Improved mode I interlaminar fracture toughness of random polypropylene composite laminate via multiscale reinforcing formed by introducing functional nanofibrillated cellulose

Interface engineering and phase engineering of composites offer a promising route to rationally tune the interlaminar toughness of laminates, as high toughness plays an important role in preventing interlaminar failure and ensuring the safety of components. Herein, unlike the previous melt-mixing process, we coated the second reinforcement TONFC (TEMPO-oxidized nanofibrillated cellulose) on the surface of the main reinforcement (continuous glass fiber) by sol impregnation, and successfully prepared the commingled yarn random poly-propylene (PPR) composite laminate with high interlaminar fracture toughness. The surface groups of each raw material of the composite system before and after the reaction were characterized and thereby obtaining the interface strengthening mechanism. Besides, the heterogeneous nucleation effect of TONFC and the mechanism of inducing beta-phase formation were revealed by analysis of crystallization behavior and crystal structure. Further, through a double cantilever beam (DCB) test and morphology analysis, the effect mechanism of the addition of TONFC on the interlaminar crack propagation of PPR composite laminate was explored. This work provides a rapid and efficient avenue for the interlaminar modification of commingled yarn composites.