Influence of the boundary condition on the first ply failure and stress distribution on a multilayer composite pipe by the finite element method

O A González-Estrada,A Pertuz,J S León

doi:10.1088/1742-6596/1159/1/012013

O A González-Estrada, A Pertuz + Show 1 more

Open Access

https://doi.org/10.1088/1742-6596/1159/1/012013

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Abstract

In this work, we study the influence of the boundary conditions in the stress distribution and the first ply failure of a commercially available multilayer composite pipe using a finite element model. An ASTM D2290 standard test was performed to determine the ultimate tensile strength and burst pressure. Also, an ASTM D3039 tension test performed on a longitudinal strip of the pipe was used to evaluate the elastic constants. We compared the experimental results with the numerical model to validate the material parameters used in the approximation. Hoop and axial stresses were obtained for three different boundary conditions: open, fixed and closed ends. Different failure criteria were considered to evaluate the first ply failure, and a comparison of failure criteria and boundary conditions was made. The apparent stress using finite elements corresponds to 82.31MPa, the error between the experimental test and the numerical model is 1.06%. For a nominal pressure of 5.17MPa, the composite laminate layer exhibits a hoop stress of 62MPa for the stress. For open-end pipes, first ply failure is reached at 10.48MPa under Hoffman criterion.

Highlights

During the last years, composite pipes have been successfully used in the Oil & Gas sector mostly because their mechanical properties are very attractive, especially their weight to resistance ratio and their resistance to corrosion [1]
This section describes the finite element numerical approximation for a multilayer composite pipe subjected to internal pressure
Three boundary conditions were considered: (i) open-end condition, in which it does not exist axial stresses, this condition generally applies to pipes subjected to very elastic supports, (ii) fixed-end, in which the axial displacements in the ends are restricted in the normal direction, this is the case of very long pipes, and (iii) closed-end, condition known as pressure vessel condition [20]

Summary

Introduction

Composite pipes have been successfully used in the Oil & Gas sector mostly because their mechanical properties are very attractive, especially their weight to resistance ratio and their resistance to corrosion [1]. In the matrix, microcracking is the main mode of failure This is equivalent to matrix cracks parallel to the fibre direction over the entire thickness of the ply and especially to those plies where the reinforcement is not in the same direction as the applied load. Another common mode of failure is the disunion, which equals a loss of adhesion and a relative slip between the fibre and the matrix due to differences in shear stresses at the fibre-matrix interface [26]. Tsai-Wu is widely used in the analysis of progressive damage models for laminates since it allows to determine threedimensional failure with a unique expression

Hashin criterion

Numerical model

Results and discussion

Conclusions