Challenges in Processing of a Cocured Wing Test Box Using Vacuum Enhanced Resin Infusion Technology (VERITy)

AbstractAutoclave prepreg moulding technique has been the traditionally used process for the manufacture of primary aircraft composite structures. Alternate processing technologies, which are cost effective and less energy intensive, are being explored by the industry. Techniques like liquid composite moulding, especially variants of vacuum assisted resin transfer moulding (VARTM) processes have been successfully applied to realise large sized components albeit with minimum degree of cocuring. CSIR-NAL has developed a proprietary infusion process called ‘Vacuum Enhanced Resin Infusion Technology’ (VERITy) which can be used for large scale cocuring. The objective was to realise a co-infused and cocured wing test box consisting of bottom skin, spars, ribs, gussets and stringers. The challenge lies in the usage of appropriate tooling philosophy to suit the infusion process and control of flow characteristics in a complex preform with proper infusion strategy. A ‘Rigid–Flexible’ tooling concept was adopted so that the applied pressure is faithfully transferred by tools to the preform underneath for proper consolidation, without compromising on dimensional requirements. Infusion of resin into well compacted network of reinforcement with varying thickness is tricky and difficult because of the complex flow characteristics. Infusion strategy was worked out based on the experimental data as the flow simulation at such a level is equally challenging. Both parallel and series infusions were adopted for co-infusing the wing test box. Ultrasonic scan results show that the part was defect free vindicating tooling concepts and infusion strategies adopted