Constitutive Model Building Of Carbon Fiber/Cyanate Ester Composites And Study Of Machining Micro Cracks

As a kind of carbon fiber reinforced composites,carbon fiber/cyanate ester(CF/CE)composites are widely used as structural materials in the field of satellite.With the advantages of high specific strength,high specific modulus,excellent dimensional stability,strong corrosion resistance and low coefficient of linear expansion,carbon fiber is an ideal reinforcing material for structure.Cyanate ester,as a new generation of high performance thermosetting matrix,has the advantages of good thermal stability,mechanical properties and high adhesive properties.However,defects including delamination,tearing,burrs and thermal damage often occur during the application of CF/CE composites,which usually results from material damage and micro-cracks occurring in the machining process.Therefore,to obtain higher surface quality,it is urgent to study the processing mechanism of CF/CE composites and the forming and evolution mechanism of micro cracks.A microstructure constitutive model of CF/CE composites is built in ABAQUS.Double-perturbation algorithm is used to realize the random distribution of fiber reinforced in the RVE model.Brittle material property of random strength distribution is defined on carbon fiber based on Weibull strength distribution theory and Monte Carlo method.Mechanical property of CE matrix is simulated by interpolation of strain-stress curve,and cohesive zone is used to simulate the interface property.Local mechanical model is proposed to analyze the forming rules of fiber fracture,interface damage and matrix cracks.A three-dimensional CF/CE composites cutting model is built and damage of carbon fiber,CE matrix and interface during the cutting process is analyzed and classified.Influence of cutting speed,fiber orientation and cutting edge radius on material damage and cracks is explored,specifically including deformation and fracture of carbon fiber and damage crack depth of matrix and interface.Meanwhile,the forming mechanism of burrs in the tool exiting area is analyzed.A milling experiment of CF/CE composites is conducted to analyze the material damage and micro-cracks on the processing surface.Defects including micro-cracks,surface pits and interface cracking are classified.Influential rules of cutting speed,feed rate and fiber orientation on surface damage and micro-cracks are explored.Morphology of chip is observed and compared and surface damage under different cutting conditions is comprehensively analyzed.Experimental results and FEM simulation results are compared,and the validity of simulation method is confirmed.