%% Function name
%       alpha_gtol

%% Revised:
%       13 January 2014
 
%% Author
%       Atif Amir, Trey Moore, & Autar Kaw
%       Section: All 
%       Semester: Fall 2012
 
%% Purpose
%       Given the longitudinal and transverse coefficients of thermal 
%       expansion of a unidirectional lamina, and the angle of the ply, 
%       output the coefficients of thermal expansion for an angle lamina.
 
%% Usage
%       function [alphaxy] = alpha_gtol(alpha12,angle)
% Input variables
%       alpha12=vector of thermal expansion of unidirectional lamina 
%               in 1,2 direction 
%       [alpha12]=[alpha1;alpha2;zero]
%       alpha1=longitudinal coefficient of thermal expansion
%       alpha2=transverse coefficient of thermal expansion.
%       alpha12=in-plane coefficient of thermal expansion.
%       angle=angle of ply in degrees
% Output variables
%       alphaxy=vector of coefficients of thermal expansion for angle
%               in x,y direction
%       [alphax,alphay,alphaxy]
% Keywords
%       coefficient of thermal expansion 
%       angle ply

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

%% Code
function [alphaxy]=alpha_gtol(alpha12,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 coefficients of thermal expansion for angle lamina 
alphaxy=inv(T)*alpha12;
% Calculating alphaxy
alphaxy(3)=alphaxy(3)*2;
end