Research On The Interfacial Strength And Grinding Mechanism Of Material Removal For Ceramic Matrix Composites

The fiber-reinforced ceramic matrix composites have higher anti-impact toughness and bending strength than the traditional ceramics,and are important defense equipment materials.Due to fiber enhancement,fracture of the fiber-reinforced ceramic matrix composites are similar with that of metals and they have thick skin to crack,and the fiber-reinforced ceramic matrix composites are typical difficult–to-machine materials which has high hardness and obdurability.Although grinding is the leading way of machining the fiber-reinforced ceramic matrix composites,it is still in initial stage at home and abroad at present.Since continuous fiber takes on the role of toughening and the influence mechanism between the continuous fiber and the material removal mechanism is not distinct,there are two problems needed to be solved,which seriously restricts the development of defense equipment capabilities.One is the low machining efficiency of the fiber-reinforced ceramic matrix composites,and the other is that it is difficult to control machining damage.The project chooses carbon fiber-reinforced silicon carbide ceramic matrix composites as the experimental object,studying the failure mechanism between toughening fiber/ceramic interface micromechanics and interface,establishing the constitutive models of the fiber-reinforced ceramic matrix composites.At the same time,the project studies the mechanism that continuous fiber affects the micro crack initiation and growth under the action of the grit by a single particle grinding experimental,reveals the mechanism of material removal and surface generation during grinding process,optimizes grinding process and process parameters,improves grinding efficiency and decreases machining damage.In this paper,the physical and chemical effects of fiber/matrix interface in the process of preparation of ceramic matrix composites are analyzed.The constitutive relation of the fiber/matrix interface and the failure mechanism of the interface are studied.In addition,through the analysis of the theoretical model of ceramic matrix composites,a unidirectional C/SiC model was designed and fabricated to explore the mechanism of the ceramic matrix composites.The above work provided an important basis for the research on the mechanical properties of the woven ceramic matrix composites.In ceramic matrix composites interface mechanical property test,this paper developed single fiber extrusion experiment platform using micro / nanomechanical testing technology.Through the experiment of single fiber push-out test,the two important interfacial parameters of C/SiC composites: the interfacial debonding strength(IDS)and friction stress(IFS)were tested.Obtained from the result,the IDS and IFS amount to,respectively,35 ± 5 MPa and 10 ± 1 MPa.The above work provides important theoretical basis for the mechanical analysis of composite materials and the research of the mechanism of grinding.In the micro/nano machining of ceramic matrix composites,micro/nano mechanical testing technology was used.Furthermore,the special unidirectional fiber composites were used for diamond abrasive wear tes.The failure mechanism of the interface and the removal mechanism of the material were revealed by experiments.The research provided the theoretical basis for the grinding mechanism of ceramic matrix composites and the research of composite materials.In the process of grinding mechanism of ceramic matrix composites,using diamond grinding wheel,grinding test of the model composite material is carried out.The influence of fiber orientation,grinding parameters(grinding depth,feed rate and wheel speed)on the grinding force,surface roughness,and surface microstructure characteristics were revealed.The removal mechanism of C/SiC was proved.The mechanism proved to optimize the grinding process and technological parameters of ceramic matrix composite material,which can improve the grinding efficiency and reduce the machining damage.The research results of this paper not only have important scientific value,but also have important social significance and economic value to improve the processing performance of ceramic matrix composites,expand the application range of ceramic matrix composites,and enhance the ability of defense equipment.