Disruptiving fracture toughness of adhesively bonded joints by tailoring composite substrates
Topic(s) : Special Sessions
Co-authors :
Rosemere ROSEMERE DE ARAUJO ALVES LIMA (NETHERLANDS), Ran TAO (NETHERLANDS), Sofia TEIXEIRA DE FREITAS (NETHERLANDS)Abstract :
Investing in energy transition and sustainable transportation is crucial to achieving the goal of becoming a greenhouse emissions-neutral society by 2050. In order to reduce CO2 emissions, it is important to focus on developing efficient and high-resistance lightweight structures.
Adhesively bonded joints are a high-performant joining technique for composites and multi-material structures, being the main assembling solution in wind blades and often used in trains, ships and, together with rivets, also in aircraft structures. However, it is still challenging to ensure the reliability of the adhesively bonded joints and ensure their safety throughout the entire operational life of the structures.
To increase adhesively bonded joints’ safety and reliability, it is crucial to increase their damage tolerance and invest in their structural health monitoring. A disruptive way to increase the joints’ fracture toughness is to tailor their laminated composite substrates. This work aims to further enhance the damage tolerance of secondary adhesively bonded joints under quasi-static mode I loading conditions by architecting the Carbon Fibre Reinforced Polymer (CFRP) substrates’ stacking sequences [1]. Double Cantilever Beam specimens were prepared and tested to understand how the different ply angles and their position can trigger different crack paths in the joints and their effect on the CFRP secondary adhesively bonded joints’ fracture toughness.
A travelling digital microscope and an acoustic emission monitoring system were applied for the crack tracking position and damage evolution monitoring. It is worth mentioning that artificial neural networks were used to cluster the acquired acoustic emission data to be used for the damage evolution identification and eliminate the signals related to back ground noise for an accurate data analysis post processing.
The results show that the architecting the stacking sequence of the lamintes composite substrates combined with the adhesive layer’s fracture toughness and their interaction can strongly influence the crack onset and trigger different crack paths throughout the joints’ thickness. The co-occurrence of multiple damage mechanisms (crack deflection to different plies within the substrates, matrix cracking and fibre bridging) delays the crack propagation, increasing significantly the joints’ effective fracture toughness. From this study, it was possible to recognise the benefits of moving from the traditional crack path propagation within the bonded line to outbreaking multiple crack propagation, leading to new solutions for the next generation of CFRP secondary adhesively bonded joints.
Adhesively bonded joints are a high-performant joining technique for composites and multi-material structures, being the main assembling solution in wind blades and often used in trains, ships and, together with rivets, also in aircraft structures. However, it is still challenging to ensure the reliability of the adhesively bonded joints and ensure their safety throughout the entire operational life of the structures.
To increase adhesively bonded joints’ safety and reliability, it is crucial to increase their damage tolerance and invest in their structural health monitoring. A disruptive way to increase the joints’ fracture toughness is to tailor their laminated composite substrates. This work aims to further enhance the damage tolerance of secondary adhesively bonded joints under quasi-static mode I loading conditions by architecting the Carbon Fibre Reinforced Polymer (CFRP) substrates’ stacking sequences [1]. Double Cantilever Beam specimens were prepared and tested to understand how the different ply angles and their position can trigger different crack paths in the joints and their effect on the CFRP secondary adhesively bonded joints’ fracture toughness.
A travelling digital microscope and an acoustic emission monitoring system were applied for the crack tracking position and damage evolution monitoring. It is worth mentioning that artificial neural networks were used to cluster the acquired acoustic emission data to be used for the damage evolution identification and eliminate the signals related to back ground noise for an accurate data analysis post processing.
The results show that the architecting the stacking sequence of the lamintes composite substrates combined with the adhesive layer’s fracture toughness and their interaction can strongly influence the crack onset and trigger different crack paths throughout the joints’ thickness. The co-occurrence of multiple damage mechanisms (crack deflection to different plies within the substrates, matrix cracking and fibre bridging) delays the crack propagation, increasing significantly the joints’ effective fracture toughness. From this study, it was possible to recognise the benefits of moving from the traditional crack path propagation within the bonded line to outbreaking multiple crack propagation, leading to new solutions for the next generation of CFRP secondary adhesively bonded joints.