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A Material Model for Transversely Anisotropic Crushable Foams in LS-DYNA - MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Material Law 142)

Recently new materials were introduced to enhance different aspects of automotive safety while minimizing the weight added to the vehicle. Such foams are no longer isotropic but typically show a preferred strong direction due to their manufacturing process. Different stress/ strain curves are obtained from material testing in different directions. A new material model was added to the LS-DYNA code in order to allow a correct numerical simulation of such materials. Ease-of-use was a primary concern in the development of this user-subroutine: we required stress/ strain curves from material testing to be directly usable as input parameters for the numerical model without conversion. The user-subroutine is implemented as MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM, Mat law 142 in LS- DYNA Version 960-1106. In this paper we summarize the background of the material law and illustrate some applications in the field of interior head-impact. The obvious advantage of incorporating such detail in the simulation lies in the numerical assessment of impacts that are slightly offset with respect to the foam’s primary strength direction.