Numerical Evaluation of Adhesively Bonded Repair in Composite Structures

Since seventies, the use of composite materials was used in aircraft construction to build secondary structures like flaps, elevators, slats, etc. However, only in the last few years, composite have been used in aircraft primary structures, as wings and fuselage. As a result, aircrafts like Airbus 350 or Boeing 787 rose use of composite up to 50%. In his normal life, every aircraft have damages, and this will demand in a few time new repair knowledge, procedures and technologies to adapt traditional repair method. Bolted repair technologies, as used for metallic structures, is currently the only approved and certified repair technique for aerospace composite structures. However, for large repairs and the refurbishment of a complete primary structure, bonded repair is preferred due to the obvious advantages in weight reduction, fuel efficiency due to reduced drag and weight. There is no disruption of structural integrity by hole drilling, consequently resulting in a better load transfer capability. In this work, a numerical analysis is made with Abaqus/CAE 6.13-1 (Dassault Systèmes Simulia Corp., Providence, RI, USA)to understand the behaviour of a weak bond, a bond that seems strong but have a poor strengthen. The specimen used is a 50x70 mm carbon epoxy Texipreg HS 160 RM (SEAL , Legnano, ITALY) with a hole of 10 mm diameter. The lay-up selected for the laminates is [02, 902]s with a thickness of 1,2 mm (8 x 0,15 mm). Then a bonded patch of 20 mm diameter is applied to simulate a single side bonded strap repair. Experimental data were taken from literature to validate the model (Campilho RDSG, de Moura MFSF, Domingues JJMS, Morais JJL., Tensile behaviour of three-dimensional carbon-epoxy adhesively bonded single- and double-strap repairs, International Journal of Adhesion&Adhesives 29; 2009; 678–686). The principal aim of this work was to determine, at first, adhesive thickness sensibility. Then, analysis focused on finding a correlation between strong and weak bond, using an innovative method to ...