ALAA ABDULZAHRA DELI AL-FATLAWI

The application of fiber-reinforced plastic (FRP) composites as structural elements of air vehicles provides weight saving, which results in a reduction in fuel consumption, fuel cost, and air pollution, and a higher speed. The goal of this research was to elaborate a new optimization method for a totally FRP composite construction for helicopter floors. During the optimization, 46 different layer combinations of 4 different FRP layers (woven glass fibers with phenolic resin; woven glass fibers with epoxy resin; woven carbon fibers with epoxy resin; hybrid composite) and FRP honeycomb core structural elements were investigated. The face sheets were composed of a different number of layers with cross-ply, angle-ply, and multidirectional fiber orientations. During the optimization, nine design constraints were considered: deflection; face sheet stress (bending load, end loading); stiffness; buckling; core shear stress; skin wrinkling; intracell buckling; and shear crimping. The single-objective weight optimization was solved by applying the Interior Point Algorithm of the Matlab software, the Generalized Reduced Gradient (GRG) Nonlinear Algorithm of the Excel Solver software, and the Laminator software. The Digimat-HC software solved the numerical models for the optimum sandwich plates of helicopter floors. The main contribution is developing a new method for optimizing a totally FRP composite sandwich structure—due to its material constituents and construction—that is more advantageous than traditional helicopter floors. A case study validated this fact.

The application of fiber-reinforced plastic (FRP) composite materials instead of metals, due to the low density of FRP materials, results in weight savings in the base plates of aircraft pallets. Lower weight leads to lower fuel consumption of the aircraft and thereby less environmental damage. The study aimed to investigate replacing the currently used aluminum base plates of aircraft pallets with composite sandwich plates to reduce the weight of the pallets, thereby the weight of the unit loads transported by aircraft. The newly constructed sandwich base plate consists of an aluminum honeycomb core and FRP composite face-sheets. First, we made experimental tests and numerical calculations for the investigated FRP sandwich panel to validate the applicability of the calculation method. Next, the mechanical properties of 40 different layer-combinations of 4 different FRP face-sheet materials (phenolic woven glass fiber; epoxy woven glass fiber; epoxy woven carbon fiber; and hybrid layers) were investigated using the Digimat-HC modeling program in order to find the appropriate face-sheet construction. Face-sheets were built up in 1, 2, 4, 6 or 8 layers with sets of fiber orientations including cross-ply (0°, 90°) and/or angle-ply (±45°). The weight optimization method was elaborated considering 9 design constraints: stiffness, deflection, skin stress, core shear stress, facing stress, overall buckling, shear crimping, skin wrinkling, and intracell buckling. A case study for the base plate of an aircraft pallet was introduced to validate the optimization procedure carried out using the Matlab (Interior Point Algorithm) and Excel Solver (Generalized Reduced Gradient Nonlinear Algorithm) programs. In the case study, the weight of the optimal structure (epoxy woven carbon fiber face-sheets) was 27 kg, which provides weight savings of 66% compared to the standard aluminum pallet. The article’s main added value is the elaboration and implementation of an optimization method that results in significant weight savings and thus lower fuel consumption of aircraft.

Composite material-due to low density-causes weight savings, which results in lower fuel consumption of transport vehicles. The aim of the research was to change the existing base-plate of the aluminum airplane container with the composite sandwich plate in order to reduce the weight of the containers of cargo aircrafts. The newly constructed sandwich plate consists of aluminum honeycomb core and composite face-sheets. The face-sheets consist of glass or carbon or hybrid fiber layers. The orientations of the fibers in the face-sheets were 0o, 90o and +-45o. Multi-objective optimization method was elaborated for the newly constructed sandwich plates. Based on the design aim, the importance of the objective functions (weight and cost of sandwich plates) was the same (50%). During the optimization nine design constraints were considered: stiffness, deflection, facing stress, core shear stress, skin stress, plate buckling, shear crimping, skin wrinkling, intracell buckling. The design variables were core thickness and number of layers of the face-sheets. During the optimization both the Weighted Normalized Method of the Excel Solver and the Genetic Algorithm Solver of Matlab software were applied. The mechanical properties of composite face-sheets were calculated by Laminator software according to the Classical Lamination Plate Theory and Tsai-Hill failure criteria. The main added-value of the study is that the multi-objective optimization method was elaborated for the newly constructed sandwich structures. It was confirmed that the optimal new composite sandwich construction-due to weight savings and lower fuel consumption of cargo aircrafts - is more advantageous than conventional all-aluminum container.

The purpose of the research was to develop a new sandwich plate (aluminium face-sheets and honeycomb core), which can be used for manufacturing of a lightweight base plate for air cargo containers. The application of lightweight containers results significant weight savings compared to the conventional aluminium base plate, lower fuel consumption and less environmental damage. During the single and multiobjective (weight and cost) optimization of the newly developed structure the following design constraints were taken into consideration: stiffness, deflection, facing stress, core shear stress, plate buckling, shear crimping, skin wrinkling and intracell buckling. The Interior-Point Algorithm was used to solve the single objective function. During the multiobjective optimization the Weighted Normalized Method was applied by Excel Solver and Genetic Algorithm Solver by Matlab program.

Buckling behavior of composite plate taking into account the effect of natural sisal fiber reinforcement is presented in this work. Investigating the buckling load of composite plate was done using both experimental and theoretical (including analytical and numerical) techniques. The composite plate specimens examined was reinforced with various volume fractions of natural sisal fiber. Furthermore, the composite plate was supported with different boundary conditions. The experimental and analytical data obtained for the buckling load are further supported with numerical data evaluated using the finite element method by ANSYS 14.0 commercial code. In the experimental method, the samples of the tensile test composite as well as the buckling plate are firstly manufactured. Then, the modulus of elasticity for the samples of composite plate with tensile test was evaluated, while the buckling load of plate was evaluated by the buckling test of composite plate. The results of buckling plate reveal that the reinforcement of natural sisal fibers leads to increasing the plate stiffness, and hence, causes an increase in the buckling load of composite plate. Moreover, a comparison was conducted between the data obtained for the buckling load, where a good agreement was found. The maximum error found between the results obtained experimentally and those estimated theoretically was about (12.28%), while it was about (3.9%) between the analytical and numerical predictions.

The present work investigates beam natural frequency that includes the effect of oblique crack damage with variable parameters such as crack size and location. This study was investigated both numerically and experimentally. The predicted results were compared to the measured data, where a good agreement has been observed. The beam natural frequency is evaluated for beam composite materials compound from polyester resin materials reinforced with two materials, which are glass short fiber and glass powder. The natural frequency is evaluated for different design parameters, which for composite material are the volume fractions of resin, fiber, and powder; while for crack effect they are the location, size, and orientation of the crack. The experimental results of natural frequency were evaluated through manufacturing composite beam samples, forming crack on it, testing it with vibration machine to measure the natural frequency. To numerically predict the natural frequency, tensile test samples of composite materials are manufactured firstly and then tested by tensile machine to find their mechanical properties, which are required as input data to the ANSYS Mechanical APDL commercial code. The natural frequency comparison has shown that the maximum error between the experimental and numerical data does not exceed 10.63%. The results reveals that increasing the crack orientation results in an enhancement in the natural frequency due to the reduction in the vertical crack component, while the increase in the crack size and location causes a decrease in the natural frequencies.

The aim of the research was to investigate the optimal design of solar panels for microsatellite applications. The panel consists of a honeycomb core and a facesheet of aluminum materials. In this study, a weight and/or cost optimization methodology for sandwich panel with aluminum face sheets and honeycomb core is presented. The Interior Point Algorithm algorithm was used to solve the single objective function, which is the weight or cost of the honeycomb sandwich panel as well as applying the multi-objective optimization technique to reduce the weight and cost of the sandwich panel which included Genetic Algorithm Solver with Pareto front using MATLAB program. Panel weight and/or cost are objective functions subject to the required constraints based on overall stiffness (bending and shear stiffness), total deflection (bending and shear deflection), skin stress encounter (bending load), basic shear stress, skin stress coping (final load), Plate total torsion (critical bending and shear torsion load), crimp shear load, skin wrinkle (strain and critical load) and intracellular torsion (shrinkage of the faces sheet). Design variables are core thickness and facesheets. The use of sandwich construction results in a lightweight structure.