Study On The Characterization Of Low-velocity Impact Indent Of Laminated Composite Materials Considering Creep Effect

Low inter-laminar strength and brittle properties make the laminated composite structure more sensitive to low velocity impact.After low velocity impact,various forms of damage may occur easily,and these damages greatly reduce the strength of the composite structure.Meanwhile,because the dent depth is easy to measure,the data scatter is small,and it can correspond to the impact energy one by one,in order to predict the damage effectively,the pit depth is selected as the characterization parameter of low velocity impact damage,damage impedance and the evaluation standard of residual strength.Therefore,the research of the formation mechanism of permanent pit and the accurate numerical simulation of pit depth are of great significance to evaluate the structure property and optimize the composite structure.The main content of this paper are as follows.(1)Criteria for intra-laminar and delamination failures of composite laminate were developed in which transverse pressure shear residual strain and interfacial residual open(stagger)were modeled at the basis on taking the formation mechanism of the indentation into account.Meanwhile,the generalized kelvin model was constructed which was used to calculate the indent spring-back;(2)A multi-layer block unit model was presented,which effectively shortened the model calculation time by reducing the number of units.The software ABAQUS was used as platform,the parametric modeling module of the low-speed impact damage and the post-processing damage query of composite laminates was developed by using the scripting language Python,which avoided the tedious process of modeling and post-processing;(3)Low-velocity impact test,ultrasonic C scan test and the dent depth measurement test under different energy were carried out,which studied the relationship between the pits depth,impact energy and the damage.The dent rebound of composite laminates under different hydrothermal environments was measured after low velocity impact.Numerical analysis of the dent spring-back under three kinds of impact energy(35J,40 J,50J)in normal environment was carried out.