The Model Of Interfacial Bonding Strength Of Three Kinds Of Typical Nanophases Reinforced Multiscale Composites

Fiber reinforced composites are usually composed of matrix and fiber reinforcement.The matrix binds the reinforcements together,transfers the load between the reinforcements,protects the fiber reinforcements from chemical erosion,wear and so on.The reinforcements help to improve the bearing capacity of the composites.Fiber reinforced composites have excellent properties in strength,stiffness,fatigue resistance and impact resistance,and have been applied in automotive industry,construction industry,sports equipment,aerospace and other industrial fields.Although the application of fiber reinforced composites in the aerospace field accounts for only a small part,it represents the most advanced technology in this field in terms of ensuring safety and optimal performance in extreme working environments.However,because the interlaminar mechanical properties of fiber reinforced composites are much weaker than in-plane properties,fiber reinforced composites are facing more and more challenges in practical engineering application.The macroscopic interlaminar properties of fiber reinforced composites are closely related to the microscopic interfacial properties between fiber and matrix.The interface region between fiber and matrix plays a very important role in the mechanical behavior of fiber reinforced composites.In order to enhance the interlaminar properties of composites,people try to introduce nanophases into fiber reinforced composites to improve their interfacial properties.As a result,multi-scale composites came into being.At present,the nanophases in multi-scale phase reinforced composites can be divided into three types according to their morphology: cylindrical nanophase,lamellar nanophase and spherical nanophase.In this paper,a interface strength model of nanophase modified composites is established based on the cohesion energy theory,and the transverse tensile strength of three kinds of typical nano-reinforced relative multi-scale composites is predicted respectively.The effects of morphological and quantitative parameters of nano-phase on the interfacial strength of multi-scale composites are described quantitatively,and the rationality of the model is verified by fiber bundle composite experiments and finite element simulation.The research results of this paper have important reference significance for guiding the preparation of multi-scale composites.The specific manifestations are as follows:(1)Based on the cohesion energy theory,the pull-out strength models of three typical nano-reinforced phases(carbon nanotubes(high aspect ratio fibrous),fullerene(spherical particles)and graphene(lamellar))are established.Through the potential energy change relationship between the nanophase and the matrix,the relationship between the interaction force between the nanophase and the matrix with the relative distance between the nanophase and the matrix is solved,and it is defined that the critical pull-out force of the nanophase is equal to the maximum interaction force of the nano-phase.The model quantifies the influence of nanophase morphological parameters on the critical pullout force,and the rationality of the critical pullout force model is verified by the existing experimental data of carbon nanotube pull-out.According to the critical pullout force model of nanophase,the interfacial bonding strength model of multi-scale composites was established,and the strengthening effects of different forms of nanocomposites were quantitatively described.The transverse tensile strength of the interface of multi-scale composites was predicted.(2)In order to verify the interfacial bonding strength model of multi-scale composites,multi-scale composites containing carbon nanotubes,fullerenes and graphene were prepared by silane coupling process.The transverse tensile testing technique of fiber bundle composites and digital image correlation method were used to characterize the bonding strength of the interface.The stress-displacement curve,crack growth rate and fracture morphology of the three kinds of nano-modified fiber bundle composites were compared and analyzed systematically.According to the comparison between the experimental results and the model prediction results,it is found that the predicted results are in good agreement with the experimental results,which proves the rationality of the model based on cohesive energy theory under the unified theoretical framework.Although the critical pull-out force of single carbon nanotube and graphene is greater than that of fullerene,under the condition of the same volume content,the amount of fullerene is the largest due to the smallest volume,and the resultant force at the interface is greater than that of carbon nanotube and graphene.The enhancement effect of fullerene on the interface is the best.