%% Function name
%       strainglocallaminate

%% Revised:
%       3 February 2014     

%% Author
%       Necip Kayim, Trey Moore, & Autar Kaw
%       Section: All
%       Semester: Fall 2013

%% Purpose
%       Given the number of plies, angle of each ply, as well as the global
%       strains, output the local strains at the top, middle, and bottom of
%       each laminate

%% Usage 
%       function [strainlocalplies] = strainlocallaminate(strainglobalplies,angleplies,nplies)
% Input variables
%       strainglobalplies=global strains at top, middle, and bottom of each laminate
%       angleplies=the angle of each ply in degrees
%       nplies=number of plies
% Output variables 
%       strainlocalplies=local strains at top, middle, and bottom of each laminate
% Keyword
%       local strain matrix
%       global strain matrix
%       transformation of strains

%% License Agreement
%       http://www.eng.usf.edu/~kaw/OCW/composites/license/limiteduse.pdf

%% Code
function [strainlocalplies] = strainlocallaminate(strainglobalplies,angleplies,nplies)
% Reuter matrix
R=[1 0 0;0 1 0;0 0 2];
Rinv=inv(R);
for k=1:1:nplies
% Angle of ply
    angle=angleplies(k);
% Sine of the angle of the lamina
    s=sind(angle);
% Cosine of the angle of the lamina
    c=cosd(angle);
% Transformation Matrix
    T=[c^2 s^2 2*s*c; s^2 c^2 -2*s*c; -s*c s*c c^2-s^2];
% Top, middle, and bottom global strains
    for i=1:1:3
        strainglobalTop(i)=strainglobalplies(1,i,k);
        strainglobalMid(i)=strainglobalplies(2,i,k);
        strainglobalBot(i)=strainglobalplies(3,i,k);
    end
% Top, middle, and bottom local strains
    strainlocalTop=R*T*Rinv*strainglobalTop';
    strainlocalMid=R*T*Rinv*strainglobalMid';
    strainlocalBot=R*T*Rinv*strainglobalBot';
    for i=1:1:3
        strainlocalplies(1,i,k)=strainlocalTop(i);
        strainlocalplies(2,i,k)=strainlocalMid(i);
        strainlocalplies(3,i,k)=strainlocalBot(i);
    end
end