Abstract
Adhesive bonding is one of the most suitable joining technologies in terms of weight and mechanical performance for current carbon fiber reinforced polymer aircraft fuselage structures. However, traditional joint topologies such as single overlap joints induce high peel stresses, resulting in sudden failure and low joint strength when compared to metal adherends. This drawback in using carbon fiber reinforced polymer is hindering their performance and efficiency in full-scale structures where joints are essential.The goal of this paper is to review how the joint design can help to improve the lap shear strength of composite bonded joints, to recognize the challenges that still need to be understood and to give insight into new opportunities. The focus is thereby on means to increase the matrix-dominated out-of-plane strength of the adherend in order to postpone delamination failure, as it is known to be the most prone type of failure of composite bonded joints. The paper is divided in two main parts: firstly, a review of topology-related and material-related design parameters is given and secondly, future opportunities to improve out-of-plane strength of CFRP bonded joints yet to be explored are discussed.
Highlights
With the increasing pressure to meet unprecedented levels of eco‐ efficiency, the aircraft industry aims for super lightweight structures
The paper is divided in two main parts: firstly, a review of topology‐related and material‐ related design parameters is given and secondly, future opportunities to improve out‐of‐plane strength of Carbon Fibre Reinforced Plastic (CFRP) bonded joints yet to be explored are discussed
Avila and Bueno [18,19] performed experimental and numerical studies on wavy lap joints with 25 mm overlap length, 16‐layer plain weave E‐glass/epoxy adherends and epoxy paste adhesive. It was found an increase in maximum load of 41%, compared to a reference Single Overlap Joint (SLJ)‐design, which is believed to result from the out‐of‐plane compressive stresses developed near the tip of the overlaps
Summary
With the increasing pressure to meet unprecedented levels of eco‐ efficiency, the aircraft industry aims for super lightweight structures. Composites are being joined using bolts and rivets, a joint design mainly developed for metals This leads to an increase in structural weight, since the areas where holes cut through the fibres and disturb the load path have thicker laminates. Recent studies have demonstrated how a reduction of ply thickness in composite laminates enables great freedom with respect to layup design and leads to a delay in damage onset as well as enhanced ultimate load [11,12,13] Those two developments mark a significant step in terms of manufacturing quality, allowing for more complex stacking sequences and joint topologies. Tailoring the laminate design parameters can play a key role in the reduction of detrimental peel stresses in load carrying joints and can contribute to the goal of further promoting adhesive bonding for primary aircraft structures. The goal of this paper is to review how the joint design can help to improve the lap shear strength of composite bonded joints, to recognize the challenges that still need to be understood and to give insight into new opportunities
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