The Preparation And Mechanical Properties Of Nano-CaCO₃ Glass Beads And Co-reinforced Carbon Fiber/Nylon6 Composites

Carbon fiber reinforced nylon composites have been widely used due to their excellent comprehensive performance,and now they have become one of the most significant reinforced composites.The addition of inorganic particles in carbon fiber reinforced polymer composites has become an effective way for preparing composites with better comprehensive properties.In present work,nano-CaCO₃ and glass beads?GB?were used as inorganic fillers,while carbon fiber?CF?and nylon 6?PA6?used as based reinforcements and matrix respectively.The granulation was first carried out by melt extrusion,then the ternary nano-CaCO₃/CF/PA6 composites and quaternary GB/nano-CaCO₃/CF/PA6 composites were prepared by hot pressing.The effects of nano-CaCO₃ content on the mechanical properties and fracture morphology of nano-CaCO₃/CF/PA6 composites were investigated.Then the effects of nano-CaCO₃and GB hybrid filler on the mechanical properties and fracture morphology of GB/nano-CaCO₃/CF/PA6 composites were also investigated.The toughening mechanism of inorganic particles under bending and shear conditions was discussed.The impact strength,fracture morphology and strengthening and toughening mechanism of PA6 matrix composites were compared.The results were listed as below:The addition of nano-CaCO₃ could improve the mechanical properties of nano-CaCO₃/CF/PA6 composites.When the nano-CaCO₃ content was 10 wt.%,the maximum flexural strength and modulus,shear and impact strength were 349.8 MPa,17.4 GPa,47.4.MPa and 63.2 kJ/m² respectively,which increased by 15.1%,53.2%,8.5%and 51.8%compared to CF/PA6 composites.The debonding effect and micro-crack deflection caused by nano-CaCO₃ in the system were the main reinforcement mechanisms.The introduction of modified GB into nano-CaCO₃/CF/PA6 composite could greatly improve the mechanical properties of the obtained GB/nano-CaCO₃/CF/PA6 materials.Among all the formulations,the composites prepared by adding 8 wt.%GB and 10wt.%nano-CaCO₃ possessed the best performance,and the maximum bending,shearing and impact strength were 427.9 MPa,51.6 MPa and 87.4 kJ/m²respectively.Compared with CF/PA6 composites,they increased by 40.8%,18.0%and 143.5%,respectively.Under the bending stress,the debonding effect of nano-CaCO₃,the crack deflection and pinning of the auxiliary modified GB were the main enhancement mechanism.Under shear stress,the GB debonded,while the nano-CaCO₃ combined with the matrix was poor and agglomerates were produced,which could not conducive to the increase of mechanical properties.The combination of carbon fiber and inorganic particles could significantly improve the impact strength of the material.The impact strength of the quaternary composites reached 87.4 kJ/m²,which was 13.7 times that of pure PA6,143.5%higher than that of CF/PA6.The main enhancement mechanisms were:carbon fiber pull-out and debonding of cracks;GB debonding,deflection cracking,and pinning.Nano-CaCO₃ produced micro-cracks and silver crack at the same time as debonding,which was helpful to produce a reinforcement effect for obtained materials.The synergistic effect of the above multi-scale reinforcements resulted in enhanced toughening effect.Low cost and high-performance composites were prepared successfully.