FEM model-based optimal control synthesis for curing a large composite structure with CAD imported geometry

¹ Southern Center of Russian Academy, Aircraft Technologies Department, 344006 Rostov on Don, Russia
² AP Group LLC, Department of New Materials, 192236 Saint Petersburg, Russia
³ LANIT Group, CAD Department, 129075 Moscow, Russia
⁴ National Kaohsiung Marine University, Mechanical Engineering Department, 81157 Kaohsiung city, Taiwan R.O.C.
⁵ Don State Technical University, Aircraft Engineering Department, 344000 Rostov on Don, Russia

^a Corresponding author: sergnshevtsov@gmail.com

Abstract

The paper studies a problem of optimal control synthesis for curing a large composite structure using open die moulding 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 is achieved through providing uniform distribution of degree of cure and temperature within the cured part volume. The used approach is illustrated on the example of the large CFRP aircraft panel manufactured by means of two-stage curing cycle. The forward problem combines the heat transfer and autocatalytic kinetic equations, which are linked by the specific heat capacity, thermal conductivity coefficient and by the exothermal heat source that depend on the prepreg’s degree of cure. 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 thermal-kinetic properties of prepreg and manufacturing requirements. The Pareto-based optimization algorithm, which executes the mapping of a subset of design space to the objectives space by the cyclic calling the forward problem implemented as a finite element model, allows estimating the best achievable quality indicators of manufactured composite parts, finding satisfactory parameters of the control law, and decision-making considering all imposed constraints.