%% Function name
%       stress_gtol

%% Revised:
%       16 January 2014

%% Author
%       Abigail Lambert, Trey Moore, & Autar Kaw
%       Section: All
%       Semester: Fall 2012

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

%% Usage 
%       function [stress_loc] = stress_gtol(stress_glo,angle)
% Input variables
%       stress_glo=vector of global stress applied to unidirectional lamina
%       [stress_glo]=[sx;sy;sxy]
%       sx=longitudinal global stress
%       sy=transverse global stress
%       sxy=in-plane global stress
%       angle=angle of ply in degrees
% Output variables 
%       stress_loc=vector of local stress applied to unidirectional lamina
%       [stress_loc]=[s1;s2;s12]
% 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_loc] = stress_gtol(stress_glo,angle)
% Global stresses
% 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;];
% local stress
stress_loc=T*stress_glo;
end