| In the process of automated placement, it is an essential subject for the selection of materials andthe control of laying-up technology. The character of prepreg tack during the laying-up is crucialfactor for final product’s quality, thus the representation and related mechanism of prepreg tack isbecoming the forcus in the automated molding of composite material. In this paper, with automatedplacement as background, based on the research in domestic and overseas, the method representingprepreg tack is mainly discussed through a series of experimental study, theoretical model validationand the laws of different prepreg’s tack, which provides an important theoretical guidance forpractical applications. The related research includes:Firstly, according to the principle of the mandrel stripping, a test method of prepreg tack is putforward based on automated placement, stiffness and tack are defined as quantitative indicators. Bythe reasonable design for three parameters as lay-up temperature, lay-up pressure and lay-up speed,and combining with the universal testing machine, a set of test equipment and temperature controlcarrying system is developed. Then a series of experiments are launched after the determined samplesize and process specification, which relies on the well-completed equipment.Secondly, the single factor rotation method is used, where the research focuses on the processparameters’ effect on the prepreg tack. The experimental results are as follows:1) With the lay-uptemperature increases, the stiffness of prepreg decreases, the tack of prepreg follows Arrheniusequation.2) With the lay-up pressure increases, the variation tendency of the stiffness can beexplained by the principle of the mandrel stripping. The prepreg tack is consistant with the quationorigined from elastic mechanics model combining with resin glue model.3) When the lay-up speedchanges prepreg stiffness varies in a small range, and the prepreg tack is influenced by two factors,which includes the fluidity of prepreg surface resin and the contact area between the prepreg andmould. And the maximum tack of prepreg with epoxy resin system cured at lower temperature needhigher lay-up speed than that cured at higher temperature.4) Prepreg tack almost decreases in straightline with the place time increases in the air. Meanwhile some tack test are done on different types ofprepregs, the quantitatively differences are acquired for diverse prepregs in order to select thematerials in the subsequent lay-up process.Simultaneously, the collaborative interaction between the parameters are discussed in this paper.Aimed at lay-up temperature and lay-up speed, the failure mode between the prepreg and mould is analized by viscoelasticity theory. We can summarize that cohesive failure happens in highertemperature and lower speed, interfacial failure happens in lower temperature and higher speed.Owing to the prepreg tack is sensitive to temperature and speed, Time Temperature Superpositionapplied in PSA is appropriate for the experimental results in the paper. The results provide solutionsfor the processing instability problem leaded by the change of lay-up speed in actual automatedplacement.Finally, the tack between prepregs is tested by the orthogonal interaction experiment, we can getthe rank among the process parameters, which provides the reliable basis for the research on processparameters of the prepreg. |
