دانلود رایگان مقاله انگلیسی بررسی عددی تغییرات در فرآیند تولید قطعات کامپوزیت ضخیم - الزویر 2019

ABSTRACT

Consolidation of a prepreg layup to a target thickness is critical in order to achieve the required fibre volume fraction and dimensions in a composite part. Experiments show that different processing conditions lead to different levels of compaction and variability in the thickness. This paper presents an analysis of processing conditions and their effects on consolidation of thick composite components. A model that accounts for both percolation and squeezing flow is employed to study two toughened prepreg systems – IM7/8552 and IMA/M21. This paper analyses the significance of the process parameters on the thickness of prepregs and its variability. The analysis of different layups and processing conditions suggests several strategies to control target thickness and its variability. The IMA/M21 prepreg system was found to have lower variability due to its toughening mechanism. The presented results provide a better understanding of the composite manufacturing and can be used to provide an informed choice in design for manufacture of composite structures.

Conclusions

The realistic compaction model proposed by Belnoue et al. [8] was used for the first time in the analysis of variability in the consolidation of thick laminates made from two toughened prepreg systems. The difference between the systems, captured by the experiments on smaller specimens, manifested itself in a difference in the compaction modelling of thick laminates. It was found that the toughening mechanism in IMA/M21 reduce the size effect when the plies are blocked together and, as a result, reduces the variability for certain lay-up configurations. It is envisaged that the size effect will play a significant role in consolidation of AFP layups where the narrow tapes have a higher thickness to width aspect ratio. The case study of various processing conditions provided novel results regarding the effects of processing parameters on consolidation and their significance for manufacturing highlighting some possible strategies to reduce the variability by design of the lay-up and the process. For the IM7/8552 system, which showed a stronger size effect, one such strategy can be to design a lay-up with fewer blocked plies or thinner plies. The strategy common for both systems is to ensure the maximum level of compaction by applying a higher pressure for a longer time at a high temperature. While some of these changes can be impractical due to the process or design limitations, the reduction of temperature variability can be another option. Study of IMA/M21 system showed that an informed choice of the toughening mechanism can also be used to aid management of variability and in robust design for manufacture of composite structures.