Abstract
In the present report we describe the geometrically nonlinear method for orthotropic (composite) materials that is implemented using the commercial C++ library Diffpack. The implementation is based on a module dealing with linear elasticity for isotropic materials, and the modifications performed to extend the functionality to handle orthotropic materials are explained. Analysis of composite joints is one of the main aims of the module. Such joints typically fail for laminate strains in the order of 1-2%, which indicates that sufficient accuracy may be obtained by a geometrically linear procedure. However, for non-symmetric geometries, e.g. single lap joints, geometrically nonlinear effects become crucial for loads far below ultimate strength limits. Thus, in order to be able to analyse such joints accurately, the code is extended with functionality capturing geometrically nonlinear effects.
In addition to the description of the extended functionality, the report covers some verification of the code. It is tested on a couple of examples, showing reasonable results in all cases. It should also be mentioned that in a previous study solutions obtained by the present module were in excellent agreement with ANSYS results.