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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
It is pertinent to have a correct description of fibre strength described by the twp parameter Weibull distribution when evaluating a type Iv pressure vessel using the fibre break multiscale model developed at Mines ParisTech. Earlier studies have shown a positive comparison result when T600S fibre strength were used. This study has discovered what would be the effect on the predicted strength when T700S strength is used.
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 strength of unidirectional elastic fibre composites is shown to depend on the loading rate as the viscoelastic nature of the matrix results in a fall in breaking load as the rate is reduced. The simulation of the accumulation of fibre breaks leading to failure, takes into account all physical phenomena involved fibre failure, including the stochastic nature of fibre strength, stress transfer through the matrix between reinforcements, interfacial debonding and the viscoelastic nature of the matrix. The kinetics of composite failure are seen to involve the initial formation of random fibre breaks which at higher loads coalesce into clusters of broken fibres. The rate at which this occurs depends on the viscoelastic properties of the matrix. These results have been shown to closely mirror the behaviour of carbon fibre composite pressure vessels.