Overview of Gc Tests Used to Evaluate Composite-Composite Adhesive Joints

The quality of composite-composite bonded joints is a very important issue for industries, especially for the aerospace sector. A deficient joint may stop the manufacturing process and its repairing may include very high costs. Nowadays, the quality of the joint is obtained by means of interlaminar fracture toughness tests, estimating the G(c) value (Energy Release Rate used to produce crack propagation) over coupons with (theoretically) the same conditions as those included in an actual part. Usually, G(c) is obtained by means of a Double Cantilever Beam (DCB) test. Although DCB is the reference test, it may present some drawbacks when a non-symmetrical coupon is used and when the adherents stiffness is low. An alternative to DCB is the Climbing Drum Peel (CDP) test which is able to address some of the DCB drawbacks. Nevertheless, both tests need the use of a universal testing machine, then they cannot be done in situ. In the present investigation, DCB and CDP main characteristics are analyzed and a new device, called Horizontal Drum Peel (HDP), which includes the advantages of previous tests and the possibility to perform the test over an actual part is presented.