Performance assessment of aerospace sandwich secondary structure panels using thermoelastic stress analysis

Abstract

Full scale tests carried out on polymer composite sandwich panels, which model the loads experienced by aircraft secondary wing structure, are described. The results from the tests form the basis of a performance assessment of the sandwich construction. The sandwich panel face sheets were manufactured from five different carbon fibre material architectures and were consolidated with epoxy resin using a variety of approaches. In previous work, it was shown that it was possible to significantly reduce the manufacturing costs of producing the sandwich structure by replacing the standard certificated process of unidirectional prepreg cured in an autoclave with a method that used non-crimp fabric infused in a conventional oven. In the present paper, thermoelastic stress analysis (TSA) is used during the full scale tests to obtain stress data from the five different panel types. The TSA data and measured deflection data are used to validate finite element (FE) models of each panel. The experimental validation highlighted some interesting features in the modelling approach. The face sheet materials were treated as homogeneous orthotropic blocks, which resulted in a conservative prediction of deflections. The models did not consider the woven and stitched material face sheet material configurations and therefore, omitted some of the features apparent in the experimental work. However, the validation showed that this did not affect the performance evaluation and most importantly, the validated FE showed that using different face sheet materials had little effect on the stresses in the panels.