A. Jimenez del Toro
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1
In this study, a gap filling methodology was used to evaluate the flow behaviour of carbon fibre reinforced polyphenylene sulphide (CF/PPS) tapes under various compaction conditions (force and time) and layups. At each side of the gap, a different layup was present: 0/0 and 0/90. It was observed that squeeze flow occurred under all compaction forces and times, increasing with them. The layup influenced the squeeze flow development significantly, particularly visible in the change of the 0° fibre angle of the substrate across the gap. This fibre angle increased from the 0/90 to the 0/0, as the latter showed more squeeze flow than the former due to the parallel layup. The change of fibre angle across the substrate’s width was indicative of the extent of the squeeze flow along its width. The percolation flow increased with compaction force and time, and both longitudinal and transverse flow were found. Longitudinal flow was visible at larger compaction forces, whereas transverse flow was the only flow found at lower ones. The development of transverse over longitudinal percolation flow is influenced by the layup, the sample configuration and the squeeze flow.
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In this study, a gap filling methodology was used to evaluate the flow behaviour of carbon fibre reinforced polyphenylene sulphide (CF/PPS) tapes under various compaction conditions (force and time) and layups. At each side of the gap, a different layup was present: 0/0 and 0/90. It was observed that squeeze flow occurred under all compaction forces and times, increasing with them. The layup influenced the squeeze flow development significantly, particularly visible in the change of the 0° fibre angle of the substrate across the gap. This fibre angle increased from the 0/90 to the 0/0, as the latter showed more squeeze flow than the former due to the parallel layup. The change of fibre angle across the substrate’s width was indicative of the extent of the squeeze flow along its width. The percolation flow increased with compaction force and time, and both longitudinal and transverse flow were found. Longitudinal flow was visible at larger compaction forces, whereas transverse flow was the only flow found at lower ones. The development of transverse over longitudinal percolation flow is influenced by the layup, the sample configuration and the squeeze flow.
Laser-assisted tape placement (LATP) and thermoplastic composites (TPCs) pre-impregnated (prepreg) tapes are a promising combination of technologies; given the in-situ capabilities of the TPCs and the high degree of automation achievable with LATP. However, laminate quality, measured as final void content, tends to decrease when increasing placement speed. Heating and consolidation windows in LATP of TPCs are very short, especially when increasing the placement speed. For TPCs, resin flow is heavily influenced by melt viscosity above melting temperature (Tm). Therefore, the degree of intimate contact (Dic) resulting from the compaction phase can be significantly influenced by the tape’s degree of melt at the end of the heating phase. Due to melting being a kinetically controlled process[1,2], both temperatures and times above Tm need to be considered. The relationship between the degree of melt, both through thickness and in time, prior to compaction and the final Dic has not been explored yet. In this study, the final Dic and degree of melt of a CF/PEEK tape as a function of heating power, heating length and placement speed will be evaluated and correlated. The experimental investigation will consist of calorimetric data on melting kinetics of the polymer, and LATP experiment runs with different process parameters. Simulations of the thermal history (see Figure 1) and melting in the heating phase will be performed and validated with experiments. The research aims to understand the melting behaviour of the tapes during the heating stage in LATP, its dependence on the process parameters, and how it affects the final Dic and laminate quality.
...
Laser-assisted tape placement (LATP) and thermoplastic composites (TPCs) pre-impregnated (prepreg) tapes are a promising combination of technologies; given the in-situ capabilities of the TPCs and the high degree of automation achievable with LATP. However, laminate quality, measured as final void content, tends to decrease when increasing placement speed. Heating and consolidation windows in LATP of TPCs are very short, especially when increasing the placement speed. For TPCs, resin flow is heavily influenced by melt viscosity above melting temperature (Tm). Therefore, the degree of intimate contact (Dic) resulting from the compaction phase can be significantly influenced by the tape’s degree of melt at the end of the heating phase. Due to melting being a kinetically controlled process[1,2], both temperatures and times above Tm need to be considered. The relationship between the degree of melt, both through thickness and in time, prior to compaction and the final Dic has not been explored yet. In this study, the final Dic and degree of melt of a CF/PEEK tape as a function of heating power, heating length and placement speed will be evaluated and correlated. The experimental investigation will consist of calorimetric data on melting kinetics of the polymer, and LATP experiment runs with different process parameters. Simulations of the thermal history (see Figure 1) and melting in the heating phase will be performed and validated with experiments. The research aims to understand the melting behaviour of the tapes during the heating stage in LATP, its dependence on the process parameters, and how it affects the final Dic and laminate quality.