A notched $(200200m{m}^2)$ aluminium plate $($Figure $1)$ is used to reinforce the main spar cap and subjected to $P_x=$

$178kN,P_y=-145kN$ and $P_{xy}=130kN.$ The thickness of the plate is $(8mm),$ and the diameter of the circular hole

is $(20mm).$

It is intended to replace the aluminium plate with a composite laminate.

However, due to new design constraints, the total thickness of the

composite plate should not be higher than $(4$ mm $).$ The material properties

of the selected carbon$/$epoxy laminate are given in Table $2.$ Assume that the

contribution of $0$ and $90$ ply to the laminate's shear strength is $50\%$ of

$S_{(+-45)}$

A$.$ Consider the possibility of impact damage with a diameter of $25$ mm in the notched composite laminate. Calculate

the minimum number of control plies and $\{$:$90)$ that can meet the specified design constraints.

B$.$ Following the good practice rules for the design of aerospace composite structures, suggest an acceptable laminate

stacking sequence.

C$.$ Determine the Margin of Safety $($M$.$S$.)$ of the proposed laminate $($Part B$)$ for $Nx,Ny$ and $Nxy$; and discuss the

safety issues of the composite plate based on the calculated MOS values.