Study On The Composite Laminates Patch Repair

With the rapid development of science and technology,the demand for structural performance is getting higher and higher.The appearance of advanced composite materials has greatly improved the structural performance.Advanced composite materials have many advantages such as high specific strength and large specific stiffness,which are widely used in aerospace,sports and leisure products.As a result,the repair technology of composite materials has been greatly developed.Patch repair technology is the main direction of composite material structure repair.The specific work is as follows:This paper first introduced the development status of composite materials and focused on the damage of composite patch repair.If the thickness of the patch is too small,the desired patching effect may not be achieved.If patch thickness is too large,it will affect the aerodynamic performance of the structure.In order to reduce the impact on aerodynamic of the structure,this paper proposed a method of the ladder type patch repair.The finite element study on patch repair of composite materials provides a theoretical basis for the practice of ladder-type patch repairs.Two-dimensional progressive damage model of composite materials was carried out with the aid of the finite element software ABAQUS.The solid shell element was used to simulate the laminates.The two-dimensional Hashin criterion was selected as the failure criterion for composite laminates and patches,and the secondary stress criterion was used as the damage initiation criterion for the adhesive layer.(1)The two-dimensional progressive damage model of composite laminates is established.The finite element results under unidirectional tensile load agree well with the experimental data,which proved that the damage model of composite laminates is reliable.The two-dimensional progressive damage model of patch-bonding repair is established secondly.The finite element results under unidirectional tensile load were in agreement with the experimental data of the literature.The damage expansion of the patch was consistent with the damage condition of the literature experiment,which proved that the patch repair model was reliable.(2)A two-layer staircase patch-bonding model on progressive damage was established to compare the bearing capacity of the model under different patch diameter to find the best step type patch diameter.(3)Simulating the patch-bonding repair under the different laminate angle and compare the bearing capacity of the different patch diameter model.Finally,this paper discussed the influence of the different laminate angle on the patch-bonding repair.(4)Simulating the patch-bonding repair under the thickness of different patches to compare the bearing capacity of the patch model under the condition of changing the thickness of the upper and lower layers of the patch with the thickness of the upper and lower layers,summarize and get the suitable thickness of the upper and lower layers.