Reinforcing effect of hybrid nano-coating on mechanical properties of basalt fiber/poly(lactic acid) environmental composites

Basalt fiber (BF) reinforced poly(lactic acid) (PLA) composites have promising applications in biomedical and automotive industries, but their mechanical performances are still largely restricted by poor interfacial properties between BFs and PLA. To this end, we develop a flexible/rigid hybrid nano-coating technology for fiber surface modification to improve the interfacial properties between BFs and PLA. An improved vacuum assisted prepreg process (VAPP) is proposed to prepare the high-performance modified BF/PLA composites. The SiO2 nanoparticles and poly(epsilon-caprolactone) (PCL) polymer are designed as rigid and flexible phases, respectively, in hybrid nano-coating. The hybrid coating with a more rigid phase on the BFs can significantly enhance the mechanical properties of BF/PLA composites, especially their tensile strength and interlaminar fracture toughness. These values are approximately 29% and 110% higher, respectively, than those of unmodified BF/PLA composites. The increase in tensile strength results from a higher efficiency and continuous stress transfer derived from the flexible/rigid interfacial structure. An enhanced interlaminar fracture toughness is attributed to more dissipated energy due to the matrix yielding and crack deflecting at the interface induced by a large deformation of flexible PCL and crack pinning of SiO2 nanoparticles, respectively. Furthermore, the modified BF/PLA composites with hybrid coatings of 1 wt% coating concentration exhibit optimal mechanical properties. This work provides a novel strategy for modifying the fiber-matrix interface to produce high-performance fiber-reinforced polymer composites.