one aspect considering stress in the core, is the shear forces that come into play. typically with a self bow, tension and compression limitations at the surfaces demand very good wood selection, and govern the designs and materiel selections. As a point of interest, there was recently a bow posted that had a hidden flaw in the limb that resulted in a unexpected failure. A cursory examination of the accompanying photo, looked to me, to be non-typical for a tension or compression failure. It would not surprise me if that bow failed in shear, at the central flaw, resulting in a weak spot that ultimately induced the total limb failure.
Shear failures are also often seen when a glued handle "pops off".
what reading I have done on composites, often mentions the need for careful core selection, leading me to believe that shear limitations often dictate in composite designs. this makes sense, as the sinew and horn is selected for their exceptional tension and compression qualities, asking the core to handle more shear stress that attends more radical bend radii.
I have often wondered if the preference for maple is on account of its diffuse porus qualities. It does seem reasonable that a shear force could be easily localized on the spring growth portion of a ring porus wood, especially if it were flat sawn, making it a poor choice.