Tool-part interaction in composites processing. Part I: experimental investigation and analytical model

The ability to process composite structures with a high degree of dimensional control remains a barrier to further implementation of composite materials in commercial applications. Of the numerous types of process induced deformations that occur, the warpage of flat laminates due to tool-part interaction remains a poorly understood phenomenon. This paper presents an experimental study of the effect of process conditions and part aspect ratio on tool-part interaction induced warpage. For a given lay-up and material, part aspect ratio was found to have a much greater influence than autoclave pressure on warpage, while the tool surface condition was not observed to have any significant effect. The results of the study are embodied in an empirical relation, which can be a useful guide to predict laminate warpage over a range of industrially relevant conditions. In addition, a simple analytical model is proposed which agrees well with the experimentally determined relationships. A complementary numerical model is presented in a companion paper. (C) 2004 Elsevier Ltd. All rights reserved.