Effectiveness of z-pins in preventing delamination of co-cured composite joints on the example of a double cantilever test

The effectiveness of z-pins in co-cured joints is illustrated on the model of a composite double cantilever beam (DCB) subject to a standard fracture toughness test. A comprehensive solution is presented in the paper accounting for a broad spectrum of issues that affect the problem. They include the accurate evaluation of the rotational constraint provided by the intact section of DCB, possible transverse shear deformation in the delaminated section, and effects of uniform and nonuniform temperature on the response. A simple criterion for the effectiveness of z-pins in co-cured joint is introduced and its application is illustrated on numerous examples. As follows from the analysis, z-pinning is an effective method of enhancing delamination resistance of composite joints. Even a very small volume fraction of z-pins (less than 1.5%) may arrest delamination in co-cured composite joints.