Method of designing composite material, method of evaluating composite material, and composite material

A method of evaluating a composite material in which a plurality of reinforced fiber substrates are stacked, the composite material having a thickness-varying part whose thickness in a stacking direction changes from a large thickness to a small thickness, the thickness-varying part including a fiber reinforced substrate having a drop-off portion that is an end portion cut along the stacking direction, the method comprising:

• setting, as a cut substrate, the reinforced fiber substrate that has the drop-off portion and is positioned between a base substrate and a cover substrate in the thickness-varying part, the base substrate being one of the reinforced fiber substrates overlapping in the stacking direction, the cover substrate being a reinforced fiber substrate opposed to the base substrate in the stacking direction;
• and
• performing stress analysis on the base substrate, the cut substrate, and the cover substrate to calculate an evaluation value concerning stress on the cut substrate.

A composite material in which a plurality of reinforced fiber substrates are stacked, the composite material comprising:

• a thickness-varying part whose thickness in a stacking direction changes from a large thickness to a small thickness, the thickness-varying part including a plurality of cut substrates each being the reinforced fiber substrate having a drop-off portion that is an end portion cut along the stacking direction, the thickness-varying part being formed by stacking the reinforced fiber substrates including the cut substrates, wherein
• the drop-off portions of the cut substrates have a positional relation such that, in a direction from a thick side to a thin side of the thickness-varying part, one or more of the reinforced fiber substrates are interposed in the stacking direction between the drop-off portion on the thick side and the drop-off portion on the thin side adjacent to the drop-off portion on the thick side, and
• the positional relation holds in all of the drop-off portions.