Measuring geometric imperfections of variable–angle filament–wound cylinders with a simple digital image correlation setup. (15th November 2021)

• Record Type: Journal Article
• Authors: Castro, Saullo G.P.; Almeida Jr., José Humberto S.; St-Pierre, Luc; Wang, Zhihua
• Is Part Of: Composite structures. Volume 276(2021)
• Publication Date: 2021-11-15
• Subjects: Geometric imperfection -- Digital image correlation -- Experimental characterization -- Cylindrical shells -- Variable-angle -- Filament winding; Composite construction -- Periodicals; Composites -- Périodiques; 624.18
• DOI: 10.1016/j.compstruct.2021.114497
• Languages: English
• ISSNs: 0263-8223

Abstract

Graphical abstract: Highlights: A new method is proposed to measure geometric imperfections in composite cylinders. The setup requires only a pair of DIC cameras. Optimization steps are used to convert the DIC raw data into 3D geometric imperfections. The method developed is tested on 12 variable-angle filament-wound cylinders. Abstract: Measuring the geometric imperfections in cylindrical shells is a critical step necessary to create accurate numerical models that can capture the imperfection-sensitive behavior of these structures. Modern composite structures, such as variable–angle filament–wound (VAFW) cylinders, have a unique imperfection signature that is still unknown to the scientific community. This new class of variable–stiffness structures developed by our research group combines wide tailoring capabilities with the efficient manufacturability enabled by filament winding process. The present study proposes a novel imperfection measurement method that is simple and applicable to both small and large structures. The topographic data is measured with only a pair of cameras. Practical aspects of using digital image correlation (DIC) are described and discussed in detail, such as lighting, focus adjustment, and calibration. State–of–the–art best–fit routines, based on least–squares optimization, are used to transform raw data into a common coordinate system. Finally, the transformed data is stitched to build a full 3D imperfection pattern that can be readily used in a nonlinear finite element analysis. The developed method is used to measure the imperfections of 12 VAFW cylinders. The mass of the cylinders is used to validate the geometric imperfections and evaluate the variability of the proposed methodology.