Fully controlled production environment for autoclave injection processes

Abstract

Fully Controlled Production Environment for Autoclave Injection Processes

Ensuring a reproducible, high product quality is a major goal for all production scenarios. In case of the ribs for the LOCOMACHS Lean Assembly Wing Box, geometrical accuracy was as important as the laminate quality itself and therefore a variety of measures has been investigated to actively measure and tune all quality relevant production parameters. The process that has been chosen to produce the ribs is a combination of resin infusion and autoclave technology because this combination offers a wide bandwidth of process parameter variation. The rib design with one integrated rib foot and one integrated rib post has been offered a good combination of simplicity and degree of structural integration. Since the mould line is not critical from a CTE point of view it was possible to use a cost efficient aluminium male tooling which has been designed to produce two different ribs in one cycle. Flange angle of the rib foot and rib post have been designed to compensate “Spring-In” deformations in a formally defined production window. Process-induced distortions (PID) of the ribs have been predicted with a novel pheno-numerical simulation approach that has been introduced within the LOCOMACHS project. The methodology provides efficient PID predictions due to shell-element modeling and a significant reduction of corresponding simulation parameters. To ensure that all quality relevant production parameters are in the specified production window a network of ultrasonic sensors has been installed in a special pattern. A crucial advantage of the ultrasonic sensors is that they are installed on the accessible backside of the mould and do not affect the mould line side. By measuring and analyzing sound amplitudes and propagation times it was possible to monitor flow front propagation, laminate thickness and also the cure progress in the running process. To manipulate the process conditions on the basis of the gained information, the injection pressure of the two injection lines could be used to tune resin flow, the pressure difference between autoclave and injection system could be used to control laminate thickness and the temperature profile can be manipulated in function of the cure progress. The ability to compensate most of the typical production scatter problems is major step towards the formally defined target of reproducible, high product quality. Furthermore the overall process time is no longer restricted to predefined, highly conservative cure times since the degree of cure is directly measured.