Development of a 3D finite element model for quasi-static indentation of a Type 3 pressure vessel

Abstract

Type III cylinders are hybrid structures typically consisting of a metal liner enclosed by layers of composite material. Such structures are prone to unexpected damage during service, usually as a result of a low velocity impact. The capability of the cylinder to carry load in the presence of existing damage due to an impact event has not been fully investigated for these structures. In this project, a methodology to develop a novel 3D finite element model of a Type III cylinder under quasi-static indentation loading is presented. The aim is to investigate the structure’s damage tolerance properties by predicting the residual indentation developed in the inner metal liner of the cylinder due to quasi-static load application. Previous work had indicated that this is the critical determinant of the post-indent residual fatigue life. The project is divided into three parts. First a ring specimen investigation, consisting of a short cylindrical cross section of a complete cylinder was virtually and experimentally analysed under a 2D line quasi-static compression indentation. The structure is an intermediate building block to allow improved understanding of Type III cylinders, and to allow the modelling approach to be refined on a specimen with less complexity than a full cylinder. Using this model it was possible to predict composite damage delamination as well as metal-composite separation using an explicit finite element model containing cohesive elements. Metal composite interface properties were obtained and calibrated through experimental testing. Validation was performed by comparing force-displacement curves, strain field measurements, and chronological visualisation of damage events. Analytical results showed good agreement with experimental values. Then, the interface properties obtained from the ring specimen model were transferred to a full Type III cylinder model. The model was compared with experimental results from a previous study on complete cylinders and was found to predict the quasi-static indentation response well, without further calibration or fitting of the metal-composite interface properties. It was demonstrated that the methodology developed was applicable for developing Type III cylinder models with different diameter sizes and thickness ratios. Finally, the model was used for parametric investigations in which the residual dent was evaluated under different geometric and loading conditions, including internal pressure loads. Overall, it was demonstrated that relevant damage processes associated with quasi-static indentation are reproduced. Furthermore, it was shown this model can be used to explore different design options in a virtual environment and could potentially be used in early stages of the cylinder product design cycle.

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Identifiers

ORCID for Erick Montes De Oca Valle: orcid.org/0000-0002-9394-2499

ORCID for Simon Spearing: orcid.org/0000-0002-3059-2014

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