Kevlar wrap is provided around the fan case to contain fan blades. It is
lighter in weight than armour plate but requires a clearance to allow for the
elastic expansion/contraction of the Kevlar as it catches a blade. I know it
is used on CF34-3A/B in Canadair RJ/Challenger and on BR710 in Gulfstream
V/Global Express as well as on some variants of RB 211.

Gerald Wilson