Due to the sensitivity of the results in the delamination area of composite laminates, it is necessary to use accurate theories that include all components of stress to study this area. For this purpose, in the present study, the VIRTUAL CRACK CLOSURE TECHNIQUE based on layer wise theory has been developed to analyze the propagation of delamination in a composite beam. The strain energy release rate in mode I is determined based on the properties of the material and an algorithm is proposed to implement the method. The present method has been implemented numerically in MATLAB software on a 2D and 3D Double Cantilever Beam (DCB). In order to validate the method, it has been compared with the results of previous works based on Finite Element method. An analytical solution to the problem is also presented and compared with the results of the present work. The force-displacement behavior of a DCB composite beam is analyzed, which indicates the suitable capability of this method in the analysis of propagation of delamination, and the computations are reduced relative to the three-dimensional Finite Element.

In advance composite material the propagation of CRACK is a regular failure problem in various engineering applications especially in aircrafts body. The aircraft body components are subjected to various thermal and mechanical loading conditions. It is very difficult, time-consuming and costly process of testing the aircrafts components failure due to various thermal and mechanical conditions. Strain energy release rate (SERR) is the significant parameter for the composite materials and quality of composite materials depends in SERR values.The present investigation is based on ANSYS analysis for finding the strain energy release rate (SERR) value using VIRTUAL CRACK CLOSURE TECHNIQUE ((VCCT)) to understand the fracture behavior of the composite lamina. The circular CRACK present in the middle of the composite plate and subjected to Pressure and temperature loading for different angle (cross-ply& and angle-ply) composite structure laminas. The angle-ply shows less SERR in mode I & II while cross-ply shows less SERR in mode III under the constant Pressure loading conditions. Mode II shows the maximum SERR in cross-ply compared to mode I and III for temperatures 30ºC,80ºC, 130 ºC & 180ºC. SERR for mixed-mode was found by considering the total mode of fracture and validation based on published literature for SERR due to the Thermal load of mode I (GI) for different fiber layup configurations of the circular cut-out.

In this paper the critical strain energy release rate for T300/913 carbon-epoxy laminated composites has been studied using ANSYS finite element software based on VIRTUAL CRACK CLOSURE TECHNIQUE ((VCCT)). Compact Tension (CT) specimen has been used for numerical analyses and the geometrical dimensions have been extracted from the existing references. The results obtained from the finite element analysis are compared with the existing experimental results in literature. There is good agreement between the critical energy release rate obtained from finite element analysis and the experimental results. Accuracy and simplicity of presented model make it appropriate for predicting the experimental results and improving experimental TECHNIQUEs. The innovation of the present research is the simplicity of the model for simulation of the critical strain energy release rate of the laminated composites.

Resin pocket area is a common defect in manufactruring of sandwich composites using vacuum infusion process (VIP). A numerical study is performed on CRACK growth behavior and failure modes of a sandwich composite wind turbine blade by means of extended finite element method (XFEM) and considering VIRTUAL CRACK CLOSURE TECHNIQUE ((VCCT)). The effect of resin pocket area on CRACK growth is investigated by considering different sizes for this area. Results of numerical analysis have shown that CRACK growth in the specimen initiates in foam core under loading nose and propagates through the middle of foam core and decreases its angle and grows towards the tapered area until it reaches to the core-face interface. Calculation of stress intensity factors has shown that first and second fracture modes are dominant modes in CRACK initiation and propagation steps, respectively. It is also observed that small and average sizes of resin pocket area in sandwich composite specimens delays the damage propagation and large resin pocket area accelerates damage progress. Finally, numerical and experimental results of CRACK growth path and load-displacement behavior of four-point bending test have shown a good accordance.

In this paper, the equivalent layup method to estimate the delamination initiation of asymmetric double cantilever beam (ADCB) is presented. A relation for critical strain energy release rates (SERR) of unidirectional (UD) and multidirectional (MD) laminates, as a criterion for CRACK growth initiation, was presented. For finite element analyses, the ADCB specimens were modeled in ABAQUS/Standard software and SERR is determined using the VIRTUAL CRACK CLOSURE TECHNIQUE ((VCCT)). According to this method, the ability of estimating delamination initiation without using experimental tests and finite element modeling of MD specimens is provided. This method reduces the volume of calculations FEM and experimental tests significantly. Accuracy of the proposed method has been verified by experimental data. Also, the total strain energy release rate analyzed by this method is compared with the FEM and theoretical results. Results show that SERR of MD lay-ups can be predicted by measuring SERR of the unidirectional specimens using FEM method with an error less than 10%.

In this paper a new method to determine the fracture properties and strain energy release rate for carbon-polyester composite has been introduced. Fracture characteristics such as: critical stress intensity factor and critical strain energy release rate for mode I, mode II and mixed mode loading were determined using Arcan type specimen. 130 layers of carbon fiber polyester woven composite with each of 0.2mm thickness were put on each other. Theoretical studies to determine strain energy release rate were done using three methods: Corrected Beam Theory (CBT), Compliance Calibration Method (CCM), VIRTUAL CRACK CLOSURE TECHNIQUE ((VCCT)), and results were recorded and compared with the results from experimental and numerical attempts. Critical loads were recorded through experimental attempts then applied to the finite element software. Results were recorded and compared with each other to determine the best method. Results show that CCM and (VCCT) determine strain energy release rate value closer to J-integral in comparison with corrected beam theory. Finally, the fracture surfaces were examined by scanning electron microscope to gain insight into the failure responses that shows the fracture surface for mode II is rougher than the fracture surface for mode I and mixed mode.

Background: Today Narcotic abuse has a high incidence among people and many of young go to hospital because of adverse effects of this abuse everyday. CRACK is a narcotic that accompany with many complications like gastrointestinal perforation who has high mortality but it is not due to acid. The goal of this study was the evaluation of the effect of Omental patch CLOSURE.Methods: An interventional without control study that was done on 35 patients in Loqman Hakim Hospital on 1385-1386.0mental patch CLOSURE was done for all the patients who inter the study. Datas was analyzed by SPSS soft ware.Findings: The average age was 32.3.two of them has a history of peptic ulcer. About 80%of them had Air under diaphragm.2 patients died that was in ASA class 5 at arrival time. Two of them referred due to Dyspepsia that controlled by Omeprazole. 31 patients had good result without any serious complications.Conclusion: The CRACK induced peri pyloric perforation is seen in many patients that are 10-12 years younger than expected age. Omental patch CLOSURE is a good surgical procedure for them whit acceptable results. But more studies control group is valuable in further decision.

This study develops a three-dimensional finite element simulation model for the prediction, propagation, and improvement of adhesion failure in an adhesively bonded laminated T-joint structure using smart piezoelectric materials. Initially, three-dimensional stresses (normal and shear) and failure locations in the composite T-joint (all the layers of the web and flange) were evaluated. In the identified failure location, VIRTUAL CRACK CLOSURE TECHNIQUE ((VCCT)) of fracture mechanics was employed to compute the Strain Energy Release Rate (SERR) values for different pre-embedded adhesion failure lengths. The developed coupling analysis model was employed to evaluate the SERR responses for the laminated composite T-joint with single/multiple piezoelectric layers. The efficacy and improved performance (resistance to adhesion failure) of the laminated smart Tjoint structure were analyzed in detail by considering different in flouncing parameters, i. e., orientation schemes, material types, piezoelectric layers, thicknesses, and number of laminate layers.

In this paper, edge CRACK problems under mechanical loads have been analysed using extended finite element method (XFEM) as it has proved to be a competent method for handling problems with discontinuities. The XFEM provides a versatile TECHNIQUE to model discontinuities in the solution domain without re-meshing or conformal mesh. The stress intensity factors (SIF) have been calculated by domain based interaction integral method. The effect of CRACK orientation and interaction under mechanical loading has been studied. Analytical solutions, which are available for two dimensional displacement fields in linear elastic fracture mechanics, have been used for CRACK tip enrichment. From the present analysis, it has been observed that there is monotonous decrease in the SIF-1 value with the increase in inclination, while SIF-II values first increases then it also decreases. Next study was performed for first edge CRACK in the presence of second CRACK on opposite edge. The results were obtained by changing the distance between the CRACK tips as well as by changing the orientation of second CRACK. SIFs values decrease with increase in distances between the CRACK tips for collinear CRACKs. In next study, for the first CRACK in presence of inclined second edge CRACK and it was found that SIFs increase initially with the increase in inclination and decrease after that. It emphasizes the fact that CRACKs at larger distances act more or less independently. In next study, with the use of level set method CRACK growth path is evaluated without remeshing for plate with hole, soft inclusion & hard inclusion under mode-I loading and compare with available published results.