Storing the matrix values in a loop

having problem storing the values for the T matrix. I keep getting 3x39 matrix for T instead of 3x3 matrix. So that I can plot later

 %aluminum 2024-T3 – IM7 carbon composite composites%
E1f=290E9;
E2f=21E9;
Em=73E9;
G12f=14E9;
Gm=26.6E9;
Vf=0.60;
af1=-0.2e-6;
af2=10e-6;
am=23;
Vm=1-Vf;
v12f=0.2;
v12m=0.33;
E1=(Vf*E1f)+(Vm*Em);
% transverse shear modulus%
xi=2;
eta_E2=((E1f/Em)-1)/((E1f/Em)+xi);
E2=(Em*(1+xi*eta_E2*Vf))/(1-eta_E2*Vf);
v12=(Vf*v12f)+(Vm*v12m);
v21=(E2/E1)*v12;
eta_G12=((G12f/Gm)-1)/((G12f/Gm)+ xi);
G12=(Gm*(1+xi*eta_G12*Vf))/(1-eta_G12*Vf);
% alpha unit m/m/deg celcius %
alpha_1=(E1*af1*Vf)+(Em*am*Vm)/(E1f*am*Vm)+(Em*Vm);
alpha_2=(af2*Vf)*(1+Vf)+(am*Vm)*(1+Vm)-(v12*af1);
alpha_0= [alpha_1;alpha_2;0];
S11=1/E1;
S12=-v12/E1;
S21=-v21/E2;
S22=1/E2;
S33=1/G12;
%compliance matrix @ 0%
S0=[S11 S12 0;S21 S22 0;0 0 S33];
% stiffness matrix @ 0 %
C=inv(S0);
%Qo=1/S0=inv(S0)=C%
% theta range %
theta=[-90:15:90];
N=length(theta);
T=cell(N,1);
Sxy=cell(N,1);
alpha_theta=cell(N,1);
for i=1:N
   
m=cosd(theta);
n=sind(theta);
R=[1 0 0;0 1 0;0 0 2];
% T is transform matrix%
T{i}=[m.^2 , n.^2 , 2.*m.*n; 
   n.^2 , m.^2  , -2.*m.*n;
   -m.*n  , n.*m  ,(m.^2-n.^2)];
% Transformed complaince matrix%
Sxy{i}=R*inv(T{i,1})*inv(R)*T{i,1}*S0;
Ex(i)=1/Sxy{i,1}(1,1);
Ey(i)=1/Sxy{i,1}(2,2);
Gxy(i)=1/Sxy{i,1}(3,3);
vxy(i)=-Sxy{i,1}(1,2)*Ex(i);
% vyx(i)=vxy(i)%
Nsx(i)=Gxy(i)*Sxy{i,1}(1,3);
Nsy(i)=Gxy(i)*Sxy{i,1}(2,3);
Nxs(i)=Ex(i)*Sxy{i,1}(3,1);
Nys(i)=Ey(i)*Sxy{i,1}(3,2);
alpha_theta{i}=inv(R)*inv(T{i})*R*alpha_0;
Axy(i)=alpha_theta{i,1}(3,1);
end
plot(Ex)

Answer 1

[Walter Roberson]

theta=[-90:15:90];
N=length(theta);
[...]
for i=1:N
   
m=cosd(theta);
n=sind(theta);

why bother iterating over the length of theta when you are going to operate on all of theta inside the loop?