The biggest problem with the entrance of these blades was the resistance to FOD, The other big engine manufacturers were also keen to develop composite blades and needed to address the serviceability of these after they entered service. The FAA at that point had already noted the sensitivity of the early GE gun drilled fan blades and was shall we say gun shy of the ruggedness of the now developing composite blade following the RR lead, I seem to recall a funded developments through the Dayton Ohio folks in the 60's. The idea was concentrating around a protective covering at the leading edge to resist erosive properties of fine sand as well as a sacrificial resistance to larger particles such as small stones, hail etc.. and of course stay around long enough to get home after eating birds up to 1.5 lbs.
I believe that history suggests it took another 20 years of industry wide development before these problems were addressed.