Placement of modifier material in resin-rich pockets to mitigate microcracking in a composite structure

A method of manufacturing a composite structure comprising:

• associating a plurality of fibers with a manufacturing tool;
• including a modifier in resin-rich pockets associated with the fibers configured to be at least partially embedded within a resin and provided in at least one of a flattened fiber tow of a unidirectional ply, a stack of composite plies, a tape, a woven fabric or cloth;
• the modifier being limited to the resin-rich pockets and excluded from non-resin-rich pockets, the modifier having at least one modifier characteristic that is different than a resin characteristic, the modifier being non-integral with the fibers;
• wherein the resin-rich pockets are locations in the composite structure where the resin-rich pocket without the modifier would have a lower fiber-volume-fraction than the fiber-volume-fraction at other locations in the composite structure, the resin-rich pockets being limited to the following areas or any combination thereof:
• limited to along one or more outer edges on laterally-opposing sides of a flattened fiber tow of the unidirectional ply or on laterally-opposing sides of the tape;
• in divots and at intersections of the fibers of the woven fabric or cloth;
• and
• at a ply step in the stack of composite plies.

A method of resisting microcracking within a composite structure, comprising the steps of:

• applying a load to a composite structure having a resin, a plurality of fibers at least partially embedded within the resin and provided in at least one of a flattened fiber tow of a unidirectional ply, a stack of composite plies, a tape, a woven fabric or cloth, and a modifier located in resin-rich pockets associated with the fiber, the modifier being limited to the resin-rich pockets and excluded from non-resin-rich pockets of the composite structure, the modifier having at least one modifier characteristic that is different than a resin characteristic, the modifier being non-integral with the fibers;
• wherein the resin-rich pockets are locations in the composite structure where the resin-rich pocket without the modifier would have a lower fiber-volume-fraction than the fiber-volume-fraction at other locations in the composite structure, the resin-rich pockets being limited to the following areas or any combination thereof:
• limited to along one or more outer edges on laterally-opposing sides of a flattened fiber tow of the unidirectional ply or on laterally-opposing sides of the tape;
• in divots and at intersections of the fibers of the fabric or cloth;
• and
• at a ply step in the stack of composite plies;
• and
• resisting the load with a load resistance that is different that the load resistance provided by a composite structure lacking the modifier in the resin-rich pockets.