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A comparison between uncreped and creped handsheets was performed to study the effect of fiber morphology and creping process on fiber web structure and tissue properties. Four wood and non-wood pulps refined at different levels were used to manufacture uncreped and creped handsheets using a creping simulator. A characterization of the fiber web structure using scanning electron microscopy (SEM) and evaluation of tissue properties (e.g. tensile strength, water absorbency, softness) was performed on the uncreped and creped handsheets. The results obtained with the creping simulator were compared with commercial products to evaluate the significance of the creping simulator results. The SEM images of the fiber web structure showed that the creping process promoted buckling and distortion of fibers, delamination of surface fiber layer, development of free fiber ends and creation of crepe folds, which enhanced water absorbency and softness at the expense of reduced tensile strength. Short and thin fibers seemed to be more effectively creped than long and coarse fibers. Long and coarse fibers seemed to offer higher resistance to the compressive forces acting at the creping blade. A reasonable correlation between the performance of uncreped and creped handsheets made with different fibers was observed. The results indicate that the performance of uncreped handsheets can be used as a semi-quantitative indication of the performance of creped handsheets. The performance of the creped handsheets were similar to commercial products, which indicates that the creping simulator can be used as an alternative to study the creping process at laboratory scale. [ABSTRACT FROM AUTHOR]

The Scott bond test method has been used extensively in the paper industry over the years as a means to assess the bond strength of paper. The method has been a subject of some controversy lately since it does not always correlate to the sensitivity of the material to fracture by delamination. To gain some further insight into which parameters govern the fracture process in a Scott bond test a simplified approach has been chosen in order to formulate an analytical mathematical/mechanical model of the test. The model is dynamic in the sense that inertia effects are included. The material model utilised is a simple cohesive theory that assumes a linear behaviour between stress and crack opening when the material has started to degrade. This choice of material model makes the mathematical model very nonlinear. In fact, a system of three coupled nonlinear second order partial differential equations have to be solved and adjusted to the correct initial conditions. The material parameters needed for the model are the elastic modulus in the thickness direction, the transverse shear (elastic) modulus, the tensile strength (in the thickness direction) and the fracture work (per unit area) for a delamination crack. To investigate the ability of the model, a Scott bond testing apparatus have been equipped with a piezoelectric load sensor. The load cell was mounted on the apparatus’ pendulum so that the load acting on the sample holder could be recorded during the whole impact stage. This was done for a number of different initial velocities of the pendulum and it is found that the model gives a fair prediction of the contact load. [ABSTRACT FROM AUTHOR]

Delamination in carbon fiber reinforced polymer (CFRP) composite structures plays a significant role in reducing the stiffness and strength of the structure, thus downgrading the integrity and reliability of the system. Aiming at the problem that traditional linear Lamb wave technology is not sensitive to the layered defects of composite materials and the existing nonlinear Lamb wave method is difficult to locate and detect damage, this paper proposes an ultrasonic tomography method based on Lamb waves to detect and reconstruct the delamination defects in CFRP plate. The dynamic finite element analysis method is used to simulate the propagation process of A0 mode Lamb waves in the 14-layer cross-layer CFRP defect plate. Sixty-four sensors perform fan-beam scanning on the composite plate in an equal-angle arrangement to obtain time-of-flight data corresponding to the sensing path. The layered defects of the composite material are imaged and evaluated by the filtered back-projection method. The experimental results show that this method can obtain high-quality reconstructed images of layered defects. [ABSTRACT FROM AUTHOR]

Purpose: The main purpose of this paper is to detect the damage of interior delamination in composite laminate using a new non-destructive testing method of highly nonlinear solitary waves. We studied the coupling mechanism between highly nonlinear solitary waves and interior delamination composite plate. Methods: The discrete element method is used for the one-dimensional particle chain, based on the residual stiffness model, Hertz's contact law and the composite plate vibration differential equation are used, we obtained the coupled differential equations for one-dimensional particle chain and interior delamination composite plate. We used the fourth-order Runge–Kutta method to solve the differential equations, and obtained the velocity curve and displacement curve of each particle in the particle chain. The influence of the thickness of the damaged composite plate, the average diameter of the interlaminar cracks, and the density of the interlaminar cracks on the reflected solitary waves are analyzed. We used one-dimensional homogeneous particle chain and one-dimensional composite particle chain to detect damaged composite plate with different material properties. Results: The results shows that the reflected waves are sensitive to the thickness of the plate, the average diameter of the interlaminar cracks and the density of the interlaminar cracks. We find that the propagation time of solitary waves in the composite particle chain is shorter and faster, and the detection efficiency can be increased by 23.5% at most. Conclusions: The characteristic information carried by reflected waves can be used for non-destructive testing of damaged composite plate. The research results of this paper enrich and improve the non-destructive testing of composite materials, and accelerate the practical application of one-dimensional particle chain. [ABSTRACT FROM AUTHOR]

In this paper, pultruded GFRP bars are investigated to determine their fracture properties. The double cantilever beam test (DCB) is used to assess fracture behavior under mode I loading conditions. However, due to the presence of the R-curve effect (variable fracture energy dependent on the length of the crack), it is necessary to introduce a nonstandard approach to determine fracture properties. The mixed experimental–numerical approach is proposed to deal with this issue. Numerical simulations were carried out in Simulia Abaqus, and with Python scripting it was possible to generate models and obtain R-curve for the material. The numerical model built based on the experimental results has very good agreement with it (force–displacement and delamination length–time characteristics) which allows the use of the mentioned model in the analysis of more complex structures. Acoustic emission analysis was introduced as an auxiliary technique. The delamination obtained from both the numerical model and the experiment complies with the registered acoustic emission events. The proposed method can be used in preparing a material model for other composite materials, which display the presence of the R-curve effect. [ABSTRACT FROM AUTHOR]

This paper presents a new method of piercing the carbon fibre reinforced polymer (CFRP) with abrasive water jet (AWJ), which can avoid delamination. The method consists of adding the abrasive particles in the water jet at the very beginning of jet formation, thus obtaining a mixed abrasive water jet during the first impact with the composite work piece. A new cutting system was designed and set up based on the proposed piercing method and was compared with a conventional AWJ cutting system. The main added values brought by this paper are: it validates our original concept; provides synthetic analyses, the effects of the AWJ homogeneity, and the abrasive inlet angle on the CFRP delamination, and it brings a complete set of recommendations on how to overcome the industrial difficulties caused by the delamination of the composite materials, during the piercing with AWJ. [ABSTRACT FROM AUTHOR]

The focus of the present paper is on the mode-II (shear mode) interlaminar fracture of laminated composite materials with randomly distributed defects such as those generated due to the manufacturing process. The study is conducted using cohesive-zone Finite Element (FE) models of the Interlaminar Shear (ILS) and the End Notch Flexure (ENF) geometries with explicit inclusion of defects on a representative interlaminar plane. The effective interlaminar shear strength and the effective mode-II fracture energy are obtained by comparing the FE analysis with explicit defects against corresponding homogeneous models. Based on the parametric FE results it was found that the effective ILS strength and the mode-II fracture energy are significantly affected by the defects present on the critical interlaminar fracture plane, and when the defects are small, they follow a linear scaling with the defect area fraction. Simulations with various defect sizes reveal that for defects larger than the size of the delamination process-zone, the concept of the effective ILS strength and effective mode-II fracture energy is not valid, and defects must be represented explicitly in the models. [ABSTRACT FROM AUTHOR]

Besides the determination of the force and the energy needed to break individual fibre to fibre joints, the investigation of the formerly bonded area (FBA) is of essential importance to learn more about the failure mechanisms of fibre-fibre bonds in general. In this study the surfaces of paper fibres and the FBA of fibre-fibre joints after the determination of the breaking force as well as the bonding energy were analysed by means of low voltage scanning electron microscopy and atomic force microscopy. A comparison between the contact zone of fibres broken at different loading rates as well as under cyclic loading showed that there seems to be no significant difference in the appearance of the FBA in these cases. Only minor delamination of the cell wall could be found in the bonding zone, which indicates no mechanical interlocking of fibrils in the bonding zone. Furthermore, it is shown that some glues used for specimen preparation of fibre-fibre bond strength measurement are forming a glue film on the fiber surface and migrate into the bonding region. [ABSTRACT FROM AUTHOR]

Among a variety of solar cell types, thin-film solar cells have been rigorously investigated as cost-effective and efficient solar cells. In many cases, flexible solar cells are also fabricated as thin films and undergo frequent stress due to the rolling and bending modes of applications. These frequent motions result in crack initiation and propagation (including delamination) in the thin-film solar cells, which cause degradation in efficiency. Reliability evaluation of solar cells is essential for developing a new type of solar cell. In this paper, we investigated the effect of layer delamination and grain boundary crack on 3D thin-film solar cells. We used finite element method simulation for modeling of both electrical performance and cracked structure of 3D solar cells. Through simulations, we quantitatively calculated the effect of delamination length on 3D copper indium gallium diselenide (CIGS) solar cell performance. Moreover, it was confirmed that the grain boundary of CIGS could improve the solar cell performance and that grain boundary cracks could decrease cell performance by altering the open circuit voltage. In this paper, the investigated material is a CIGS solar cell, but our method can be applied to general polycrystalline solar cells. [ABSTRACT FROM AUTHOR]

Composite laminates often produce delamination due to a series of factors during the manufacture and service process. In order to research the effect of containing oblique elliptical and circular initial delamination damage on the compressive strength of composite laminates, numerical and experimental methods are used in this paper. Finite element models (FEMs) and the progressive damage subroutine USDFLD are developed to predict the damage initiation and extension behavior of the intralaminar of the laminate. Interlaminar damage is predicted based on cohesive zone models (CZM). At the same time, four compression tests containing different initial delamination damage are performed. The results show that experimental measurements of compression tests concur with the numerical predictions and validate the FEMs. The strength and stiffness of the specimens gradually decrease with the increase of the initial delamination area. It reveals that, for the compression process, the delamination damage extends from the edge of the initial damage to the surroundings. The bearing capacity of the composite laminates is mainly determined by the material properties of the fibers and matrix, rather than the initial delamination. [ABSTRACT FROM AUTHOR]

Composite materials, due to their properties (high specific strength and low weight), are currently among the most demanded materials used in creating objects for many purposes. The strict modern safety standards require timely monitoring of the occurrence and development of defects, in particular, delaminations. In this respect, considerable attention is paid to the development and improvement of methods of flaw detection. This paper presents a numerical study of the possibility of detecting and localizing delaminations in structures made of laminated composite materials by using vibrational approaches. The approach proposed is based on the excitation of vibrations with an increased amplitude in the region of the defect. This is possible due to the rise of natural vibration frequencies, the maximum amplitude of which is localized exactly in this place. In the first stage of numerical experiments, it was found that such natural frequencies depend weakly on the location of the defect but are strongly correlated with the size of the delamination. In the next stage, for an adequate description of the vibrational processes in the structure, forced steady-state vibrations were simulated taking into account the necessary dissipative parameters of the composite material. The frequency of the external action was chosen in accordance with the natural vibration frequency corresponding to the defect obtained from the modal analysis. The calculation results showed a significant increase in the vibration amplitude in the delamination region in comparison with the defectless structure if the frequency of the external action is chosen correctly. The effectiveness of the approach depending on the distance from the place of the application of the forced oscillation to the delamination region was tested. The method of defect monitoring proposed in the paper makes it possible to justify the possibility of developing, based on the vibtrational processes, a system for detecting delaminations in composite materials and to determine the main parameters of such a system. [ABSTRACT FROM AUTHOR]

In this two-part paper we introduce a new formulation for modeling progressive damage in laminated composite structures. We adopt a multi-layer modeling approach, based on isogeometric analysis, where each ply or lamina is represented by a spline surface, and modeled as a Kirchhoff-Love thin shell. Continuum damage mechanics is used to model intralaminar damage, and a new zero-thickness cohesive-interface formulation is introduced to model delamination as well as permitting laminate-level transverse shear compliance. In Part I of this series we focus on the presentation of the modeling framework, validation of the framework using standard Mode I and Mode II delamination tests, and assessment of its suitability for modeling thick laminates. In Part II of this series we focus on the application of the proposed framework to modeling and simulation of damage in composite laminates resulting from impact. The proposed approach has significant accuracy and efficiency advantages over existing methods for modeling impact damage. These stem from the use of IGA-based Kirchhoff-Love shells to represent the individual plies of the composite laminate, while the compliant cohesive interfaces enable transverse shear deformation of the laminate. Kirchhoff-Love shells give a faithful representation of the ply deformation behavior, and, unlike solids or traditional shear-deformable shells, do not suffer from transverse-shear locking in the limit of vanishing thickness. This, in combination with higher-order accurate and smooth representation of the shell midsurface displacement field, allows us to adopt relatively coarse in-plane discretizations without sacrificing solution accuracy. Furthermore, the thin-shell formulation employed does not use rotational degrees of freedom, which gives additional efficiency benefits relative to more standard shell formulations. [ABSTRACT FROM AUTHOR]

In order to solve the issue that it is difficult to removing the powder chips of carbon fiber–reinforced polymer (CFRP), the chip morphology prediction model for single-layer composite materials and the 3D drilling model and the chip formation process for laminated composites are developed to study the chip formation mechanism. It is concluded that drilling chips are mainly tower-shaped chips and rice chips, with a small number of micro-circular chips and rectangular chips. If the temperature is too high, fiber pull-out starts to occur and C-shaped chips appear. A CFRP drilling test platform was built, and it was found that, if other conditions remain unchanged, the chip size decreases with an increase in the rotation speed, but increases with an increase in the cutting depth. As the cutting depth increases, the chip failure section also tends to be flat. Overall, the experimental tests confirmed the accuracy of the prediction model. This paper provides a reference for improving the quality of chip removal and the efficiency of CFRP suction-type internal chip removal systems. [ABSTRACT FROM AUTHOR]

In this paper, the sub-laminate local buckling, global buckling and delamination propagation behavior of composite laminates with circular embedded delamination were studied numerically. First, linear buckling analyses were performed and buckling loads and modes of local sub-laminate and global buckling were identified. Next, geometrically nonlinear post-buckling and delamination propagation analyses were performed. Buckling deformation was instigated by seeding finite element meshes with a small amount of combined linear buckling modes. In-plane failure and interface delamination were accounted for by a continuum damage mechanics method and cohesive zone modeling, respectively. Analyses were performed to investigate the interaction between local sub-laminate buckling, global buckling, in-plane failure, and delamination propagation. The dependence of buckling behavior on the size and depth of location of pre-delamination was also investigated by a series of parametric studies. [ABSTRACT FROM AUTHOR]

Carbon fiber–reinforced plastic (CFRP) composites are extensively being applied in manufacturing sectors because of their extraordinary characteristics. However, CFRP composites often require some extra machining processes to improve the dimensional accuracy and component integrity of CFRP composites in manufacturing industries. The ultrasonic machining (USM) process progressively has been examined due to its greater ability in machining difficult to cut, brittle, and hard materials such as CFRP composites and due to its relatively low machining cost. Furthermore, USM shows to be a promising process with better surface quality, lower cutting force, less or no fiber fracture, laminate delamination, and lower tool wear rate. Recently, USM has been extensively investigated by many researchers for the machining of CFRP composites. This paper explores the literature and presents a comprehensive review of the advances in USM of CFRP composites by classifying the studies reported in two perspectives. First, the review summarizes most of the reported studies starting from 2011 to 2020 based on the applied USM process, equipment/system/platform used to carry out experiments, considered process parameters and output variables, and challenges investigated or gap filled. Then, the reported studies are summarized considering the type of USM process variant, CFRP composite, adopted process parameters on machining characteristics, and their respective results and conclusions. The aim is to present the current research status in USM of CFRP composites and thus provide guidance and foundation for future research. [ABSTRACT FROM AUTHOR]

Drilling high quality holes is a necessary prerequisite to ensure efficient and accurate connection and assembly of CFRP components. In addition to cutting force, cutting heat is another important factor affecting the quality of CFRP drilling. In this paper, a drilling experiment of CFRP laminate is carried out, and the method of prefabricating thermocouple holes on the edge of the test-hole is used to study the influence of fiber direction and processing parameters on the drilling temperature. Results show that when drilling along the fiber direction of 0°, the heat conduction in the edge area of test-hole wall is better than that of drilling along the fiber direction of 90°. Accordingly, the drilling temperature is obviously higher. Under this experimental condition, the temperature difference of the edge area of test-hole caused by the fiber direction is as high as 44 °C. At the feed rate of 0.04 mm/rev, when the speed increases from 1500 rpm to 4500 rpm, the axial force decreases by 13.9 %, and the peak temperature at p1 and v1 increase by 63.2 % and 22.2 %, respectively. At the spindle speed of 3000 rpm, when the feed rate increases from 0.02 mm/rev to 0.06 mm/rev, the drilling axial force increases by 35.0 %, and the peak temperature at p1 and v1 decreases by 31.1 % and 30.0 %, respectively. [ABSTRACT FROM AUTHOR]

The significant advantages of nanoparticles have motivated engineers to focus on development of structural integrity by use of these materials. This paper presents a comprehensive experimental study on the impact of nanomodification in laminated composite structures. The influence of nanomaterials on the mechanical performance is examined through the assessment of "residual stress," "weight loss under thermal fatigue" and "delamination damage in machining operations" of glass fiber-reinforced polymer (GFRP) composites. In this case, different composite specimens were fabricated with 0% and 1% weight fraction of multi-walled carbon nanotubes (MWCNTs). Then, the slitting method as an accurate semi-destructive technique was performed to measure the non-uniform residual stresses in terms of MWCNTs content. Also, the role of MWCNTs in the weight loss of the specimens with different thicknesses under thermal fatigue was analyzed. Additionally, the rotary ultrasonic drilling technique as a high-tech drilling operation was carried out and delamination damage of the GFRPs under machining process was measured. The results indicated that the addition of 1% MWCNTs results in a decrease of 30% and 2.33% in residual stress and delamination states, respectively. [ABSTRACT FROM AUTHOR]

Drilling is one of the most widely used machining processes in the aerospace industries. However, maintaining delamination free and high productivity in the machining of carbon fibre reinforced plastic (CFRP) can be a challenge due to the excessive thrust force or the relative low feedrate. The paper presents an improved method for machining the 2-mm thickness CFRP plate with three proposed patterns of pilot holes in high-speed drilling. Pilot drilling pattern (a), well adopted in the past, can reduce the thrust force dramatically, but it significantly increases both dynamic loading and drilling torque and causes excessive tool wear that occurred on the periphery of the drill tool. The paper also provides a FEA simulation, which is used to solve the Johnson-Cook constitutive material model and related damage modelling, and to further explain the excessive drill tool deflection induced by the pilot drilling pattern (a) in comparison with none pilot drilling. The paper then describes another two patterns, pilot drilling pattern (b) and pattern (c), that have provided advantages of reducing both the thrust force and drilling torque significantly and conducive to achieve delamination free drilling performance, as well as extending tool. [ABSTRACT FROM AUTHOR]

In the recent years with greater emphasis on the environmental and sustainability aspects of engineering materials, natural fiber reinforced composites (NFRCs) are gaining more importance because of their numerous advantages. Several researchers have developed NFRCs using various natural fibers as well as matrix materials. However, real-world applications of NFRCs require some secondary operations in order to complete the assembly of the components or parts. Very few researchers have discussed issues related to the machinability of these NFRCs. In this paper, for the first time, a comprehensive literature review on machining of NFRCs is discussed with focus on drilling operation. The paper also reviews the studies on milling and turning of NFRCs. The distinct feature of this review is that it identifies the factors that affect the quality of the machined feature and provides general recommendations for the selection of process parameters so as to generate better quality holes during drilling. In addition, the review also discusses the challenges that hinder machining of NFRCs which is a significant contribution to the field of NFRCs. [ABSTRACT FROM AUTHOR]

Composite structures are more susceptible to manufacturing defects than conventional materials. Fiber misalignment, cracks, and voids are typical types of manufacturing defects in laminated composites. Defects can greatly reduce structural integrity and load carrying capacity, so their effects on material and structural strengths must be understood. In this paper, the effect of manufacturing defects on the progressive delamination behavior was studied for carbon/epoxy composite laminated L-beam under four-point bending test conditions. The defects of wavy plies and pure resin that had flowed out were characterized from surface photography and then transformed into finite element modeling using semi-automatic approach to which pre-delamination and void were included. Next, progressive failure analyses were performed with the interface delamination and matrix direction failure accounted for by cohesive zone modeling. Numerical results were examined focusing on the effects of defects on the peak load reduction and the variation of delamination pattern. The stacking sequence effect was also investigated. [ABSTRACT FROM AUTHOR]

Drilling performance of carbon fiber reinforced polymer (CFRP) aggravates significantly with serious tool wear caused by highly abrasive fibers. Because of the anisotropy of CFRP, the angle between fiber orientation and cutting direction, namely, fiber cutting angle, also plays a crucial part in the drilling performance. To enhance drilling performance, this paper initially conducts a comprehensive experimental study on the effects of tool wear on thrust force, exit temperature, and hole wall defect in different fiber cutting angles in the drilling of unidirectional CFRP. The results demonstrate that the profile of worn cutting edge is an approximate elliptical arc and the half axis lengths of the elliptical arc are utilized to evaluate cutting edge wear. Tool wear on the cutting edge, flank face, and rake face all deteriorates with the number of drilled holes. Tool wear has a more significant influence on thrust force in the fiber cutting angle region of 0~90° than in the fiber cutting angle region of 90~180°. With increasing tool wear, the exit temperature distribution can still be approximate to an ellipse. The variation of exit temperature caused by tool wear in the major axis direction is still no less than that in other directions. In addition, on hole wall, tool wear causes severe crack defects in the fiber cutting angle region of 0~90° and cavity defects in the fiber cutting angle region of 90~180°. [ABSTRACT FROM AUTHOR]

To examine the crack propagation in quasi-brittle materials, cohesive models have been suggested by the works of researcher. They treat the existence of a process zone at the crack tip, with a suitable constitutive law, linking the tensile normal stress T and the relative displacement among the two crack edges. In this paper, we employed the cohesive model which examines the mode I interlaminar fracture into stitched reinforced composite laminates. The test configuration that we used in this study was a stitched reinforced double cantilever beam samples. A bilinear damage-rate-dependent cohesive traction–separation law is implemented to design the woven composite fracture and discrete nonlinear spring elements to characterize the stitches influence, its advantages and disadvantages. A novel macroscopic law adopted from a 1D micromechanical-stitching model is invented to model the stitches effect along the interface. The numerical simulations of double cantilever beam test with the present model present a significant agreement compared to the experimental results. [ABSTRACT FROM AUTHOR]

Ceramic coatings are ideal materials for thermal protection systems such as the thermal shield of the space shuttle. In a high-temperature environment, material properties of ceramics strongly depend on the temperature. The severe mismatch of material properties between the ceramic coating and the substrate can result in progressive mechanical failure of thermal protection system. This paper investigates delamination and buckling behaviors between a temperature-dependent ceramic coating and a porous substrate. The shear stress intensity factor at the tips of the delamination crack and buckling region are derived. Based on the stress intensity factor, the critical temperature of the coating buckling from the substrate is obtained. A fitting formula of the critical buckling temperature with respect to the length-to-thickness ratio of the coating, and the buckling region is obtained. It is found that the effect of the temperature dependence of material properties on delamination and buckling is more significant for higher temperatures than for lower temperatures. The critical temperatures of delamination and buckling are overestimated if the temperature dependence of material properties is neglected. The critical temperatures of delamination and buckling increase with the porosity of the substrate. [ABSTRACT FROM AUTHOR]

Delamination, an inter-ply debonding failure phenomenon, is considered as the most undesirable and challenging failure mode in hole making of carbon fiber-reinforced plastic (CFRP) composite laminates. The existence of delamination, even small ones, noticeably damages the strength and stability of the assembled products. It is reported that delamination is responsible for up to 60% of composite components' rejection during assembling. In order to reduce delamination, rotary ultrasonic machining (RUM) has been studied and utilized in hole making of CFRP composites. Existing investigations on delamination of CFRP composites in RUM hole making are experimental studies, in which several methods (such as adjusting input variables and the use of supportive plate) to reduce delamination are reported. To understand delamination generation mechanisms and predict delamination initiation, theoretical investigations are needed. Cutting force models in RUM of CFRP composites have been developed, and it is well accepted that delamination is correlated to thrust force. However, there are no reported investigations to predict delamination initiation and study the impact of thrust force on the delamination of CFRP composites in the RUM hole-making process. Finite element analysis (FEA) could be an effective way to study the delamination in the RUM process. In this paper, FEA was conducted to predict delamination initiation and establish the relationship between the thrust force and delamination thickness in RUM, for the first time. In addition, experiments were conducted to validate the FEA model. The proposed model was proved to be effective in predicting delamination initiation, and the trends of the FEA results agreed well with those of the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on abrasive waterjet (AWJ) drilling of Inconel 718 and AISI 1040 steel, with an aim to understand the AWJ hole drilling performance and to investigate the process monitoring strategy by using acoustic emission (AE). In the experiments, pressure levels were set from 200 to 350 MPa at intervals of 50 MPa, and drilling time between 5 and 30 s at intervals of 5 s. It is found that the hole depth increases along with the drilling time at a slowing down penetration rate. A higher pressure results in a higher penetration rate. While there exists a direct influence of the material property on the drilling efficiency, it has limited significance with regard to the diameter of the hole produced. AE-RMS signal is demonstrated to be able to reflect the decreasing trend of the penetration rate and the influence of the pressure. A strong correlation between the penetration rate and AE-RMS values in AWJ hole drilling is shown through correlation analysis. The AE-RMS is also substantially affected by the material properties. A discrepancy of the AE-RMS under similar condition may suggest an anomaly in this cutting run. [ABSTRACT FROM AUTHOR]

Bilinear delamination failure criteria proposed by Reeder for mixed-mode (I–II) fracture of composite laminates has four limitations: require mixed-mode (I–II) fracture data by the more complex MMB test; determination of bilinear constants by two independent curve fits; failure of bilinear equations to intersect at G I m / G II m = 1 ; and the data representation by G I m versus G II m instead of the conventional G c m versus G II m / G T . Some of these limitations were overcome by limited input bilinear criteria (LIBC) proposed by Davidson and Zhao by replacing the MMB test data by DCB, ENF, and SLB (single leg beam) test data. But the LIBC retained the two discontinuous forms of the equations for no specific reason in a continuous material system. This paper eliminates the two equations by a single power law equation that covers the whole domain of fracture as in Benzeggagh and Kenane's empirical equation. This simplified mixed-mode delamination fracture criterion we call "Limited Input B–K (LIBK) criterion in recognition of the works of Davidson and Zhao, and Benzeggagh and Kenane. The criterion was validated by a large number of test data in the literature. [ABSTRACT FROM AUTHOR]

Process-induced damages, such as burrs and delamination, frequently occur and are the critical hole quality issues for CFRPs. These damages are strongly influenced by the axial cutting force. By employing the novel drill-milling process, the influence of the axial cutting force may be completely eliminated, and the process-induced damages can be remarkably removed. The drill-milling tools with a better performance are very critical to the drill-milling process. In this paper, according to the drill structure with V-shaped cutting edges and the mill structure with double-crossed helix flutes, two different new drill-milling tools are designed, and a series of tests are conducted on CFRPs. The result indicates that the influences of the cutting forces on the damages can be remarkably reduced during the helical milling phase by employing the drill-milling process. Under the same cutting conditions, the cutting forces of T2 are significant less than that of T1. The re-trimming effect of T2 is superior significant than that of T1 during the helical milling phase. The damages can be significantly reduced by using these two tools, especially by using T2 tool. [ABSTRACT FROM AUTHOR]

This paper studies the detection of hidden polymer matrix composite delaminations with a pitch–catch ultrasonic testing system and an agglomerative clustering algorithm. Existing ultrasonic testing methods characterize damage through normal-incidence pulse-echo measurements. Yet, these pulse-echo methods are ineffective at detecting delaminations underneath other delaminations. The ultrasonic waves only reflect off the top delamination. As a result, no information about the lower delamination is transmitted to the receiver. To address this problem, we investigate an oblique-angle pitch–catch ultrasonic testing method to transmit ultrasonic waves underneath the delaminations. The ultrasonic waves interact with the lower delaminations and carry that information to the receiver. We describe and discuss our experiments, which use two polytetrafluoro-ethylene (PTFE) inserts to simulate delaminations. We show that applying agglomerative clustering to the experimental data can successfully distinguish three regions: regions with two PTFE inserts, regions with only an upper PTFE insert, and regions with only the lower PTFE insert. Normal-incidence measurements only observe two regions. [ABSTRACT FROM AUTHOR]

Drilling holes on carbon fiber reinforced plastic/polymer (CFRP) and Ti stack structures is significantly important assembling process in aerospace manufacturing. However, it is quite a challenge that the excessive and completely different drilling loads of two materials with distinguish physical and mechanical properties will lead to frequent CFRP drilling damages and Ti burrs, as well as rapid tool failures. Therefore, understanding and controlling the drilling loads are crucial to ensure low damage and high efficiency drilling of CFRP and Ti stacks. In this paper, a novel mechanistic model was established to predict the thrust force and the torque in the drilling of CFRP and Ti stacks. The cutting loads of a twist drill were discretized along chisel edge, primary cutting edge, and minor cutting edge. An orthogonal cutting model and an oblique cutting model were proposed to represent the discretized cutting load for CFRP and Ti with the consideration of fiber cutting angles, flank face friction, and drilling parameters. Integrating the discretized cutting load, a mechanistic model for predicting thrust force and torque was developed for drilling of CFRP/Ti stack. After the coefficient calibrations, verification experiments showed that the developed model has accurately predicted the thrust force and torque under various spindle speeds/feed rates as well as the changing fiber cutting angles. [ABSTRACT FROM AUTHOR]

One of the most severe, costly, and time-consuming problems in the drilling operation is the loss of circulation. The drilling fluid accounts for 25–40% of the total cost of the drilling operation. Loss of the drilling fluid will increase the total cost of the drilling operation. Uncontrolled lost circulation of the drilling fluid may result in dangerous well control problem and in some cases the loss of the well. Fluid losses can occur in different formations such as natural fracture, induced fracture, unconsolidated, and cavernous and vugular. The objective of this paper is to deeply understand and illustrate different types of loss of circulation, techniques used to determine the loss rate, and detection of loss zones. In addition, losses mitigation techniques, different lost circulation materials (LCM), and the apparatus used to evaluate the available LCM will be explained in detail. The deep literature review illustrated that lost circulation costs 10–20% of the cost of drilling high-pressure high-temperature wells and 90% of these losses occur in fractured formations. The loss rate depends on the drilling fluid types, and it is generally higher in the case of water-based drilling fluid than in the case of oil-based drilling fluid. It is important to utilize an advanced measurement for losses with high frequency to detect the occurrences of lost circulation quickly and correctly. The measurements of flow rate (flow in and flow out) should be supported by additional data such as logging data, lost circulation information (loss rate and depth), mud properties, and surface drilling parameters. The preventive approach is the most efficient to mitigate the loss of circulation since the use of conventional LCM is not successful in most of the cases because of their limitations. It is vital to consider the size of different fractures encountered while drilling and modify the laboratory equipment to simulate this problem. Loss of circulation is affected by many parameters that are related to formation characterization, drilling parameters, fluid properties, and a lot of other known and unknown factors. Therefore, it is a challenge to predict the loss of circulation. To overcome such challenge, it is recommended to develop a new technique such as artificial intelligence to predict the thief zones and the loss rate by capturing the changes in the drilling mechanical parameters and the fluid properties. [ABSTRACT FROM AUTHOR]

The paper discusses a method for measuring changes in the electric resistance of a unidirectional carbon-fiber-reinforced plastic (CFRP) to detect an internal delamination. A numerical solution was obtained by the four-probe method for measuring the electric resistance. The influence of distance between electrodes on the efficiency of delamination detection was investigated. The problem was solved by the method of planning of experiments and constructing a surface response by using a 2D finite-element model. The distance between electrodes and the length of delamination were selected as parameters of the study. Distances between the internal and external electrodes for an effective detection of delaminations are determined. [ABSTRACT FROM AUTHOR]

Fatigue fracture of fiber-reinforced polymer composites (FRP) occurs when microcracks are induced by debonding, pull-out and delamination at the interface between the matrix and fiber. This microcrack area increases with increase in fatigue cycles and a damage region is formed. In our previous paper, fatigue life of a short fiber-reinforced polymer composite consisting of glass fibers and polycarbonate matrix was found to be related not to the main crack growth behavior but to the progression behavior of the damage region. In this paper, using our proposed real time observational system, we performed detailed observations on the behavior of fatigue damage and clarified the mechanism of damage progression. Furthermore, mechanical considerations were performed by finite-element elastic-plastic stress analysis. The results mentioned above indicate that control of short fiber alignment makes it possible to release the stress concentration caused in the matrix, and disperse fatigue damage. This results in an enormous improvement in fracture toughness. [ABSTRACT FROM AUTHOR]

Over-melting and vaporization of resin matrix are usually found along a cut in the laser machining of carbon fiber reinforced plastic (CFRP). This is considered as the heat-affected zone (HAZ) and it has to be minimized to avoid the delamination of CFRP laminates. This paper presents the use of water flow to cool down the CFRP during the laser machining process. A thin flowing water layer induced by the impingement of low-pressure waterjet was formed on the workpiece surface, where a laser beam performed the ablation underneath the water layer. With this technique, the excessive heat and cut debris can be carried away from the workpiece by water. In this study, the effects of laser traverse speed, orientation of carbon fiber, water flow rate, and flow direction on cut dimensions and HAZ size were experimentally investigated. Using high water flow rate can limit the expansion of HAZ and also assist the material removal. In addition, the water flow directed along the laser traverse direction can increase the cut depth. The groove aspect ratio produced by the presented technique was found to be the same level as the laser ablation in air but the HAZ size was 20% smaller than the dry ablation. A predictive model for cut depth based on energy balance was also developed and analyzed in this study. The experimental findings and theoretical model presented in this work could enable a better understanding of the laser ablation in the flowing water layer and highlight the potential use of this technique for processing CFRP and other similar materials. [ABSTRACT FROM AUTHOR]

Drilling of carbon fiber-reinforced polymer (CFRP) is one indispensable machining operation to produce holes for final assembly of structural parts. Excessive cutting forces during drilling processes will lead to machining defects, such as fiber breakage, burrs, micro cracks, and plies delamination within laminate. This paper aims to simulate the variation of instantaneous cutting forces in CFRP drilling considering the influences of fiber orientation, machining parameters, and tool geometries. The cutting edges are split into infinitesimal elements; the instantaneous cutting forces are obtained by the accumulation of elemental forces exerted on all engaged elements. The overall cutting forces are the combination of forces contributed by the cutting lips and chisel edge using different machining mechanisms; oblique cutting and mechanistic modeling approaches are applied to the cutting lips while the principle of contact mechanics is adopted for the chisel edge. An integrated artificial neural network (ANN) and genetic algorithm (GA), ANN-GA is developed especially for predicting the specific cutting force coefficients, which are functions of the fiber orientation and can account for the variation of cutting forces. Meanwhile, the change of geometrical parameters along the cutting lips is analyzed, and the effects of fiber orientation and tool geometries are integrated in the model. Results showed the proposed model is able to predict the instantaneous cutting forces in CFPR drilling. Model predictions agree well with experimental data and are beneficial for optimizing the machining processes of CFRP composite laminates. [ABSTRACT FROM AUTHOR]

In aerospace manufacturing, drilling carbon reinforced composites is one of the dominant processes. The exit-ply delamination, directly related to the drilling thrust force, occurs more often despite all precautions. In this paper, a new analytical model is presented to predict the critical thrust force at which delamination will start. The model takes into account the thermo-mechanical loads and considers a mixed mode of fracture occurring in the delamination area. This model explains how the delamination area starts with a circular cross-sectional area in the entrance layer and grows into an ellipsoid, in the same direction of the fibers, in the exit layer. Besides, the distribution of the load in the delamination area includes a center point load for the chisel edge of the drill bit and a linearly distributed load for the cutting lips. The results of the proposed model are compared with previous analytical models using three different sets of experimental data and the comparison showed that the presented model is more accurate. [ABSTRACT FROM AUTHOR]

During the research on high-quality hole drilling technology for glass fiber–reinforced polymer (GFRP), more and more researchers have discovered and focused on the coupling effect between the machining parameters on the damage at the hole exit. Most of them have verified and described this phenomenon by mathematical statistics, but there is no further analysis for its mechanism. In this paper, a set of orthogonal experiments were conducted to investigate the coupling effect between the clearance angles of outer cutting edges, the spindle speed, and the feed speed when drilling the GFRP materials with candlestick drills. Through the experimental results shown by the response surface, the influencing factors of the exit damage were divided into the pushing effect, cutting effect, and the physical properties of the material according to the special damage formation process. It was found that the reason for the coupling effect of the machining and tool parameters was that the change of these parameters would have different effect on the pushing, cutting, and physical properties of the materials at the same time. In addition, the optimal machining parameters for each candlestick drill were also given according to the experimental results. [ABSTRACT FROM AUTHOR]

Accurate exit-delamination morphology (i.e., shape and size) is of great significance both to evaluate and to control for the delamination during the drilling of carbon fiber-reinforced plastics. However, the morphology of the exit delamination in different fiber orientations is still difficult to precisely predict. In this paper, a theoretical model is established based on the classical bending theory of beam and the linear elastic fracture mechanics for determining the exit-delamination morphology. Based on this theoretical model, the accurate exit-delamination morphology can be precisely predicted. The results show that the exit-delamination zone is near to the elliptical shape, and its size decreases with the increasing of the cutting speed but increases with the increasing of the feed speed. Both the Zhang model and the beam theory model can predict the exit determination morphology. The beam theory model can reflect effectively the influences of the cutting speed and the feed speed on the exit delamination. [ABSTRACT FROM AUTHOR]

This paper presents a new mathematical model for analytical investigation of global buckling behavior of slender concrete-filled steel tubular (CFST) columns with circumferential gaps and partial debonding between the concrete core and the steel tube. The analytical buckling load of circular and slender CFST columns with circumferential gaps and partial debonding is derived for the first time. The critical buckling load decreases as the magnitude and length of the circumferential gap increases. Nevertheless, it is shown that if the length of the circumferential gap is smaller than the length of the CFST column, this effect is less than 4%. On the other hand, for a fully delaminated CFST column, this effect can be up to approximately 40%. Similarly, the first buckling shape modes proved to be notably affected by the circumferential gap only if its length is greater than 75% of the CFST column length. The results can be used as a benchmark solution for the buckling problem of slender circular CFST columns with circumferential gaps and partial debonding between the materials. [ABSTRACT FROM AUTHOR]

In this paper, the recently-developed floating node method is extended for damage analysis of laminated composites with large deformations. Strong discontinuities including interfacial delamination and matrix cracks are explicitly represented by geometrically nonlinear kinematics. Interactions between these two kinds of failure patterns are enabled through enriched elements equipped with floating nodes. A cohesive zone model is utilized for the damage process zone. A general implicit procedure with user-defined elements is developed for both quasi-static and dynamic analysis. The performance of this formulation is verified with two benchmark simulations, involving buckling-induced delamination and low-velocity impact damage. The results presented show good quantitative and qualitative agreements with results from literature. [ABSTRACT FROM AUTHOR]

This paper studies the effect of Sb and Y additions on the microstructure and mechanical properties of the AZ91 alloy. The results indicate that the Sb and Y additions lead to the formation of MgSb and AlY phases. These phases modify the morphology of the β-MgAl phase, and hence refine the microstructure. The effects of Sb and Y additions on the aging behavior have also been investigated. Aging of the AZ91 alloy results in the formation of continuous and discontinuous types of precipitates. Whereas Sb and Y additions to AZ91 alloy suppresses the formation of discontinuous precipitate. The paper also reports the mechanical properties of as-cast and aged Sb-added AZ91-xY alloys for room and high temperatures. The optimum tensile properties are obtained with the alloy having the combined addition of 0.5 wt pct Sb and 0.6 wt pct Y. The fracture surface of AZ91-0.5Sb-0.6Y alloy reveals more quasi-cleavage type of failure with a cleavage fracture than the base alloy. At HT, the AZ91-0.5Sb-0.6Y alloy displays more cleavage facets connected with tearing ridges and shallow dimples than AZ91 alloy. Furthermore, it observed the improvement in wear resistance through the addition of Y. The worn surface reveals abrasion, oxidation, delamination, and plastic deformation wear mechanisms. [ABSTRACT FROM AUTHOR]

An increasing trend can be seen in the use of CFRP and titanium as hybrid materials in the aerospace industry, but machining them still remains the main challenge due to their anisotropic mechanical behavior and poor machinability. Since helical milling, in open literature, has been found to produce better results with CFRP/Ti stack, different milling strategies were experimentally designed, with the main goal of this paper being to obtain the milling strategy with best hole quality. The key factors monitored during the experiments were milling order, thrust force, temperature, and hole quality. The four strategies included the first two, with milling the 12 mm hole diameter in one attempt; the other two, with a three-step milling process, while all the strategies differ from each other in terms of machining order of the workpiece. It is showed that thrust forces are linearly proportional to the feed rates and inversely proportional to the cutting speeds. Among the first two strategies, the CFRP/Ti order stack experienced less damage compared to the Ti/CFRP one. However, the three-step milling definitely brought better hole quality results in terms of significant reduction in delamination, and to further prove this point, SEM scans were essential for delamination factors to be calculated for each strategy. Even though the delamination factor was lower in the three-step milling, the order of the stack also played a major role in reducing the degree of delamination. When starting with CFRP as the top layer, the titanium plate acts as a support to prevent push-down delamination in CFRP. [ABSTRACT FROM AUTHOR]

In this two-part paper we introduce a new formulation for modeling progressive damage in laminated composite structures. We adopt a multi-layer modeling approach, based on Isogeometric Analysis (IGA), where each ply or lamina is represented by a spline surface, and modeled as a Kirchhoff-Love thin shell. Continuum Damage Mechanics is used to model intralaminar damage, and a new zero-thickness cohesive-interface formulation is introduced to model delamination as well as permitting laminate-level transverse shear compliance. In Part I of this series we focus on the presentation of the modeling framework, validation of the framework using standard Mode I and Mode II delamination tests, and assessment of its suitability for modeling thick laminates. In Part II of this series we focus on the application of the proposed framework to modeling and simulation of damage in composite laminates resulting from impact. The proposed approach has significant accuracy and efficiency advantages over existing methods for modeling impact damage. These stem from the use of IGA-based Kirchhoff-Love shells to represent the individual plies of the composite laminate, while the compliant cohesive interfaces enable transverse shear deformation of the laminate. Kirchhoff-Love shells give a faithful representation of the ply deformation behavior, and, unlike solids or traditional shear-deformable shells, do not suffer from transverse-shear locking in the limit of vanishing thickness. This, in combination with higher-order accurate and smooth representation of the shell midsurface displacement field, allows us to adopt relatively coarse in-plane discretizations without sacrificing solution accuracy. Furthermore, the thin-shell formulation employed does not use rotational degrees of freedom, which gives additional efficiency benefits relative to more standard shell formulations. [ABSTRACT FROM AUTHOR]

Thanks to its good specific strength and modulus, carbon fiber-reinforced plastic (CFRP) is widely used in such fields as aerospace and automotive. Nonetheless, it is very likely that the serious tool wear and some surface quality defects occur in machining, such as delamination, tear, burr, and so forth. Thus, this paper carried out the experimental research into the tool wear in milling carbon fiber composites with spiral staggered diamond-coated milling cutter. According to the evolution of tool wear micro-morphology, the tool wear process was obviously divided into two stages, i.e., coating particle wear and coating shedding. It was found that the former was dominated by the abrasive wear mechanism and the latter the fatigue wear mechanism. In addition, wear mechanism and cutting force variation of each stage were analyzed. In addition, the coating shedding happened obviously in advance with the increase of milling speed. In the period of coating particle wear, the tool was in good cutting performance, and its cutting force changed slowly, while after it came into coating shedding period with the aggravation of tool wear, the cutting force increased greatly and the cutting performance worsened obviously. Thus, the appropriate control over the tool wear of spiral staggered diamond-coated milling cutter is the key to improving the machining quality of carbon fiber composites. [ABSTRACT FROM AUTHOR]

The paper considers multilayer composite nanostructured modified Ti-TiCN-(Ti,Al)CN coatings for metal-cutting tools. The coatings under the study have identical elemental composition (Al 30 at.%, Ti 70 at.%) and thickness (5 µm), but differ in the thicknesses of the nanolayers. The mechanical characteristics of the coatings were studied, and the tool life tests were carried out for carbide tools with the above coatings for dry turning of steel C45 a t v c = 300, 350, and 400 m/min. Microstructural studies (using SEM) of the nature of wear and failure of metal-cutting tools with the coatings under study were conducted. It was found that, with the same strength of adhesion bond to the substrate, a coating with thicker sub-nanolayers has a greater tendency toward interlayer and inter-sublayer delamination. A tool with a coating characterized by a lower thickness of subnanolayers showed the longest tool life at all cutting speeds. [ABSTRACT FROM AUTHOR]

Drilling is an indispensable process for assembling the composites components. The drilling-induced delamination damage generally refers to the peel up delamination on the entrance surface and the push down delamination on the exit surface. Many researchers have carried out studies on drilling force and delamination damage in composites using special drills. Candle stick drills have been recognized as advantageous tools for the reduction of thrust force and delamination damage in drilling composites. Drilling experiments of glass fiber-reinforced plastic (GFRP) composites and finite element simulations were carried out in this paper. Three candle stick drills with different drill tip geometries and one twist drill were compared in terms of thrust force, peel up delamination, and push down delamination. The results revealed that, compared to twist drill, not all candle stick drills could get relatively good drilling results. What is more, drilling results of candle stick drills had a great relationship with the drill tips geometry angles. Finally, an optimized candle stick drill with appropriate drill tip geometry achieved relatively excellent drilling results. [ABSTRACT FROM AUTHOR]

The delamination of a circular thin film at micro/nanoscale is studied using the Kirchhoff plate theory incorporating surface effects in this paper. Bending of a clamped circular nanoplate subjected to a concentrated force at the center or a uniformly distributed force over a lateral surface is solved. The bending deflection is derived in closed form. The adhesion energy and its release rate for delamination are determined when surface effects are taken into account. The influences of surface residual stress and surface elasticity along with the film’s size on the energy release rate of debonding advance or interfacial adhesion of a thin film bonded to an elastic substrate are analyzed for applied loading or given displacements. Analytic results are compared with experimental data and satisfactory agreement is confirmed. [ABSTRACT FROM AUTHOR]

Surface quality plays a vital role in fabricating high-precision components. Taper cutting experiment with increased depth of cut from 0 to 20 μm was conducted on oxygen-free high conductivity (OFHC) copper and C37700 brass workpiece in this paper. It was found that surface delamination phenomenon occurred in diamond micro-grooved surface of OFHC copper workpiece at a depth of cut larger than 11 μm, while there was no delamination being found on brass workpiece. It was suspected that the formation of surface delamination on OFHC copper workpiece was influenced by the plastic deformation and stress state of the material in the subsurface area in diamond micro-machining process. [ABSTRACT FROM AUTHOR]

The growing use of thermoplastic composites (TPCs) like low-melting polyaryletherketone (LM-PAEK) matrices reinforced with unidirectional carbon fiber (CF) in aircraft structures presents a significant challenge in terms of lightning strikes and electromagnetic interference shielding during aircraft operations. This is due to the weak electrical conductivity of TPC structures, which results in widespread damage when struck by lightning. The repair and maintenance of these extended damaged sites can increase operational costs and loss of flights. Several lightning strike protection (LSP) systems have been developed and implemented to address these concerns. This study evaluated a highly conductive coating with a low filler rate for its effectiveness as an LSP solution for TPCs on exterior aircraft surfaces. The TPC panel without any coatings was first studied. Subsequently, the level of conductivity was increased by incorporating the nanoscale conductive fillers, silver-coated copper (Ag/Cu) nanoflakes, with a silver content of 20 wt.% (Ag20/Cu) and 30 wt.% (Ag30/Cu), correspondingly, into the coating at two loadings of 55 wt.% and 70 wt.% in an epoxy carrier for the surface coatings. The behavior of electrical and surface conductivity was thoroughly examined to understand the impact of Ag/Cu with a high aspect ratio and the effectiveness of the LSP solution. In addition, the spray-coated TPC panels underwent rigorous Zone 2A lightning strike testing using simulated lightning current, in agreement with the industry standard of Society of Automotive Engineers (SAE) Aerospace Recommended Practice (ARP) 5412B. Despite the higher resistance due to the lower conductive coating weight, the TPC panels with Ag30/Cu at loading of 70 wt.% achieved better results than those with Ag30/Cu at loading of 55 wt.%. This is evidenced by the minor structural delamination and CF breakage on the front surface, which proposes a new economic route for a sustainable post-processed LSP system in the aviation industry. [ABSTRACT FROM AUTHOR]

The impact-echo method (IE) is a non-destructive testing method commonly used in civil engineering. We propose a completely new approach for air-coupled actuation based on supersonic jet flow. The impinging jet sound generates continuously high sound pressures with a broad frequency bandwidth. This novel concept of utilising aeroacoustic sound for air-coupled IE was evaluated on two concrete specimens and validated using a classical IE device with physical contact. The results show a high agreement with the expected frequencies. Delaminations are correctly detected in depth and size. This proves the high reliability of air-coupled IE based on supersonic jet flow. [ABSTRACT FROM AUTHOR]

This paper is a continuation of Survey I [], where the historical background and general remarks on the problem formulation and solution methods were outlined and results related to plane-strain problems were reviewed. In the present paper, a review of axisymmetric and 3D buckling delamination problems is presented. [ABSTRACT FROM AUTHOR]