Simulation and validation of air flow and heat transfer in an autoclave process for definition of thermal boundary conditions during curing of composite parts

Abstract

Aerospace carbon fibre-reinforced components are cured under high pressure (7 bar) and temperature in an autoclave. As in an industrial environment, the loading of an autoclave usually changes from cycle to cycle causing different thermal masses and airflow pattern which leads to an inhomogeneous temperature distribution inside the carbon fiber-reinforced plastic part. Finally, the overall process can be delayed and the part quality can be compromised. In this paper, the heat transfer in a small laboratory autoclave has been investigated using calorimeter measurements and a fluid dynamic model. A complex turbulent flow pattern with locally varying heat transfer coefficient has been observed. Especially, the pressure and the inlet fluid velocity have been identified as sensitive process parameters. Further finite element simulations with adjusted boundary conditions provide accurate results of the curing process inside of the components for selective process control. The heat transfer coefficient has been found to be almost stationary during the observed constant pressure autoclave process allowing a separated investigation of the heat transfer coefficient and the curing of the components. The presented method promises therefore a detailed observation of the autoclave process with reduced computational effort.

Influence of Mold and Heat Transfer Fluid Materials on the Temperature Distribution of Large Framed Molds in Autoclave Process

“…The different temperatures and heating rates were determined by the variation in flow velocity of the air through the mold. Figure 4 a also shows that when the autoclave was pressurized at t = 150 min, the heating rate at each point increased, reflecting the influence of the operating pressure on the heating rate [ 38 ]. The abnormal fluctuation observed at point 15 was due to the failure of the thermocouple; owing to this, point 15 was excluded from the subsequent discussion.…”

Method for residual strain modeling taking into account mold and distribution of heat transfer coefficients for thermoset composite material parts

“…The validation of the CFD simulation of the HTC in an autoclave was carried out according to the results given in [28]. Figure 19 shows the temperature distribution fields on the part surface at different times, corresponding to the thermal cycle areas with a constant air flow temperature (110, 180, 20°С).…”

“…But material model in this research does not take into account the effect of resin chemical shrinkage. Airflow simulation and estimation of convection boundary conditions in autoclave are presented in [27][28][29].…”

A quasi-transient coupling approach to the modeling of conjugate heat transfer in the autoclave

“…It is assumed here that the convective heat transfer coefficient, h = 70 Wm À2 K À1 , was one of the lowest values found in the conducted measurements. 17 The autoclave temperature is assumed to be 20°C higher than the part temperature. In this study, ε 1 = 0.1 was used for the smooth surfaces of the aluminum plate.…”

“…Finally, the transient temperature fields of the calorimeter inside an autoclave are simulated using the CFD-FEM coupled model with two different coupling procedures. For validation of the proposed approach, a comparison of computational results obtained with known experimental data 17 is presented. This simulation approach demonstrates great potential for an industrial application and in a thermal optimization of autoclave processing with reasonable computational cost and accuracy.…”