Presence Of Delamination Research Articles

A modified arthroscopic en masse suture bridge repair is effective for delaminated rotator cuff tears.

This study aimed to clarify the characteristics of delaminated rotator cuff tears (RCTs) and evaluate the clinical outcomes of a modified arthroscopic en masse suture bridge repair for delaminated RCTs. Patients with full-thickness RCTs, who underwent arthroscopic suture bridge repair with a minimum 2-year follow-up, were retrospectively reviewed. Patients were categorized into two groups based on the presence of delamination. Delaminated RCTs were treated using a modified en masse suture bridge technique, while nondelaminated RCTs received a conventional suture bridge technique. Preoperative and postoperative Constant scores and American Shoulder and Elbow Surgeons (ASES) scores were determined to evaluate clinical outcomes. Postoperative magnetic resonance imaging (MRI) was carried out to identify the integrity and retear of the repaired rotator cuff. A total of 172 patients were included in our study cohort, in which 67 (39%) delaminated RCTs were confirmed intraoperatively. The prevalence of delamination was significantly higher in large tears (53/102, 52%) compared to medium tears (14/70, 20%) (p < 0.001). No significant differences in age (n.s.) or gender (n.s.) were observed between the two groups. Both groups showed significant improvements in Constant and ASES scores postoperatively (both p < 0.001), with no significant differences between the groups (n.s.). The retear rates were 2/67 (3.0%) in the delamination group and 3/105 (2.9%) in the nondelamination group, showing no significant difference (n.s.). The modified arthroscopic en masse suture bridge technique was effective for repairing delaminated RCTs, yielding favourable clinical outcomes comparable to those of nondelaminated tears. Level IV.

Predictive modeling of buckling in composite tubes: Integrating artificial neural networks for damage detection

Tubular structural composites are widely used in applications where high stiffness and low weight are required. This work proposes the study and evaluation of the influence of damage on the structural responses of thin-walled structures made of composite materials, as well as the development of a buckling prediction model using artificial intelligence. The methodology is approached on a few main fronts, namely: i) numerical modeling of the direct problem of the structure in finite elements, ii) modeling and parameterization of delamination in the elliptical shell model; iii) obtaining a database through finite element updating and iv) formulation and construction of the regression and prediction model using artificial neural networks. The numerical results showed that, as expected, the presence of delamination has a significant impact on the occurrence of buckling. The study also showed that it is possible to predict buckling values, with extremely satisfactory results - an error of around 1%, provided that more complex regression methods are used, such as regression by artificial neural networks, since the relationship between damage and buckling values is not trivial.

Tribological Properties of Aluminium Matrix Syntactic Foams Manufactured with Aluminium Smelter Waste

Aluminium smelter waste (ASW) is a big contributor to landfills, and its recycling has been of great interest. This study investigates the tribological properties of aluminium matrix syntactic foams manufactured using an Al 6082 alloy and ASW. Ball-on-disc tests were conducted under both dry and lubricated conditions. Under dry sliding conditions, the coefficient of friction (COF) had an initial sharp increase, followed by a gradual decrease and finally a steady state as the sliding distance increased. The wear surfaces showed the presence of adhesive, abrasive and oxidative wear, with some presence of delamination. Syntactic foams containing small ASW particles led to a decrease in surface roughness, decrease in the average COF and decrease in specific wear. Heating large ASW particles before manufacturing the syntactic foams enhanced overall wear properties because the particles are hardened due to a compositional change. The T6 treatment of the syntactic foams enhanced the wear properties due to the hardening of the Al matrix. The average COF of the ASW syntactic foams was higher than that of the E-sphere syntactic foam, which was predominantly abrasive wear. The specific wear of the ASW syntactic foams can be higher or lower than the E-sphere syntactic foam, depending on the ASW particle size. Under lubricated sliding test conditions, the wear was reduced significantly, and the type changed from predominantly adhesive to predominantly abrasive. The porous ASW particles acted as lubricant reservoirs and provided a constant supply of lubricant, further improving the lubrication effect.

Genetic Multi-Objective Optimization of Sensor Placement for SHM of Composite Structures

Increasingly often, due to the high sensitivity level of diagnostic systems, they are also sensitive to the occurrence of a significant number of false alarms. In particular, in structural health monitoring (SHM), the problem of optimal sensor placement (OSP) is appearing due to the need to reach a balance between performance and cost of the diagnostic system. The applied approach of considering nondominated solutions allows for adaption of the system parameters to the user’s expectations, treating this optimization problem as multi-objective. For this purpose, the NSGA-II algorithm was selected for the determination of an optimal set of parameters in the OSP problem for the detection of delamination in composite structures. The objectives comprise minimization of type-I and type-II errors, and number of sensors to be placed. The advantage of the proposed approach is that it is based on experimental data from the healthy structure, whereas all cases with a presence of delamination were acquired from numerical experiments. This makes it possible to develop a customized SHM system for the arbitrary location of damage.

Delamination Effect on the Buckling Behaviour of Carbon–Epoxy Composite Typical Aeronautical Panels

The instability of structures due to compression is one of the most critical issues related to aircraft components. Especially in composite materials, which have poor out-of-plane mechanical properties, the buckling load must be assessed to ensure that the structures are within the safe limits compared to the operating loads. In the presence of delamination, the compression instability of structures becomes catastrophic, as the propagation of delamination can dramatically reduce the stiffness of the structure almost instantaneously. During the operational life of composite aircraft components, one of the most common events that can occur is low-velocity impact with foreign objects, which is one of the primary reasons for delamination. In this paper, a sensitivity analysis is presented on a typical aerospace reinforced panel with a circular delamination, representative of an impact damage. Different configurations have been analysed, varying the radius and position along the thickness of the delamination. Furthermore, some geometric parameters of the panel have been modified to evaluate how the buckling load and the propagation of interlaminar damage evolve.

Discrimination between weak adhesion, delamination and kissing bond at the interfaces of composite bonded assemblies

In this work, the impact of delamination, weak adhesion and kissing bond defects at the interfaces of trilayer composites structures, are numerically investigated in order to differentiate these three phenomena that are usually encountered in composite bonded assemblies. The structure is composed by two carbon-epoxy composites with 1.8 mm bonded by an adhesive epoxy of 0.5 mm. The Stiffness Matrix Method (SMM) is used to calculate the transmission and reflection coefficients of bulk waves likely to propagate in a trilayer structure immersed in water. Then, the behaviors of the symmetric and antisymmetric Lamb modes are analyzed. Four different states of interfaces are considered: (a) nominal interfaces with good adhesion, (b) interfaces with weak adhesion, (c) interfaces with delamination and (d) interfaces containing kissing bond defects. The carbon-epoxy composite is considered as an orthotropic layer and the epoxy adhesive interface as an isotropic layer. Results show that, only the antisymmetric Lamb modes are affected by the presence of kissing bond defects while the symmetric and antisymmetric Lamb modes are affected by the presence of delamination at the interfaces. In addition, weak adhesion only partially preserves the symmetric modes (with a shift in their frequencies) and introduces a reduction in amplitude compared to kissing bond like defect. The potential of the proposed method for the qualification of bonded composite structures is clearly demonstrated, with the ability to discriminate among three categories: weak adhesion, delamination and kissing-bond-like defect.

Assessment of Defects under Insulation Using K-Medoids Clustering Algorithm-Based Microwave Nondestructive Testing

Composite insulations, such as ceramics, are commonly utilized in the turbine system as a thermal coating barrier to protect the metal substrate against high temperatures and pressure. The presence of delamination in the composite insulations may cause turbine failure, leading to a catastrophic accident. Thus, regular non-destructive testing is required to detect and evaluate insulation defects. Among the non-destructive testing techniques, the microwave technique has emerged as a promising method for assessing defects in ceramic coatings. Although the method is promising, microwave non-destructive testing suffers from poor spatial imaging, making the defect assessment challenging. In this paper, a novel technique based on microwave non-destructive testing with a k-medoids clustering algorithm for delamination detection is proposed. The representative ceramic coating sample is scanned using a Q-band open-ended rectangular waveguide with 101 frequency points that operated between 33 to 50 GHz. The measured data is transformed from the frequency domain to the time domain using an inverse fast Fourier transform. The principal component analysis is then used to reduce the dimensionality of 101 time steps into only 3 dominant attributes. The attributes of each inspected location are classified as defect or defect-free using the k-medoids clustering algorithm for accurately detecting and sizing the defects in the ceramic insulation. The results reported in this paper highlight the superiority of the k-medoids clustering algorithm in delamination detection, with an accuracy rate of 95.4%. This is a significant step forward compared to earlier approaches for identifying ceramic defects.

Advantages of water droplet machining over abrasive waterjet cutting of carbon fiber reinforced polymer

The cutting of carbon fiber reinforced polymer (CFRP) sheets with conventional tooling, such as an end-mill, results in excessive tool-wear, high-heat generation, and dust emission. Abrasive waterjet (AWJ) cutting has been used as an alternative method; however, this technique often leads to delamination of the composite material, especially around the pierce locations. Moreover, AWJ requires considerable post processing of the machined part to remove residual abrasive particles in addition to the high nozzle and conduit wear rates. A new advancement in pure waterjet cutting, Water Droplet Machining (WDM), has shown success in cutting CFRP sheets without the detrimental effects of delamination. In this paper, the results of cutting 5.5mm-thick CFRP sheet are presented using an AWJ and the WDM process. The cutting performance of the two methods is assessed based on the surface roughness of the cut edge, the presence of delamination, and the geometric accuracy of a variety of basic shapes cut from the sheet.

Computational modelling of mechanical response of glulam beams due to moisture inducted delamination

Glued laminated timber beams are nowadays used as load-bearing beams of large-span structures that operate in various humidity conditions. Typical application areas are aqua parks with high humidity as well as market halls with low humidity. It is related to the possibility of the occurrence of cracks typical for the drying of wood, even with such controlled conditions of production technology as glued laminated timber. Cracks visible on the used girders raise doubts as to the safe operation of the structures. The subject of this paper is the computational simulation and the evaluation of the influence of beam delamination on the mechanical response of the structure. The attention was established on a typical two-span beam of constant height with a slight slope to the horizontal. The numerical analysis was carried out for three variants of the location of potential delamination of different scope. The beams were modeled as a problem of the linear theory of elasticity in a plane stress state with orthotropic material properties. The calculations were made in the Abaqus software environment. The results obtained in the paper allow to determine the areas in which the presence of delamination or cracks should be considered dangerous from the point of view of the safety of operation. Computational analysis is helpful in assessing the safety of structures where cracks appear. Theoretical considerations are supplemented by an example from engineering practice.

Static and free vibration analyses and dynamic control of smart variable stiffness laminated composite plate with delamination

The present work is mainly focused on the static and dynamic analysis of curvilinear fiber laminated composite plate integrated with piezoelectric layers acting as actuators and sensors. Delamination is an inevitable phenomenon in composite structures encountered often in real life operating conditions. The presence of delamination within the structure may significantly affect the dynamic response due to the reduction of stiffness of the structure. An eight-noded isoparametric element using first-order shear deformation theory based finite element formulation is adopted for discretizing the domain. The accuracy and adaptability of the present FE model are established through various validation studies. Further, various parametric studies are conducted to investigate the effect of different delamination sizes and positions on the static and dynamic behavior of smart composite plates with curved as well as straight fiber laminates for various boundary conditions. It is observed that the curved fiber laminates provide the flexibility to adjust the fiber orientation within the lamina in such a fashion that frequency reduction due to delamination can be reduced. An attempt is made to effectively damp out the vibration of a smart delaminated plate with the use of active feedback control.

Investigation of delamination effect on nonlinear vibration behaviors of a composite plate resting on nonlinear elastic foundation

The aim of the present work is to investigate the delamination effect on nonlinear vibration behaviors of composite plate resting on nonlinear elastic foundation. The composite plate is assumed to be pre-delaminated with various delamination locations and modeled with an improved layerwise theory and finite element method. The delamination is simulated by the Heaviside unit step function allowing for the discontinuity of displacement fields. By means of the variational principle, the nonlinear governing equations can be obtained and further solved by the direct iterative method. The model takes into account three foundation parameters so as to investigate their effect on the nonlinear vibration characteristics. Three longitudinal locations and three interfacial locations are considered, and both clamped-free and clamped–clamped boundary conditions are considered to investigate the nonlinear vibration behaviors. The results show that different from the linear vibration, with the existence of delamination, the nonlinear fundamental frequencies may exceed the fundamental frequency of the healthy plate when the vibration amplitude ratio reaches a certain value. This finding may help engineers understand the nonlinear vibration behaviors and further detect the delamination in composite plate resting on nonlinear foundations in presence of delamination.

Atlas of Micromorphological Degradation of Archaeological Birch Bark

In this paper we present an atlas of micromorphological degradation of archaeological birch bark for the first time. We analysed the morphology of 13 samples extracted from ice-logged, waterlogged and cave-retrieved objects dated from the Neolithic to the Middle Age by means of light microscopy (LM) and transmission electron microscopy (TEM). We then compared their morphology to that of a contemporary sample, both intact and decayed. In all samples, 13 morphological characteristics that can be associated with fungal, bacterial, chemical, mechanical and light degradation are defined and described, and example LM and TEM images are provided. This novel atlas provides conservator-restorers a much-needed tool to relate the macroscopic appearance to the microscopic structure of birch bark objects. The most important macroscopic features allowing estimation of the state of preservation at the cell level are colour changes, loss of pliability, presence of delamination and increased brittleness. Colour change and delamination can be connected to microscopic features, and microscopic analysis can trace whether they were caused by biotic, chemical or physical decay. However, increased brittleness cannot be connected to a specific microscopic feature.

Predicting Delaminations and Residual Strength of Carbon Fibre Reinforced Polymers (CFRP) After One-Sided Thermal Loading by Means of Infrared Spectroscopy

This study investigates the change of chemical, structural, and mechanical properties of carbon fibre reinforced polymers (CFRP) after one-sided thermal loading. Therefore, CFRP samples (HexPly® 8552/IM7) with varying thickness (4 and 8 mm) are irradiated at different heat fluxes (15, 30, and 50 kW/m2). For a depth-resolved view on matrix degradation inside the CFRP, infrared spectroscopy (ATR-FTIR) is applied along a ground incline plane. A change of structural properties in the form of developing delaminations is investigated with microfocused computed X-ray tomography (µCT). The loss of residual strength is determined by means of interlaminar shear strength testing (ILSS). The evaluation of the data shows that delaminations occur predominantly dependent on temperature and only beyond a certain level of matrix degradation traceable by IR spectroscopy. It is also shown that delaminations are mainly responsible for the loss of strength. Furthermore, linear discriminant analysis (LDA) is performed to predict the presence of delaminations. This information provides a basis for a reliable prediction of the residual strength by IR spectroscopy after one-sided thermal loading.

On the deformation of coated functionally graded structures with delamination

The paper considers problems for extensional inhomogeneous layered structures with functionally graded coatings in the presence of delamination. An approach that allows, from a single point of view, to study the problem of equilibrium of a strip non-uniform along the vertical coordinate with a delaminated coating and the problem of steady-state oscillations of a cylindrical waveguide with a ring crack is developed. Using the Fourier transform, the problems for the strip and waveguide are reduced to canonical systems of differential equations with variable coefficients with respect to transformants of the stress tensor components and displacement vector. Based on the formulation of several auxiliary Cauchy problems, a scheme for constructing a system of integral equations with hypersingular kernels with respect to jumps of displacements on the banks of delamination is presented. The asymptotic behavior of the Fourier symbols of kernels of integral operators for large values of the transformation parameter is investigated. A computational scheme for solving the system of integral equations based on the boundary element method is developed. The results of computational experiments on the determination of the disclosure functions of the delamination banks for a strip and a waveguide in the presence of a discontinuity in the elastic moduli at the boundary of the main body and the coating are presented.

Experimental, Numerical and Finite Element Vibration Analysis of Delaminated Composite Plate

The vibration of the delaminated composites concerns the structure safety and dynamic behavior of the composite structures as it can be vital in the presence of delamination. In this research paper, the finite element simulations, numerical simulations and the experimental work are combined to analyze the vibration behavior at different delamination size, different stacking sequences and different boundary conditions. The finite element analysis software packages like Ansy and Abqus are used to fetch the vibration response of carbon fiber reinforced polymer composite plate for different boundary conditions, stacking sequences and delamination sizes. Experiments are carried out to study the vibration behavior. Numerical results were obtained using the first order shear deformation theory. Rayleigh-Ritz method was used to derive the governing equations to find the natural frequencies and the results were computed using Matlab tool. The results from finite element, numerical and experimental analysis were then compared and verified that the maximum percentage of error is ignorable. It is seen that the natural frequencies of carbon fiber reinforced polymer decreased with an increase in delamination size subjected to all boundary conditions. The higher values of natural frequencies found for all sides clamped boundary conditions.

Behavioural study of surface Rayleigh waves in concrete structure containing delamination

Delamination is one of the defects that cause concrete structures to fail in structural integrity. For this reason, the assessment of concrete delamination without affecting the serviceability and functionality of concrete structure is essential. Non-destructive tests (NDT) are developed and applied to serve this purpose without damaging the structure components. In this study, Rayleigh wave (R-wave) is proposed to determine the extent of delamination in concrete. Numerical simulations were carried out to examine the behaviour of R-waves propagated through the concrete medium with different concrete delamination conditions, i.e., top delamination and bottom delamination. The relationships between the changes of R-wave group velocity and peak frequency with the existence of delamination were established. The established data were then verified with experimental measurements. It is found that the R-wave group velocity is reduced in the presence of delamination. Furthermore, the group velocity of R-wave is relatively faster while propagating through the delamination layer which is closer to the testing surface. In addition, the peak frequency retrieved from R-wave power spectrum also reduced in the presence of delamination. Owing to these observed changes, the potential of utilising R-wave group velocity and peak frequency in the assessment of concrete delamination is high.

Development of Functionally Graded Tubes Based on Pure Al/Al2O3 Metal Matrix Composites Manufactured by Centrifugal Casting for Automotive Applications

This paper studies the influence of main parameters on the mechanical properties and wear behaviour of functionally graded materials pure Aluminum reinforced by various weight fractions of aluminium oxide (Al2O3). A Functionally graded (FG) pure aluminium/Al2O3 tube was processed by horizontal centrifugal casting method. The hollow tube dimensions are 230 mm outer diameter x 12 mm thickness x 180 mm length. The properties of these FG tubes were compared with unreinforced alloy. Hardness and tensile results in the radial direction showed that the hardness and tensile in accordance with the gradient microstructure was improved from inner zone to outer zone. Wear tests were carried out for different test duration at a constant sliding speed of 8 m/s and loads applied are 14, 24 and 40 N. In all test conditions the wear rate in the outer layer was minimum compared to other layers. In the surface analysis, scanning electron microscope indicated the presence of delamination, wear debris and cracks. FG tubes reinforced by Al2O3 particles have increased mechanical properties and wear resistance compared to its unreinforced alloy (matrix alloy) and is suitable for use in automobile and transport applications.

Vibration Analysis of Cracked Composite Laminated Plate: A Review

Composites are one of the rapidly consuming materials due to their utmost attractive applications ranging from the aerospace to the agricultural products. The composite structures usually experience vibration during service. Experiments showed that presence of delamination in composite structures is one of the major causes of failures in laminated structures. Presence of delamination in a structure not only significantly impacts the stiffness of the structure with declining trends but also affect their vibration properties. The purpose of this paper is to review the literature studies on the effect of vibration on composite delaminated structures subjected to different boundary conditions. The literature studies have been classified on the basis of methodology adapted to analyze the problem i.e experimental work, analytical approaches and finite element methods. In this review particular attention has been given to the study of results attained from the analytical analysis, finite element and experimental works. Comparison of the results conducted by other researchers in the field of the free and forced vibration behavior of the composite laminates subjected to delamination or cracked structures has also been studied. Studies have shown that the location and size of delamination in composite structures significantly impacted the natural frequencies and mode shapes.

Analysis of the Stressed State of a Pipe of Gas Pipeline with Hydrogen-Induced Macrodefect

The long-term operation of gas mains may lead to the appearance of large-scale delamination inside the pipe wall under the conditions of its hydrogenation from the inner surface. The role of the source of hydrogen is played by transported hydrocarbons. We analyze the stressed state of a pipe of gas pipeline with hydrogen-induced macrodefect in its wall under the combined action of the working pressure of gas in the pipe and the pressure of molecular hydrogen inside the defect. The stressed state of the pipe metal is found as a function of the pressure of hydrogen in the macrocavity and computed for the specific geometric parameters of the pipe and a working pressure of natural gas in the presence of delamination detected at a certain depth. The results of calculations can be used to predict the risk of appearance of the macrodefect on the outer surface of the pipe.

Environmental, mechanical and materialistic effects on delamination damage of glass fiber composites: Analysis and optimization

Machining process of glass fiber composites usually induces delamination damage. The presence of delamination may cause changes in the mechanical characteristics of the composite structures. In this research, a comprehensive experimental study is performed to analyze the influence of different parameters such as thermal fatigue, lay-up arrangement, resin type, feed rate and cutting velocity on the delamination of glass fiber composites under different drilling processes. Besides, influence of ultrasonic vibration exerting on the tool as a new and high-tech process is investigated. To follow this aim, different composite specimens with various resin types and lay-up arrangements are fabricated and a thermal fatigue condition is provided. Additionally, the Taguchi method is employed to obtain the optimized damage reduction condition in terms of mentioned parameters. The results indicated that thermal fatigue and unsymmetrical lay-up arrangement result in more delamination damage. It was also established that the influence of mentioned parameters is more considerable in higher cutting velocities. Moreover, ultrasonic vibration application is suggested to have the least delamination damage.