Influence of Process Parameters on the Tack Behaviour of Dry Fibre Materials in the Context of Automated Dry Fibre Placement

Kurzfassung

With the increasing demand for manufacturing sustainable aerospace parts, along with costeffectiveness and preciseness. Automated Dry Fibre Placement(ADFP) has emerged as a promising solution. ADFP combines these goals and enables the production of precise and cost-effective aerospace components with the potential for reduced defects. Tack, which is the adhesion between fibre layers during deposition, plays an important role in achieving high-quality preforms. Tack is essential for securely holding down the plies. Insufficient tack leads to final part defects like wrinkling contributing to the stability of the final part. This study investigates the influence of nip point temperature, layup speed, and compaction force on the tack behaviour of Hexcel HiTape® dry fibre material during the Automated Dry Fibre Placement (ADFP) process. It also assesses the applicability of an existing tack model, developed for Solvay TX1100 dry fibre material, to the Hexcel HiTape®, possessing a different binder distribution and different fibre architecture. Tack was evaluated using 90-degree peel tests for specimens manufactured using different parameter combinations. Initial statistical analysis of the main parameter effects and interactions used a 2-level factorial design of experiments. To investigate the non-linear behaviour of the parameters, this design was extended to a 3-level face-centred central composite design of experiments. The results show that temperature is the most dominant factor affecting tack, with higher temperatures significantly increasing tack forces due to binder activation and polymer diffusion at the interface. Layup speed also had a notable influence, with higher speeds leading to increased tack forces, which contrasts with the inverse relationship predicted by the existing model. This is likely due to the material architecture of Hexcel HiTape ®, where faster speeds reduce binder seepage through perforations, allowing more binder to remain at the interface. Compaction force had a minor impact on tack behaviour and the results of this analysis deemed the effect to be statistically insignificant. Additionally, while interaction effects between the parameters were analysed, they were not statistically significant at the 95% confidence level. The findings suggest that the independent contributions of temperature and velocity are key, but deviations from expected behaviour may be due to material-specific characteristics such as perforations and fibre structure. The behaviour of the material in relation to the statistically significant parameters shows that there is non-linearity. To test the generalisability of the model, the existing tack model for Solvay TX1100 dry fibre was applied to Hexcel HiTape ®. This model did not fit the data of Hexcel HiTape ® material. The observed positive relationship between speed and tack, contrary to the Solvay TX1100 model’s inverse relationship, shows the need to adapt the model to Hexcel HiTape ® and indicates limitations in generalising tack models across dry fibre materials. Additionally, fibre fraying of Hexcel HiTape® was also observed during peel tests, marking a finding that warrants further investigation to help quantify the effect, aiding in understanding the dry fibre material behaviour.