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Carbon fiber reinforced polyetheretherketone polymer (CF/PEEK) thermoplastic composites have a marked plastic yield stage compared to thermoset composites with epoxy matrix. During the interference fit riveting process, extrusion between rivet and composites laminate creates plastic deformation on the hole wall, which will enhance the bearing capacity of composites hole. Therefore, it is expected that the interference fit will play a greater advantage in enhancing the bearing strength of CF/PEEK riveted joint. Numerical and experimental study are applied to investigate the effect of interference fit on bearing strength of CF/PEEK riveted joint. Results show that the plastic deformation of CF/PEEK composites hole wall is positively correlated with the bearing strength of CF/PEEK riveted joint. When the interference fit size exceeds 2.6%, the bearing capacity of CF/PEEK riveted joint reduces because of the increase of fiber damage. It is concluded that the plastic deformation of riveted hole wall can enhance the bearing capacity of CF/PEEK riveted joint, while fiber damage reduces the bearing capacity of CF/PEEK riveted joint. As the increase of interference‐fit size, bearing strength of CF/PEEK riveted joint raises first then decreases, the appropriate interference‐fit size is in the range of 2.0% ~ 2.6%, which is larger than that of thermoset composites. [ABSTRACT FROM AUTHOR]

In this study, we join the thermoplastic composite using thermoplastic composite fastener (TPCF), and a physics-guided neural network is designed to predict the fatigue life of the all-composite joint. The experimental results show that TPCF is only 19.0% of the weight of the titanium rivet. Under a proper joining pressure of 1.50 MPa, the all-composite joint is well connected by an 'S-shape' interlayer, the fatigue resistance is improved. After hot-press joining, the lower cooling rate of 1 °C/min prolongs the crystallization process of TPCF and composite hole wall, thus enhancing the fatigue life to 10 5.8 cycles. The experimental results are summarized as physics constraints guiding the neural network. Similar fatigue data are migrated by producing a significant constraint. The loss function is the negative logarithm of the likelihood, which can predict both mean and deviation of fatigue life. The predicted results agree well with the experiments. • Innovating a light-weight and high-strength all-composite joint by joining thermoplastic composite with thermoplastic composites fastener (TPCF). • Developing a physics-guided neural network fusing physical knowledge and migration data to predict the fatigue life of all-composite joints. [ABSTRACT FROM AUTHOR]

The thermoplastic composite fasteners (TPCF) are applied to join the composite sheets with interference-fit in the present study, aiming at producing a lightweight and high-strength composite joint. The interference-fit installation process and tensile process of TPCF joint are analysed by experimental and numerical methods. For the interference size of 0.55% and 1.04%, the interference induces uniform pre-compression stress at the hole wall, the damage of the hole wall and the TPCF is acceptable. As the interference size raises to 2.06%, the damage is catastrophic, the radial stress of the hole wall becomes uneven. The ultimate strength of TPCF joint increases first and then decreases as the interference size increases. The ultimate strength reaches the maximum value of 363 MPa when interference size is 1.04%, which increases by 19% compared to clearance-fit joint. The specific strength of TPCF joint is over three times higher than that of titanium bolted joint. • Proposing a lightweight and high-strength joining method using CF/PEEK thermoplastic composites fastener. • Proving the proper interference size can enhance the strength of TPCF joint. • The specific strength of TPCF joint is three times higher than that of titanium bolted joint. [ABSTRACT FROM AUTHOR]

Composite materials are widely used in the aerospace structures due to their characteristics of light weight and high strength, while composite material components are currently joined by heavy titanium fasteners. We propose here a novel joining method using unidirectional CF/PEEK thermoplastic composites fastener (TPCF). CF/PEEK TPCFs are prepared via mechanically machining unidirectional CF/PEEK composites laminates. The joining of TPCF is through a hot-press and cooling process. Single-lap joints reinforced by CF/PEEK TPCFs are subjected to tensile tests and compared with titanium riveted joint. Experiments results show that the failure of the TPCF joint is shear off in fastener, while the composite laminate of titanium riveted joint undergoes a bearing failure and the rivet is pulled out from the laminate. The TPCF joint strength is lower than that of titanium riveted joint, but the TPCF joint has a higher specific joint strength. The TPCF joint strength increases with increasing carbon fibre mass fraction of TPCF. Also, we find that the TPCF joint strength increases with decreasing cooling rate. The DSC tests of TPCF show that the low cooling rate leads to an increase in crystallinity, which enhances the mechanical property of TPCF and then improves the joint strength. This provides a new process to control the TPCF joint strength by changing its cooling rate. The fracture face of TPCF is observed. It is found that the TPCF has a 'U-shaped' stepped fracture face after structure failure, which is caused by shear force and impact load. • Proposing CF/PEEK thermoplastic composites fastener. • Increasing crystallinity enhances the fastener strength. • Increasing carbon fibre content enhances the fastener strength. [ABSTRACT FROM AUTHOR]