In this paper by implementing Energy based theory, growth of induced delamination due to matrix cracking have been studied in symmetric composite laminates subjected to constant in-plane stresses and constant thermal stresses. Two unconstrained and generalized plane strain states have been analyzed here. Matrix cracking as a primary assumption has been supposed in both states and the impact of matrix cracking and delamination on the stiffness degradation is calculated. Afterwards some thermoelastic constants, which are only depended on, ply material properties of composite lamina are. Then by relating stiffness matrix elements using these constants, a simple equation due for Gibbs free Energy acquired. By differentiating the Gibbs free Energy equation for delamination length other simple equation was obtained to compute Energy release rate. To verify the obtained results, ANSYS finite element software is used. The obtained results reveal that there is good agreement between the extended and FE approaches.

In this paper, the effect of carbon nanotubes on mode I strain Energy release rate at crack growth initiation of epoxy-based nanocomposites was studied analytically. In this theoretical model, effect of carbon nanotubes debonding from its surrounding resin at the crack tip was postulated as one of the causes of increasing of the strain Energy release rate of nanocomposites in comparison with the pure resin. Furthermore, a representative volume element was considered at the nanoscale. The assumed representative volume element contains carbon nanotubes, surrounding resin and the interphase. The available mechanical properties and the thickness of the interphase in the literature were used. Finally, a model for increasing the strain Energy release rate of nanocomposites due to presence of carbon nanotubes was introduced based on mechanical properties and geometric parameters of carbon nanotubes and resin. It must be noted that enhancement of strain Energy release rate in comparison with the pure polymer was investigated by correlation between nano, micro and macro-scales. To validate the proposed analytical model, results were compared with other experimental results available in the literature. The results show that the present model has a reasonable error and is able to model the effect of single-wall and multi-wall carbon nanotubes on nanocomposites strain Energy release rate.

Dual laminate pipes made of thermoset polymer composite structure and thermoplastic liner are the only alternative in pipelines conveying high temperature corrosive fluids. Investigating the bonding between thermoset composite and thermoplastic liner is very important in these pipelines. Calculating the strain Energy release rate of first mode of failure is very important criteria in bonding strength and failure of doulas pips. ASTM-D5528 is the standard for experimental test procedure of strain Energy release rate of symmetric double cantilever beam. In this study, using the classical laminates theory, the general equation for determination the laminates thicknesses in unlike double cantilever beam is presented, for the first time. To study the validity of the equation, in unlike double cantilever beam samples consists of laminates with different thicknesses are manufactured for the experimental tests. Upper, lower and bonding regions consist of composite made of unidirectional fiberglass/Vinylester resin, PVCU and epoxy or Vinylester primers, respectively. The samples of this study are manufactured base on the practical case studies of chemical fluid pipelines with chlor-alkali process like Arvand Petrochemical units. The main aim of this work is to help manufacturers of these unites equipment to have practical guideline. To qualify the efficiency of the proposed equation, finite element simulation base on the virtual crack closure technique is presented. Good agreement is achieved in comparing the numerical and experimental results that shows the efficiency and accuracy of the proposed equation.

Owing to the increasing demand in the industry for materials possessing favorable mechanical properties and a high strength-to-weight ratio, the utilization of laminated composites has seen a surge in popularity. Nevertheless, laminated composite materials are susceptible to delamination because of their inadequate out-of-plane strengths and poor adhesion at the interface of composite laminated layers. This research aimed to enhance the mode II critical strain Energy release rate in glass/epoxy laminated composites by using the inter-layering method and polyvinyl alcohol as the interlayer. To achieve this purpose, end-notch flexure samples (ENF) were fabricated using the hand lay-up technique. The experimental results indicate that the presence of a polyvinyl alcohol interlayer led to a significant increase of 177% in the initiation fracture toughness and 36% in the propagation fracture toughness. The reason for this is to increase the adhesion between the composite layers and reduce their tendency to slide relative to each other. Furthermore, the examination of the fracture surface of ENF samples demonstrated that the utilization of the interlayer induced a transition in the failure mechanism from adhesive failure to cohesive failure, thereby generating a rougher fracture surface in comparison to the neat sample. It is important to note that examining the crack growth resistance curve and comparing the strain Energy release rate obtained from the CCM and CBBM methods demonstrated a favorable agreement.

In this paper, a new model to obtain the Energy release rate (ERR) for pull-out test specimens, based on a variational approach, is introduced. To include radial dependency, due to axial deformations of a matrix, in an efficient and accurate way,.a continuous displacement function is introduced which satisfies the required geometrical as well as kinetical boundary conditions. The displacement function includes the shear deformation. While obtaining the parameters of displacement function from the principle of total potential Energy, two distinct solutions are recognized which have different physical interpretations. One solution demonstrates shear deformation and radial dependency, whereas the other solution represents a constant normal strain. Employing the proposed modeling, the effects of various geometrical and material parameters on ERR were studied. Numerical results are presented to show the accuracy and efficiencyof this model in comparison with other such modelings.

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.

In biological fluids, chitosan hydrogel has become a potential candidate for carriers of bioactive molecules and controlled release of drugs in their swollen state. The prepared film of cross-linked chitosan utilized as a medium for delivery of podophyllotoxin in skin diseases. The drug delivery systems can reduce side effects of toxins and provide a high concentration of drug at the site. Physicochemical properties of prepared film, such as swelling behavior and release rate were studied. Some parameters have influenced on hydrogel swelling including cross linker concentration, temperature, and pH. The prepared hydrogel shows maximum swelling at the lowest PH. Hydrogel films with 15% glutaraldehyde as a cross linker have good behavior for drug release. Formulations prepared from chitosan and acryl amide have good behavior, but the concentration of cross linker has a negative effect. Drug release profile in this film follows the first rate model.