Sk. Sharma et Bv. Sankar, SUBLAMINATE BUCKLING AND COMPRESSION STRENGTH OF STITCHED UNIWEAVE GRAPHITE EPOXY LAMINATES/, Journal of reinforced plastics and composites, 16(5), 1997, pp. 425-434
Effects of through-the-thickness stitching on the sublaminate buckling
and residual compression strength (often referred as compression-afte
r-impact or CAI strength) of graphite/epoxy uniweave laminates are exp
erimentally investigated. Primarily, three stitching variables: type o
f stitch yarn, linear density of stitch yarn and stitch density were s
tudied. Delaminations were created by implanting teflon inserts during
processing, The improvement in the CAI strength of the stitched lamin
ates was up to 400% compared to the unstitched laminates. Stitching wa
s observed to effectively restrict sublaminate buckling failure of the
laminates. The CAI strength increases rapidly with increase in stitch
density. It reaches a peak CAI strength that is very close to the com
pression strength of the undamaged material. All the stitch yarns in t
his study demonstrated very close performance in improving the CAI str
ength. It appears that any stitch yarn with adequate breaking strength
and stiffness successfully restricts the sublaminate buckling.