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The reduced volume method has found a particular zone to be used for evaluating the strength of unidirectional composite materials. To validate the method, modelling an experimental test where it has the same basic assumption of the model had been carried out. The result was favourable as the model can predict the average value from the experiment and also the time dependent effect.
The developed model has certain limitations of the element size to be used in the simulation to characterise the strength of composite materials. A reduced volume method is proposed in order to reduce the number of degree of freedom of the finite element simulation.This study has revealed certain configuration to be followed to speed up the computation time.
Defining a Reduced Volume Zone for the Simulation of Burst Test on a Composite Pressure Vessels
(2018)
The random nature of fibre break in composite materials has to be modelled in all part of the structure as it may contain millions of fibres. The reduced volume method was introduced to determine a smaller zone where we could characterise the strength based on the accumulation of fibre break, hence increasing the computation time
The Reduced Volume Method (RVM) has been used to evaluate the multiscale fibre break model developed at Mines ParisTech. It allows the model to be assigned only at certain part of the structures without necessarily compromising the final prediction. An attempt to model a simple unidirectional composite structure has also been carried out and gave a satisfying result. This paper deals with the application of the RVM to real scale type IV composite cylinders, where its stacking sequence was evaluated through micro-CT scans conducted with the collaboration of the University of Southampton. Two modelling geometries were evaluated and compared with the corresponding experimental results.
The stacking sequence of a real scale type IV pressure vessels has been found. Feasibility study of a multiscale model has been carried out by modifying the original stacking sequence. All of the results were displayed in a Sample Performance Chart (SPC), where different burst pressure in terms of mean and scatter had been found.
A general explanation of reduced volume method was introduced. This has allowed the simulation runs much faster without compromising the failure prediction of the multiscale fibre break model. The validation results with a material samples were shown. A certain mesh configuration to evaluate the cylinder has also been found to be the most effective in terms of computation time and prediction accuracy.
Defining a reduced volume zone for the simulation of burst test on composite pressure vessels
(2018)
The developed model uses a Monte-Carlo simulation to evaluate the accumulation of fibre breaks on composite structures. As the micromechanical aspects affecting the accumulation process is evaluated within a particular finite element size (0.1 mm x 0.1 mm x 8 mm), the industries would not be able to use the model on a real-size structure. Therefore, the reduced volume method is used to provide the statistical information between the required number of elements and simulations.
A high resolution micro-CT scan of a hoop layer from type IV cylinder has been carried out. The directional Gradient function had been used to analyse the in-plane and out-of-plane fibre misalignment from the Micro-CT Images. A correlation Analysis of the directional Gradient has also been performed and compared with the existing results from the cited paper.
The fibre-break model developed at Mines ParisTech has been able to show the effect of pressurisation rate on pressure vessels. This simulation however had to use a smaller model, as the computation time becomes enormous for simulating a real-scale pressure vessel. Reduced volume method then has been studied on different model configuration. The study showed that the method can be used only on certain configurations. It also gives a positive insight to reduce the computation time.
The reduced volume method has been studied using the fibre break model from Mines ParisTech. This method allows less 3D finite elements to be used for predicting the failure of real scale composite structures. A favourable comparison results with racetrack specimens has been achieved. However, the comparison study with a type IV pressure vessels still requires more Evaluation.