Journal articles: 'Delamination mechanism'

1

Hosseini-Toudeshky, Hossein, M. Saeed Goodarzi, and Bijan Mohammadi. "Multiple Delaminations Growth in Composite Laminates under Compressive Cyclic Loading in Post-Buckling." Applied Mechanics and Materials 225 (November 2012): 195–200. http://dx.doi.org/10.4028/www.scientific.net/amm.225.195.

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Due to discontinuity of mechanical properties in composite laminates, failure occurs in different damage mechanisms. Delamination growth of adjacent layers is a major failure mechanism in laminates with various layup configurations. Pre existing delamination may initiate in composite laminate before use, due to impact in assembly and fabrication process. Cyclic compressive loading may cause delamination growth due to both post-bucking behavior and fatigue nature of loading. In this paper, a 3D mixed-mode interface element model has been developed to simulate the growth of multiple delaminations under compressive cyclic loading. For this purpose, the presented model should be able to handle the geometry nonlinearity of post-buckling and material nonlinearity of cohesive zone constitutive law under cyclic loading at interfaces. Because of mixed-mode condition of stress field at the delamination-front of post-buckled laminates, a mixed-mode bilinear constitutive law has been used as user material in this model. Paris Law has been used to relate the energy release rate to the fatigue crack growth in cohesive zone. A composite laminate with pre-existing delamination under buckling load, available from the literature has been reproduced with the present approach. Finally, laminates containing multiple delaminations in various interface layers have been analyzed under compressive fatigue loading. It is shown that the pre-existing delamination with more depth from the surface of laminate causes more initial static and fatigue delamination growth rate.

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Dong, Hui Ru, Wanlin Guo, and Zheng Yang. "Mechanism of Delamination and Its Effects on Fracture of Surface Crack Bodies in Ductile Pipeline Steel." Key Engineering Materials 297-300 (November 2005): 1235–40. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.1235.

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The effects of three-dimensional crack configurations and delaminations on fracture mechanism and fracture toughness Jc of pipeline steel were investigated experimentally by use of tensile specimens having surface cracks of different depth to length ratio. Comparison with test results of through-thickness cracks and mechanism analyses are made as well. When 3D stress constraint is larger than the strength in the thickness direction the delamination forms. As no delamination occurs in the interior of a surface crack, the constraint is higher and the fracture toughness is lower than that of the through-thickness cracks. Therefore, the nominal fracture toughness obtained from through-thickness cracked specimens is not a real material constancy, and not suitable for safety assessment of pipelines.

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Brenneman, Jacob, Derya Z. Tansel, Gary K. Fedder, and Rahul Panat. "Interfacial delamination and delamination mechanism maps for 3D printed flexible electrical interconnects." Extreme Mechanics Letters 43 (February 2021): 101199. http://dx.doi.org/10.1016/j.eml.2021.101199.

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Wei, Z., L. H. Yam, and L. Cheng. "Delamination Assessment of Multilayer Composite Plates Using Model-based Neural Networks." Journal of Vibration and Control 11, no. 5 (May 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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Jeevan Kumar, N. "Analysis of Mode-I crack growth arresting mechanism in curved laminated joint." International Journal of Computational Materials Science and Engineering 08, no. 01 (March 2019): 1950001. http://dx.doi.org/10.1142/s2047684119500015.

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The critical damage for carbon fiber structures, which are being employed in aircraft structures, is known as delamination/crack. Fasteners are commonly installed to arrest the delamination by clamping the laminate together. Fasteners are installed in each corner of the delaminated zone to provide significant arrest capability, shifting the failure mode away from delamination under most conditions. The Finite Element Analysis (FEA) model is constructed to study the effectiveness of the fastener as crack arrest mechanism. The FEA results show that the fastener provides significant crack retardation capability in Mode-I condition. An analytical model is developed for the delamination embedded between the skin and stiffener interface of the joint. The fasteners are modeled with spring elements. The analysis is solved with Virtual Crack Closure Technique (VCCT) approach. The primary objective of the current research work is to enhance the safety of bonded joint by providing arrest mechanisms.

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Riccio, Aniello, Angela Russo, Andrea Sellitto, Cinzia Toscano, Davide Alfano, and Mauro Zarrelli. "Experimental and Numerical Assessment of Fibre Bridging Toughening Effects on the Compressive Behaviour of Delaminated Composite Plates." Polymers 12, no. 3 (March 3, 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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Djamaluddin, Rudy, Hijriah, Rita Irmawati, Faharuddin, and Rossy T. Wahyuningsih. "Delamination mechanism of GFRP sheet bonded on the reinforced concrete beams." MATEC Web of Conferences 258 (2019): 03009. http://dx.doi.org/10.1051/matecconf/201925803009.

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Fiber reinforced polymer (FRP) has been developed to be applied for a strengthening of the deteriorated structures. In the form of a sheet, the FRP may be applied for the strengthening of the structures by bonding it to the concrete surface. Glass composed FRP (GFRP) sheet is most commonly used due to its relatively lower cost compared to the other FRP materials. GFRP sheet is applied externally by bonding it on the concrete surface. The strengthened structures should be monitored periodically to ensure the health of the strengthened structures. Regarding the development of monitoring system of the strengthened structure, it is important to study the delamination phenomenon of the bonded GFRP. Therefore the delamination mechanism is important to be clarified. Many studies have been done to investigate the bonding characteristics of GFRP sheet under direct tensile loading. However, the studies on the bonding characteristics of GFRP sheet on the strengthened beams due to flexural loadings are still limited. A series of concrete beams strengthened with GFRP sheet on extreme tension surface were prepared. The beam specimens ware loaded under four-point bending test gradually up to the ultimate capacity. Results indicated that prior to final delamination, a local delamination occurred which was indicated by the suddenly decreasing of an applied load. The delamination of the GFRP sheet may be initiated by the flexural cracks occurred on the beams.

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Wang, Ligang, and Dan G. Zollinger. "Mechanistic Design Framework for Spalling Distress." Transportation Research Record: Journal of the Transportation Research Board 1730, no. 1 (January 2000): 18–24. http://dx.doi.org/10.3141/1730-03.

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Spalling is a distress form in concrete pavements that often manifests as the breakdown of the joint of a slab within 15 cm (6 in.) of the joint or crack and can occur at both longitudinal and transverse joints. Efforts have been under way at Texas A&M University to formulate mechanistic spalling models derived from data gathered in recent Texas Department of Transportation studies related to spall development. Extensive field studies have led to the establishment of a spalling mechanism consisting of a step-by-step process that can be characterized with engineering mechanics. These findings indicate that spalling is the result of damage initiated in the form of a shear delamination that is oriented parallel to and at a shallow depth below the surface of the pavement. Conditions necessary for formation of the delaminations include low interfacial strength between the aggregate and mortar and sufficient evaporation of pore water from the hydrating concrete, resulting in differential drying shrinkage near the pavement surface. Delaminations have been noted to initiate early in the life of the pavement and, once formed, extend later into spalls as a result of incompressibles, freeze-thaw cycles, traffic loading, and other such effects. A design framework for delamination formation and subsequent spalling development is presented in a practical format in which to mechanistically design concrete pavement systems relative to spalling distress.

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Liu, Chang, and Yaolin Shi. "Initiation of Triangle Zones by Delamination, Shear, and Compaction at the Front of Fold-and-Thrust Belts." Journal of Earthquakes 2016 (March 16, 2016): 1–21. http://dx.doi.org/10.1155/2016/6302546.

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The interest of this paper is to investigate the initiation of triangle zones at the front of fold-and-thrust belts by analyzing the virtual velocity fields in triangle wedges. It allows achieving five collapse mechanisms by delamination, shear, and compaction of competing for the formation of triangle zones as follows. The first mechanism is the classical Coulomb shear thrust. The second is delamination at the frontal part of the décollement with straight back thrust, while the third is delamination with curvy back thrust. The fourth is the combination of ramp with Coulomb shear and shear-enhanced compact fault, while the fifth is the combination of the exchanging motion on the ramp and thrust. The dominating mechanism in the formation of triangle zones relies on the competition of the least upper bound of each mechanism when subjected to tectonic force. The controlling factors of the competition are discovered as follows: (1) the frictional characters and cohesion of horizontal décollements and thrust, (2) the slope of the topography of accretion wedge, and (3) the thickness and rock density of the front toe of accretion wedge.

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10

Wakamoto, Keisuke, Takukazu Otsuka, Ken Nakahara, and Takahiro Namazu. "Degradation Mechanism of Pressure-Assisted Sintered Silver by Thermal Shock Test." Energies 14, no. 17 (September 4, 2021): 5532. http://dx.doi.org/10.3390/en14175532.

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This paper investigates the degradation mechanism of pressure-sintered silver (s-Ag) film for silicon carbide (SiC) chip assembly with a 2-millimeter-thick copper substrate by means of thermal shock test (TST). Two different types of silver paste, nano-sized silver paste (NP) and nano-micron-sized paste (NMP), were used to sinter the silver film at 300 °C under a pressure of 60 MPa. The mean porosity (p) of the NP and MNP s-Ag films was 2.4% and 8%, respectively. The pore shape of the NP s-Ag was almost spherical, whereas the NMP s-Ag had an irregular shape resembling a peanut shell. After performing the TST at temperatures ranging from −40 to 150 °C, the scanning acoustic tomography (SAT) results suggested that delamination occurs from the edge of the assembly, and the delamination of the NMP s-Ag assembly was faster than that of the NM s-Ag assembly. The NMP s-Ag assembly showed a random delamination, indicating that the delamination speed varies from place to place. The difference in fracture mechanism is discussed based on cross-sectional scanning electron microscope (SEM) observation results after TST and plastic strain distribution results estimated by finite element analysis (FEA) considering pore configuration.

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Kantarci, Husniye, Andrea Gerberding, and Bruce B. Riley. "Spemann organizer gene Goosecoid promotes delamination of neuroblasts from the otic vesicle." Proceedings of the National Academy of Sciences 113, no. 44 (October 19, 2016): E6840—E6848. http://dx.doi.org/10.1073/pnas.1609146113.

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Neurons of the Statoacoustic Ganglion (SAG), which innervate the inner ear, originate as neuroblasts in the floor of the otic vesicle and subsequently delaminate and migrate toward the hindbrain before completing differentiation. In all vertebrates, locally expressed Fgf initiates SAG development by inducing expression of Neurogenin1 (Ngn1) in the floor of the otic vesicle. However, not all Ngn1-positive cells undergo delamination, nor has the mechanism controlling SAG delamination been elucidated. Here we report that Goosecoid (Gsc), best known for regulating cellular dynamics in the Spemann organizer, regulates delamination of neuroblasts in the otic vesicle. In zebrafish, Fgf coregulates expression of Gsc and Ngn1 in partially overlapping domains, with delamination occurring primarily in the zone of overlap. Loss of Gsc severely inhibits delamination, whereas overexpression of Gsc greatly increases delamination. Comisexpression of Ngn1 and Gsc induces ectopic delamination of some cells from the medial wall of the otic vesicle but with a low incidence, suggesting the action of a local inhibitor. The medial marker Pax2a is required to restrict the domain of gsc expression, and misexpression of Pax2a is sufficient to block delamination and fully suppress the effects of Gsc. The opposing activities of Gsc and Pax2a correlate with repression or up-regulation, respectively, of E-cadherin (cdh1). These data resolve a genetic mechanism controlling delamination of otic neuroblasts. The data also elucidate a developmental role for Gsc consistent with a general function in promoting epithelial-to-mesenchymal transition (EMT).

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TODOROKI, Akira, Hideo KOBAYASHI, and Kunio ADACHI. "Delamination Mechanism of Multidirectional Reinforced CF/Epoxy Composites." Journal of the Society of Materials Science, Japan 42, no. 474 (1993): 304–10. http://dx.doi.org/10.2472/jsms.42.304.

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13

Quan, Yan Ming, and Lu Hua Sun. "Surface Characteristic and its Mechanism of the Drilled CFRP." Advanced Materials Research 591-593 (November 2012): 333–36. http://dx.doi.org/10.4028/www.scientific.net/amr.591-593.333.

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The drilled surface characteristic of epoxy resin reinforced by multi-directional carbon fibers is investigated based on experiments. With the emphasis on the effect of fiber direction, the mechanism of inhomogeneous surface topography is discussed. Besides, the mechanism of drilling-induced delamination and splitting defects are analyzed, and the drill condition and drilling parameters are also considered. It is indicated that the varied fiber direction is the main cause resulting in the inhomogeneous topography; delamination is easy to occur between two adjacent laminas which have different fiber directions, and it is more serious near the exit of drilled hole.

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Bosco, E., A. S. J. Suiker, and N. A. Fleck. "Crack channelling mechanisms in brittle coating systems under moisture or temperature gradients." International Journal of Fracture 225, no. 1 (June 29, 2020): 1–30. http://dx.doi.org/10.1007/s10704-020-00461-3.

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AbstractCrack channelling is predicted in a brittle coating-substrate system that is subjected to a moisture or temperature gradient in the thickness direction. Competing failure scenarios are identified, and are distinguished by the degree to which the coating-substrate interface delaminates, and whether this delamination is finite or unlimited in nature. Failure mechanism maps are constructed, and illustrate the sensitivity of the active crack channelling mechanism and associated channelling stress to the ratio of coating toughness to interfacial toughness, to the mismatch in elastic modulus and to the mismatch in coefficient of hygral or thermal expansion. The effect of the ratio of coating to substrate thickness upon the failure mechanism and channelling stress is also explored. Closed-form expressions for the steady-state delamination stress are derived, and are used to determine the transition value of moisture state that leads to unlimited delamination. Although the results are applicable to coating-substrate systems in a wide range of applications, the study focusses on the prediction of cracking in historical paintings due to indoor climate fluctuations, with the objective of helping museums developing strategies for the preservation of art objects. For this specific application, crack channelling with delamination needs to be avoided under all circumstances, as it may induce flaking of paint material. In historical paintings, the substrate thickness is typically more than ten times larger than the thickness of the paint layer; for such a system, the failure maps constructed from the numerical simulations indicate that paint delamination is absent if the delamination toughness is larger than approximately half of the mode I toughness of the paint layer. Further, the transition between crack channelling with and without delamination appears to be relatively insensitive to the mismatch in the elastic modulus of the substrate and paint layer. The failure maps developed in this work may provide a useful tool for museum conservators to identify the allowable indoor humidity and temperature fluctuations for which crack channelling with delamination is prevented in historical paintings.

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Hu, K. X., C. P. Yeh, X. S. Wu, and K. Wyatt. "An Interfacial Delamination Analysis for Multichip Module Thin Film Interconnects." Journal of Electronic Packaging 118, no. 4 (December 1, 1996): 206–13. http://dx.doi.org/10.1115/1.2792154.

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Analysis of interfacial delamination for multichip module thin-film interconnects (MCM/TFI) is the primary objective of this paper. An interface crack model is integrated with finite-element analysis to allow for accurate numerical evaluation of the magnitude and phase angle of the complex stress intensity factor. Under the assumption of quasi-static delamination growth, the fate of an interfacial delamination after inception of propagation is determined. It is established that whether an interfacial delamination will continue to grow or become arrested depends on the functional behavior of the energy release rate and loading phase angle over the history of delamination growth. This functional behavior is numerically obtained for a typical MCM/TFI structure with delamination along die and via base, subjected to thermal loading condition. The effect of delamination interactions on the structural reliability is also investigated. It is observed that the delamination along via wall and polymer thin film can provide a benevolent mechanism to relieve thermal constraints, leading to via stress relaxation.

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Tay, Andrew A. O. "Modeling of Interfacial Delamination in Plastic IC Packages Under Hygrothermal Loading." Journal of Electronic Packaging 127, no. 3 (July 28, 2004): 268–75. http://dx.doi.org/10.1115/1.1938209.

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Ever since the discovery of the “popcorn” failure of plastic-encapsulated integrated-circuit (IC) packages in the 1980s, much effort has been devoted to understanding the failure mechanism and modeling it. It has been established that such failures are due to the combined effects of thermal stresses and hygrostresses that arise during solder reflow of plastic IC packages. In recent years interfacial fracture mechanics has been applied successfully to the analysis of delamination or crack propagation along interfaces in plastic IC packages. This paper presents some fundamental aspects of interfacial fracture mechanics and describes some of the numerical techniques available for calculating the strain energy release rate and mode mixity at the tips of cracks at interfaces in plastic-encapsulated IC packages. A method of calculating the combined effects of thermal stress and hygrostress on the energy release rate is also described. Some case studies are presented that illustrate how the techniques are applied to predicting delaminaton in IC packages. Some experimental verification of predictive methodology is also presented.

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Liu, Yinghonglin, Jiang Peng, Wei Li, Chang Yang, Ping Sun, and Xiaowei Yan. "Predicting the Delamination Mechanisms of Multidirectional Laminates Using the Energy Release Rate Obtained from AE Monitoring." Materials Evaluation 80, no. 1 (January 1, 2022): 34–47. http://dx.doi.org/10.32548/10.32548/2022.me-04254.

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This study investigates delamination damage mechanisms during the double cantilever beam standard test using the strain energy release rate. The acoustic emission parameter is used to replace the original calculation method of measuring crack length to predict delamination. For this purpose, 24-layer glass/epoxy multidirectional specimens with different layups, and interface orientations of 0°, 30°, 45°, and 60°, were fabricated based on ASTM D5528 (2013). Acoustic emission testing (AE) is used to detect the damage mechanism of composite multidirectional laminates (combined with microscopic real-time observation), and it is verified that the strain energy release rate can be used as a criterion for predicting delamination damage in composite materials. By comparing the AE results with the delamination expansion images observed by microvisualization in real time, it is found that the acoustic emission parameters can predict the damage of laminates earlier. Based on the data inversion of the acoustic emission parameters of the strain energy release rate, it is found that the strain energy release rate of the specimens with different fiber interface orientations is consistent with the original calculated results.

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Liu, Yinghonglin, Peng Jiang, Wei Li, Chang Yang, Ping Sun, and Xiaowei Yan. "Predicting the Delamination Mechanisms of Multidirectional Laminates Using the Energy Release Rate Obtained from AE Monitoring." Materials Evaluation 80, no. 1 (January 1, 2022): 34–47. http://dx.doi.org/10.32548/2022.me-04254.

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This study investigates delamination damage mechanisms during the double cantilever beam standard test using the strain energy release rate. The acoustic emission parameter is used to replace the original calculation method of measuring crack length to predict delamination. For this purpose, 24-layer glass/epoxy multidirectional specimens with different layups, and interface orientations of 0°, 30°, 45°, and 60°, were fabricated based on ASTM D5528 (2013). Acoustic emission testing (AE) is used to detect the damage mechanism of composite multidirectional laminates (combined with microscopic real-time observation), and it is verified that the strain energy release rate can be used as a criterion for predicting delamination damage in composite materials. By comparing the AE results with the delamination expansion images observed by microvisualization in real time, it is found that the acoustic emission parameters can predict the damage of laminates earlier. Based on the data inversion of the acoustic emission parameters of the strain energy release rate, it is found that the strain energy release rate of the specimens with different fiber interface orientations is consistent with the original calculated results.

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Mahato, Biltu, Stepan V. Lomov, Aleksei Shiverskii, Mohammad Owais, and Sergey G. Abaimov. "A Review of Electrospun Nanofiber Interleaves for Interlaminar Toughening of Composite Laminates." Polymers 15, no. 6 (March 10, 2023): 1380. http://dx.doi.org/10.3390/polym15061380.

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Recently, polymeric nanofiber veils have gained lot of interest for various industrial and research applications. Embedding polymeric veils has proven to be one of the most effective ways to prevent delamination caused by the poor out-of-plane properties of composite laminates. The polymeric veils are introduced between plies of a composite laminate, and their targeted effects on delamination initiation and propagation have been widely studied. This paper presents an overview of the application of nanofiber polymeric veils as toughening interleaves in fiber-reinforced composite laminates. It presents a systematic comparative analysis and summary of attainable fracture toughness improvements based on electrospun veil materials. Both Mode I and Mode II tests are covered. Various popular veil materials and their modifications are considered. The toughening mechanisms introduced by polymeric veils are identified, listed, and analyzed. The numerical modeling of failure in Mode I and Mode II delamination is also discussed. This analytical review can be used as guidance for veil material selection, for estimation of the achievable toughening effect, for understanding the toughening mechanism introduced by veils, and for the numerical modeling of delamination.

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Song, Sam Hong, and Cheol Woong Kim. "The Fatigue Crack and Delamination Behavior on the Fuselage-Wing Intersection Containing Variable Notches." International Journal of Modern Physics B 17, no. 08n09 (April 10, 2003): 1540–46. http://dx.doi.org/10.1142/s0217979203019290.

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The delamination and the fatigue crack propagation behavior in aramid fiber reinforced metal laminates(AFRMLs) containing a saw-cut and circular hole such as the fuselage-wing intersection was investigated. The fatigue crack propagation in aluminum layer is accompanied with the delamination between aluminum layer and fiber layer. The delamination deteriorates the fiber bridging mechanism in the crack tip of AFRMLs. Therefore, this study evaluates the stress distribution of AFRMLs containing a saw-cut and circular hole using the Average Stress Criterion (ASC) model. The delamination zone was observed by ultrasonic C-scan images. As the result of this study, in case of AFRMLs containing a saw-cut specimen. the fatigue crack propagation always occurred in aluminum layer and the delamination zone formed along the fatigue crack. However, in case of AFRMLs containing a circular hole specimen, the delamination zone was formed in two types. First, delamination zone was formed along the fatigue crack in aluminum layer. Second, delamination zone was formed without any fatigue crack around the circular hole. Consequently, delamination zone was formed dependently on the notch shape and the stress distribution.

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KIKUCHI, Masanori, and Satoshi ICHIKAWA. "Estimation of the Delamination Shape of CFRP Composite by Transverse Loading. (Analysis of the Delamination Mechanism)." Transactions of the Japan Society of Mechanical Engineers Series A 62, no. 596 (1996): 930–36. http://dx.doi.org/10.1299/kikaia.62.930.

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Chung, C. L., James Fan, M. L. Huang, and F. J. Tsai. "Study on Failure Mechanism of PCT Reliability for BT Substrate Based CSP (Chip Scale Package)." Journal of Electronic Packaging 124, no. 4 (December 1, 2002): 334–39. http://dx.doi.org/10.1115/1.1498265.

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In this paper, the study on failure mechanism of moisture sensitivity reliability is reported. It focuses on the PCT conditions which are 121°C, 2atm, 100RH%, and 168 hr. The general failure mode is delamination on the interface between die attach material and die backside. Interestingly, the delamination exists as a gap of 20∼40 μm. In addition, the paper discusses the relative materials influences — for example, the moisture uptake of mold compound systems and die backside surface property effects. The degradation of the die attach material was analyzed by Dynamic Mechanic Analysis (DMA). The delamination surfaces are analyzed by Scanning Electron Microscope (SEM), and Optical Microscope (OM). Furthermore, Scanning Acoustic Tomograph (SAT) through scanning results reveals that the mold compound formula affects the amount of moisture uptake, which obviously would affect the PCT reliability.

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Huang, Teng, Dongdong Zhang, Jun Yang, Yuan Lin, and Yaxin Huang. "Compressive bearing capacity and failure mechanism of CFRP–aluminum laminate column with single-channel cross section." Science and Engineering of Composite Materials 28, no. 1 (January 1, 2021): 48–63. http://dx.doi.org/10.1515/secm-2021-0004.

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Abstract The axial compressive bearing capacity, failure modes, and failure mechanisms of carbon fiber-reinforced aluminum laminate (CARALL) columns with single-channel cross sections were studied in detail. In this study, two types of short CARALL specimens with a 5/4 configuration were first fabricated using 2024-T3 aluminum alloy and different fiber orientations ([0°/90°/0°]3, [45°/0°/−45°]3) via a pressure-molding thermal-curing forming process. The short CARALL columns were then subjected to static loading tests to determine their axial compressive behaviors in terms of ultimate bearing capacity and failure modes. Thereafter, the user-defined FORTRAN subroutine VUMAT, which is based on ABAQUS, was used to investigate the failure mechanism of the proposed CARALL columns. Meanwhile, based on the classic laminated panel mechanics theory, a theoretical method was proposed to predict the safe bearing capacity of the designed compressive CARALL columns. The results indicated that the ultimate failure of both types of short CARALL columns was a strength failure caused by the delamination of the layers. When the short CARALL columns were subjected to an axial compressive load, the fiber spread angle of the carbon fiber-reinforced polymer prepregs in the laminate panels had a significant influence on the resistance to interlaminar delamination. A smaller fiber layer angle resulted in greater resistance to interlaminar delamination. Setting a certain number of fiber layers with angles between 0° and 45° could increase the toughness of the compression column member against interlaminar shear delamination at the initial stage. Comparisons of the experimental, numerical, and theoretical results demonstrated good agreement, indicating that the proposed theoretical method is feasible for predicting the safe bearing capacity of CARALL columns with a single-channel cross section and can be applied to the design of compressive laminate pillar components.

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Vishwanath, K. S. "Computational Investigation of Square Embedded Delamination of a Composite Laminate using VCCT." International Journal for Research in Applied Science and Engineering Technology 9, no. VI (June 10, 2021): 381–84. http://dx.doi.org/10.22214/ijraset.2021.34923.

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The fiber reinforced polymer laminates are widely implemented in aviation industry due to its advantages and applications other materials in terms of strength to weight ratio, dsign features and many more. The strength of the interface compared to longitudinal and lateral directions of the plies are comparatively less and give rise too poor transverse direction strength. Hence a failure mechanism called delamination will occur in case when tools are dropped or due to poor manufacturing which would give rise to interface delamination. In this paper, VCCT is employed at the interface between base and sub laminate to investigate for a square shape delamination geometry of 20mm buckling driven delamination growth. The computational prediction of delamination growth initiation is obtained by solving a T300/976 specimen for geometric non linearity using SC8R continuum shell elements of Abaqus CAE and by plotting the required energy release rate at the delamination geometry.

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Hausbrand, René, Martin Stratmann, and Michael Rohwerder. "Corrosion of zinc–magnesium coatings: Mechanism of paint delamination." Corrosion Science 51, no. 9 (September 2009): 2107–14. http://dx.doi.org/10.1016/j.corsci.2009.05.042.

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Ibrahim, Ghalib R., A. Albarbar, and Khaldoon F. Brethee. "Progressive failure mechanism of laminated composites under fatigue loading." Journal of Composite Materials 55, no. 1 (July 28, 2020): 137–44. http://dx.doi.org/10.1177/0021998320944990.

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A cohesive zone model for delamination propagation in laminated composites under static and fatigue loading has been derived and validated with experimental data under different mode conditions. This study presents a new approach to quantify fatigue delamination degradation based on damage mechanics to evaluate the rate of fatigue damage ([Formula: see text]). The static damage evaluation and fatigue damage degradation are derived from damage surface concept. Both static and fatigue damage linked each other to establish fatigue crack growth formula in the laminated composites. A user-defined subroutine, UMAT, has been employed to develop and implement a damage model in ABAQUS. Two different specimens; a double cantilever beam and a single lap joint were used to investigate the effectiveness of the new method. The simulation results revealed that the developed model had good agreement with experimental data available in literature.

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Tan, T. L., C. L. Gan, A. Y. Du, Y. C. Tan, and C. M. Ng. "Delamination-induced dielectric breakdown in Cu/low-k interconnects." Journal of Materials Research 23, no. 6 (June 2008): 1802–8. http://dx.doi.org/10.1557/jmr.2008.0222.

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Delamination at an interface with the weakest adhesion strength, which is found to be between the SiC(N) capping layer and the SiOCH low-k dielectric, is a potential failure mechanism contributing to time-dependent dielectric breakdown (TDDB) reliability. Bond breaking at that interface is believed to be driven by a field-enhanced thermal process and catalyzed by leakage current through the capping layer based on physical analyses and TDDB measurements. Delamination is found to be easier in terminated tips and corners than in parallel comb lines due to the layout orientation of the Cu lines. Moreover, TDDB activation energy Ea can be an indicator of the ease of delamination, whereby a lower Ea corresponds to an easier delamination.

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Leng, A., H. Streckel, and M. Stratmann. "The delamination of polymeric coatings from steel. Part 1: Calibration of the Kelvinprobe and basic delamination mechanism." Corrosion Science 41, no. 3 (March 1998): 547–78. http://dx.doi.org/10.1016/s0010-938x(98)00166-8.

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Alil, Luminita Cristina, Michel Arrigoni, Lorena Deleanu, and Marcel Istrate. "Assessment of Delamination in Tensylon� UHMWPE Composites by Laser-induced Shock." Materiale Plastice 55, no. 3 (September 30, 2018): 364–71. http://dx.doi.org/10.37358/mp.18.3.5031.

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Ultra-High Molecular Weight Polyethylene (UHMWPE) composites are the result of recent developments in material research for ballistic protection due to their ability to absorb the kinetic energy of the bullet by various mechanisms of dissipation, among which an important one is delamination. In order to study this mechanism independently, the laser induced shock wave testing procedure has been used on thin Tensylon� laminate samples. Laser-induced shock represents a modern approach that can be used for assessing the interlaminar bond strength between two plies of a composite material, in dynamic conditions, at high strain rates representative for a ballistic impact. Through this technique, a delamination failure stress threshold can be determined. In the present work, the laser induced shock technique was applied on the commercial UHMWPE material called Tensylon�. The delamination threshold of this material was determined by using the Novikov approach, and, compared to the literature, the results match the values determined by other means of measurement.

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Wong, Fu-Mauh, and K. N. Seetharamu. "Investigation of Delamination Between Leadframe and Mold Compound on a LED Package." Journal of Microelectronics and Electronic Packaging 1, no. 4 (October 1, 2004): 269–81. http://dx.doi.org/10.4071/1551-4897-1.4.269.

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Delamination between mold compound and leadframe is found in a customized LED through-hole package. The delamination was initiated near the die paddle location under moisture condition. Subsequently, the delamination propagates throughout the package during the wave soldering process. An adhesion test has been performed to identify the mechanism of the delamination and to determine the adhesion shear strength between leadframe and mold compound. Finite Element Analysis (FEA) is conducted to analyze the thermal stress distribution at room temperature and the temperature distribution of package during wave soldering process. The delamination between leadframe and mold compound is initiated under moisture condition if the maximum-shear-stress for the package exceeds the measured adhesion shear strength. It is found that the package is at high risk of delamination if the temperature near the die paddle is higher than the glass transition temperature (Tg) of the mold compound. Parametric study has been performed to identify the controlling leadframe parameters that contribute to the thermal stress at room temperature and the temperature of the package during wave soldering process. The leadframe has been optimized based on the findings and the delamination has been minimized.

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Wang, Changhong, Tao Chen, Guangyue Wang, and Wenyuan Xu. "Machining Strategy and Experimental Study of Ultrasonic-Assisted Bidirectional Progressive Spiral Milling of Carbon Fiber Holes." Applied Sciences 12, no. 12 (June 14, 2022): 6029. http://dx.doi.org/10.3390/app12126029.

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Carbon fiber-reinforced composites (CFRP) are widely used in aerospace structural holes due to their superior mechanical properties. However, fiber pulling, delamination, burr and other defects often occur in the parts, which seriously affect the accuracy and service life of the products. The traditional cylindrical milling cutter is easy to lead to the exit delamination defects due to the large axial force at the bottom edge, concentrated wear at the periphery edge, and weak rigid constraint at the exit machining position. Therefore, this paper proposed a new hole machining strategy, analyzed the kinematic law of the tapered progressive spiral milling hole, studied the cutting mechanism of the four stages of the tapered spiral bidirectional milling hole, explored the material removal force state of the ultrasonic augment-assisted progressive milling hole, and established the prediction of the layered axial force of the ultrasonic progressive milling hole. Finally, combined with the material removal mechanism of ultrasonic vibration, the self-designed bidirectional progressive spiral milling cutter was used to verify the mechanism of material removal by progressive milling, in which the axial force could be effectively reduced. After 60 and 90 holes were processed, the axial force was about 18.5 and 23.3 N, respectively, the critical force of delamination could be improved, and the hole quality could be guaranteed without obvious burr and delamination phenomena.

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Goyal, D., and A. H. King. "TEM observations of the mechanism of delamination of chromium films from silicon substrates." Journal of Materials Research 7, no. 2 (February 1992): 359–66. http://dx.doi.org/10.1557/jmr.1992.0359.

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We have observed the complete delamination of polycrystalline chromium films from single crystal silicon substrates during deposition due to the formation of high internal stresses. These intrinsic stresses can give rise to interfacial defects which assist in the separation of the film from the substrate. Stresses in the film are balanced by stresses in the substrate, which cause mechanical failure in the substrate near the interface. Extensive arrays of dislocations and cracking of the substrate have been observed. We find that the delamination of the films from the substrate is initiated by the formation of damage in the substrate, rather than to the film or the interface.

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Yao, Xiao Fei, Fa Qin Xie, Guo Xian Zhao, Yong Han, and Xiang Qing Wu. "Compare of Wear Properties and Analysis of Wear Mechanism about TC4 Alloy and P110 Tubing Steel in Dry Condition." Advanced Materials Research 314-316 (August 2011): 147–50. http://dx.doi.org/10.4028/www.scientific.net/amr.314-316.147.

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Using as high strength and corrosion resistance of tubing material, the wear properties of TC4 alloy and P110 tubing steel were comparatively studied, the differences and similarities were analyzed that are weight loss of wear rate and friction coefficient and topography of wear mark, the wear mechanism was discussed. The results showed that the topography of TC4 alloy and P110 tubing steel are different entirely, TC4 alloy is furrow, P110 tubing steel is wear pit, the wear resistance of P110 tubing steel is excelled obviously than TC4 alloy, the wear mechanism of TC4 alloy is delamination wear and adhesive wear and fatigue wear. The wear mechanism of P110 tubing steel is delamination wear and abrasive wear.

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Tuo, Hongliang, Zhixian Lu, Xiaoping Ma, and Hongyu Guo. "Study on delamination damage evolution of composite L-shaped adhesive joint based on cohesive behavior." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 39, no. 2 (April 2021): 309–16. http://dx.doi.org/10.1051/jnwpu/20213920309.

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The adhesive joint of composite materials is one of the typical structures in aircraft structures, and the delamination damage is one of the most important damage modes in composite adhesive joints. In this paper, static and fatigue tests were carried out on L-shaped adhesive joints to analyze the damage evolution and failure modes of delamination damage under static and fatigue loadings. Based on the cohesive constitutive models, the static and high-cycle fatigue delamination constitutive models were developed. The static and fatigue numerical models of composite L-shaped adhesive joints were established by using finite element software. The stress distribution, deformation modes and delamination propagation laws were systematically studied. The simulation results are in good agreement with the experimental results. The delamination damage initiation, evolution and failure mechanism of L-shaped adhesive joints under static and fatigue loads were revealed by combining the experimental and the numerical results, which will provide theoretical and engineering guidance for strength and fatigue analysis of composite adhesive structures.

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Vishwanath, K. S. "FEA of Circular Embedded Delamination with Variations in Temperature in a Composite Laminate using VCCT." International Journal for Research in Applied Science and Engineering Technology 9, no. VI (June 30, 2021): 5058–61. http://dx.doi.org/10.22214/ijraset.2021.36122.

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The FRP laminates are widely implemented in aviation industry due to its advantages and applications other materials in terms of strength to weight ratio, design features and many more. The strength of the interface compared to longitudinal and lateral directions of the plies are comparatively less and give rise too poor transverse direction strength. Hence a failure mechanism called delamination will occur in case when tools are dropped or due to poor manufacturing which would give rise to interface delamination. In this paper, VCCT is employed at the interface between base and sub laminate to investigate for a circular shape delamination geometry of 60mm buckling driven delamination growth with variations in temperature for -20C, room temperature, 523C, 773C and 1273C. The computational prediction of delamination growth initiation is obtained by solving a CFRP specimen for geometric non linearity using SC8R continuum shell elements of Abaqus CAE and by plotting the required energy release rate versus inplane strains and inplane loads versus compressive strains.

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Lee, Na-Ri, Hyoung-Seuk Choi, and Duck-Kyun Choi. "Failure Analysis of a Nickel-Plated Electronic Connector Due to Salt-Induced Corrosion (ENGE 2014)." Journal of Nanoscience and Nanotechnology 15, no. 10 (October 1, 2015): 7498–502. http://dx.doi.org/10.1166/jnn.2015.11157.

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When electronic connectors in mobile devices are miniaturized, the thickness of plating decreases. However, this thin plating is expected to decrease the life of the connector due to problems with corrosion. In this study, salt spray aging tests were performed on miniaturized nickel-plated stainless steel electronic connectors to observe failure mechanisms in realistic environments. The tests were performed three times using a 5% NaCl solution in an atmosphere of 45 °C; each test included several cycles where one cycle was one 24-h period consisting of 8 h of salt spray and 16 h without salt spray. The nickel-plating layers were periodically observed by electron probe X-ray micro-analyzer, wavelength dispersive spectroscopy, and field-emission scanning electron microscopy to analyze and identify the corrosion mechanism. We found that the primary failure mode of the nickel plating is blistering and delamination. The corrosion mechanism is typically a chain reaction of several corrosion mechanisms: pitting corrosion → stress corrosion cracking → hydrogen-induced cracking → blistering and delamination. Finally, we discuss countermeasures to prevent corrosion of the nickel layer based on the corrosion mechanisms identified in this study.

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Vishwanath, K. S. "Computational Investigation of through the Width Delamination of a Composite Laminate using VCCT." International Journal for Research in Applied Science and Engineering Technology 9, no. VI (June 10, 2021): 128–31. http://dx.doi.org/10.22214/ijraset.2021.34890.

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The fiber reinforced polymer laminates have found extensive applications because of its advantages over other materials in terms of strength, stiffness, stability, weight saving features, resistance to corrosion and erosion and many more. But due to poor transverse direction strength, a failure mechanism called delamination will occur in case of poor manufacturing or when tools are dropped which would make an impact. In this paper, VCCT is implemented at the interface between base and sub laminate to investigate for 20mm through the width buckling driven delamination growth. The computational prediction of delamination growth initiation is obtained by solving a T300/976 specimen for geometric non linearity using SC8R continuum shell elements of Abaqus CAE and by plotting the required energy release rate at the edge of delamination geometry.

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Zhang, Xiao-Yu, Zhen-Bing Cai, Jin-Fang Peng, Jian-Hua Liu, Min-Hao Zhu, Run Du, Xin-Lu Yuan, and Ping-Di Ren. "Experimental study of the fretting wear behavior of Inconel 690 alloy under alternating load conditions." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 11 (January 12, 2018): 1343–51. http://dx.doi.org/10.1177/1350650117750790.

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This study investigated the fretting wear behavior of the nuclear power material Inconel 690 alloy. An improved PLINT high-temperature fretting tester was used on an Inconel 690 tube against a 1Cr13 cylinder at different temperatures (25 ℃ and 300 ℃) under alternating load conditions. The fretting-wear mechanism and the kinetic characteristic of Inconel 690 alloy were analyzed. Results showed that the fretting running behavior was closely related to the normal excitation frequency. In parallelogram shaped Ft– D curves, the friction fluctuates periodically, and accordingly the fretting was running in the slip regime. The steady-state friction force at room temperature in air was higher than that at 300 ℃. Moreover, the damage behavior of the fretting for Inconel 690 alloy strongly depended on the normal load, displacement amplitude, temperature, and excitation frequency in atmospheric environment. A superposition effect of fretting wear behavior was discovered because of the combined effect of alternating normal and tangential forces; thus, delamination became more significant. Abrasive wear and delamination were the major mechanisms in Inconel 690 alloy at room temperature in ambient air. The dominant mechanisms at 300 ℃ were the abrasive wear, oxidation wear, and delamination.

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Zumelzu, E., C. Ortega, F. Rull, and C. Cabezas. "Degradation mechanism of metal–polymer composites undergoing electrolyte induced delamination." Surface Engineering 27, no. 7 (August 2011): 485–90. http://dx.doi.org/10.1179/026708410x12687356948436.

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King, W. W., and C. J. Aloisio. "Thermomechanical Mechanism for Delamination of Polymer Coatings From Optical Fibers." Journal of Electronic Packaging 119, no. 2 (June 1, 1997): 133–37. http://dx.doi.org/10.1115/1.2792219.

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Sometimes the polymer coating on an optical fiber is observed to have separated from the fiber over a small portion of the interface. Irregularities on the capstans and sheaves of draw, rewind, coloring, and cabling machines can initiate such delaminations. Subsequent growth would not be anticipated under the condition of radial compressive stress that might be expected for a coating shrinking over a relatively rigid fiber as the composite cools during manufacture. Compressive stress is indeed found at the interface when a single-layer coating is used. However, for a two-layer system, having a high-modulus secondary over a low-modulus primary (for improved protection against microbending), the different rates of thermal expansion can lead to radial tension at the silica/primary interface, and this tension can “drive” the growth of delaminations. A principal result of this study is that the analysis predicts the primary coating, although rubbery, to be approximately in a state of uniform hydrostatic tension. This tensile stress is of substantial magnitude because of constraints imposed by the relatively stiff secondary coating and by the fiber. The existence of significant radial tension at the fiber surface is consistent with experimental observations of induced delaminations, which are seen to grow long after cessation of external disturbances.

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41

Kim, Ig-Hyeon, Seon-Hyo Kim, and Kyoung-Bo Kim. "Delamination mechanism in relation to adhesion of cubic boron nitride." Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 16, no. 4 (July 1998): 2295–99. http://dx.doi.org/10.1116/1.581412.

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Virkar, Anil V. "Mechanism of oxygen electrode delamination in solid oxide electrolyzer cells." International Journal of Hydrogen Energy 35, no. 18 (September 2010): 9527–43. http://dx.doi.org/10.1016/j.ijhydene.2010.06.058.

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43

McGugan, Malcolm, and Leon Mishnaevsky. "Damage Mechanism Based Approach to the Structural Health Monitoring of Wind Turbine Blades." Coatings 10, no. 12 (December 14, 2020): 1223. http://dx.doi.org/10.3390/coatings10121223.

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A damage mechanism based approach to the structural health monitoring of wind turbine blades is formulated. Typical physical mechanisms of wind turbine blade degradation, including surface erosion, adhesive fatigue, laminate cracking and in some cases compressive kinking and failure are reviewed. Examples of a local, damage mechanism based approach to the structural health monitoring of wind turbine blades are demonstrated, including the monitoring of leading edge erosion of wind turbine blades, adhesive bond failure, plydrop delamination, static and dynamic plydrop tests, and bolt and laminate fatigue. The examples demonstrate the possibilities of monitoring specific damage mechanisms, and specific localizations of wind turbine blades.

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Dhanawade, Ajit, and Shailendra Kumar. "Experimental study of delamination and kerf geometry of carbon epoxy composite machined by abrasive water jet." Journal of Composite Materials 51, no. 24 (January 9, 2017): 3373–90. http://dx.doi.org/10.1177/0021998316688950.

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The present article focuses on mechanism of delamination and kerf geometry in abrasive water jet machining of carbon epoxy composite. In the present study, four process parameters of abrasive water jet machining namely hydraulic pressure, traverse rate, stand-off distance, and abrasive mass flow rate are considered. The experiments are performed on the basis of response surface methodology as a statistical design of experiment approach. Delamination in machined samples is observed by using scanning electron microscope. Analysis of variance is performed in order to investigate the influence of process parameters on delamination, kerf taper ratio, and kerf top width. It is found that delamination decreases with increase in pressure and abrasive mass flow rate and decrease in stand-off distance and traverse rate. Kerf taper ratio decreases with increase in pressure and decrease in traverse rate and stand-off distance. Kerf top width decreases with decrease in stand-off distance and increase in traverse rate. Based on analysis, mathematical models are developed to predict the maximum delamination length, kerf taper ratio, and kerf top width. Further, a multi-response optimization is performed on the basis of desirability function to minimize delamination, kerf taper ratio, and kerf top width.

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Hong, Hai Ming, Ming Li, Jian Yu Zhang, and Yi Ning Zhang. "Experimental Research on the Low Velocity Impact Damage of CCF300/QY8911 Composite Laminates." Advanced Materials Research 583 (October 2012): 179–82. http://dx.doi.org/10.4028/www.scientific.net/amr.583.179.

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A group of low-velocity impact tests on CCF300/QY8911 composite laminates were implemented by the low-velocity drop hammer test machine. The dent depth and the internal damage pattern with corresponding impact energy were studied, the internal delamination damage state of laminates after impact were observed through thermal layer exposing tests, and the mechanism of low-velocity impact delamination damage were discussed. The results indicated that there existed a significant inflection point in the curve of impact energy verse dent depth of CCF300/QY8911 composite material, which was also the transition point of different damage patterns. When the impact energy was smaller than the inflection energy, the damage pattern consisted mainly of matrix flaws and delamination damages, but when the impact exceeded the inflection energy, delamination damage hardly expanded while the expansion of damage was mainly fiber break.

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You, Peiyu, Chen Chen, Ye Wu, Baohua Zhang, Xiaojun Tang, Dalei Zhu, Zhenxue Liu, and Yunsheng Ma. "An experimental study on the failure and enhancement mechanism of bolt-strengthening GFRP T-joint subjected to tensile loading." Science and Engineering of Composite Materials 29, no. 1 (January 1, 2022): 466–72. http://dx.doi.org/10.1515/secm-2022-0169.

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Abstract The aim of this article is to investigate the failure and enhancement mechanism of bolt-strengthening glass fiber-reinforced polymer (GFRP) T-joints under quasi-static tension. One-step molding technology based on the vacuum-assisted resin infusion process is carried out to fabricate the GFRP T-joints structures. Then, a special fixture and constraint condition are set up to take the quasi-static tensile test with high reliability. Moreover, it is demonstrated that the T-joints structures may decrease their bearing capacity, resulting in interlaminar delamination at the corner region. Further, to strengthen the T-joints, the bolts are employed to effectively prevent the initiation and propagation of interlaminar delamination in the tensile loading. At the same time, as their enhancement and failure mechanisms are revealed deeply, the strengthening method is optimized as well.

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Liu, Xiao Yu, Tian Yi Hu, and Zheng Yang. "The Effect of Specimen Orientation and Thickness on the Initiation of Delamination Crack in X80 Pipeline Steel." Advanced Materials Research 668 (March 2013): 625–29. http://dx.doi.org/10.4028/www.scientific.net/amr.668.625.

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The effect of weak interfacial orientation, thickness and the main crack depth on the initiation of delamination crack and main crack in three-point bending specimens of X80 pipeline steel are investigated, using 3D finite element method. Considering the different fracture mechanism of delamination crack and main crack, two different criteria are adopted for them in the simulation. The results reveal that, when the delamination cracks initiates, the initiating position is fixed and the Jz integral of the main crack is a constant for specific weak interfacial orientation specimens with different main crack depth and a certain thickness. When specific weak interfacial orientation specimens have different thickness and a certain main crack depth, the initiating position of delamination crack is equal to the above mentioned, but the Jz integral of the main crack has a ripad decline with the increasing of thickness and then tend to stable. In particular, the delamination crack will not appear for specimens with thin thickness. The thicker the specimen is, the higher the ultimate weak interface strength is needed to prevent the initiation of the delamination crack for specimen with a certain main crack depth. The larger delamination crack will generate, when the specimens have a lower ultimate weak interface strength, a smaller Jz integral of main crack and a larger thickness.

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Mahato, Anirban, Yang Guo, Narayan K. Sundaram, and Srinivasan Chandrasekar. "Surface folding in metals: a mechanism for delamination wear in sliding." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, no. 2169 (September 8, 2014): 20140297. http://dx.doi.org/10.1098/rspa.2014.0297.

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Using high-resolution, in situ imaging of a hard, wedge-shaped model asperity sliding against a metal surface, we demonstrate a new mechanism for particle formation and delamination wear. Damage to the residual surface is caused by the occurrence of folds on the free surface of the prow-shaped region ahead of the wedge. This damage manifests itself as shallow crack-like features and surface tears, which are inclined at very acute angles to the surface. The transformation of folds into cracks, tears and particles is directly captured. Notably, a single sliding pass is sufficient to damage the surface, and subsequent passes result in the generation of platelet-like wear particles. Tracking the folding process at every stage from surface bumps to folds to cracks/tears/particles ensures that there is no ambiguity in capturing the mechanism of wear. Because fold formation and consequent delamination are quite general, our findings have broad applicability beyond wear itself, including implications for design of surface generation and conditioning processes.

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Barile, Claudia, Caterina Casavola, Benedetto Gambino, Alessandro Mellone, and Marco Spagnolo. "Mode-I Fracture Behavior of CFRPs: Numerical Model of the Experimental Results." Materials 12, no. 3 (February 8, 2019): 513. http://dx.doi.org/10.3390/ma12030513.

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In the last decades, the increasing use of laminate materials, such as carbon fibre reinforced plastics, in several engineering applications has pushed researchers to deeply investigate their mechanical behavior, especially in consideration of the delamination process, which could affect their performance. The need for improving the capability of the current instruments in predicting some collapse or strength reduction due to hidden damages leads to the necessity to combine numerical models with experimental campaigns. The validation of the numerical models could give useful information about the mechanical response of the materials, providing predictive data about their lifetime. The purpose of the delamination tests is to collect reliable results by monitoring the delamination growth of the simulated in situ cracking and use them to validate the numerical models. In this work, an experimental campaign was carried out on high performance composite laminates with respect to the delamination mode I; subsequently, a numerical model representative of the experimental setup was built. The ANSYS Workbench Suite was used to simulate the delamination phenomena and modeFRONTIER was applied for the numerical/experimental calibration of the constitutive relationship on the basis of the delamination process, whose mechanism was implemented by means of the cohesive zone material (CZM) model.

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Hussein, Ramy, Ahmad Sadek, Mohamed A. Elbestawi, and M. Helmi Attia. "An Investigation into Tool Wear and Hole Quality during Low-Frequency Vibration-Assisted Drilling of CFRP/Ti6Al4V Stack." Journal of Manufacturing and Materials Processing 3, no. 3 (July 27, 2019): 63. http://dx.doi.org/10.3390/jmmp3030063.

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The use of lightweight material such as CFRP/Ti6Al4V in stacked structures in the aerospace industry is associated with improved physical and mechanical characteristics. The drilling process of nonuniform structures plays a significant role prior to the assembly operation. However, this drilling process is typically associated with unacceptable CFRP delamination, hole accuracy, and high tool wear. These machining difficulties are attributed to high thermal load and poor chip evacuation mechanism. Low-frequency vibration-assisted drilling (LF-VAD) is an advanced manufacturing technique where the dynamic change of the uncut chip thickness is used to manipulate the cutting energy. An efficient chip evacuation mechanism was achieved through axial tool oscillation. This study investigates the effect of vibration-assisted drilling machining parameters on tool wear mechanisms. The paper also presents the effect of tool wear progression on drilled hole quality. Hole quality is described by CFRP entry and exit delamination and hole accuracy. The results showed a significant reduction in the thrust force, cutting torque, cutting temperature, and flank wear-land.

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Journal articles on the topic 'Delamination mechanism'

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