The Analysis And Design Of Composite Laminate Patch Bonding Repairing Parameters

With high strength and light weight,durability and designability,extending the application of composite in various fields is not only in line with the current concept of sustainable development,but also contribute to innovation and development in various fields.While in the use of composite materials,the occurrence of damage is inevitable,and it derived many problems about the repair and replacement of composite materials.With cost-saving,energy conservation and environment protection in mind,it is important to repair damage composite in a reasonable manner within the allowable range.At present,lap and scarf repair is the most common two types of composite adhesively bonded repair methods.Both methods have different advantages and disadvantages,their applicable scope also varies.But whatever the method,in order to reduce maintenance cost as much as possible on the premise that the structure can reaches the application accuracy demand after repair,the design of composite patch parameters is very critical.The paper focuses on the double-sided repair method,using experimental and finite element analysis to design and analysis the parameters of repairing.Vacuum assisted molding process is used to prepare undamaged composite laminates,laminates with a central hole and double-sided adhesively bonding repaired laminates.Static strength of these laminates was studied.The influence of repair parameters on the restoration ratio of static strength was analyzed and compared.Furthermore,a 3D finite element model for predicting static strength was established based on the progressive failure analysis.The damage criterion and performance degradation model of plate and patch in the repaired structure were modified Hashin criterion and Camanho property degradation model.The maximum stress criteria was used to predict the occurrence of the damage of the adhesive layer,and mixed-mode strain energy release rate criterion was used to judge the damage propagation of the adhesive layer.Failure modes of composite laminates are very complex under tensile loads.The progressive failure analysis can fully reflect the failure modes which may appear,which is beneficial to improving the accuracy of prediction and contribute to study the failure mechanisms of damaged laminates and repaired laminates.The results of finite element analysis are coincident with the results of experiments,after a combination of observations.(1)The error between predicted strengths and experimental values is 1%-18%,which is within the allowed range;(2)Both methods show different repair parameters can affect the strength of repaired structures.When the diameter of patch is 2.0-2.5 times of the diameter of the central hole and the thickness of patch is 0.5-0.8 times of the thickness of parent plate,it has a good repair result that the restoration ratio of strength can achieve about 80%.While the effect of the ply of patch on the restoration ratio of strength is associated with the diameter of patch;(3)The failure of laminates containing central hole start and develop from hole's edge where exist stress concentration.Lap repair can ameliorate the stress concentration,then achieve the aim to improve the strength of laminates;(4)Lap repair can delay the failure of laminates,but different parameters have different effects.