• Composite materials
• Abaqus
• FEM
• Indentation
• Contact law
• Low-velocity impacts

Carbon fiber reinforced plastics are extensively used in several engineering applications. Foreign objects impacts are a constant concern for these materials, because the created damage can remarkably decrease the strength of the structures and it can be difficult to be detected with visual inspections.
This work refers to a previous master’s thesis focused on impact test simulations on a CFRP specimen, where the necessity to study indentation laws arises. The present work deals with contact mechanics, fundamental topic in the study of impacts on composite structures. The complexity behind the characterization of contact laws for composite laminates requires an extensive use of experimental tests and numerical analyses. The experimental reference work is an article published by Tan and Sun in 1985, where results of indentation tests are reported. Numerical simulations using Abaqus are carried out to try to obtain the same results of such tests. Several parameters are taken into consideration, such as loading rate, mesh size, contact stiffness setting, boundary conditions and shear deformations. In the second part of the work, the detailed impact model, created in the previous thesis, is used to verify that concepts observed for simple indentation tests take place also for more realistic impact conditions. Finally, the possibility to introduce material damping to the composite layup is discussed, in order to improve the correspondence of the contact force response with experimental results.