Composites C-shape ribs are made of carbon fiber fabric prepreg on the male moulds under certain curing process. A coordinate measuring machine is used to measure the surface of the moulds

the inner surface of the ribs under three conditions (three flanges closed

large end cut and three flanges trimmed after large end cut)

and the outer surface of the ribs when the large end is cut and the three flanges are trimmed. The springback of the ribs are measured and analyzed. The results shows that the springback compensation of the two side flanges of the ribs is 1.35°

and the springback compensation of the large end flange is 0.32° when the three flanges are closed. The springback results varied a lot before and after the large end is cut

but varied little before and after the flanges are trimmed. The springback compensation is 1.69° for the two side flanges

and 1.62° for the big end flange when the ribs are cut at the large end.