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Damage Behavior of Stitched CFRP Laminate on High-Velocity Rigid Body Impact



Stitched carbon/epoxy laminated composites have excellent mechanical properties such as higher delamination toughness, better impact resistance under low-velocity impact than those of conventional CFRP laminates. The stitching technique is expected that it can also improve high-velocity impact resistance. In this study, highvelocity impact test against the stitched material was performed and its delamination and absorbed energy was acquired. The damage process of the stitched laminate on high-velocity impact was simulated and compared with the experimental results. The high-velocity impact tests were performed with an air gun. Steel balls are used as projectiles. Two stitching parameters, density and thread thickness were considered. Non-stitched specimens were also experimented for comparison. Impacted specimens were investigated by ultrasonic inspection. The results suggest that stitched specimens have smaller delamination area than those not stitched. The thicker the stitching threads are and the denser the stitches are, the delamination area become smaller. A finite element model for the impact test was constructed to reveal the damage mechanisms of the stitched material. In spite of the analyses underestimated the delamination area, energy absorbed by specimen during impact load was calculated with accuracy. Damage propagation process of the stitched material during the highvelocity impact load was discussed.

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