Numerical simulations of Carbon Fiber ReinforcedPolymers under dynamic loading

Abstract: The ability to withstand dynamic loading represents an important design criteria for crucial applications such as those adopted in the automotive and aerospace industries. Numerical simulations can lead to a reduction of time and costs for designing composite structures by replacing testing campaigns that are performed in order to assess whether the design requirements of the structure are met. The present thesis deals with the development of a robust simulation methodology within the FE explicit commercial code PAM-CRASH in order to predict the damage behaviour of Carbon Fiber Reinforced Polymers when loaded dynamically. The strain rate dependence of the carbon/epoxy composite under study is identified and a material-characteristic strain rate model is developed starting from experimental data. A delay damage model based on a Continuum Damage Mechanics approach is used to predict the response of composite laminates under dynamic loading. The simulation methodology is validated against experimental data from a patch to a coupon level by using solid elements to model the plies of the laminate. A dynamic three-point bending simulation is performed at the sub-component level by modelling the composite structure through the use of solid elements for the plies and cohesive elements for the interfaces between them. Rather good agreement is found in terms of stiffness and strength between the results from the numerical simulations and those obtained from the experimental tests. Limitations are identified in the sensitivity of the strain rate model to the damage limits set to stop the scaling of the lamina elastic moduli and in severe dynamic effects, e.g. stress waves, which affected the simulations at high strain rates.