EnginSoft - CAE Conference Abstracts

EnginSoft International Conference 2011
CAE Technologies for Industry

Synergy between LS-DYNA and modeFRONTIER to Predict Low Velocity Impact Damage on CFRP Plates

Borrelli Rosario - CIRA - Italian Aerospace Research Centre (Italy)
Primavera Vito - EnginSoft (Italy)
Perillo Marco - EnginSoft (Italy)

Abstract

Engineering structural components made of composite materials are increasing in use in several engineering applications. Composite materials are preferred with respect to the competing traditional metals due to a range of potential advantages: high strength-to-weight ratio, high stiffness-to-weight ratio, resistance to corrosion, low coefficient of thermal expansion, etc. Nevertheless, composite materials do suffer from poor resistance to impact loading. This results in damage that can cause severe structural degradation such as reduction in compressive strength. The situation is more critical for low-velocity impacts which induce significant internal damage undetectable by visual inspection.
Thus, numerical models able to simulate impact events (which can occur during maintenance operations), are needed in order to assess the residual structural capacity of a composite structure and, at same time, to reduce the experimental tests which are quite expensive.
In this paper an LS-DYNA numerical model was developed and coupled with modeFRONTIER which is a process integration and design optimization tool that is capable of exploring the design space (i.e. the free parameters dominions) and finding the configurations which satisfy several objective functions. Indeed, the definition of some numerical parameters of the LSDYNA model (time step, damping coefficient, contact stiffness, etc.) is a very big challenge because no reliable data are available in literature and they are mainly chosen on the base of the analyst experience. The LSDYNA – modeFRONTIER integrated procedure developed in this work allowed to obtain both a better understanding of the influence of such parameters on the simulation results (sensitivity analysis) and the configuration which provided the best agreement with the experimental data (optimization). The procedure was validated against a test case extracted from the literature which consists in a rectangular composite plate impacted by an hemispherical steel impactor with an energy impact of 40 Joule. The experimental data used for the validation activity were:
• Contact force vs. time curve
• Deflection vs. time curve
• Absorbed Energy

For each of these quantities, an objective function to be minimized (3 relative errors) was taken into account. The integrated procedure allowed to identify the configurations which are good compromises with respect to the above mentioned objective functions.