Composite Skin-Stringer Assembly: Innovative Manufacturing and Stability Analysis

摘要

Stiffened composite structures are increasingly being used in the primary structures of both commercial and military aircraft. One key component in these structures is the assembly between the skin and the stringer. The very purpose of the stringers assembled in-between two thin layers of skin is to provide structural integrity to a relatively weak skin-structure. Current practice is to fabricate the skin and the stringer separately, bond them with adhesives and then co-cure the entire assembly in an autoclave. The reliability of the joint manufactured in this fashion is however, not dependable, and hence FAA has mandated riveting of the skin with the stringer by hundreds of mechanical fasteners. Although the mechanical fastener improves the joint reliability, it certainly increases the weight and reduces the strength of the structure by introducing stress concentration points around the rivet holes. To eliminate these disadvantages, an innovative and low cost manufacturing technique has been developed. Skin-stringer assembly with plain weave carbon fabric and SC-15 epoxy resin is fabricated in one integral step by using Vacuum Assisted Resin Transfer Molding (VARTM) process. Stability of the skin-stringer assembly under in plane compression is also investigated both experimentally and by using finite element method (FEM). Critical loads for buckling has been determined and various modes of failure have been studied. A reasonably good correlation between the FEM prediction and the experimental data has been observed. Details of the manufacturing procedures and stability analysis are described in the paper.