Hybrid laminates, materials that consist of alternate aluminium alloy and composite laminae, are functionally graded material systems of particular interest to the aerospace industry. In this study, the use of genetic algorithm in STACKING SEQUENCE optimization of thin rotating hybrid laminated cylindrical shells is studied. The centrifugal and Coriolis forces are included in the theory and the Navier-type solutions are presented for simply supported boundary conditions. To validate the formulation, results are compared to those from other shell theories. For the optimization problem, two different objective functions that include the weight and Natural frequency of the rotating cylinder are considered. the objective functions are constrained for the maximum number of contiguous plies. OPTIMAL STACKING SEQUENCEs at different rotational speeds are presented.

The use of graphene-based composites, particularly in aerospace and structural applications, has received extensive attention in recent years. Graphene nanoplatelets are normally used to enhance composite materials' mechanical, thermal, and electrical properties. The present research investigates the biaxial buckling of two- and three-phase angle ply laminated plates reinforced with carbon or glass fibers.  The simply supported plate in this study is defined as a 16-ply symmetric and balanced laminate with uniform distribution of the fiber and graphene content through the thickness. The objective of this work is to produce a cost-effective design using the minimum amount of expensive reinforcement while maximizing the compressive buckling load. The desired results are achieved by finding the OPTIMAL STACKING SEQUENCE of reinforcement fibers, as well as selecting an OPTIMAL amount of graphene nanoplatelets and fiber volume content. Numerical results are first obtained for two-phase laminates with different ratios of applied loads. Further, three-phase laminates are studied and, among other things, the relationship between the fiber and graphene content is analyzed. The optimization procedures were performed by particle swarm optimization (PSO) for continuous optimization and genetic algorithm (GA) for integer optimization. The software applications were written by the authors and proved to be very fast and efficient.

In this paper, the STACKING SEQUENCE optimization of a laminated cylindrical shell has been studied for obtaining maximum natural frequency and buckling stress, simultaneously. An anisotropic cylindrical shell has a finite length with simply supported conditions at both ends. Three-dimensional elasticity approaches are used for free vibration analysis and the buckling stress function is based on the theory of classic shells. A genetic algorithm is used for optimization and, regarding the two-objective problem, a Pareto-OPTIMALly curve is used to help determine the best way to simultaneously satisfy all objectives. Finally, numerical results are presented for the optimization of a six-layer cylindrical shell.

Based on 3-D elasticity approach, differential quadrature method (DQM) in axial direction is adopted along with Globalized Nelder–Mead (GNM) algorithm to optimize the STACKING SEQUENCE of a laminated cylindrical shell. The anisotropic cylindrical shell has finite length with simply supported boundary conditions. The elasticity approach, combining the state space method and DQM is used to obtain a relatively accurate objective function. Shell thickness is fixed and orientations of layers change in a set of angles. The partial differential equations are reduced to ordinary differential equations with variable coefficients by applying DQM to the equations, then, the equations with variables at discrete points are obtained. Natural frequencies are attained by solving the Eigen-frequency equation, which appears by incorporating boundary conditions into the state equation. A GNM algorithm is devised for optimizing composite lamination. This algorithm is implemented for maximizing the lowest natural frequency of cylindrical shell. The results are presented for STACKING SEQUENCE optimization of two to five-layered cylindrical shells. Accuracy and convergence of developed formulation is verified by comparing the natural frequencies with the results obtained in the literature. Finally, the effects of mid-radius to thickness ratio, length to mid-radius ratio and number of layers on vibration behavior of optimized shell are investigated. Results are compared with those of Genetic Algorithm (GA) method, showing faster and more accurate convergence.

In this study, the effect of STACKING SEQUENCE on the impact behavior of fiber metal laminates under the drop weight impact test was investigated. Four groups of specimens with layups of [Al-(0.90)8-Al], [Al-(±45)8-Al], [Al-(0.90)4-(±45)4-Al] and [Al-(±45)4-(0.90)4-Al] were fabricated and tested. Fiberglass -aluminum composite specimens were made of Al 2024-O sheets and woven glass fabrics with epoxy resin. These specimens were tested using a drop weight impact testing machine with an energy of 44.13 J and speed of 3.43 m/s. The results obtained showed a higher load-bearing capacity before failure of the outer aluminum layer for specimens with [Al-(±45)8-Al] layups. Fiber metal laminates with [Al-(0.90)8-Al], [Al-(0.90)4-(±45)4-Al] and [Al-(±45)4-(0.90)4-Al] layups had lower load-bearing capacities than the first group of specimens, respectively. The form of damage progression in the second layer of aluminum of specimens was completely dependent on the STACKING SEQUENCE of composite layers. Numerical modeling of the drop weight impact test was carried out using ABAQUS 6.9 software. A detailed analysis of the failure mechanisms in the aluminum layer has been presented. A comparison between experimental results and the numerical simulation was performed to verify the simulation procedure.

A rotating composite shaft can be used with power transmission applications in the rotating machinery industry. A composite power transmission shaft usually has higher natural frequencies and critical speeds than a conventional metal power transmission shaft. Accurate determination of the natural frequency of the shaft is of great importance in its design, especially in the case of composite shafts due to the anisotropy of composite materials. In this paper, first in a rotating state, finite element results of a composite shaft of eight layers of carbon/epoxy in the case of two steel discs in the middle are symmetric with different diameters are compared with the results of previous research and the accuracy of the results is verified. A hollow composite shaft of eight layers of carbon/epoxy and glass/epoxy is modeled with two steel discs on the elastic supports. Applying the Lagrange equations, the equations of motion of the hybrid composite shaft are obtained using the modified equivalent modulus beam theory. By writing code in MATLAB software and numerical solution, the amplitude diagram in terms of frequency in the rotating state is obtained and compared with the results of the composite shaft simulation in Ansys software, and validation is performed. Finally, the effect of STACKING SEQUENCE parameters such as fiber angle, arrangement of use carbon/epoxy, and glass/epoxy on natural frequencies is investigated.

The progress of damage in quasi-isotropic carbon/epoxy laminates under tensile loading has been investigated microscopically. One significant mode of failure in laminated composites is delamination initiating at free edges. The interlaminar stress in the boundary ply along the free edges of a laminated composite is the main factor to cause delamination. The laminate STACKING SEQUENCE affects the interlaminar stress distribution and consequently may change the mode of failure. It is of design importance to determine a suitable criterion based on stress analysis to obtain the best STACKING SEQUENCE. In the present work, tensile properties of six samples with different STACKING SEQUENCEs have been examined. Results showed that stress analysis at distance very close to the free edges is a suitable criterion to predict the initiation of delamination and the STACKING SEQUENCE of [90/45/0/-45]s has the highest strength among the other samples. Furthermore finite element analysis showed that the adjacent  ±45 plies cause premature delamination during tensile loading.