PSI - Issue 42

788 4

Md Niamul Islam et al. / Procedia Structural Integrity 42 (2022) 785–792 Md Niamul Isla et al. / Structural Integrity Procedia 00 (2019) 00 –000

00:00

Chronometer

Pressurised-gas cylinder

Bullet chamber

Plate fixture (Front view)

Gas-gun barrel

Pressurised-gas outlet

Control panel

Fig. 3. Gas-gun setup for ballistic impact test.

The experimental conditions for the ballistic test were reproduced in FEA-based simulations (Fig. 4), using a similar method to the one demonstrated in Islam et al. (2021), which showed good results for the ballistic-impact model of AM nylon polymer-matrix reinforced with short carbon fibres (Nylon SCF). The material properties were introduced in tabulated format and the dynamic-explicit solver was used. The 3D plate was discretised using 8-node linear brick elements and the meshing was 2 mm for the inner 50 mm circle and 4 mm for the rest of the plate. The bullet was modelled as a rigid object, while the global interactions were considered frictionless for the tangential behaviour and hard contact (for pressure-overclosure) for the normal behaviour. The Hashin damage VUMAT was applied for the dynamic fracture of ballistic impact (Islam et al., 2021) and, additionally, cohesive-surface modelling was implemented using a bilinear traction-separation law to model the delamination failure in the model. Table 2 summarises the laminate constants used to model the material’s elastic properties ( – Young's modulus, – Poisson's coefficient, – shear modulus, – tensile strength, – compressive strength, – shear strength, – coefficient for stiffness proportional damping, – density), while Table 3 lists the parameters for cohesive contacts ( – damage initiation traction, – traction stiffness, – fracture energy). Further tests and benchmarking were conducted for the estimated parameters applied at this stage.

100 mm

2 mm (not to scale)

100 m s -1

50 mm

100 mm

9 mm

y

y

z

x

Fig. 4. Configuration for FE (dimensions in mm) for the numerical model of ballistic impact.