US Patent 7993727 Advanced grid structure

An advanced grid structure has high strength and low thermal expansion, and includes first, second, and third tape prepreg groups each including a plurality of tape prepregs. Each tape prepreg includes carbon fibers that are aligned in a first, second, or third direction and that form respective first, second, and third grid sides. A plurality of each the first, second, and third grid sides are spaced apart at equal intervals in the respective first, second, or third direction to form respective first, second, and third grid side groups. A structure ratio of the advanced grid structure is larger than 0 and 0.107 or less, 0.053 or less, or 0.040 or less. A thermal expansion coefficient of the advanced grid structure is −0.9 ppm/K or more and 0.9 ppm/K or less. The carbon fibers have a tensile modulus of elasticity of 280 GPa or more and 330 GPa or less.