브레이딩/VARTM공정으로 제작된 복합재 토션 박스의 구조해석 검증

Abstract

Since 2015, composite manufacturing technologies have increasingly focused on out-of-autoclave (OOA) to enable mass production. The torsion boxes of the A220 and B787 aircraft have been integrally manufactured using the prepreg/autoclave process; however, there have been no reported cases of applying Out-of-Autoclave (OOA) processes to the development of torsion boxes for horizontal stabilizers. In this paper, the buckling stiffness of an integrally braided composite torsion box manufactured via the Braiding/VARTM(Vacuum assisted resin transfer molding) process was predicted and its structural strength was experimentally validated through structural testing. The torsion box structure was fabricated by laminating braided carbon fabrics for both the skins and spars, followed by oven curing to achieve a one-piece composite structure. Following a screening test was performed in order to evaluate the material properties, B-basis allowables were calculated using the statistical methodology prescribed in CMH-17. The structure was designed to initiate lower skin buckling at 100% design limit load (DLL), and subsequent design ultimate load (150% DLL) tests and failure load structural tests were performed to ensure compliance with aircraft structural design. Excellent correlation between the finite element analysis (FEA) predictions using NASTRAN and the static test results confirmed the validity of the analytical approach.