Deformation Damage Monitoring And Cluster Analysis Of Acoustic Emission Characteristics Signals Of Composites

Composite materials have a series of excellent properties such as fatigue resistance,light texture,and corrosion resistance,which can satisfy working conditions in different environments.Composite materials are widely used in the fields of machinery manufacturing,aerospace,and energy industries.However,during the production of composites,wrinkle defects often occur.Due to external impact,defects such as delamination or holes often occur during the service process.Therefore,to study the deformation behavior and evolution of composite wrinkle defects and delamination damages,it is of great practical significance to monitor the structural health of composite materials during production and service.Firstly,in this paper,a variety of composite specimens with different aspect ratio folds are designed using prefabricated surface folds as reference variables.Combining Acoustic Emission(AE)and Digital Image Correlation(DIC)complementary techniques monitor the compressive process of composite specimens.The purpose is to study the effect of different aspect ratio wrinkles on the bearing capacity of the composites and verify that AE and DIC complementary technology can effectively monitor the damage process of composite materials.Secondly,in this paper,uniaxial compression tests are performed on composite specimens with prefabricated damages of different sizes and locations.The effects of the factors such as the size and location of the delamination on damage of the composites are analyzed,and the AE signals and surface deformation field changes of the damage process are revealed.Combining the mechanical theory of composite materials and the cluster analysis of AE signals,the correlations between mechanical properties,AE characteristics and surface deformation field in the process of delamination damage of composite materials,and the damage and failure mechanism of delamination composites are studied.Some important conclusions are summarized as follows(1)The failure load of the specimens with prefabricated delaminated composites is smaller than that of the composite specimens without no delamination;(2)With the same size of delamination defect,the delamination which is closer to the specimen surface has more serious effect on carrying capacity of specimen.When the position of delamination is same,the specimen which has a larger size of delamination has lower carrying capacity;(3)According to cluster analysis of AE signals,AE signals of composite compressive damage process can be divided into three clusters.The ranges of characteristic frequency are 0-60,100-150 and 200-450 kHz,respectively.And three clusters correspond to the three kinds of damage modes such as matrix creaking,fiber/matrix debonding and fiber breakage.(4)The displacement and strain field information obtained by the two-dimensional digital image correlation method,which reflects the deformation and damage characteristics of glass fiber composites in the process of delamination damage.The complementary technology of acoustic emission technology and two-dimensional digital image correlation method provides a reference for damage assessment,damage prediction and health monitoring.