A $0-90$ laminate composite provides improved in$-$plane properties in two orthogonal directions. The elastic moduli in these directions can be estimated using the isostrain rule$-$of$-$mixtures by considering the overall volume fraction fiber oriented in each direction. For example, a $0-90$ laminate composite has $40\%$ fiber in each alternating layer. However, considering the overall composite there is $20\%$ fiber in each orthogonal direction. Use this estimation method to solve the problem below below.

A wind turbine blade requires elastic moduli of $50$ GPa and $20$ GPa in the $0$ and $90$ directions, respectively, and the lowest possible density. Using the materials shown, specify:

$1.$the best fiber$/$matrix combination, and

$2.$the volume fraction fiber in each of the two alternating layers.