Manufacturing distortions of a CFRP box-structure - A semi-numerical prediction approach

Counteracting undesired manufacturing distortions of carbon-composite structures is still a challenge for manufacturers. This paper presents a semi-numerical methodology to predict manufacturing-induced distortions of complex composite parts. The novel approach uses a combination of experimental, analytical and numerical procedures whereas standard shell elements are used for the FE calculations. The main innovation is the significant parameter reduction. Only one simulation parameter is necessary to predict the manufactured shape of a complex CFRP structure. For validation purposes, two CFRP box structures with dimensions of 798 mm × 206 mm × 55 mm (l × w × h) were manufactured and process-induced distortions are evaluated in detail using a high-precision 3D full-field measurement system. Measurements show that manufacturing distortions are mainly driven by the spring-in effect. However, a global curvature of the part is obtained which is likely due to forced-interaction induced by the aluminum male tool. The predicted process-induced deformations match precisely with the measurement results. Evaluation of the predicted distortions allow a clear distinction between spring-in induced and forced-interaction induced deformations. In consequence, obtained results show that effects due to forced-interaction need to be considered for suchlike structures fabricated on metallic tools when CTE_tool is larger than CTE_CFRP