Composite fan inlet blade containment

A ribbed composite shell includes an annular grid of relatively thick crack arresting ribs embedded in a relatively thin annular shell and relatively thin panels in thin annular shell between arresting ribs wherein each of panels are completely surrounded by a set of relatively thick adjoining ones of ribs. A shell forward flange may extend radially inwardly from thin annular shell. Arresting ribs may include radially stacked layers of strips between radially stacked annular layers of shell. Annular grid may include a rectangular grid pattern, a diamond grid pattern, or a hexagonal grid pattern. A nacelle inlet may have the ribbed composite shell within one or both of radially spaced apart composite inner and outer skins of an inner barrel. Nacelle inlet may be part of attached to a fan casing and axially disposed forward of fan blades circumscribed by the casing. The inlet may be on an engine nacelle.