%% Function name
%       stress_ltog

%% Revised:
%       21 January 2014

%% Author
%       Casey McKenzie, Trey Moore, & Autar Kaw
%       Section: All
%       Semester: Fall 2012

%% Purpose
%       Given the local stresses and the angle of the ply for a unidirectional
%       lamina, output the global stresses

%% Usage 
%       function [stress_glo] = stress_ltog(stress_loc,angle)
% Input variables
%       stress_loc=vector of local stress applied to unidirectional lamina
%       [stress_loc]=[s1;s2;s12]
%       s1=longitudinal local stress
%       s2=transverse local stress
%       s12=in-plane local stress
%       angle=angle of ply in degrees
% Output variables 
%       stress_glo=vector of global stress applied to unidirectional lamina
%       [stress_glo]=[sx;sy;sxy]
% Keyword
%       local stress matrix
%       global stress matrix
%       transformation of stress

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

%% Code
function [stress_glo] = stress_ltog(stress_loc,angle)
% 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;];
% Calculating the global strain vector using the Tinv matrix
stress_glo=inv(T)*stress_loc;
end