%% Function name
%       strain_ltog

%% Revised:
%       21 January 2014

%% Author
%       Ahmad Hares, Trey Moore, & Autar Kaw
%       Section: All
%       Semester: Fall 2012

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

%% Usage 
%       function [strain_glo] = strain_ltog(strain_loc,angle)
% Input variables
%       strain_loc=vector of local strain applied to unidirectional lamina
%       [strain_loc]=[eps1;eps2;eps12]
%       eps1=longitudinal local strain
%       eps2=transverse local strain
%       eps12=in-plane local strain
%       angle=angle of ply in degrees
% Output variables 
%       strain_glo=vector of global strain applied to unidirectional lamina
%       [strain_glo]=[epsx;epsy;epsxy]
% 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 [strain_glo] = strain_ltog(strain_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
strain_glo=inv(T)*strain_loc;
% Calculating espxy
strain_glo(3)=strain_glo(3)*2;
end