Strengthening of composite T-joints using Ø 0.11 mm Z-pins via an ultrasound-guided insertion process

•The novel ultrasound-guided fine Z-pin insertion units are developed and arranged in an array of 2 × 5 into an industrial robot.•The composite T-joints are reinforced with Ø 0.11 mm carbon or steel pins by the ultrasound-guided fine Z-pin insertion system.•Thinner pins can increase the peak load and total energy absorption capacity of composite T-joints more effectively than conventional size Z-pins.