Theoretical and experimental study on the continuum damage mechanical (CDM) behavior of RTPs under axial tension

Abstract

An analytical model is proposed to investigate the linear and nonlinear mechanical response of reinforced thermoplastic pipes (RTPs) under axial tension, in which the existing homogenization method, failure criteria and material degradation models are combined to predict the CDM behavior in an iterative and cyclic way. To obtain damage sequences, the homogenization method is modified by a stress correction factor to consider the effect of cross-sectional curvature. Once corrected stresses of homogenous layers satisfy von Mises criterion, Ramberg-Osgood curve is used to update elastic constants of isotropic materials. For composite laminates, a nonlinear stiffness degradation model is adopted to update the stiffness matrix if Hashin-Yeh failure criterion is satisfied. Quasi-static uniaxial tension tests were conducted on two RTP specimens to verify the proposed model. Besides, numerical simulation by calling a VUMAT subroutine were performed to observe the stress field in 3D composites. The proposed model was found to give accurate prediction on stiffness characteristics and stress field, and have functions including identifying damage location, predicting failure mode, and analyzing damage propagation. Furthermore, the effects of winding angles are studied, which showed that dominant failure mode would change from tensile fiber to tensile matrix as winding angles rise.