Low-Speed Impact Response Of Bolted And Hybrid Bonded- Fastened Joints In Composite Structures

More and more complex composite structures are designed in modern aerospace structures,and the assembly of individual composite components become significant to the overall performance of the structures.Bolted joints are widely adopted connection strategy for fiber reinforced composites in complex composite structures.however,the dynamic responses of these joints still need insightful understandings.In this paper,the anti-impact performance of single-lap bolted carbon fiber reinforced composite joints has been investigated under dynamic loading from 1m/s to 4m/s to compare failure mode,strength and energy absorption with the result loaded under quasi-static.The sensitivity of low-speed impact response to design factors is investigated,including the diameter of bolt,the bolt arrangement number and the addition of adhesive boding.Both experiments and finite element modeling were conducted to understand the fracture mechanisms of these bolted joints under different loading conditions,the finite element method were used to analyses the experimental phenomenon.It can be found that the diameter of the bolt was critical to the failure mode of the bolted joints,the failure mode shift from fastener fracture to bearing damage with the increase of bolt diameter,and the energy absorption increase significantly.The characteristic of loaddisplacement curves shown differences under variety dynamic load speed,while the final failure mode was invariant.The existence of adhesive zone for single-bolt bolted joint failed due to fastener fracture can enhance the energy absorption and peak load,while remain the final failure mode unchanged.The bolted joint failed due to bearing damage with adhesive zone shown no significant increase in the energy absorption and strength.The double-bolt hybrid bonded-fastened joint failed due to fastener fracture shown an increase in the energy absorption and failure displacement under dynamic loading.There was delay in the damage of adhesive zone.These findings provide evidence for the design of connections for modern composite structures.