Research On Fracture Toughness Of T300/69 Laminates With 90 Degree Sublay-up And Fiber Bonding

Fiber reinforced composite is a typical advanced composite material with the advantage of high strength and high elongation,which many other traditional materials do not has.This makes fiber reinforced composite occupy an important position in aviation,aerospace,construction engineering,machinery and other fields of national defense and civil engineering,and has been more an d more widely used.However,90°sub-ply and fiber debonding are ignored in the current study of fracture toughness of orthotropic composites,which can not be widely applied to all working conditions.Therefore,it is of great theoretical significance and application value to study the fracture toughness theory of mult idirectional laminates.In this paper,T300/69 fiber reinforced composite laminates are taken as the research object,and ABAQUS finite element software is used to assist the calculation.The modified fracture toughness calculation results considering 90° sub-ply and fiber debonding are compared with the results of compact tensile test to verify the correctness and reliability of the theoretical method.The main research contents are as follows:(1)ABAQUS was used to simulate the crack growth.The fracture toughness of composite laminates with central through cracks is obtained by using XFEM.Meanwhile,the normalized energy release rate is calculated by virtual crack closure Technology(VCCT),which provides theoretical basis for subsequent processing of test data.(2)The fracture toughness of T300/69 composite laminates with different ply patterns was studied by experimental method.The compact tensile test is designed and completed,and the fracture toughness of composite laminates with different ply patterns is calculated by using the load displacement data.By observing the fracture morphology,with the increase of thickness,the effect of 90° sub-ply on the overall fracture toughness of the composite laminates is more obvious,and the fiber debonding phenomenon also affects the overall fracture toughness of the composite laminates.(3)A modified fracture toughness model of com posite laminates considering 90°sub-ply and fiber debonding is proposed.Based on the existing calculation methods of fracture toughness of multidirectional laminates,consid ering the energy released by90° sub-ply and fiber debonding under different ply modes,the fracture toughness formula is modified.Compared with the existing calculation methods,the calculation results of the modified model are closer to the experimental results.