Mechanics of Composite Materials最新文献

The coir fiber, boron nitride and fly ash-reinforced epoxy polymer composites were fabricated for testing and analysis. The design of the experiment method of response surface methodology (RSM) is considered to prepare the specimens. Central composite design, a model available in RSMб was used to obtain different composition of specimens. The significance of reinforcing parameters like wt% of coir fiber, boron nitride, and fly ash on the impact energy of composite were investigated by performing an analysis of variance (ANOVA). The regression equation, obtained by means of ANOVA reveals that the wt% influence of the coir fibers is more significant than that of boron nitride and fly ash. Optimization study was carried out to determine the combination of optimized parameters to get maximum impact energy. The confirmation experiment validates the optimization study.

To address the issues of the poor corrosion resistance and the low safety of the metal pipes used for oil and gas transportation, a glass-fiber-reinforced polyethylene thermoplastic composite pipe was developed. The finite-element analysis was employed to investigate the internal pressure resistance of each layer of the pipe. The impact of the winding angle, layer number, and diameter-to-thickness ratio were investigated. The optimum performance of the pipe was achieved when the ± 45° winding angle was set, but the layer number and diameter-to-thickness ratio met the relevant standards. To calculate the maximum bearing pressure of the pipe, two methods were compared: using the Tsai–Hill failure criterion and theoretical calculation of bursting pressure. The analysis revealed that the Tsai–Hill failure criterion better reflected the pipe failure situation.

The development of different textile structures and their composites for automotive leaf spring applications were considered. Owing to the good mechanical performance of epoxy, it was used as the matrix material in advanced structural applications. Initially, the different textile reinforcement architectures considered were in the form of E-glass unidirectional (UD) tow, bidirectional (2D) plain weave, and 3D woven solid orthogonal and interlock structures. The effect of reinforcing structure on the damping and wear performance of the composites was analyzed for their utilization in automotive leaf springs. Later, four different 3D orthogonal structures were developed to investigate the influence of binder percentage on their damping and wear performance. The damping performance was analyzed in terms of free vibrations, hysteresis damping, and dynamic mechanical properties. A wear analysis was carried out to determine the effect of different reinforcing elements on the friction and specific wear. The 3D reinforced composites considered exhibited the optimum damping and wear behavior.

The effects of thermal aging on the failure behavior of single-lap bonded joint composites were investigated experimentally. The single-lap bonded joints specimens were made of [0]₈ layered woven glass fiber/epoxy composite plates joined together by adhesive. Two different thermal aging processes were applied to adhesive- bonded single-lap joints specimens. In the first process, temperatures of 75, 100, and 150°C were applied during the aging time of 4 h. In the second process, a constant temperature of 150°C was applied for aging times of 2, 4, and 8 h. Additionally, this study was carried out in a temperature-controlled oven, without considering humidity, using three different adhesive thicknesses (0.2, 0.4, and 0.6 mm) and three different overlap lengths (15, 30, and 45 mm). After the thermal aging process, the specimens were subjected to a tensile test to determine the failure loads. Furthermore, the hardness values of both the adhesive and the composite plate were investigated under the conditions of 4 h at 150°C. The failure loads and microstructural changes determined were compared with the results for control specimens kept at room temperature (25°C). It was found that the increase in hardness values positively affected the strength of both the adhesive and the composite. With increasing the thermal aging time, temperature, and overlap length, the failure loads increased by 8.4 to 79.1%, 14.4 to 79.1%, and 9.5 to 50.9%, respectively. However, an increasing the adhesive thickness resulted in a decreasing the failure loads by 4.6 to 23.8%.

The mechanical properties and failure mechanisms of self-piercing riveted-adhesive joints of carbon fiber-reinforced polymers/6061-T6 aluminum plates was investigated. The effects of riveting pressure, aluminum surface treatment, and lap length on the mechanical properties of the joints were analyzed. The microscopic morphology of the joint at each stage of the failure process was obtained by tensile-shear test and electron microscopy scan, on which the changes of CFRP, aluminum plate, rivet, and adhesive layer at different stages were further discussed to reveal the failure mechanism of the joint. The results showed that the joint strength could be improved by appropriately increasing the riveting pressure. The surface treatment of aluminum plate could improve the surface properties of the joint, and the joint strength showed a trend of first increasing and then decreasing with the increase of the sandpaper mesh. Increasing the lap length led to an increase in joint strength; however, when the lap length was increased to a certain value, the increase in joint strength was not obvious. The failure process of the adhesive riveted specimen was from the failure of the adhesive layer to the failure of the rivet, and after rivet failure, the joint failed completely.

A framework of the topology optimization incorporated with the phase field method considering the interfacial damage for optimizing the fracture resistance of inclusion-matrix composites is presented. The topology optimization was performed to redistribute the inclusion phase in order to reduce its volume while keeping the fracture resistance value of the initial design unchanged. The phase field method uses two scalar phase field variables: one is for the bulk crack and the other is for the interfacial crack. The decomposition of the strain tensor into compression and tension parts was incorporated into this phase field method to improve the mechanical behaviors of the materials. These compression and tension strain parts are orthogonal in the context of the inner product in which the tensor of elastic stiffness behaves as a metric. Moreover, in the simulation process, an investigation of the effects of the interfacial parameters on the numerical results was discussed. Through the obtained results, the method proposed is demonstrated to be accurate and efficient in eliminating spurious effects and singularity points on the behavior curves in the damage process.

The damage mechanism of 2D woven fiberglass panels under random vibration loadings was investigated by means of an experimental analysis and compared with the damage mechanism under constant-amplitude loadings. Based on experimental observations, it was found that the failure mode under vibration loadings was delamination, and predicting the vibration fatigue life using the traditional S – N curve would result in significant errors. Therefore, a prediction method was proposed to accurately estimate the vibration fatigue life of a 2D woven fiberglass panel by modifying the conventional S – N curve. An experimental verification showed that this method has a high level of prediction accuracy.

Based on the proposed multi-arc curved edge concave adjustable Poisson’s ratio cell, five kinds of sandwich panels with negative Poisson’s ratio (NPR) were constructed by changing the in-plane thickness of cells: homogeneous, positive gradient, negative gradient, symmetrical positive gradient, and symmetrical negative gradient. The failure mechanical properties of the sandwich panels under the action of local impact were numerically studied. The influences of impact speed and gradient arrangement modes on the failure mode of the sandwich panels, the punch contact force (PCF) and the energy absorption effect (EAE) were investigated. It is found that the failure behavior of sandwich panels is different under different impact speeds. At the same impact speed, the thickness distribution pattern of the sandwich panel core layer will significantly affect the shock resistance of the panel. The study shows that the EAE of sandwich panels can be effectively enhanced by introducing gradient design method, and the sandwich panels with negative gradient arrangement show the best energy absorption effect.

The stability of axially functionally graded (AFG) heavy columns was analyzed. Consideration in stability analysis of the column is given to the free vibration and bucking problems. The mass density and Young’s modulus of the AFG heavy column vary along the column axis through a power-law function. Unified modeling of the differential equations with the associated boundary conditions governing the deformed shape of the free vibrations and buckling of the column was developed. Using a combination of direct numerical integration method and numerical solution method of nonlinear equation, differential equations were solved to calculate the natural frequency and the critical buckling load. Calculation results for the natural frequency and buckling load compare well with the FEM results. As a result of numerical experiments, the effects of material and geometric properties on the natural frequency and the buckling load were reported and discussed in detail.

The incorporation of a “graphene-carbon nanotube-graphene” structure as a filler in polyimide composites to enhance their mechanical and thermal properties was investigated. The performance of the composites was evaluated by molecular dynamics simulations. Findings revealed that this arrangement significantly enhanced the mechanical strength and stiffness of the composites, improving their tensile and shear properties.