Interlaminar fracture and crack-healing capability of carbon fiber/epoxy composites toughened with 3D-printed poly-epsilon-caprolactone grid structures

In this study, carbon fiber (CF)/epoxy (EP) composites are toughened with 3D-printed poly-epsilon-caprolactone (PCL) grid structures which are produced by fused deposition modeling at three different areal weight densities and place between dry plain-weave carbon fabrics prior to resin infusion. Three-point bending, Mode-I fracture toughness, interlaminar shear strength (ILSS), and Charpy impact tests are carried out on the prepared composite specimens. The results show that the PCL interlayers can enhance Mode-I fracture toughness up to seven times (693%). The main toughening mechanism is the crack bridging due to the formation of PCL fibrils. It is shown that there is a quadratic relationship between the amount of PCL and Mode-I fracture toughness improvement. The thermal healing efficiencies (eta) for the first and second healing of PCL reinforced composites are determined as 44.1% and 28.2%, respectively. DMA results indicates that the tan delta values are increased almost 10 times with the addition of PCL interlayers. The flexural properties are decreased due to the reduced fiber volume fraction, higher void content, and plasticization effect of PCL interlayers.