Autoclave manufacturing of thick composites

Autoclave manufacturing of thermoset composites is determined mainly by heat transfer phenomena. As a matter of fact, the consolidation of composite laminates takes place by the progress of the polymerization, which is activated thermally. The design and control of the autoclave process relies on the capability to manage the relationship between the temperature-pressure cycle of the heat carrier fluid and the temperature distribution through the manufacturing part. In particular, in industrial cases, the main limitations reside in the correct evaluation of the local convective heat transfer conditions through the autoclave and in the evaluation of the local thermal inertia arising from the bagging-tooling system. In this study, the autoclave manufacturing of thick laminates has been addressed by modeling the heat transport phenomena occurring through the composite, the bagging and the tooling system. A new methodology for the evaluation of the energy transfer regimes has been proposed accounting for the heat fluxes from the bag and the tool side, the temperature through-the-thickness gradients and the heat generated by the resin polymerization reaction. The proposed approach enables the prediction of the temperature history of the autoclave assembly without knowledge of the effective thermal inertia of the two external layers, which could be difficult to evaluate owing to possible deformations of the bag during the manufacturing cycle and nonuniform shape of the metallic tool along the part. Experimental data from industrial autoclave runs have been collected and analyzed to validate the method.