High Potential Process Acceleration by Selective and Volumetric Heat Transfer Methods

Abstract

To meet the demands of future composite manufacturing concepts it is essential to significantly reduce the production time. Since heating and cooling is usually a crucial time factor the DLR institute of Composite Structures and Adaptive Systems together with its partners investigated innovative heating methods on the basis of selective and volumetric heat transfer mechanism. For preforming activities inductive heating has been investigated, because it is a highly efficient, inoffensive and cost efficient approach. Since heat is only generated in limited regions of the preform (selective heating) not only heating but also cooling is highly effective and quick. To further reduce preforming time process parameters have been optimized for volumetric heating allowing even thick performs (10-30 mm) to be consolidated in one shot. To reduce processing time the application of microwave heating promised to be successful, because here it is possible to selectively heat only the laminate set-up. Tooling and autoclave (oven) which account for more than 90% of the thermal mass remain cold which in turn means that besides a significant time reduction also an enormous energy saving is possible. In principle e-beam curing is also a selective heat transfer method even though the boundary conditions are more stringent. If e-beams are used to generate x-rays a volumetric heating is possible as well. On the other hand occupational health and safety aspects cannot be ignored when x-ray processing is considered for commercial composite manufacturing. To point out the respective advantages and disadvantages the lecture will focus on a comparison of the above mentioned technologies.