Evaluation of the damage degree to carbon-fiber composite materials under impact

The work presents the results of an experimental research of changes in the residual mechanical properties of the samples of carbon-fiber composites of various structures under combined low-velocity impact and static loads. The main objectives of this study were to obtain new experimental data on the processes of deformation and fracture of carbon-plastic composite materials under shock impact and static loads, as well as the creation of methods analyzing the degree of damage and tolerance to damage after shock loads using different non-destructive testing. Eight types of reinforcement structures were selected for the research. The experimental part was carried out at PNRPU Experimental Mechanics Center using the CEAST 9350 drop-weight test systems and the electromechanical Instron 5982. The test method was based on the standards ASTM D7136 and D7137. After the impact, the depth of the dents and, using non-destructive testing by the sherography method, the size of the discontinuity of the samples were measured. Damage tolerance was assessed using the magnitude of damage after impact. An assessment of the prospects of using the entered values for the design and manufacture of products from carbon-fiber composite materials of various reinforcement structures is given. The calculation of the destruction as a result of the impact was made. The process of the low-velocity impact is described in the diagrams of the dependence of force on displacements at various energy levels. The test results are presented in the form of diagrams of the maximum breaking load under compression describing the change in residual mechanical properties after the impact. The features of using direct and indirect methods of assessing the performance characteristics of the damaged samples are noted. The effect of the impact on the nature of fracture and deformation properties of the samples of carbon-fiber composite materials is analyzed.