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Eingeladener Vortrag
- nein (13)
The objective of this work is to find a method that describes the degree of damage from an impact experiment. This experiment was performed on Composite Pressure Vessels (CPV) in order to find the correlation of impact damage to the residual burst pressure. Computed Tomography (CT) approach was used to capture the before and after impact condition of the CPVs. The Wasserstein function was used to calculate how much the after impact image has differed from the original one. In the end, a good correlation was obtained to the residual burst pressure.
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.
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.
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.
Accumulation of fibre breaks under time-dependent loads in CFRP materials of pressure vessels
(2017)
For the moment, there is no existing method to quantify the time-dependent effect on carbon fibre pressure vessels or composite pressure vessels (CPV) in general. Hence, BAM started to investigate how to proof this phenomenon. Several researches has been done and discovered that it is possible for aged pressure vessels to have higher burst pressure value than a new vessels. However, the scientific explanation behind is still an on-going research. Whether the existing model can be used or using another measurement method to gain more data is still in question. Therefore, it is required to find a suitable method to explain such phenomenon and even develop furthermore to give a strength criterion for certain types of pressure vessels
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.
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.