Design, modeling, optimization, manufacturing and testing of variable-angle filament-wound cylinders

Variable-angle filament-wound (VAFW) cylinders are herein optimized for minimum mass under manufacturing constraints, and for various design loads. A design parameterization based on a second-order polynomial variation of the tow winding angle along the axial direction of the cylinders is utilized to explore the nonlinear steering-thickness dependency in VAFW structures, whereby the thickness becomes a function of the fiber angle. Particle swarm optimization coupled with several Kriging-based metamodels is developed to find the optimum designs. A single-curvature Bogner-Fox-Schmit-Castro finite element is formulated to accurately and efficiently represent the variable stiffness properties of the shells, and verifications are performed using a general-purpose plate element. Alongside the main optimization studies, a vast analysis on the design space is performed using the metamodels, showing a gap in the design space for the buckling strength that is confirmed by genetic algorithm optimizations. Extreme lightweight whilst buckling resistant designs are found, along with non-conventional optimum layouts thanks to the high degree of thickness build-up tailoring.

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Measuring geometric imperfections of variable-angle filament-wound cylinders with a simple digital image correlation (DIC) set up

10.31224/osf.io/kn6x5 ◽

2021 ◽

Author(s):

Saullo G. P. Castro ◽

José Humberto S. Almeida ◽

Luc St-Pierre ◽

Zhihua Wang

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Experimental Tests ◽

Variable Stiffness ◽

Filament Winding ◽

Image Correlation ◽

Geometric Imperfections ◽

Variable Angle ◽

Filament Wound ◽

Set Up

The experimental measurement of geometric imperfections of cylindrical shells is a fundamental step towards achieving representative models that are capable of capturing the imperfection-sensitive behavior of this type of shells and generate predictions that are comparable with experimental tests. The present study proposes an imperfection measurement method that is simple and applicable to both small and large structures, whereby the topographic data measured with one pair of cameras is obtained at six circumferential positions. Practical aspects of using digital image correlation are discussed, such as lighting and focus adjustments, and calibration. State-of-the-art best-fit routines are used to transform the obtained raw imperfection data onto a common coordinate system by means of least-squares optimization steps. Finally, the transformed data is stitched to build the full imperfection patterns that can be readily used in nonlinear finite element analyses. The developed method is demonstrated in the present study by measuring 12 variable-angle filament-wound cylinders, a novel class of variable-stiffness structures developed by our research group that combines a wide tailoring capability coming from the variable stiffness with the efficient manufacturability enabled by the filament winding process.

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Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138932 ◽

1995 ◽

Vol 53 ◽

pp. 512-513

Author(s):

L. Mulestagno ◽

J.C. Holzer ◽

P. Fraundorf

Keyword(s):

Sample Preparation ◽

Milling Time ◽

High Density ◽

Low Density ◽

Ion Milling ◽

High Quality ◽

Variable Angle ◽

Major Disadvantage ◽

Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

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