PSI - Issue 71

Deepak Kumar et al. / Procedia Structural Integrity 71 (2025) 380–387

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Table 4: Flax-epoxy mechanical properties.

Flax-epoxy composite lamina properties

Density

1500 kg/m 3

E 1 = 31420 MPa; E 2 = E 3 = 5580 MPa G 12 = 1850 MPa; G 13 = G 23 = 1300 MPa 12 = 0.36; 13 = 23 = 0.06 X T = 286.7 MPa; Y T = Z T = 33.86 MPa X C = 127.11 MPa; Y C = Z C = 79.94 MPa S 12 = S 23 = S 13 = 20.8 MPa Max normal traction = 10 6 MPa

Stiffness properties

Strength properties

Interface properties

Table 5. Stacking sequence of different laminate configurations considered in the present work.

Laminate configuration

Stacking sequence [0/+45/-45/90] 2S

CCCC CFFC CSSC CFSC

[(0/+45/-45/90) C (0/+45/-45/90) F ] S [(0/+45/-45/90) C (0/+45/-45/90) S ] S

[(0/+45/-45/90) C (0/+45/-45/90) (0/+45/-45/90) S (0/+45/-45/90) C ]

FFFF SSSS

[0/+45/-45/90] 2S [0/+45/-45/90] 2S

3.2. Modelling strategy The composite plate set for each configuration is a rectangular plate (125 mm x 75 mm), with 4 mm thickness and a stacking sequence [0º/±45º/90º] 2S having each ply thickness as 0.25 mm. The model used in this study is based on the in-built Hashin criteria for plane stress formulation. The boundary conditions applied in this study are as shown in Fig 2. The impactor, a spherical impactor with a diameter of 6.35 mm, is assigned rigid concentrated masses of 0.412 kg, 5 kg, and 7 kg, each with initial velocities of 1.7 m/s, 3 m/s, and 5 m/s, respectively, in the z-direction. The impactor movement is restricted in the x and y directions, allowing motion only along the z-axis. The plate is clamped along all four edges. The gravitational forces are considered to account for the inertial effects of the impactor's mass. The interaction between the plate and the impactor is modeled as frictionless. The impactor is modeled as an analytical rigid body to prevent deformation and is meshed with eight-node solid hexahedral elements. Every layer of the laminates is meshed using four-node shell quadrilateral elements. A global element size of 3 mm is used in the FE model and the total mesh consists of 2676 nodes and 2494 elements as shown in Fig 3. 4. Results and discussion All the hybridized and non-hybrid laminates are subjected to repeated impacts at three distinct velocity levels (1.7 m/s, 3 m/s, 5 m/s) with varying impactor mass of 0.412 kg, 5 kg, 7 kg. During the simulation process, the energy-time and force-time history curves are recorded as given in the following table, and various damage modes are observed.

Fig. 2: Boundary conditions applied to the composite laminate.

Fig. 3: Meshed geometry of composite with the impactor.