%% Function name
%       strain_gtol

%% Revised:
%       16 January 2014

%% Author
%       Howard Fox, Trey Moore, & Autar Kaw
%       Section: All
%       Semester: Fall 2012

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

%% Usage 
%       function [strain_loc] = strain_gtol(strain_glo,angle)
% Input variables
%       strain_glo=vector of global strain applied to unidirectional lamina
%       [strain_glo]=[epsx;epsy;epsxy]
%       epsx=longitudinal global strain
%       epsy=transverse global strain
%       epsxy=in-plane global strain
%       angle=angle of ply in degrees
% Output variables 
%       strain_loc=vector of local strain applied to unidirectional lamina
%       [strain_loc]=[eps1;eps2;eps12]
% 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_loc] = strain_gtol(strain_glo,angle)
% Sine of the angle of the lamina
s=sind(angle);
% Cosine of the angle of the lamina
c=cosd(angle);
% Reuter Matrix
R=[1 0 0; 0  1  0;0  0  2];
% 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 strain
strain_loc=R*T*inv(R)*strain_glo;
end