Flat-cross-section glass fiber, glass-fiber-reinforced resin composition, and glass-fiber-reinforced resin molded product

Flat-cross-section glass fiber comprising a plurality of flat-cross-section glass filaments each having a cross-section in flat shape, the cross-section having a major axis in a range of 20.0 to 35.0 μm, a minor axis in a range of 5.0 to 10.0 μm, and an irregular shape ratio R, being a ratio of the major axis to the minor axis (major axis/minor axis), in a range of more than 3.0 and 5.0 or less, wherein

• the flat-cross-section glass fiber has a packing rate P, being a ratio of a cross-sectional area of each flat-cross-section glass filament to an area of a rectangle circumscribing a cross-section of the flat-cross-section glass filament (cross-sectional area of flat-cross-section glass filament/area of rectangle circumscribing cross-section of flat-cross-section glass filament), in a range of 77.0 to 92.0%, and the irregular shape ratio R and the packing rate P satisfy formula (1) below, and
• the flat-cross-section glass fiber comprises SiO2 in a range of 52.0 to 62.0% by mass, Al2O3 in a range of 10.0 to 20.0% by mass, and CaO in a range of 16.7 to 28.1% by mass with respect to a total amount of the flat-cross-section glass fiber:
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