Experimental and numerical investigation of the effects of porosity on the in-plane shear properties of CFRPs using the V-notched rail shear test method

Voids occurred after the manufacturing process are a common defect of composite materials. They appear to have a negative impact on the matrix-dominated material properties, the gravity of which depends upon the porosity content, the shape and the volume of pores. In the present work, the effects of porosity on the shear mechanical properties of unidirectional carbon fiber-reinforced plastic composites are evaluated via mechanical testing and numerical simulation. In this framework, the V-Notched Rail Shear test method is applied on carbon fiber reinforced plastic specimens of four porosity levels. Moreover, two finite element methodologies are utilized for simulating this particular mechanical test namely the progressive damage model (PDM) and the Virtual Crack Closing Technique (VCCT). Double cantilever beam (mode I) and end notched flexure tests (mode II) are also conducted for the development of the VCCT model. The results from the shear mechanical tests reveal a considerable drop in both the elastic properties and strength. In addition to that, for larger porosity contents, more cracks are present and crack initiation and propagation occur at a faster pace. Finally, the advantages and disadvantages of the two numerical methods are presented and assessed revealing a satisfying consistency with the results obtained by the mechanical tests.