Multi-scale analysis of wrinkling during consolidation of thermoset composites
- Publication Type:
- Thesis
- Issue Date:
- 2022
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Carbon fibre is known for its high strength, light weight and durability. The aerospace and automotive industries have demonstrated a strong interest in utilising carbon fibre when designing their structural parts. However, there are still barriers preventing other industries from realising the full potential of such advanced laminated composites. Among these challenges are the formation of wrinkles and defects throughout the manufacturing process. Currently, manufacturing composite parts with mitigation of defects greatly relies on the designers’ experience and the outcomes of trial-and-error procedures. Due to the high cost of experiments and a large number of process parameters involved in composite manufacturing, an improved understanding of wrinkle formation is desirable for industries. Therefore, predictive modelling to aid design engineers in their understanding of the wrinkling phenomenon has become vital over the past two decades.
According to a few recent studies, fibre waviness, misalignment and the complex viscoelastic behaviour of a composite’s layered structure during cure are the primary causes of defects, wrinkle formation, and eventual rejection of large composite components. However, the relationship between these factors and the wrinkling of plies caused by micro-buckling has not been investigated quantitatively. Furthermore, these effects are not fully captured in current process models. This research aims to develop an efficient strategy for analysing the multi-scale mechanisms of wrinkling due to buckling of plies during the composite consolidation process. A multi-scale approach that can be incorporated into current process models is proposed for this purpose. Using the suggested approach, the wrinkling response of plies under compressive and bending loads are predicted numerically. Wrinkling wavelengths and critical buckling strength of flat laminates are compared with wrinkling profiles and the strength values reported in the literature. Unlike previous studies, the viscoelastic contribution of resin as well as fibre stiffness and fabric architecture (for woven composites) are taken into account. The effect of these parameters on the buckling behaviour of fibres and the orthotropic nature of plies are also investigated at different scales, quantitatively. Results highlight that the viscoelastic properties of the resin have a considerable effect on the buckling response of woven composites and thus on wrinkle formation during the early stage of cure. Experimental studies are suggested for characterizing the viscoelastic behaviour of resins and its effect on the micro-buckling response of fibres during cure.
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