An Experimental and Numerical Study of Repairs on Composite Substrates with Composite and Aluminum Doublers Using Riveted, Bonded, and Hybrid Joints

Abstract

In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The performance of the repairs using different doubler materials and joining techniques are compared under static loading. The experimental results show that riveted joints have the lowest strength, while adhesive bonded joints have the highest strength, irrespective of the doubler material. Finite element analysis (FEA) of the studied joints is also performed using commercial FEA tool Abaqus. In the FEA model, point-based fasteners are used for the rivets, and a cohesive zone contact model is used to simulate the adhesive bond. The FEA results indicate that the riveted joints have higher tensile stresses on the metal doublers compared to the composite doublers. As per the failure modes, interestingly, for hybrid joints using composite doublers, the doublers fail due to net-section failure, while, for hybrid joints using metal doublers, it is the composite substrate that fails due to net-section failure. This suggests vulnerability of the composite structures to mechanical fastener holes. Lastly, the Autodesk Helius composite tool is used for prediction of first-ply failure and ply load distribution, and for progressive failure analysis of the composite substrate.

The visual research of changes in the geometry of a rivet joint for material model effect for simulation riveted joints made of EN AW 5251

“…In addition, the results were verified with numerical investigations and shear damage models were also used to model the initiation of the damage in the joints. Furthermore, Pitta [30] presented an experimental and numerical analysis of repairs on carbon fiber-reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures. In the work [2], the authors described a numerical analysis of a single-lap hybrid (bonded/bolted) composite joint in tension with different load values and different bolt configurations.…”

Material Model Effect for Simulating a Single-Lap Joint with a Blind Rivet

“…Armentani [ 17 ] conducted a numerical analysis of a single-lap hybrid (bonded/bolted) composite joint in tension with different load values and different bolt configurations. Pitta also discussed a wide range of rivet types [ 18 , 19 ]. Pitta [ 19 ] also presented an experimental and numerical analysis of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, repaired with riveted, adhesive-bonded, and hybrid joints.…”

“…Pitta also discussed a wide range of rivet types [ 18 , 19 ]. Pitta [ 19 ] also presented an experimental and numerical analysis of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, repaired with riveted, adhesive-bonded, and hybrid joints. Piątek [ 20 ] described that the experimental analysis of anchorages made of steel plates connected to CFRP strips with steel rivets and epoxy adhesive.…”

Influence of the Arrangement of Mechanical Fasteners on the Static Strength and Fatigue Life of Hybrid Joints

“…The pursuit of aviation transport constructors, especially of aircraft, to lower the weight has led to the replacement of a very large number of designed metal components with composite elements. Composite structures are joined in three different ways—by using mechanical joints [ 1 , 2 ], by means of an adhesive [ 3 ], or by a combination of these two methods [ 4 , 5 ].…”