Experimental and numerical investigation of heat evolution inside the autoclave for composite manufacturing

Temperature uniformity inside the autoclave and in the manufactured thermoset composite part is the key to enhancing curing performance. The present study incorporated experimental setup, multiphysics and computational fluid dynamics (CFD) models to provide insight into the gas flow pattern and temperature distribution inside the autoclave besides temperature and curing evolution in composite parts during the manufacturing process. The ultimate goal is to help improve the uniformity of the degree of curing and produce robust composite parts. The used numerical models were validated by experiment and the predicted results were in agreement with experimental efforts with a difference of 5%. A maximum temperature difference of 3 K was observed for panel 1, 1 K for panel 2, and 4 K for panel 3 during the curing stages. The variation was more pronounced during the post-curing stage, especially at the center. Correspondingly, less degree of curing (DOC) occurred at the center. The DOC variation between the center and the sides at the base of the panel is 2.5%. Variation in DOC across the thickness of the composite panels was also observed due to thermal spikes and uneven heat transfer. The DOC variation between upper surface and midplane is about 11%. Regions of high turbulence intensity lead to better heat transfer while regions of low speed such as confined regions under the tooling table had the poorest heat transfer. The study provided some practical implications to reduce the non-uniformity in temperature distribution and improve part curing.