Mechanics of Composite Materials最新文献

The responses of sandwich cylindrical shells containing fluid to free vibrations and low-velocity impact were studied. The high-order shear deformation theory and Bernoulli’s equation for the structure-fluid interface were used. To solve the equations obtained and validate the results, the Galerkin method and Abaqus finite element software were employed. The main innovation of this research is the calculation of the effective mass of the top layer and the entire sandwich cylindrical shell containing fluid using displacement field relations, their equivalent density, and indentation force due to impact. In addition, to calculate the impact force and the structure-fluid interaction, a two-degree-of-freedom model of mass, spring, and damper with the effect of the crushing resistance of the core was used. The results show that the fluid is an important and effective factor in calculating the natural frequency and low-velocity impact on the structure. The presence of fluid reduces the fundamental natural frequency of the sandwich cylindrical shell by 69%. Parameters such as core and layer thickness, length, and radius of the sandwich cylindrical shell, presence of the fluid, various boundary conditions, wave number, fiber orientation angles, velocity, and mass of the impactor are essential and influential factors in studying vibrations, impact, and optimal design of structures.

To improve the reliability of the glass fiber-reinforced plastic (GFRP) mortar culvert structure more effectively, their failure modes were estimated by combining the Tsai–Wu and Tang failure criteria. The reliability of GFRP mortar culverts was analyzed using the Monte Carlo method. According to the characteristics of structure of GFRP mortar pipe culvert, the adaptive adjustment weights were introduced to improve the whale optimization (WOA) algorithm. The improved WOA algorithm was used to optimize the structure design of the GFRP mortar pipe culvert with its reliability as the objective function under a certain weight. It was determined that the laminated structure produces different optimal lamination angles with different relative thicknesses of single layers. As the number of layers increases, the optimal angle of fibers increases significantly. The optimization based on three design variables gave better results than based on two design variables. It was determined the optimal characteristics to reach maximum reliability of structure of GFRP mortar pipe culvert.

A thermoelastic model for a solid cylinder consisting of two different isotropic thermoelastic homogeneous materials is created. Boundary conditions for the heat flow and stress tensors were discussed. A dual-phase lag model was applied to investigate its thermophysical properties. For their numerical evaluation, a two-layered structure with an interfacial thermal contact resistance and an integral elastic wave resistance, as well as some special cases, were considered. This study will be useful for theoretical modeling the thermoelasticity at the nanoscale and for designing nano and multilayered devices, plates, and surface coatings.

The homogenized and local behavior of wavy brick-and-mortar structures accounting for the piezoelectric multiphysics effect was studied in a systematic manner. The information on the connection between composite microstructure and their macro-properties serves as the directives for devising and crafting engineered materials that align with specific target performance criteria. Secondly, we scrutinized the potential of the multiphysics finite-volume direct averaging micromechanics (MFVDAM) method and compared it with finite element techniques in simulating the effective and local piezoelectric response within wavy brick-and-mortar architectures. The numerical findings demonstrated robust agreement between the two methods, underscoring that the MFVDAM stands as a convincing alternative to the finite element approach for examining multiphysics challenges encompassing various microstructures and scales. This establishes a benchmark for comparison against conventional micromechanics techniques.

The free vibrations of graphene-reinforced composite sandwich plates resting on a Winkler-Pasternak foundation were analyzed. The sandwich structure was divided into three layers including two thin facesheets made of a functionally graded graphene-reinforced composite and a thick core from a soft lightweight polymer foam. Five different functionally graded distribution patterns were considered for the facesheets. A refined high order theory was employed for kinematic assumptions. The transverse flexibility of the core and zero transverse shear stress conditions at the lower and upper surfaces of the plate were taken into account. The Hamilton’s principle was used to obtain the equations of motion and the analytical solutions were presented. Effects of the elastic foundation, plate geometry, and the graphene platelets properties on the natural frequencies of the sandwich plate were explored. The accuracy and reliability of the present modeling and results were examined and verified in specific cases. Results showed that reinforcing the facesheets of sandwich plates by graphene platelets increases their natural frequencies.

The determination and verification of repair tolerance of patch-repaired laminates based on progressive failure analysis method was studied. The axial tensile tests of intact, perforated, and repaired specimens of T700SC/EC240A composite laminates were carried out. The damage process of composite laminates under tensile load was numerically simulated using the progressive damage degradation model of 3D Hashin–Ye failure criterion. A method for determining the repair tolerance of patch-repaired laminates was proposed, and the upper and lower limits of repair the composite laminates were derived. The result verified by the strength index of Boeing Company showed that the method for determining the repair tolerance proposed is reasonable and feasible.

The tensile characteristics of a novel TWARMAT hybrid fabric with a weight of 600 g/m², comprising aramid and E-glass fibers were assessed. Additionally, a conventional 205-g/m² plain glass and 160-g/m² plain carbon fiber fabrics were also tested for comparison. The results obtained reveal that TWARMAT exhibited superior stiffness and density ratios. To confirm these experimental results, the rule of mixtures was utilized. The close agreement between the two sets of data, with mean relative errors of 5.5 and 1.05% for Young’s modulus and density respectively, confirms the reliability of the methods applied.

To expand plaster utilization as a binder, mechanical behavior of sandwich panels consisting of two faces of plaster reinforced with fiberglass fabrics and a core of extruded polystyrene foam was studied. Using software based on the finite element method, computational models were utilized to simulate the four-point bending test. Two scenarios were examined: assuming a linear stress-strain curve for the material and employing nonlinear geometric analysis. These computational simulations allowed to determine loading limits and vertical displacements. After determining the flexural stiffness, the vibration response was calculated via an analytical procedure. This investigation proved that sandwich panels with greater thicknesses and volumes of reinforcements on the plaster faces exhibited greater load-bearing capacity, smaller displacements, greater resistance to traction and compression, and greater stiffness. Notably, panel 3, which had the thickness and volume content of reinforcement in the composite faces 24.71 and 66.67% higher, respectively, than reference panel, presented the best static and vibrational responses.

A novel hybrid polyester composite comprising jack tree and jute fibers reinforced with eggshell filler is presented addressing the global need for sustainable alternatives to synthetic materials. The comprehensive analysis of physical and mechanical properties, such as tensile strength, impact resistance, hardness, water uptake was carried out using Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The manual hand layup technique was employed to ensure reproducible composite production. The resulting materials exhibited favorable mechanical properties, with the tensile strength and elongation balanced between jute and jack tree fibers, augmented by the reinforcing effect of the eggshell filler. Jack tree fibers significantly enhanced impact strength, contributing to the overall toughness of the composite. Hardness testing revealed higher crystallinity attributed to jack tree fibers. Water absorption characteristics demonstrated a nuanced interaction between cellulose abundance and fiber mass. FTIR spectroscopy provided molecular insights, while SEM analysis visually depicted the intricate structure of the composite. The amalgamation of jack tree and jute fibers with an eggshell filler not only enhances mechanical prowess but also aligns with global environmental efforts. This research advances sustainable composite materials, offering nuanced insights into the interplay between natural fibers, fillers, and matrices, with implications for eco-friendly solutions in diverse industries. The findings contribute to a greener, more sustainable future in industrial applications.

Materials based on hybrid bimetallic particles with a polyacrylamide shell can act as an efficient centers of energy dissipation in filled composites and reveal more effectiveness than nanoparticles, which, due to their higher surface-to-volume ratio and low interfacial adhesion, can affect the final composite performance. Two types of fillers were obtained as part of polymer-mediated synthesis and subsequent thermolysis and later encapsulated into a LDPE matrix. The metal-polymer complex increases the damping capacity of the hosting material up to 25% at higher concentration. However, the nanoparticles showed a strong increase at 5 wt% (by 20%) and then a sharp decline, which makes metal-polymer particles more suitable for damping purposes.