Characterization of Mode I Properties of Full-Depth Z-Fiber Stubble in Co-Bonded Composites (Preprint).

摘要

Z-pins are small-diameter carbon rods that are ultrasonically inserted through composite laminates in the z-direction to provide extra resistance to crack growth and delamination. They are normally inserted through co-cured composites, but this paper presents an experimental study on a new z- pin stubble manufacturing technique that is compatible with the co-bonding process. Stubble lengths were 0.125 and 0.250 inch. Double cantilever beam (DCB) specimens were used to characterize the effect of stubble diameter and height on the Mode I crack resistance. It was determined that the new approach using a second ultrasonic step is indeed necessary for stubble heights on the order of 0.125 inch. It was also found that increasing the stubble height from 0.04 inch to 0.125 inch resulted in a much more significant improvement in Mode I properties than increasing the aerial density from 2 % to 4 %. Finally, taking that final step of increasing the stubble height from 0.125 to 0.250 inch did not improve the properties as much as would be expected from previous studies.