Twisted Pathways Towards Tougher Interlaminar Regions in Laminated Composites

In this paper, we build upon a previously introduced interface enhancement fabrication method that has shown to improve interlaminar fracture toughness of laminated polymeric composites by 25% in mode-I and by 76% in mode-II. This method utilizes filament extrusion 3D printers to precisely deposit molted polymer directly onto carbon fiber prepreg. Upon bonding with the prepreg, these interlaminar polymer reinforcements act as barriers to a planar crack, causing the crack to tilt – requiring more energy, and manifesting as an increased fracture toughness. In the current study, we optimize the pattern of the printed reinforcement to induce crack twisting alongside crack tilting to further increase the interlaminar fracture toughness. In Mode-II, we see a further improvement of ~17% while still using the same amount of polymeric material deposited in the interlaminar region – that is an overall improvement of ~95% compared to pristine samples. Using microscopy and microcomputed tomography ( 𝜇 𝐶 𝑇􀈌, we observe the wavy crack path during delamination.