During the manufacture of curved or angled shell composite structures, the
enclosed angle of such structures tends to be reduced after cure. This phen
omenon is referred to as "spring-in". It is believed that such distortion i
s caused mainly by the significant difference between the in-plane coeffici
ent of thermal expansion (CTE) and the through-thickness CTE. This might re
sult in a larger out-of-plane contraction than the in-plane contraction dur
ing the time that a composite structure is cooling down from the curing tem
perature. In this paper, a 3-D Finite Element Analysis procedure was develo
ped to predict "spring-in" resulting from anisotropy for both thin and thic
k angled composite shell structures. The results of the FE analysis were ev
aluated together with those from the analytical study and experimental inve
stigation conducted by Jain at the Cooperative Research Centre for Advanced
Composite Structures (CRC-ACS) in Australia. It was concluded, based on th
ese results, that the FE model gives more accurate results than the analyti
cal model, particularly for thicker composite shells. The corner radius eff
ect, shell thickness effect, and lay-up effect on "spring-in", together wit
h the effect of tool/part interaction on the total distortion were also dis
cussed. Comparison was made with the experimental results reported by Radfo
rd and Rennick.