Thermal Aspects for Composite Structures - From Manufacturing to In-Service PredictionsI

Abstract

Manufacturing of composite structures with a high degree of dimensional accuracy remains a challenge in modern fabrication. Residual stresses in fibre reinforced laminates which develop during the autoclav processing lead to a variety of process induced deformations. Dimensional changes such as spring-in of angled structures and warpage of flat sections are characteristic for composite manufacturing. This paper presents an engineering approch for a thermo-elastic simulation of the spring-in effect on large airframe structures based on the FE method performed at the DLR Institute of Composite Structures and Adaptive Systems. Due to the use of Ni36 as tooling material it was possible to blank out the influence of varying CTE between tool and part which are responsible for warpage. Investigations on small manufactured L-profiles with a flangelength of 50mm deliver the necessary simulation parameters for the constitutive model of the relevant airframe structure. For estimating the influence of different autoclav processes on the amount of spring-in, investigations with different temperature profiles were conducted and will be presented.