EXPERIMENTAL DETERMINATION OF ENERGY RELEASE RATE OF CFRP STRUCTURES BY MEANS OF TRANSVERSE CRACK TENSION TESTS

摘要

The use of cost effective infused materials like Vacuum Assisted Process (VAP) needs of splicing technique when manufacturing large fuselage components and structures. Only resin fills the area between these butt joined semi-finished products, where cracks generate under high loading. Afterwards these cracks develop to delamination. Delamination and their susceptibility to growth are normally characterized using strain energy release rate parameter (G). Compression After Impact (CAT) test has become a key experiment to gather damage tolerance performance data during the design or certification phase of a new structure or material, involving composites. However, this procedure cannot specify information about damages in varying depths and the kind of damage. An alternative procedure is the use of the Transverse Crack Tension (TCT) specimens. This work presents the results obtained for G under mode II loading (GIIc) by means of TCT-tests for different infusion and Prepreg materials used at the present time in aeronautical industry. It is shown that results using standard specimens as Double Cantilever Beam (DCB) and End-Notch Flexural (ENF) specimen and non-standardised specimens, TCT, agree. Furthermore, the use of TCT method let reconstruct the initiation and development of damages by means of delamination under static loading, which will help on opening the floodgates to the next generation of sizing criteria and numerical tools. Extensive static test sets were accomplished, which made a fundamental understanding available of initiation and damage process.