Barley is meant to be chewy but it sounds like it was harder than that. Did the recipe specify whether to use hulled barley or pearled barley? Pearled barley cooks quicker and has a softer consistency (though is less nutritious).
It could also depend on how old the barley was. I agree it should have been fully cooked after 40 minutes. Sometimes it can help to soak the grain overnight before you cook it (a tip I got from Maria Speck's wonderful book Ancient Grains for Modern Meals).