PSI - Issue 37

A. Vescovini et al. / Procedia Structural Integrity 37 (2022) 439–446 A. Vescovini, L. Lomazzi, M. Giglio, A. Manes/Structural Integrity Procedia 00 (2019) 000 – 000

442 4

Figure 1: Blast simulation methodology: pure Lagrangian (a) and coupled Eulerian-Lagrangian (b)

3.2. Structural modelling The target structure is modelled using Lagrangian elements and applying a double symmetry in order to reduce computational time.. Fully integrated solid elements have been chosen since it was verified by the authors that the CEL approach works better with this type of elements. The simulations proving this statement are not reported because they lie outside the scope of this paper. The composite target has been modelled adopting a macro-homogeneous discretization, i.e., each ply is modelled with a layer of solid elements with 2 mm dimension, as suggested in the work in Gargano et al. (2019) and one element in the thickness. The intra-laminar mechanical properties are defined employing the LS-DYNA® built-in material model defined as MAT_054 (*MAT_ENHANCED_COMPOSITE_DAMAGE). This material model is based on Hashin failure criteria (Hashin, 1980) and allows to describe also woven composite behavior with the 2WAY = 1 flag in the material keyword. The equation governing the ply failure are reported in Error! Reference source not found. . The main non-default parameter used in this work are reported in Error! Reference source not found. , according to those reported in the work in Gargano et al. (2019). In Error! Reference source not found. DFAILT and DFAILC are intentionally set to large values to avoid element deletion and to replicate the same conditions assumed in the simulations of Gargano et al. (2019). In addition, SC was set to a high value in order to avoid its contribution in material failure, according to the paper of Gargano et al. (2019).

Table 1. Woven composite failure criteria. Failure modes Criteria Tensile failure ( 11 ) 2 + ( 12 )

2 ≥ 1 (1) 2 ≥ 1 (2)

2 + ( 12 ( 11 ) ( 22 ) ( 12 )

( 22 )

) 2 ≥ 1 2 ≥ 1 2 ≥ 1

Compressive failure

(3)

(4)

Shear failure

(5)

Table 2. Carbon-Polyester laminate ply parameters - MAT_054. Material property

Value 1600 kg ⋅ m −3 55 GPa 55 GPa

LS-DYNA symbol

Density

RO EA EB EC

In-plane longitudinal Young modulus In-plane transversal Young modulus

Out-of-plane Young modulus In- plane Poisson’s ratio In-plane shear modulus Out-of-plane shear modulus Out-of-plane shear modulus

7 GPa

PRBA

0.25

GAB GBC GCA

4.5 GPa 1.8 GPa 1.8 GPa

Woven composite failure criteria flag Maximum strain value for fiber tension Maximum strain value for fiber compression

2WAY

1 1

DFAILT DFAILC

-1

Longitudinal compressive strength Longitudinal tensile strength Transversal compressive strength

XC XT YC YT

240 MPa 680 MPa 240 MPa 680 MPa

Transversal tensile strength