Influence of material, lay-up, and geometry on the radius of curvature of spoolable composite tubulars

Abstract

The focus of this study is the design and analysis of the structural behavior of filament-wound composite tubes capable of being coiled onto large spools for ease of storage, handling, and installation. The objective is to identify the minimum spool radius without introducing damage in the tube during storage. Experimental and analytical studies are utilized to assess the influence of different material systems, lay-ups and tube geometry on the stress-strain response induced in bending. Four-point flexure tests are conducted to simulate the spooling conditions where angle-ply asymmetric glass and carbon polymeric matrix composite tubes with various lay-up and radius/thickness ratios are loaded until failure. The loading grips are designed to prevent crushing of the tube while allowing cross-sectional ovalization and accommodating lateral movement of the specimen. Throughout the loading sequence of each specimen, the moment-curvature relationship is plotted to characterize the structural response of the tube under bending. Finite element models of the specimens under the loading scenario are created with the ABAQUS package utilizing two-dimensional S8R shell elements. The models incorporate non-linear geometry effects as well as a material subroutine (UMAT) to detect progressive failure, that is, to predict damage initiation and its progression. Residual stresses from processing are also incorporated to provide a realistic foundation for progressive failure calculations. The moment-curvature response using Maximum Stress, Hashin-Rotem and Hashin failure criteria are compared with experimental data. The models are used to conduct parametric studies of the effects of lay-up, geometry, and constitutive material on the flexural behavior of the composite tubes.