An Expert System for Autoclave Curing of Composites

Abstract

A rule based expert system was developed for controlling the autoclave temperature and pressure during cure of fiber reinforced thermosetting matrix composites. Rules were established which ensure that the temperatures and pressures remain within the required limits, the laminate is fully compacted and fully cured, the void content is minimum, and the residual (curing) stresses are low. The inputs to the expert system are the measured instantaneous autoclave temperature and pressure, the composite midpoint and surface temperatures, composite thickness, and ionic conductivity. These inputs are examined by preestablished rules and, on the basis of decisions dictated by the rules, the autoclave heater, cooler and pressure controllers are adjusted to the appropriate settings. An algorithm was written and hardware was developed for collecting and processing the data, for applying the rules, for making the decisions, and for controlling the autoclave. The software and hardware were integrated into a control system which was validated by simulated as ndl as actual cures of flat graphite-epoxy laminates ranging in thickness from 0.1 to 6.5 inches. The tests showed that the control system (designated as SECURE) performed all its required functions well, resulted in reduced cure times, and produced laminates whose mechanical properties were as good as those cured by conventional methods.

Thermal control system for thick composite laminates based on forecasting

“…The limited success of sensor-based systems eventually led to mathematical models and rule-based expert systems to evaluate the cure process off-line (4). The knowledge-base process parameters gained from the off-line system along with sensor-based data collected for pressure, temperature, and ionic conductivity of the resin were then applied to the on-line system to derive appropriate cure cycles.…”

Monitoring of Filler Distribution in Resin with an Electromagnetic Wave Transmission Line

“…It is very important to monitor the curing process of polymer matrix composites, since its quality depends heavily on the manufacturing process [1]. Dielectric monitoring [2][3][4][5], optical fibres [5][6][7][8] and ultrasonic monitoring [8] have been investigated as monitoring method.…”

Manufacture of Thick Cross-Section Composites Using a Pre-Catalyzed Fabric Technique

“…Expert systems rely on direct measurement of critical system properties rather than models to make decisions about autoclave temperatures and applied pressures. All expert systems for composite curing measure the temperature of the composite interior, and more complex systems measure internal pressures and resin electrical conductivity as well [9,10]. By continuously measuring these properties during the curing process one can control the external pressure and temperature of the composite to prevent thermal spiking and to promote uniform and complete consolidation.…”