopting stress-based criteria. The results (in terms of delamination initiation impact force and delamination size) have been compared to the ones obtained by adopting the Davies-Zhang approach.
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Lee, C. M., K. S. Jeon, B. G. Jung, Y. M. Lee e M. W. Kang. "Prediction and measurement of acoustic transmission loss of acoustic window with composite sandwich structure". Noise Control Engineering Journal 69, n.º 5 (1 de setembro de 2021): 422–30. http://dx.doi.org/10.3397/1/376939.
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Underwater acoustic detection sensors are mounted on the outside of the submarine; the acoustic window for protecting these sensors must be structurally robust while also minimizing any deterioration of sensor's sound detection performance. These two conditions are typically satisfied simultaneously by using composite materials with acoustic window materials. However, since such composite material is manufactured by laminating fibers, there is the probability that delamination occurs, in which an air layer is formed inside, due to manufacturing process errors. Delamination inside the acoustic window degrades the sensor's acoustic performance and results in a failure of military operations. In the case of composites composed of sandwich structures located in the central part, the possibility of internal delamination is higher than in a single composite material. Therefore, it is very important to discriminate the presence or absence of internal delamination after producing an acoustic window. This article uses numerical and analytical methods to determine the internal delamination of the acoustic window fabricated with a sandwich structure. In addition, the results were analyzed and compared through ultrasonic measurement and acoustic transmission loss test.
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Liu, Peng-fei, Jun Yang e Xiong-qi Peng. "Delamination analysis of carbon fiber composites under hygrothermal environment using acoustic emission". Journal of Composite Materials 51, n.º 11 (10 de agosto de 2016): 1557–71. http://dx.doi.org/10.1177/0021998316661043.
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Non-destructive test technique for monitoring delamination failure under complex load and environments is still not mature until now. The purpose of this paper is to study mixed-mode delamination failure properties of carbon fiber/epoxy composite laminates under hygrothermal environment using acoustic emission. Different water-saturated composite specimens with initial intralaminar and interlaminar defects are tested. Two loading modes including single-leg and over-leg three-point bending are applied under hygrothermal environment. By analyzing the responses of acoustic emission parameters including amplitude and energy, the effects of the hygrothermal environment, layup pattern and initial defect on the delamination behaviors of composite specimens are studied. Besides, different failure modes are observed through scanning electron microscope. Quantitative acoustic emission results show hygrothermal environment and load mode affect the delamination properties of composites remarkably.
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Rahme, P., Y. Landon, F. Lachaud, R. Piquet e P. Lagarrigue. "Delamination-free drilling of thick composite materials". Composites Part A: Applied Science and Manufacturing 72 (maio de 2015): 148–59. http://dx.doi.org/10.1016/j.compositesa.2015.02.008.
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Thouless, M. D., H. C. Cao e P. A. Mataga. "Delamination from surface cracks in composite materials". Journal of Materials Science 24, n.º 4 (abril de 1989): 1406–12. http://dx.doi.org/10.1007/bf02397080.
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Thouless, M. D., H. C. Cao e P. A. Mataga. "Delamination from surface cracks in composite materials". Journal of Materials Science 24, n.º 4 (abril de 1989): 1406–12. http://dx.doi.org/10.1007/pl00020229.
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Song, Yuan Jia, Wei Zhang, Dong Dong Wang e Guo Feng Jin. "Research of Detectivity for Ultrasonic Infrared Thermography NDT in Composite Materials". Applied Mechanics and Materials 148-149 (dezembro de 2011): 914–18. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.914.
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In this paper, the ultrasonic infrared thermography (UIT) technique was applied to detect the composites damage. The frictional heating and thermal conductivity at the location of crack of the composites under ultrasonic excitation was simulated by finite element method (FEM). The excitation parameters including time, amplitude and frequency were studied. The composite involving delamination was detected by the ultrasonic generator. The results show that the UIT can identify the contacting interface-type damages at the surface or subsurface of composites rapidly, for example, delamination, fatigue crack et al.The excitation time, amplitude and frequency are impotent detection parameters. It can be seen accurately and intuitively of location of the damage, and there is no uniform heating problems from the experiment. Suitable coupling material can improve testing quality and eliminate “standing wave” effectively.
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Papanaboina, Mastan Raja, Elena Jasiuniene, Vykintas Samaitis, Liudas Mažeika e Paulius Griškevičius. "Delamination Localization in Multilayered CFRP Panel Based on Reconstruction of Guided Wave Modes". Applied Sciences 13, n.º 17 (27 de agosto de 2023): 9687. http://dx.doi.org/10.3390/app13179687.
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Multi-layered composite materials are being used in various engineering fields, such as aerospace, automobile, and wind energy, because of their superior material properties. Due to various impact loads during the service life of composite structures, different types of defects can occur, such as matrix cracking, fiber breakage, delaminations, etc. In this research, a novel SHM technique for delamination detection and localization using a minimum number of sensors is proposed. The analytical, numerical, and experimental analysis of GW was performed to increase the probability of detection and localization of delaminations in CFRP material. A new analytical model was developed, which enables identifying converted and transmitted modes in the presence of multiple GW modes. A 2D FFT-based spatial filtering was used to filter the GW modes. The dominant A0 mode was separated to inspect the delamination. Phase velocity is one of the important features in GW inspection to localize the delamination. A phase spectrum approach was developed to reconstruct the phase velocity dispersion of the GW modes in case material properties are unknown.
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Prakash, M., e PVS Dileep Aditya Dhar. "Investigation on the effect of drilling parameters on the tool wear and delamination of glass fibre-reinforced polymer composite using vibration signal analysis". Journal of Composite Materials 52, n.º 12 (29 de agosto de 2017): 1641–48. http://dx.doi.org/10.1177/0021998317728109.
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Glass fibre-reinforced polymer composite materials are widely used in industrial, aerospace and automotive sector. It has excellent properties such as high strength to weight ratio, higher fatigue limit, high stiffness to weight ratio, corrosion resistance and design flexibility. The strength of the composite highly depends upon orientation of the fibre material. Drilling is one of the major machining operations that are carried out on Glass fibre-reinforced polymer composite materials to the need for components assembly. There are many problems encountered while drilling glass fibre-reinforced polymer composites. The major problems are excessive tool wear and delamination of the composite during drilling, which reduce the strength of the composite during application. In the present study, the experimental investigations are carried out to analyse the effect of various machining parameters, i.e. cutting speed and feed rate on the tool wear and delamination. The time and frequency domain analysis of vibration signals measured using sound sensor is also used to predict the effect of machining parameters on delamination as well as to develop the tool replacement strategy.
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Ho-Cheng, H., e C. K. H. Dharan. "Delamination During Drilling in Composite Laminates". Journal of Engineering for Industry 112, n.º 3 (1 de agosto de 1990): 236–39. http://dx.doi.org/10.1115/1.2899580.
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Delamination is the major concern during drilling of composite laminates. Delamination, in addition to reducing the structural integrity of the laminate, also results in poor assembly tolerance and has the potential for long-term performance deterioration. Drilling-induced delamination occurs both at the entrance and at the exit planes. This paper presents an analysis of delamination during drilling. The analysis uses a fracture mechanics approach in which the opening-mode delamination fracture toughness, a material parameter, is used with a plate model of the laminate. The analysis predicts an optimal thrust force (defined as the minimum force above which delamination is initiated) as a function of drilled hole depth. Good agreement is achieved with data obtained from drilling carbon fiber-epoxy laminates. An advantage of the model is that it can predict varying degrees of delamination for other materials, such as glass fiber-epoxy, and for hybrid composites. In addition, the optimal thrust force for no delamination can be used to control a drilling machine with thrust force feedback for maximizing productivity.
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Wu, Cui Qin, Wei Ping Wang, Qi Gang Yuan, Yan Jun Li, Wei Zhang e Xiang Dong Zhang. "Infrared Thermography Non-Destructive Testing of Composite Materials". Advanced Materials Research 291-294 (julho de 2011): 1307–10. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1307.
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To detect the delamination, disbond，inclusion defects of the glass fiber composite materials applied in the solid rocket motor, active infrared thermographic non-destructive testing(NDT) is researched. The samples including known defects are heated by pulsed high energy flash lamp. The surface temperature of the samples is monitored by infrared thermography camera. The results of the experiments show that the active infrared thermography technique is a fast and effective inspection method for detecting the defects of delamination, disbond，inclusion of the composites. The samples are also detected by underwater ultrasonic c-scans. The paper concludes that the active infrared thermography NDT is more suitable to rapidly detect the defect in large-area and the underwater ultrasonic c-scans is more suitable to quantitatively identify the defect in local-area.
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Tsao, Chung Chen, Kei Lin Kuo, I. Chien Hsu e G. T. Chern. "Analysis of Core-Candlestick Drill in Drilling Composite Materials". Key Engineering Materials 419-420 (outubro de 2009): 337–40. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.337.
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Unlike ductile metals cutting mechanism, the interfaces between fiber and matrix as a transitional layer experience mismatched deformation in machining process. In general, the most frequent operation performed on composite materials is drilling with a twist drill to generate a hole owing to their versatility and low production cost. However, delamination is one of the most common defects in drilling laminated fiber-reinforced composites and can cause a significant reduction in the load-carrying capacity of a structure. At the periphery, using such special drills as saw drill, candlestick drill and core drill, reducible to causing delamination damage than the twist drill. Experimental results indicated that the diameter ratio and feed rate have statistical and physical significance on the thrust force obtained with a core-candlestick drill.
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Shen, Yiou, Jiayi Tan, Luis Fernandes, Zehua Qu e Yan Li. "Dynamic Mechanical Analysis on Delaminated Flax Fiber Reinforced Composites". Materials 12, n.º 16 (11 de agosto de 2019): 2559. http://dx.doi.org/10.3390/ma12162559.
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It is well-known that the presence of the delamination in a plant fiber-reinforced composite is difficult to detect. However, the delamination introduces a local flexibility, which changes the dynamic characteristics of the composite structure. This paper presents a new methodology for composite laminate delamination detection, which is based on dynamic mechanical analysis. A noticeable delamination-induced storage modulus reduction and loss factor enhancement have been observed when the delaminated laminate was subjected to a forced oscillation compared to the intact composite laminate. For delamination area of 12.8% of the whole area of the composite laminate, loss factor of approximately 12% increase was observed. For near-to-surface delamination position, loss factor of approximately an 18% increment was observed. The results indicate that the delamination can be reliably detected with this method, and delamination position shows greater influence on the loss factor than that of the delamination size. Further investigations on different frequencies and amplitudes configurations show that the variation of loss factor is more apparently with low frequency as well as the low amplitude.
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Riccio, Aniello, Angela Russo, Andrea Sellitto, Cinzia Toscano, Davide Alfano e Mauro Zarrelli. "Experimental and Numerical Assessment of Fibre Bridging Toughening Effects on the Compressive Behaviour of Delaminated Composite Plates". Polymers 12, n.º 3 (3 de março de 2020): 554. http://dx.doi.org/10.3390/polym12030554.
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Increasing the Mode I inter-laminar fracture toughness of composite laminates can contribute to slowing down delamination growth phenomena, which can be considered one of the most critical damage mechanisms in composite structures. Actually, the Mode I interlaminar fracture toughness (GIc) in fibre-reinforced composite materials has been found to considerably increase with the crack length when the fibre bridging phenomenon takes place. Hence, in this paper, the fibre bridging phenomenon has been considered as a natural toughening mechanism able to replace embedded metallic or composite reinforcements, currently used to increase tolerance to inter-laminar damage. An experimental/numerical study on the influence of delamination growth on the compressive behaviour of fibre-reinforced composites characterised by high sensitivity to the fibre bridging phenomenon has been performed. Coupons, made of material systems characterised by a variable toughness related to a high sensitivity to the fibre bridging phenomenon and containing artificial through-the-width delaminations, were subjected to a compressive mechanical test and compared to coupons made of standard material system with constant toughness. Out-of-plane displacements and strains were monitored during the compression test by means of strain gauges and digital image correlation to assess the influence of fibre bridging on delamination buckling, delamination growth and on the global buckling of the specimens, including buckling shape changes. Experimental data were combined with a numerical study, performed by means of a virtual crack closure technique based procedure, named SMart Time XB – Fibre Bridging (SMXB-FB), able to mimic the crack bridging effect on the toughness properties of the material system. The combination of numerical results and experimental data has allowed the deformations and the buckling shape changes to be correlated to the onset and evolution of damage and, hence, contributes to improving the knowledge on the interaction of the failure mechanisms in the investigated composite specimens.
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Nagarajan, VA, S. Sundaram, K. Thyagarajan, J. Selwin Rajadurai e TPD Rajan. "Refined delamination characterization for composite laminates using digital means". Journal of Composite Materials 46, n.º 13 (6 de outubro de 2011): 1535–47. http://dx.doi.org/10.1177/0021998311421042.
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Drilling is most widely applied to composite materials; nevertheless, the damage induced by this operation on composite materials may reduce drastically the component performance. In order to establish the damage level, delamination is measured quantitatively using digital means. A comparison between the conventional ( FD) and adjusted ( FDA) delamination factor is presented. In order to quantify the delamination effectively, ‘a refined delamination factor ( FDR)’ is proposed. The accuracy of the proposed criteria is validated using experimental results.
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Teng, Hsing Ming, Ming Chang Wu, Jin Yi Kao, Chun Yao Hsu e Chung Chen Tsao. "The Effect of Thrust Force in Drilling Composite Materials Using a New Step Core-Ball Drill". Key Engineering Materials 830 (fevereiro de 2020): 77–84. http://dx.doi.org/10.4028/www.scientific.net/kem.830.77.
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Compared with conventional metal materials, composite materials can sustain more loads under lower weight and lower space, which is more suitable to use in high strength environment for structure parts application in aerospace, military, transportation and leisure. The enormous aeronautical components and structures of composite materials require assembly and machining. Drilling is the most important making-hole process in the final assembly. However, conventional drill cannot avoid delamination in drilling composite materials effectively depending on tool geometry only. Delamination caused by drilling thrust has been showed as one of the most problematic defects after drilling composite laminates. Drilling of composite plates using a new step core-ball drill (NSCBD), which is a special drill to improve the chip flow and reduces the thrust force (delamination) at the exit of hole, is studied and compared to the traditional step core-ball drill (TSCBD). The thrust force of new step core-ball drill in drilling composite materials was investigated in this study. The theoretical analysis and experimental results show that the NSCBD can improve the thrust force (delamination) and efficiency than TSCBD in drilling composite materials.
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Pang, Yan Rong, Ya Juan Li, Ran Liu, Shuai Qi, Ru Yue Liu e Wei Zhou. "Effect of Porosity on Mechanical Property and Acoustic Emission Signals of Composite Materials". Advanced Materials Research 912-914 (abril de 2014): 115–18. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.115.
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In order to achieve the effect of porosity on the mechanical property and acoustic emission (AE) signals of composite materials with mode I delamination, unidirectional tensile tests and real-time AE monitoring of high property and low property composites were conducted. The results show that the porosity of composite materials made a detrimental effect on the mechanical properties. As the load increases to an inflection point, the slope of the curve becomes smaller. And the slope of the high porosity specimen is lower than that of the other one. With the increase of the porosity of composite material, the failure load and tensile strength decrease. AE monitoring data show that different porosity materials lead to different evolution process of the delamination. And the corresponding AE amplitude distribution, relative energy signals are also different. Different from high porosity composites, low porosity composites generated unstable expansion at the inflection point of the load curve in the stretching process. And the highest amplitude and relative energy were obtained at the inflection point.
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Marino, Salvatore Giacomo, Florian Mayer, Alexander Bismarck e Gergely Czél. "Effect of Plasma-Treatment of Interleaved Thermoplastic Films on Delamination in Interlayer Fibre Hybrid Composite Laminates". Polymers 12, n.º 12 (28 de novembro de 2020): 2834. http://dx.doi.org/10.3390/polym12122834.
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Safe, light, and high-performance engineering structures may be generated by adopting composite materials with stable damage process (i.e., without catastrophic delamination). Interlayer hybrid composites may fail stably by suppressing catastrophic interlayer delamination. This paper provides a detailed analysis of delamination occurring in poly(acrylonitrile-butadiene-styrene) (ABS) or polystyrene (PS) film interleaved carbon-glass/epoxy hybrid composites. The ABS films toughened the interfaces of the hybrid laminates, generating materials with higher mode II interlaminar fracture toughness (GIIC), delamination stress (σdel), and eliminating the stress drops observed in the reference baseline material, i.e., without interleaf films, during tensile tests. Furthermore, stable behaviour was achieved by treating the ABS films in oxygen plasma. The mechanical performance (GIIC and σdel) of hybrid composites containing PS films, were initially reduced but increased after oxygen plasma treatment. The plasma treatment introduced O-C=O and O-C-O-O functional groups on the PS surfaces, enabling better epoxy/PS interactions. Microscopy analysis provided evidence of the toughening mechanisms, i.e., crack deflection, leading plasma-treated PS to stabilise delamination.
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Nanda, Namita. "Spectral finite element method for wave propagation analysis in smart composite beams containing delamination". Aircraft Engineering and Aerospace Technology 92, n.º 3 (29 de janeiro de 2020): 440–51. http://dx.doi.org/10.1108/aeat-02-2019-0026.
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Purpose The purpose of the study is to present a frequency domain spectral finite element model (SFEM) based on fast Fourier transform (FFT) for wave propagation analysis of smart laminated composite beams with embedded delamination. For generating and sensing high-frequency elastic waves in composite beams, piezoelectric materials such as lead zirconate titanate (PZT) are used because they can act as both actuators and sensors. The present model is used to investigate the effects of parametric variation of delamination configuration on the propagation of fundamental anti-symmetric wave mode in piezoelectric composite beams. Design/methodology/approach The spectral element is derived from the exact solution of the governing equation of motion in frequency domain, obtained through fast Fourier transformation of the time domain equation. The beam is divided into two sublaminates (delamination region) and two base laminates (integral regions). The delamination region is modeled by assuming constant and continuous cross-sectional rotation at the interfaces between the base laminate and sublaminates. The governing differential equation of motion for delaminated composite beam with piezoelectric lamina is obtained using Hamilton’s principle by introducing an electrical potential function. Findings A detailed study of the wave response at the sensor shows that the A0 mode can be used for delamination detection in a wide region and is more suitable for detecting small delamination. It is observed that the amplitude and time of arrival of the reflected A0 wave from a delamination are strongly dependent on the size, position of the delamination and the stacking sequence. The degraded material properties because of the loss of stiffness and density in damaged area differently alter the S0 and A0 wave response and the group speed. The present method provides a potential technique for researchers to accurately model delaminations in piezoelectric composite beam structures. The delamination position can be identified if the time of flight of a reflected wave from delamination and the wave propagation speed of A0 (or S0) mode is known. Originality/value Spectral finite element modeling of delaminated composite beams with piezoelectric layers has not been reported in the literature yet. The spectral element developed is validated by comparing the present results with those available in the literature. The spectral element developed is then used to investigate the wave propagation characteristics and interaction with delamination in the piezoelectric composite beam.
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Nayak, Bijaya Bijeta, Souranil Kundu, Sasmita Sahu, Sudesna Roy e Shiv Sankar Das. "Support Vector Regression approach for prediction of delamination at entry and exit during drilling of GFRP Composites". E3S Web of Conferences 391 (2023): 01162. http://dx.doi.org/10.1051/e3sconf/202339101162.
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The demand for Composites in the modern era have increased immensely due to its vast applications and superior properties over conventional materials. Glass Fibre Reinforced Plastic (GFRP) is one of the economic alternative to conventional engineering materials due to its high specific modulus of elasticity, high specific strength, good corrosion resistance, high fatigue strength and lightweight. Components made out from GFRP composites are usually near net shaped and require holes for assembly integration. Drilling is an important process as concentrated forces can cause major damage to the composite. Drilling of GFRP causes various damage such as thermal degradation, fibre breakage, matrix cracking and delamination. A substantial damage is caused by delamination which can occur both on the entry and exit sides of the composite, exit side delamination considered more severe. Therefore, selection of proper process parameters during drilling operation is very much essential. In the present work, a support vector regression (SVR) model is developed to predict the delamination at entry and exit during the drilling of GFRP composites. The model is developed based on the data obtained from experimentation. The model accuracy is evaluated by the three performance criteria including root mean square error (RMSE), Nash–Sutcliffe efficiency co-efficient (E) and co-efficient of determination (R2). The model provides an inexpensive and time saving alternative to study the delamination at entry and exit of the GFRP composite actual drilling operation.