PSI - Issue 72

Muhammad Zainnal Mutaqin et al. / Procedia Structural Integrity 72 (2025) 445–452

449

In validating the experimental impact test, the numerical method using the Johnson-cook constitutive model is used to capture the nonlinearity of materials during impact. The Johnson-Cook model takes into account the influence of temperature, strain rate, strain, and stress triaxiality on the equivalent fracture strain behavior (Ul Haq and Narala, 2024). To describe the elastic-plastic deformation and failure damage of a sandwich structure during loading (Zhang et al., 2022). The Johnson-cook equation is modeled in Equation 1. ̅ = [ + ( ̅ ) ][ ͳ + ln( ̅̇ ̇ Ͳ )][ ͳ − ̂ ] (1) where σ is yield stress related to the strain rate, A, B, n are yield stress, hardening modulus and hardening index of the material at reference strain rate Ͳ̇ , ̅ is equivalent plastic strain, ̂ is dimensionless temperature. To define the damage evolution in the sandwich panel structure using Equation 2. ̅ = [ ͳ + ʹ ( ͵ )][ ͳ + Ͷ ln( ̅̇ ̇ Ͳ )][ ͳ + ͷ ̂] (2) where d 1 -d 5 are corresponding damage parameters, and p q is stress triaxiality. The fracture criterion is mainly founded on damage calculation that it is assumed when damage parameter D exceeds the value of unity, the damage is initiated. =∑ ̅ ̅ (3) The failure mode of the panel sandwich in the form of deformation depth varies with the thickness of the face sheet. The thickness of the face sheet affects the increase in the stiffness strength of the sandwich structure (Qin et al., 2023). The greater the value of the thickness of the face sheet can absorb energy, the better it is shown by the decrease in the maximum deflection of the back face sheet (Zhang et al., 2022a). The amount of load-bearing materials involved in the structure directly influences the damage mechanisms (Li et al., 2024). the honeycomb core dissipates energy primarily through global bending and stretching, partial crushing (i.e., both crushing near the front face sheet and crushing in the perforation channel), and shearing, where these results are observed in the experiments (Li et al., 2023) .

3.2 Bending load

In bending testing, researchers typically employ experimental methods, including three-point and four-point bending tests. Three and four-point static bending tests were performed to obtain information about the static bending strength of the investigated structure and the effect of the strain rate (Palomba et al., 2019; Thakur, 2024). A summary of previous research on honeycomb sandwiches in bending load testing is shown in Table 2.

Table 2. Summary of sandwich panel composition variations bending study. Core material Face sheet material Focused parameters

Year

Damage of composite honeycomb sandwich structures under in-plane compression and 4-point bending (Hang et al., 2023) . Damage of composite honeycomb sandwich panels under three-point bending load (Ma et al., 2021) . Strength, stiffness, and panel peeling strength of carbon fiber-reinforced composite sandwich structures with aluminum honeycomb cores (Wang et al., 2018) .

2023

Nomex NRH- type

Carbon fiber reinforced

QF210/5528A glass fiber reinforced

2021

Nomex honeycomb

2018

Aluminum

Carbon fiber reinforced