Abstract

A comparative study of four different finite element (FE) models is presented, to determine the thermal deformations in a typical aeronautical structure. A detailed FE model with solid elements is used as a reference to determine the accuracy given by three FE model with shell elements. The component consists in four planar laminates with (relatively small) curved zones at the joints. The analysis shows that a correct modelling of the curved laminates is needed for obtaining accurate results. If the FE model with shell elements ignores the existence of the curved zones, as is typically done in models used for stress calculations under pressures and loads, unsatisfactory results are obtained. Precision is not significantly increased if the curved zones are modelled in detail and the properties of the shell elements are defined as in the planar zones. For this reason, a technique for modifying the in-plane thermal properties of the elements modelling the curved laminates, that forces them to follow the same shape changes observed in the real curved laminates is presented. The FE model with shell elements obtained with this technique provides the same accuracy than the FE model with solid elements, with a significantly lower computational cost.

Abstract

A procedure for measuring simultaneously the coefficients of thermal expansion (CET) in the in-plane and the thickness directions in L-shaped composite laminated samples is presented. Measurements are carried out using digital image correlation, from which the displacements in one of the faces of the samples are measured when de sample undergoes a temperature increment inside an oven.

From the in-plane displacement measurements, the in-plane strain tensor components and the corresponding CTE are determined. Results show that the presented technique is capable of determining these CTE with high accuracy.

Displacement measurements in the direction normal to the face, enables determining the rotation of the face and consequently the difference between the CTE in the thickness direction and the CTE in the in-plane direction affected by the curvature.

Results obtained for the CTE in the thickness direction show, first, values significantly higher than the CTE of the material in the in-plane direction normal to the fibres and, second, a high dispersion from one stacking sequence to another. These discrepancies were expected and are caused by the misalignment of the fibres in the corner zone of the samples.