Railcar bogie plate spring

A railcar bogie plate spring comprising:

• an upper surface member constituted by a first fiber reinforced plastic including a plurality of first resin-impregnated layers, each first resin-impregnated layer including a plurality of first continuous reinforced fibers extending in at least a lengthwise direction of the first resin-impregnated layer and forming a first continuous sheet of fibrous material, the plurality of first resin-impregnated layers being stacked so that the plurality of first continuous reinforced fibers extend in a longitudinal direction of the railcar bogie plate spring;
• a lower surface member constituted by a second fiber reinforced plastic including a plurality of second resin-impregnated layers, each second resin-impregnated layer including a plurality of second continuous reinforced fibers extending in at least a lengthwise direction of the second resin-impregnated layer and forming a second continuous sheet of fibrous material, the plurality of second resin-impregnated layers being stacked in a stack direction extending from a lower surface of the lower surface member toward an upper surface of the upper surface member so that the plurality of second continuous reinforced fibers extend in the longitudinal direction of the railcar bogie plate spring;
• a core member arranged between the upper surface member and the lower surface member, the core member being constituted by a third fiber reinforced plastic including a plurality of third resin-impregnated layers, each third resin-impregnated layer including a plurality of third continuous reinforced fibers forming a third continuous sheet of fibrous material, the plurality of third resin-impregnated layers being entirely stacked in a width direction perpendicular to the stack direction of the upper surface member and the lower surface member, and in a side view of the core member, the third continuous reinforced fibers of each of the plurality of third resin-impregnated layers are angled relative to a bending neutral axis of the core member so as to intersect with one another;
• and
• a lower surface of the railcar bogie plate spring is constituted by:
• (i) straight portions respectively extending from end portions of the railcar bogie plate spring toward a center of the railcar bogie plate spring so as to be angled relative to the bending neutral axis, and (ii) a central concave arc-shaped portion formed at a middle portion between the straight portions, the central concave arc-shaped portion being below the end portions of the railcar bogie plate spring in the stack direction, wherein
• the upper surface member, the lower surface member, and the core member extend continuously from one end to another end of the railcar bogie plate spring.