Optimal cure control synthesis for FEM model of aircraft composite part with CAD imported geometry

Abstract

The paper studies a problem of optimal control synthesis for curing the shell-like composite structure using open die molding in an autoclave. The necessary control should eliminate early hard skin formation, emergence of resin-rich or resin-dry areas, insufficient consolidation, and uneven cure. This purpose can be achieved through providing uniform distribution of temperature and degree of cure within the cured part volume. The used approach includes the joint CAD model of cured part and mould rectification to eliminate the topological errors, next import the repaired model to the finite element modeling system, where we formulate the transient cure process problem; its repeated simulation with varied durations of heating-up and isothermal holds to find their best values, which provide the acceptable objectives. The control synthesis problem is formulated as a multi-objective optimization problem where minimized objectives are deviations of temperature and degree of cure within a cured part considering constraints imposed by the properties of prepreg and manufacturing requirements. The Pareto-based optimization procedure allows estimating the best achievable quality indicators of cured composite parts, finding satisfactory control law, and decision-making.