Addressing structural certification challenges with FEM analysis in electric seaplane CFRP wing

Abstract

This study explores the structural certification challenges and business objectives for an electric seaplane in the general aviation category, emphasizing the verification of the composite structure under EASA CS-23. Sandwich structures and bonded joints offer significant weight reduction and structural efficiency advantages, crucial for electric aircraft. However, a fatigue damage and tolerance evaluation under CS-23 Level 4 increase these challenges, requiring exhaustive testing, analysis, and documentation to meet stringent regulatory standards. Certification complexities are further intensified by the differences in passenger capacity constraints between Level 3 and Level 4 aircraft, suggesting pursuing Level 3 certification and impacting on the business case of the emerging sustainable aviation. To evaluate the impact on the weight penalties, this study conducts a comprehensive FEM validation and comparison of two different CFRP wing structural analyses: one to comply with Level 3 certification using a monocoque sandwich structure with a bonded assembly, and the other to comply with Level 4 certification using semi-monocoque with a mechanically fastened assembly. The use of different strain allowable values for both levels defined the current strain constraints range for the composite wings, where the monocoque structure analysis showed a mass reduction of up to 19 % on average.