PSI - Issue 61

Yogesh Kumar et al. / Procedia Structural Integrity 61 (2024) 322–330 Y. Kumar et al., / Structural Integrity Procedia 00 (2019) 000 – 000

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elements for efficient formulation with the mesh size of 0.1 mm. The material direction for each of the lamina in the cross-ply laminate was defined with vectors referenced to the global axis system of the model controlled through the AOPT option in the material model [*MAT_55_ENHANCED_COMPOSITE_DAMAGE]. The composite sample was fixed at the bottom through [*SPC_NODE_SET] and constraints were defined in all the translation and rotational directions. The loading plate is only permitted to have Z-directional (translation) motion, as shown in Fig. 5a. It is worth noting that the material models does not includes effect of strain rate sensitivity, which is a valid assumption due to the low loading rate in the experiments.

Table 2. [*MAT_138_COHESIVE_MIXED_MODE] parameters. Properties

LS-Dyna Symbol [Unit]

Value

Density

RHO [kg/m 3 ] EN [MPa/mm] ET [MPa/mm] GIC [N/mm]

1200

Normal cohesive stiffness Tangential cohesive stiffness Mode-I energy release rate Peak traction in normal direction

6.4 × 10 5 6.4 × 10 5

0.32

T [MPa]

43

Ultimate displacement in normal direction Peak traction in tangential direction Ultimate displacement in tangential direction

UND [mm]

0.10

S [MPa]

50

UTD [mm]

0.10 1.30 -1.45

Mode-II energy release rate

GIIC [N/mm]

Exponential for mixed-mode criteria

XMU

The contact definition used for the interlaminar behaviour utilizes the Benzeggagh-Kenane (B-K) law damage model (Benzeggagh and Kenane, 1996) as OPTION 9 in the LS-Dyna environment. For implementation and parameterize the B-K law damage model, an additional double cantilever beam zero-thickness cohesive elements based FEM was developed and validated from the experimental dataset provided in (Ramji et al., 2020a) for an estimation of the Mode-I fracture energy. The geometrical features of this model were based on the (ASTM D5528 01, 2014) standard. A set of zero-thickness cohesive elements was generated and assigned with element formulation of Type 19 (4-point cohesive elements), and bi-linear cohesive zone material model [*MAT_138_COHESIVE_MIXED_MODE]. An offset of 50 mm from the tip of the model was provided for initial delamination length or pre-crack. To avoid the contribution of the composite layers in the fracture energy, the [*MAT_55] material model was used with inactive failure strains. The loading rate was applied over the set of nodes using prescribed motion to replicate the hinge position from experiments, as shown in Fig. 4a. The parameters involved in the Benzeggagh-Kenane (B-K) law driven [*MAT_138] are summarized in Table 2. Further details on the formulations of material models used in this work can be found in the (Hallquist and (LSTC)., 2018).

Table 3 [*MAT_55_ENHANCED_COMPOSITE_DAMAGE] non-physical parameters (Kumar et al., 2024). Non-physical parameters Value DFAILM 0.35 YCFAC 2.50 FBRT 0.08 TFAIL 10-7 DFAILC -0.55 BETA 0.50 DFAILT 0.25 ALPH 0.25 DFAILS 0.50 SOFT 0.55