Experimental determination and control of prepreg tack for automated manufacture

Abstract

The automated tape laying (ATL) process has been examined and found to be sensitive to tack and stiffness properties of the prepreg material being laid. A comparison of existing aerospace and newly developed ATL prepreg tapes has revealed significant differences in tack response to temperature and feedrate. Examination of constituent resin rheology has found that tack, and the two observed failure modes, are somewhat dependent upon viscoelastic stiffness. Observation of temperature and feedrate response revealed a time–temperature superposition relationship. The Williams–Landel–Ferry equation was utilised to make predictions of the temperature response based on the feedrate response. Tack levels were stabilised over the feedrate range by making temperature adjustments. Results from the peel test, where mould conditions at lay-up were recreated, were found transferable to the ATL, where a suitable lay-up feedrate under ambient conditions was predicted.

Keywords:

• ATL
• Automated manufacture
• WLF
• Prepreg
• Tack
• Stiffness
• Rheology

This work was conducted as part of the AIRPOWER project which is focused on the development of materials and rapid production methods for large scale rotor blades for the wind energy industry. The authors would like to thank all the industrial partners, particularly Hexcel for prepreg materials, BAE systems for use of ATL equipment and Solent composites for mould supply. Cofunding of the project is provided by the UK Technology Strategy Board for which the consortium is grateful.

Notes

This paper is part of a special issue on Latest developments in research on composite materials