The properties of composite materials are highly dependent on the fiber and matrix fraction and on the porosity resulting from micro voids. This paper addresses void content characterization and the constituent content of composite materials by resorting to a comparison of destructive and non-destructive methods. The work presents the detailed procedures of two destructive methods, using acid digestion of epoxy resins matrices, and compares their processes. It also presents the results of a non-destructive method, by means of Micro Computed Tomography (MicroCT). The results of both destructive and non-destructive methods are compared, and a recommendation is made based on the application and the type of composite being analyzed. The MicroCT showed better and more consistent results in detecting voids in the material, while the acid digestion tests provided better results about the fiber and matrix percentage. Exported results from the MicroCT scanning with actual locations of voids were used in numerical analysis, to examine the feasibility of using them, whether by developing models that map damage in the proximity of the void, or by developing models that predict the properties of the entire material with respect to the content, shape, and distribution in the material.
This paper describes the design and optimization of the shape of the wings of "OASYS" research project underwater glider, by maximizing the lift to drag ratio through using computational fluid dynamics. Different wing layouts were examined based on the resulting lift and drag forces. The best NACA profile for this application was selected based on the lift and drag coefficients, the stall angle and the angle of attack that generates the highest lift to drag ratio. The shape of the wing was then determined by examining the effect of the sweep angle, front and back tapering angles, and the combination of the two on total lift and drag forces. Two dimensional and three-dimensional simulations were performed in "XFOIL" and "ANSYS Fluent" software, the type of simulation depending on the property examined. This resulted in 91 simulations. The results of each wing layout were assessed based on lift forces, drag forces, and the ratio between the two.
Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000.
This paper presents the design and testing process of the hull of a deep small autonomous underwater vehicle, rated at 2000m depth. Starting from setting the geometrical constraints for the design to mass production. None of the previous literature, to the authors' knowledge has presented similar work. Carbon Fiber Reinforced Epoxy material was chosen given their high strength to weight ratio and similarity of its compressibility to sea water. Material characterization was performed to obtain the material properties under loading conditions using a modified method of the Combined Loading Compression testing technique. A specific fixture was designed and manufactured to test filament-wound tubes. An analytical model was developed on MATLAB, a finite element model was created on ABAQUS, and the results of both models were compared. Then a quality control set of tests was performed including seawater absorption under high pressure and void analysis using destructive and non-destructive tests. Pilot samples were manufactured and tested in a pressure vessel, where one was cycle tested and inspected using visual and ultrasonic testing, and the other one was fail tested where it failed at ~93% of the expected load.
<p>This paper presents the design and testing process of the hull of a deep small autonomous underwater vehicle, rated at 2000m depth. Starting from setting the geometrical constraints for the design to mass production. None of the previous literature, to the authors’ knowledge has presented similar work. Carbon Fiber Reinforced Epoxy material was chosen given their high strength to weight ratio and similarity of its compressibility to sea water. Material characterization was performed to obtain the material properties under loading conditions using a modified method of the Combined Loading Compression testing technique. A specific fixture was designed and manufactured to test filament-wound tubes. An analytical model was developed on MATLAB, a finite element model was created on ABAQUS, and the results of both models were compared. Then a quality control set of tests was performed including seawater absorption under high pressure and void analysis using destructive and non-destructive tests. Pilot samples were manufactured and tested in a pressure vessel, where one was cycle tested and inspected using visual and ultrasonic testing, and the other one was fail tested where it failed at ~93% of the expected load.</p>
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