Simulation Study On The Effect Of Common Defects On The Mechanical Properties Of Carbon Fiber Reinforced Polymer Composites

With the innovation of aircraft,traditional metal materials have been unable to meet the requirements of modern aircraft.Carbon fiber reinforced polymer(CFRP)composite have the excellent advantages of lightweight and high strength,wear resistance,corrosion resistance,and fatigue resistance,gradually replacing metal materials in the aerospace field.However,in the preparation of CFRP,manufacturing defects will inevitably be formed,among which void defects and delamination defects are more common and harmful.Defects can seriously affect the performance and lifespan of CFRP.Therefore,it is still important to study the relationship between defects and mechanical properties of CFRP.At present,the finite element method has been widely used to study void and delamination defects at home and abroad.However,at present,research on voids mainly focuses on void content,while research on delamination mainly focuses on delamination size,lacking systematic research on the effect of defect characteristics on performance.Based on finite element analysis(FEA),establishes CFRP macro and micro models with void defects and delamination defects using ABAQUS.The effects of void content,void section shape and void distribution on the tensile mechanical properties of CFRP were systematically studied by using the representative volume element model containing void defects.The effects of delamination area,delamination depth and delamination leading edge shape on the compressive mechanical properties of CFRP were systematically studied by using the composite laminate model containing delamination defects.The results of void study show that the effect of void defects on the longitudinal tensile property is very slight and negligible,but the effect on the transverse tensile property is significant.The transverse tensile properties are most sensitive to void content.The higher the void content,the lower the Young’s modulus,yield strength and tensile strength.The void section shape has a significant effect on the transverse tensile properties.The smaller the inner angle of void section shape,the lower the transverse tensile performance,and the larger the inner angle,the better.Moreover,the transverse tensile properties are also affected by void distribution.When the void distribution tends to be dispersed,the transverse Young’s modulus,yield strength and tensile strength are better,but if the void distribution tends to be aggregated,it is the opposite.In addition,the effect of void defect on Young’s modulus is less than that of yield strength and tensile strength.The results of delamination show that the delamination area has a significant effect on the compression performance of CFRP within a specific range.When the delamination area is limited,the effect of delamination on CFRP is minimal.When the delamination area exceeds 100mm~2,the larger the delamination area,the lower the compressive Young’s modulus and compressive strength.The delamination depth has a significant impact on compression performance within a specific range.When the delamination depth exceeds 1/4 of the thickness of the model,the defects have little effect on the compression properties of the composite.When the delamination depth is lower than this value,the higher the delamination depth,the lower the compressive Young’s modulus and compressive strength.The delamination leading edge shape has no obvious effect on the compression performance of CFRP.When the shape of the delamination leading edge is round,it is friendly to the compression performance of CFRP.In addition,the feasibility of using finite element models to predict the effect of defects on the mechanical properties of CFRP was verified by comparing simulation results and experimental results.The research conclusion provides a certain reference for predicting the mechanical properties of CFRP with different defects,and provides a theoretical basis for screening CFRP components with strong safety.