| Due to its unique material composition,carbon fiber composites have a series of advantages,such as high specific stiffness,high specific strength,corrosion resistance,fatigue resistance,good designability,etc.,which are widely used in the aerospace field in pursuit of light weight and high strength.Due to the needs of structural functional design,connection between parts and easy maintenance,it is often necessary to open holes in the composite structure,which will destroy the overall continuity of the fiber,produce serious stress concentration,decrease the strength of the structure,and may have a bad impact on its stability,thus affecting the strength and life of the composite structure.In order to improve the bearing capacity of the structure,local reinforcement is usually used to alleviate the stress concentration near the hole.In this paper,the composite laminates with open-hole are taken as the research object,considering the different reinforcement methods such as intercalation reinforcement,patch reinforcement and variable angle curve placement,the experimental and numerical simulation research on the buckling performance and post buckling bearing capacity of the composite laminates with open-hole under shear load is carried out.Firstly,shear tests of composite laminates with open-hole were carried out to study the effects of hole shape,reinforcement type and reinforcement thickness on buckling performance,bearing capacity and failure mode.At the same time,based on the Hashin failure criterion and Comanho stiffness degradation model,the progressive damage analysis of the composite laminates with reinforcement near the hole is carried out by ABAQUS software,and the failure mechanism of the composite laminates with reinforcement near the hole is studied.Through the comparison of the test and numerical simulation,it is found that the buckling load,ultimate load and failure mode of the two are in good agreement,which proves the effectiveness of the finite element analysis method in this paper.Through the experimental test and numerical simulation analysis of the composite laminates with open-hole after reinforcement,it is found that the fiber tensile breakage along the loading direction and delamination are the main reasons for the failure of the composite laminates with open-hole under shear load.Local reinforcement at the hole edge can effectively restrain the displacement near the hole,greatly improve the buckling load and ultimate load of the structure,relieve the stress concentration near the hole and improve the stability and strength of the structure.The ultimate bearing capacity of different types of reinforced laminates with open-hole are compared,the results show that the bearing capacity of composite laminates with circular hole is better than that of rectangular hole.The influence of intercalation reinforcement and patch reinforcement on the bearing capacity of the composite laminates with open-hole is similar.The reinforcement thickness is an important factor to improve the ultimate load of structure.In the study of variable angle curve placement laminates,the comparative analysis of different curve tracks of the composite laminates with open-hole is carried out,and it is found that the laminates which the curve fiber has a larger component in the loading direction represent better mechanical properties;the laminates with open-hole adopting three different laying schemes,namely,laminates with only straight-fiber layers,laminates with only curvilinear-fiber layers and laminates with both straight-fiber layers and curvilinear-fiber layers,are compared and analyzed,and it is found that the laminates with open-hole adopting the last laying scheme have the most significant effect on improving the buckling load and ultimate load of the structure.The above research shows that the buckling performance and load-bearing performance of composite laminates with open-hole can be improved by choosing reasonable curved fiber path and laying scheme. |
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