Enhancing Fatigue Life and Strength of Adhesively Bonded Composite Joints: A Comprehensive Review

Abstract

Adhesive bonding is widely seen as the most optimal method for joining composite materials, bringing significant benefits over mechanical joining, such as lower weight and reduced stress concentrations. Adhesively bonded composite joints find extensive applications where cyclic fatigue loading takes place, but this might ultimately lead to crack damage and safety issues. Consequently, it has become essential to study how these structures behave under fatigue loads and identify the remaining gaps in knowledge to give insights into new possibilities. The fatigue life of adhesively bonded composite joints is influenced by various parameters, including joint configuration and material properties of adherends and adhesive. Numerous studies with varying outcomes have been documented in the literature. However, due to the multitude of influential factors, deriving conclusive insights from these studies for practical design purposes has proven to be challenging. Hence, this review aims to address this challenge by discussing different methods to enhance the fatigue performance of adhesively bonded composite joints. Additionally, it provides a comprehensive overview of the existing literature on adhesively bonded composite joints under cyclic fatigue loading, focusing on three main aspects: Adherends modification, adhesive modification, and joint configurations. Since the effect of modifying the adhesive, adherends, and joint configurations on fatigue performance has not been comprehensively studied in the literature, this review aims to fill this gap by compiling and comparing the relevant experimental data. Furthermore, this review discusses the challenges and limitations associated with the methods that can be used to monitor the initiation and propagation of fatigue cracks.

Delamination prevention of composite joints with asymmetric carbon-fiber reinforced plastic adherends

“…This has led to the widespread adoption of composite materials, such as carbon fiber reinforced plastics (CFRP), which offer superior specific stiffness, excellent strength-to-weight ratios, and reduced overall weight. 1–15 Alongside composite materials, adhesive bonding has emerged as a promising alternative joining method, offering the potential for improved weight efficiency and joint performance. 15–19 Despite these benefits, the aviation industry has been slow to adopt adhesive bonding for primary aircraft structures due to concerns related to non-destructive testing limitations and occurrence of delamination, due to high peel stresses.…”

“…1–15 Alongside composite materials, adhesive bonding has emerged as a promising alternative joining method, offering the potential for improved weight efficiency and joint performance. 15–19 Despite these benefits, the aviation industry has been slow to adopt adhesive bonding for primary aircraft structures due to concerns related to non-destructive testing limitations and occurrence of delamination, due to high peel stresses. 20 Therefore, while adhesive bonding has found some applications, overcoming these notable challenges is imperative for its wider acceptance within the aeronautical industry.…”

Effect of Selective Z-Pinning on the Static and Fatigue Strength of Step Joints between Composite Adherends

“…Derived from these basic observations, several techniques have been suggested to improve the strength of bonded or co-cured composite joints [5,7]. As an example, these 2 of 14 techniques include the adoption of wavy or reverse-bent joint configurations [8,9], the optimization of the geometries of the terminations of the adherends [10,11], and the increase in the number of joining interfaces [7,12].…”

“…Derived from these basic observations, several techniques have been suggested to improve the strength of bonded or co-cured composite joints [5,7]. As an example, these 2 of 14 techniques include the adoption of wavy or reverse-bent joint configurations [8,9], the optimization of the geometries of the terminations of the adherends [10,11], and the increase in the number of joining interfaces [7,12]. Another strategy involves introducing translaminar reinforcement across the thickness of the joint, using either continuous threads (stitching) or carbon or metal pins (z-pinning) [13][14][15][16][17][18][19][20][21][22].…”

Characterization of Interfacial Corrosion Behavior of Hybrid Laminate EN AW-6082 ∪ CFRP

“…Sector-specific materials, e.g., carbon fiber-reinforced polymers (CFRP) with high specific strength, and light metals, such as aluminum with high impact strength and excellent formability, are predestined for synergetic hybridization. This combination of the individual advantages can be achieved by means of multi-material systems, which are also termed hybrid structures [1][2][3][4]. The joining technology is of utmost importance as it defines the load transmission within the hybrid structure.…”