A numerical methodology for simulating the mechanical behavior of CFRP laminates containing pores using X-ray computed tomography data

Pores are the most common defect in carbon fiber reinforced plastics (CFRPs). Numerical predictive tools capable of taking into account the porosity characteristics, as detected by efficient non-destructive testing techniques, could be potentially contribute to the quality control process applied by the industry in manufacturing of CFRP parts. In the present paper, a numerical methodology is developed for simulating the mechanical behavior of porous CFRP unidirectional (UD) laminates by exploiting data extracted from X-ray computed tomography scans. The analysis of detected pores is performed using the VG Studio MAX software. The software parameters are validated by optical microscopy measurements. The progressive damage modeling method is applied in three simulation levels. In the first level, the behavior of the epoxy resin, in the presence of small pores, is simulated by means of a representative unit cell (RUC). In the second level, the behavior of the epoxy resin, in the presence of small and large pores, is simulated by means of a RUC comprising the epoxy resin, in which the behavior simulated from the first level simulation is assigned, and a single pore (MObject) in which all large pores are clustered. The elastic properties and strengths of the porous UD ply, needed in the simulation of the specimen (third level), are computed using analytical micromechanics relations. The proposed methodology was used to simulate the transverse tensile behavior and predict the properties of three different UD CFRP laminates containing pores of different content. The numerical results show a small decrease of transverse stiffness and a significant decrease of transverse tensile strength with increasing the pore content. The methodology was validated through comparison with tension tests.