Startseite Effect of stacking sequence of the hybrid composite armor on ballistic performance and damage mechanism
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Effect of stacking sequence of the hybrid composite armor on ballistic performance and damage mechanism

  • Zhicheng Liu , Shiying Lu , Ruyi Ji , Yuxuan Zhu EMAIL logo , Ruizhi Zhang , Jiuxiao Sun EMAIL logo , Guoqiang Luo , Peng Cao , Yubin Ma und Ming Yang
Veröffentlicht/Copyright: 16. September 2025
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Abstract

The fiber hybridization and stacking sequence of composite armors can significantly improve the ballistic performance and enhance the safety and survivability of military equipment. This article proposes a new structure (buffer/rigid/toughness/energy absorbing layers) of the carbon/aramid/ultra-high molecular weight polyethylene hybrid composite armor (K3C6K12U6) based on multi-scale simulations, and the residual velocity decreased by 20 m·s−1 and ballistic protection index increased by 16%. The buffer layer at the facing surface disperses the stress concentration and increases the transverse strain and energy absorption. The rigid layer absorbs the kinetic energy through shear deformation. The toughness layer increases the stress area and friction effect through the stretching of aramid fibers. The energy absorbing layer on the rear surface decelerates delamination failure and enhances energy absorption and penetration resistance of the composite armor. This article provides a theoretical basis for the structural design and performance optimization of the composite armor, which is of great significance for modern warfare and national defense construction.

Graphical abstract

Keywords: fiber-reinforced composites; ballistic performance; multi-scale simulation; damage mechanism

1 Introduction

With the sudden change of the international situation and intensification of regional armed conflicts, military defense security is particularly important, and higher requirements are put forward for the protective performance of equipment (1,2). Composite armors (3,4,5), composed of high-performance fiber-reinforced composite materials, are widely used in military equipment, transportation, aerospace, and personal protective fields due to their light weight, high strength (6), corrosion resistance, and good damage tolerance (7).

The ballistic performance of composite armors, including the residual velocity (8), ballistic performance index (BPI), and failure mechanism, is related to fiber hybridization and stacking sequence (9). Larsson and Svensson (10) found that the energy absorption of carbon fiber/polyethylene fiber and carbon fiber/poly(p-phenylene-benzobisoxazole) fiber hybrid composite armors was better than that of single-fiber composite armors. Zulkifli et al. (11) found that the ballistic limit of carbon/ultra-high molecular weight polyethylene (UHMWPE) fiber composite armor was improved by 5.6% compared with the UHMWPE composite plate. Bandaru et al. (12) hybridized carbon/aramid fibers (C/K) and glass/aramid fibers (G/K) and found that carbon/aramid fibers (C/K) have the best ballistic performance, while aramid/glass (K/G) fibers have the worst. Mousavi and Khoramishad (13) found that the energy absorption of the carbon/aramid hybrid composite armor was improved by 35% based on an artificial neural network algorithm. Bao et al. (14) indicated that the carbon fiber content was 20% and the energy absorption of the carbon/aramid hybrid composite armor improved by 4%. Li et al. (15) found that the energy absorption of the carbon/aramid/UHMWPE hybrid composite armor was improved by 16.4% compared with the aramid composite armor. Nettles and Lance (16) showed that adding a thin layer of UHMWPE at the front of the carbon fiber layer enhanced the energy absorption of the composite plate in the drop hammer impact test. Yang et al. (17) believed that arranging fibers in a descending order of modulus improved the energy absorption of the composite plate. Although existing research systems have characterized the energy absorption characteristics of hybrid systems, most of the studies are still limited to experimental parameterization studies and have not provided a detailed explanation of the hybrid mechanism.

The composite armor undergoes various failure mechanisms such as shear, tension, and delamination due to impact loads (18), resulting in complex internal wave interactions (19,20). Conventional testing methods cannot characterize the dynamic response process. Zhang et al. (21) found that as the thickness of the composite plate increased, the proportion of energy absorption caused by shear failure gradually decreased, and the delamination phenomenon became more pronounced. Li et al. (22) found that the carbon/aramid hybrid composite armor increased the tension of the fibers in the back layer, resulting in greater strain. Chen et al. (23) investigated the hybridization of woven fabric and UD fabric of UHMWPE and found that the hybrid panel exhibited more obvious delamination compared to the woven fabric panel. Multi-scale simulation can significantly reduce computational complexity and optimize resource allocation by simultaneously analyzing features at different scales. Cross-scale collaboration mechanisms can improve solution efficiency while ensuring accuracy. However, the conversion of parameters such as stress, strain, and boundary conditions between different scales still requires integrated analysis through multiscale theory combined with experimental calibration.

Although many scholars have mixed fibers and concluded that the rigid/flexible layer composite armor has the best ballistic performance, this article proposes a better combination method, which can improve the ballistic performance by adding a thin buffer layer in front of the rigid layer. This article proposes a new structure (buffer/rigid/toughness/energy absorbing layers) of the carbon/aramid/UHMWPE hybrid composite armor based on multi-scale simulations and investigates the effect of stacking sequence on the ballistic performance (residual velocity and ballistic protection index) of the composite armor under different impact velocities. The failure mechanism is elucidated through stress distribution, deformation modes, and damage morphology.

2 Materials and methodology

2.1 Preparation and characterization of the hybrid composite armor

The hybrid composite armor composed of plain weave fabrics of aramid fibers (Yantai Tayho Advanced Materials Co., Ltd.), carbon fibers (Zhongfu Shenying Carbon Fiber Co., Ltd.), UHMWPE fibers (Sinopec Yizheng Chemical Fiber Co., Ltd.), and thermoplastic urethane (TPU, Huizhou Jianli Environmental Protection New Materials Co., Ltd.) was prepared by an integrated gradient hot pressing process: first hot pressing under conditions of temperature of 90°C, pressure of 3 MPa, and insulation time of 1 h; second hot pressing under conditions of temperature of 110°C, pressure of 6 MPa, and insulation time of 1 h; third hot pressing under conditions of temperature of 120°C, pressure of 10 MPa, and insulation time of 1 h; then stop heating; hold pressure for 1 h.

The mechanical properties of aramid/TPU, carbon/TPU, and UHMWPE/TPU composites were tested with a universal mechanical testing machine (68FM-100, Instron) five times per sample according to the standards ASTM D3039 and ASTM D3518. The ballistic performance of the hybrid composite armor was conducted in accordance with the standard GB/T32493-2016, and the ballistic testing device is shown in Figure 1(a). The target specimen (150 mm × 150 mm) fixed onto the fixture was impacted by a spherical bullet with a mass of 4 g, a diameter of 8 mm, and an impact velocity of 615 m·s−1. The residual velocity and damage morphology of hybrid composite armors were observed using a high-speed camera. The energy absorption during the ballistic impact process of composite armor was determined by the following equation:

(1) E a = 1 2 m ( v 0 2 − v 1 2 )

where E a represents the total absorbed energy, m represents the mass of the bullet, v 0 represents the initial velocity of the bullet, and v 1 represents the final velocity of the bullet.

Figure 1 (a) Schematic diagram of the ballistic testing device; (b) multiscale modeling schematic; (c) hybrid composite armors with different layer sequences.
Figure 1

(a) Schematic diagram of the ballistic testing device; (b) multiscale modeling schematic; (c) hybrid composite armors with different layer sequences.

The formula for the BPI (24) is

(2) E ad = E a / AD

where E ad represents the energy absorption per unit area named BPI and AD represents the areal density of the composite armor.

The hybrid composite armors with buffer/rigid/toughness/energy absorbing layers named according to the sequence of bullet impact, as shown in Figure 1(c). K represents aramid fibers, C represents carbon fibers, and U represents UHMWPE fibers. For example, a composite armor consisting of 3 layers of aramid fibers as the buffer layer, 6 layers of carbon fibers as the rigid layer, 12 layers of aramid fibers as the toughness layer, and 6 layers of UHMWPE fibers as the energy absorbing layer was named K3C6K12U6, and K27 represents 27 layers of aramid fibers.

2.2 Multiscale computational theory

This article investigates the ballistic impact resistance of fiber-reinforced composite materials combining micro- and macro-scale calculations, as depicted in Figure 1(b): Ⅰ – a unit cell model for single-layer fiber-reinforced composites was established using Texgen. Based on mesomechanics, representative volume elements (RVEs) of fiber-reinforced composite materials are constructed (25) through mean-field homogenization theory and obtained constitutive parameters such as the stiffness matrix; Ⅱ – a uniform plywood model for 27-layer fiber-reinforced composites was developed. The unit cell model’s stiffness matrix was imported into Abaqus to obtain constitutive parameters for each layer; Ⅲ – a ballistic impact model was established using an 8 mm diameter spherical steel projectile impacting the 27-layer composite laminate at a high velocity. The ballistic penetration resistance was simulated through a macroscopic finite element (FE) model of the composite armor system.

The macroscopic/average strain components ε x , ε y , ε z , γ xy , γ yz , and γ xz under the boundary conditions of an RVE can be regarded as physical entities, treated as key degrees of freedom (DOFs) (26). In such special nodes, the corresponding macroscopic strains can be directly given without obtaining them by averaging the calculations of all unit cells. The concentrated forces F x , F y , F z , F xy , F yz , and F xz can be directly used as loads for their macroscopic/average stress components σ x , σ y , σ z , τ xy , τ yz , and τ xz .

(3) σ x = F x / V σ y = F y / V σ z = F z / V

(4) τ x y = F x y / V τ y z = F y z / V τ x z = F x z / V

In woven fabric-reinforced composites, the fiber orientations are conventionally assumed to be orthogonally aligned to simplify the modeling of their mechanical behavior, where warp and weft yarns are perpendicularly interlaced. The stress–strain constitutive relationship is formulated in a local Cartesian coordinate system whose basis vectors are aligned with the principal fiber orientation and through-thickness direction, respectively. For in-plane elastic behavior, the stress–strain relationship under an orthotropic damage-elasticity framework can be expressed as:

(5) ε 11 ε 22 ε 12 e l = 1 ( 1 − d 1 ) E 1 − ν 12 E 1 0 − ν 21 E 2 1 ( 1 − d 2 ) E 2 0 0 0 1 ( 1 − d 12 ) 2 G 12 σ 11 σ 22 σ 12

where ε = { ε 11 + ε 12 + ε 22 e l } T denotes the elastic strain components, σ = { σ 11 + σ 12 + σ 22 } T represents the stress components, E 1 and E 2 are the Young’s moduli along the principal orthotropic directions, G 12 is the in-plane shear modulus, v 12 is the major Poisson’s ratio, d 1 and d 2 are damage parameters associated with fiber rupture along the principal orthotropic directions, and d 12 is the damage parameter linked to matrix microcracking induced by in-plane shear deformation. These damage parameters vary between 0 (intact state) and 1 (complete failure), signifying stiffness degradation due to material damage, with the material experiencing fracture failure when any damage parameter reaches unity.

The mean-field homogenization theory associates the heterogeneity at the mesoscale with the overall properties at the macroscale of fiber-reinforced composites through the RVE and obtains the stiffness matrix of the composite material through a strain concentration tensor. Based on the evolution equation of damage variable d a , the mechanisms of fiber/matrix debonding, progressive stiffness degradation, and plastic deformation of composite materials under load are described as follows (27):

(6) d a = 1 − 1 r a exp [ − A a ( r a − 1 ) ] d a ≥ 0

(7) A a = 2 g 0 a L c G f a − g 0 a L c , g 0 a = X a 2 2 E a

where L c represents the characteristic length of the unit; G f a represents the fracture energy per unit area under axial tensile/compressive loading; g 0 a represents the elastic energy density at the onset of damage.

To accurately simulate interlaminar cracking and delamination phenomena of multi-layer structures of the composite armor under impact loading, this article establishes an interlaminar model using cohesive elements of type COH3D8, following the traction-separation criterion. During the impact process, stress interactions are complex, and the presence of shear stress prevents the normal stress reaching the peak value, leading to interlaminar separation. The quadratic stress failure criterion is expressed as follows:

(8) t n t n o 2 + t s t s o 2 + t t t t o 2 = 1

where t n and t n o are the peaks of normal stress and normal stress, respectively; t s and t s o are the peak values of shear stress and normal stress in 1 direction, respectively; t t and t t o are the peak values of shear stress and normal stress in 2 direction, respectively.

Based on the power-law damage evolution, the failure of composite armor under impact loading was determined by the power-law interaction of the energy required for a single failure (forward or shear). The formula is as follows:

(9) G I G II C a + G II G II C a + G III G III C a = 1

where G I and G IC represent the mode I fracture toughness and its peak value, respectively; G II and G IIC represent the mode Ⅱ fracture toughness and its peak value, respectively; G III and G IIIC represent the mode Ⅲ fracture toughness and its peak value, respectively.

2.3 FE model

Four unit cell models of carbon fibers, aramid fibers, UHMWPE fibers, and TPU composites with a TPU resin content of 30% were constructed. The geometric parameters of the four fabrics are as follows: the carbon fiber yarn width was 1.20 mm, aramid fiber yarn width was 0.80 mm, and UHMWPE fiber yarn width was 0.60 mm. The thicknesses of the single-layer carbon fiber fabric/TPU composite, aramid fiber fabric/TPU composite, and UHMWPE fiber fabric/TPU composite were 0.40, 0.31, and 0.18 mm, respectively. As shown in Table 2, the 27-layer aramid fiber composite armor model described in specimen 1 had a total thickness of 8.37 mm, while the models for samples 2–6, composed of a six-layer carbon fiber composite, 15-layer aramid fiber composite, and six-layer UHMWPE fiber composite, exhibited a total thickness of 8.13 mm.

To accurately simulate interlaminar cracking and delamination phenomena in laminated composites under impact stress, zero-thickness cohesive elements (COH3D8) were implemented at the ply interfaces. These elements were governed by a traction-separation constitutive law to model the progressive damage evolution between adjacent layers.

The 27-layer hybrid composite armor with dimensions of 150 mm × 150 mm was constructed with Abaqus. Continuous shell elements were employed. Interface parameters were introduced between the layers, totaling 530,000 elements, including 270,000 SC8R elements and 260,000 COH3D8 elements. For the bullet model, a spherical steel ball with a diameter of 8 mm and a mass of 4 g, which undergoes minimal deformation during ballistic impact tests, was selected. The bullet model was constructed using 3976 R3D4 elements.

When simulating the impact between the projectile and the target plate, a general contact model was utilized. The primary surface of the projectile was spherical, while the contact on the target plate was also considered as general contact. Contact properties were configured to include normal hard contact and tangential penalty contact, with a friction coefficient set to 0.3 to replicate realistic physical contact behavior. The regions along the edges of the target plate were fixed while simultaneously restricting the DOF and rotation in three directions. Additionally, appropriate impact velocity was imparted to the projectile through predefined fields.

2.4 Model parameters

Based on mean-field homogenization and mechanical tests, the material parameters and cohesive model parameters (28) of the composites are listed in Tables 1 and 2.

Table 1

Material parameters for aramid/TPU, carbon/TPU, and UHMWPE/TPU composites

Symbol Description Carbon/TPU Aramid/TPU UHMWPE/TPU
ρ Density (t·mm−3) 1.40 × 10−9 1.23 × 10−9 1.06 × 10−10
E 11 Young’s modulus in 1 direction (GPa) 33.41 14.29 10.18
E 22 Young’s modulus in 2 direction (GPa) 33.41 14.29 10.18
E 33 Young’s modulus in 3 direction (GPa) 7.10 6.00 3.26
ν 12 Poisson’s ratio ν 12 0.35 0.25 0.13
ν 13 Poisson’s ratio ν 13 0.35 0.33 0.13
ν 23 Poisson’s ratio ν 23 0.35 0.33 0.13
G 12 Shear modulus G 12 (GPa) 4.76 1.38 0.96
G 13 Shear modulus G 13 (GPa) 4.76 1.38 0.96
G 23 Shear modulus G 23 (GPa) 4.10 1.12 0.65
Table 2

Cohesive model parameters (28)

Parameters Parameter value
ρ (t·mm−3) 1 × 10−9
E (MPa) 1 × 106
t n o (MPa) 69
t s o / t t o (MPa) 79
G IC (N·mm−1) 0.9
G IIC /G IIIC (N·mm−1) 2

3 Results and discussion

3.1 Model accuracy verification

Table 3 lists the results of ballistic experimental tests and numerical simulations at an impact velocity of 615 ± 5 m·s−1, with errors less than 2%, validating the accuracy of the multi-scale simulation method. Figure 2(a) shows the residual velocity curve of the K27 composite armor, which can be divided into four stages, as shown in Figure 2(b): stage I – shear failure stage, characterized by a rapid decrease in residual velocity and predominantly shear failure morphology; stage II – tensile fracture stage, characterized by a steep decrease in residual velocity and predominantly tensile fracture morphology; stage III – delamination and bulge stage, characterized by a slow decrease in velocity, with delamination and large-area bulging damage morphology; stage IV – penetration stage, where the residual velocity no longer changes. The simulation reproduces complex damage modes such as shear failure, tensile fracture, and delamination bulging during the impact process, including shear failure on the front surface and delamination bulging on the rear surface, presenting circular localized damage rings. The simulated damage morphology is consistent with that observed in experimental testing, as shown in Figure 2(c).

Table 3

Residual velocity of K27 composite armors at an impact velocity of 615 ± 5 m·s−1

Specimens Striking velocity (m·s−1) Experimental residual velocity (m·s−1) Numerical residual velocity (m·s−1) Error (%)
K27 618.24 476.21 484.27 1.7
615.31 474.35 481.45 1.5
619.77 480.11 489.62 2.0
611.35 468.88 475.53 1.4
613.43 471.42 478.65 1.5
Figure 2 (a) Residual velocity curve, (b) cross-sectional damage morphology, (c) damage morphology on facing and rear surfaces of K27, and (d) residual velocities of composite armors at an impact velocity of 615 m·s−1.
Figure 2

(a) Residual velocity curve, (b) cross-sectional damage morphology, (c) damage morphology on facing and rear surfaces of K27, and (d) residual velocities of composite armors at an impact velocity of 615 m·s−1.

3.2 Effect of hybrid stacking on the residual velocity of hybrid composite armors

The dynamic response behaviors of the hybrid composite armors were investigated at an impact velocity of 615 m·s−1, and the residual velocities are shown in Figure 2(d). The hybrid composite armor exhibits lower residual velocities after penetration compared to the K27 (aramid) composite armor, indicating that fiber hybridization contributes to the improvement of ballistic performance of the composite armor. Under the same areal density, the stacking sequence of fiber-reinforced composites affects the ballistic performance of the composite armor. Adding appropriate aramid fiber layers (buffer layer) in front of the carbon fiber layers (rigid layer) increases the lateral stress propagation of the composite armor, enhancing the energy absorption of the carbon fiber layers. However, the thick buffer layer aggravates interlayer interactions with the front layers, reducing energy absorption and ballistic performance of the composite armor. This mechanism prolongs the energy dissipation stage, delays the occurrence of fiber fracture, and redistributes stress through the interaction between adjacent layers, allowing for the absorption of more energy through the elastic and plastic deformation of fibers and the matrix. The K3C6K12U6 composite armor exhibits the highest ballistic performance and the lowest residual velocity, with a 20 m·s−1 reduction compared to the K27 composite armor.

3.3 Effect of hybrid stacking on energy absorption of hybrid composite armors

Figure 3 shows the energy absorption of hybrid composite armors at an impact velocity of 615 m·s−1. In the process of ballistic impact, energy absorption is composed of strain energy (mainly), dissipation energy, and frictional energy. The energy absorptions of hybrid composite armors are higher than that of K27 composite armors, mainly manifested in strain energy. At an impact velocity of 615 m·s−1, the strain energy of K27 composite armor is 95.6 J, and the strain energy of K3C6K12U6 composite armor is 125.6 J, increased by 31.4%, as shown in Figure 3(b). The dissipation (plastic) energy and frictional energy of hybrid composite armors are almost unchanged but higher than that of K27 composite armor, as shown in Figure 3(c) and (d). The surface interactions between different layers generate interlayer shear stress, which promotes energy absorption through local matrix cracking and fiber matrix debonding. These phenomena enhance energy dissipation without causing instantaneous damage. Moderate aramid layer thickness can improve the performance, but excessive thickness will reduce the strain area of the subsequent layer (such as UHMWPE). This is because excessively rigid front layers tend to concentrate stress rather than disperse it, thereby limiting the activation of energy absorption mechanisms in subsequent layers. The BPI of the K3C6K12U6 composite armor is higher than that of other composite armors, up to 30.25 J·kg−1·m−2, which increased by 16.18%. Table 4 lists the residual velocity and BPI of hybrid composite armors at an impact velocity of 615 m·s−1.

Figure 3 Energy absorption of hybrid composite armors at an impact velocity of 615 m·s−1: (a) BPI, (b) strain energy, (c) frictional energy, and (d) dissipation energy.
Figure 3

Energy absorption of hybrid composite armors at an impact velocity of 615 m·s−1: (a) BPI, (b) strain energy, (c) frictional energy, and (d) dissipation energy.

Table 4

Residual velocity and BPI of hybrid composite armors

Specimens Impact velocity (m·s−1) Experimental residual velocity (m·s−1) Numerical residual velocity (m·s−1) Error (%) BPI (J·kg−1·m−2) Hoist (%)
K27 618.24 476.21 484.27 1.7 26.04 —
C6K15U6 617.52 469.36 477.45 1.7 28.76 10.45
K1C6K14U6 618.19 465.18 471.68 1.4 29.42 12.98
K2C6K13U6 613.80 458.17 467.92 2.1 30.04 15.34
K3C6K12U6 613.47 455.42 464.36 2.0 30.25 16.18
K4C6K11U6 615.22 463.27 469.89 1.5 29.29 12.50

3.4 Damage mechanism of hybrid composite armors in ballistic impact

Figure 4(a) shows the cross-sectional stress distribution of hybrid composite armors at an impact velocity of 615 m·s−1. It can be seen that penetration damage occurs in a small area along the path of projectile penetration. The back of the composite material has undergone significant deformation. Fiber breakage increases along the penetration direction, while some delamination occurs. As the impact velocity decreases, the yarn undergoes stretching, and the composite material delaminates. The velocity of the projectile significantly decreases, and the composite material is eventually perforated. The stress value and damage area of the K27 composite armor are the smallest. The K3C6K12U6 composite armor shows larger stress value and damage area. Figure 4(b) shows the cross-sectional view after a complete projectile penetration through the hybrid composite armors. The damage morphology in FE analysis is highly consistent with the actual experimental results. The FEA model effectively captures detailed damage characteristics such as yarn breakage, composite delamination, and resin damage. Optimizing the stacking sequence can improve the lateral transmission of stress in the composite armor and increase strain, decelerating impact loading and improving energy absorption.

Figure 4 (a) Stress distribution, (b) numerical simulated and experimental results of cross-sectional damage morphology, (c) damage process of the rear surface using a high-speed camera, and (d) damage morphologies on the facing and rear surfaces at an impact velocity of 615 m·s−1.
Figure 4

(a) Stress distribution, (b) numerical simulated and experimental results of cross-sectional damage morphology, (c) damage process of the rear surface using a high-speed camera, and (d) damage morphologies on the facing and rear surfaces at an impact velocity of 615 m·s−1.

Figure 4(c) shows the damage process of the rear surface using a high-speed camera and morphology on the facing and rear surfaces for the hybrid composite armors through a ballistic testing device at an impact velocity of 615 m·s−1. The rear surfaces of hybrid composite armors appear identified bulges. It can be observed that the overall damage region on the facing surface is localized in the contact region of the bullet for the hybrid composite armors. Due to the use of TPU as the resin matrix, which has high elasticity, and the composite armor is relatively thick, resulting in less obvious protrusions. As the projectile penetrates the target plate, the bulge area on the rear surface increases with prolonged impact duration, reaching its maximum. Due to TPU’s thermoplastic elastomeric properties, elastic recovery occurs once the bulge deformation peaks, and then the protrusion on the rear surface gradually diminishes. The main damage of the facing surface is fiber fracture, with the maximum damage diameter of 17.5 mm (K27) and the minimum damage diameter of 8.2 mm (C6K15U6). The rear surface of the hybrid composite armors suffered large yarn stretching and delamination during the penetration, with the maximum damage diameter of 92.1 mm (K3C6K14U6) and the minimum damage diameter of 32.4 mm (K27). The larger diameter of rear surface damage corresponds to higher energy absorption. Adding appropriate aramid fiber layers in front of the carbon layers can increase the strain area and improve the energy absorption of the hybrid fiber armor by utilizing the surface interaction between the layers.

Figure 5 displays the stress distribution of the facing surface for hybrid composite armors at an impact velocity of 615 m·s−1. Stress diffusion across all composite armors exhibit a cross-shaped pattern originating from the impact center, gradually transitioning into a ripple-like diffusion. Except for the K27 composite armor, all hybrid composite armors demonstrate a reduction in the stress area between 30 and 40 µs, indicating that hybrid stacking facilitates rapid propagation of stress waves across the plane. The K27 composite armor exhibits the lowest stress peak and the smallest stress area, while the C6K15U6 composite armor shows the highest stress peak and the largest stress area. The maximum proportion of the red stress area region for the facing surface at 40 μs is 2.5%, 8.4%, 3.8%, 3.5%, 3.4%, and 3.2%, respectively. Due to the high stiffness of carbon fibers, its stress area is the largest. However, after adding aramid layers on the facing surface, the stress area of the aramid layer increases but decreases with increasing thickness of aramid layers. The aramid layers (buffer layer) in front of the carbon layers (rigid layer) increase the stress peak and stress area on the facing surface.

Figure 5 Stress distribution of the facing surface for hybrid composite armors at an impact velocity of 615 m·s−1 : (a) K27; (b) C6K15U6; (c) K1C6K14U6; (d) K2C6K13U6; (e) K3C6K12U6; and (f) K4C6K11U6.
Figure 5

Stress distribution of the facing surface for hybrid composite armors at an impact velocity of 615 m·s−1 : (a) K27; (b) C6K15U6; (c) K1C6K14U6; (d) K2C6K13U6; (e) K3C6K12U6; and (f) K4C6K11U6.

Figure 6 shows the stress distribution of the rear surface of hybrid composite armors at an impact velocity of 615 m·s−1. The rear surface of the K27 composite armor exhibits the smallest stress peak and stress area. After 20 µs, the stress peak and area of the K3C6K12U6 composite armor surpass those of the C6K15U6 composite armor. The buffer layer can increase stress propagation, thus enhancing energy absorption. Regarding the synergistic effect of fiber hybridization, it mainly results from the surface-to-surface interaction. When the bullet impacts the front layer, the back layer impedes stress, strain propagation, and energy absorption in the front layer. Conversely, the front layer also affects the back layer due to its own stress. When the accumulated force on the front layer is excessive, it leads to the delamination failure of the back layer. The C6K15U6 composite armor outperforms the K27 composite armor primarily because of different interactions between materials. As the carbon layer exhibits minimal lateral deformation, arranging the stacking sequence of carbon/aramid/UHMWPE can mitigate the adverse effects of surface-to-surface interactions. The K3C6K12U6 composite armor demonstrates superior protective performance compared to the C6K15U6 composite armor by utilizing surface-to-surface interactions. Adding aramid layers (buffer layer) in front of the carbon layers (rigid layer) enhances energy absorption in the carbon layers, improving the overall energy absorption. The maximum proportions of the red stress zone for the rear surface at 40 μs is 4.7%, 9.7%, 10.3%, 10.4%, 10.8%, and 10.6%.

Figure 6 Stress distribution of the rear surface for the hybrid composite armor at an impact velocity of 615 m·s−1 : (a) K27; (b) C6K15U6; (c) K1C6K14U6; (d) K2C6K13U6; (e) K3C6K12U6; and (f) K4C6K11U6.
Figure 6

Stress distribution of the rear surface for the hybrid composite armor at an impact velocity of 615 m·s−1 : (a) K27; (b) C6K15U6; (c) K1C6K14U6; (d) K2C6K13U6; (e) K3C6K12U6; and (f) K4C6K11U6.

The synergistic effects in composite materials primarily arise from the hybridization of constituents with complementary mechanical properties. A rigid impact-facing layer provides shear resistance to withstand projectile penetration, while a compliant back-facing layer enables radial yarn flow and out-of-plane deformation to enhance energy absorption. The stacking sequence of these hybrid architectures governs energy dissipation mechanisms: the front layer acts as a sacrificial cushioning zone, facilitating lateral stress redistribution through controlled fragmentation. The rear layer assumes an energy-absorbing role, amplifying stress wave attenuation and interlaminar shear resistance to delay perforation. This design accommodates substantial plastic deformation and delamination, thereby maximizing energy dissipation. Stress redirection and stiffness gradation further optimize the performance: The transition from a rigid front layer to a ductile rear layer creates a stiffness gradient, which radially redirects stress waves and activates multi-stage failure modes (elastic stretching-plastic yielding interfacial debonding). This hierarchical failure progression systematically dissipates kinetic energy through sequential material response mechanisms.

4 Conclusions

This article proposed a new structure (buffer/rigid/toughness/energy absorbing layers) of the carbon/aramid/UHMWPE hybrid composite armor based on multi-scale simulations and investigated the effect of stacking sequence on the ballistic performance and elucidated the damage mechanisms during the impact process. Stacking sequence enhanced the ballistic performance of the hybrid composite armor. The ballistic performance of the hybrid composite armor with buffer/rigid/toughness/energy absorbing layers (K3C6K12U6) significantly improved the residual velocity decreased by 20 m·s−1, and the BPI increased by 16.2%.

Due to surface–surface interactions, the front layers exerted forces on the back layers and the back layers impeded stress, strain propagation, and energy absorption in the front layers. As the accumulated force on the front layer is excessive, the delamination failure of the back layers occurs. The buffer layer at the facing surface dispersed the stress concentration of the impact loading through the buffering effect of tough aramid fiber layers (thinner thickness) and increased the transverse strain and energy absorption of the composite armor; high-strength carbon fiber layers as a rigid layer absorbed the kinetic energy of bullet through shear deformation; the thicker toughness layer increased the stress area and friction effect through the stretching of aramid fibers; the energy absorbing layer on the rear surface accumulated the strain of front layers through flexible UHMWPE fibers, decelerated delamination failure caused by interlayer forces, and enhanced the energy absorption and penetration resistance of the composite armor.

Acknowledgments

This work was supported by Natural Science Foundation of Hubei Province [2025AFC029 (Yuxuan Zhu)], the Key R&D project of Hubei Provincial Research Project [JD2023009 (Jiuxiao Sun)] and National Key R&D Program of China [2021YFB38002300 (Guoqiang Luo)].

  1. Funding information: This work was supported by Natural Science Foundation of Hubei Province [2025AFC029 (Yuxuan Zhu)], the Key R&D project of Hubei Provincial Research Project [JD2023009 (Jiuxiao Sun)] and National Key R&D Program of China [2021YFB38002300 (Guoqiang Luo)].

  2. Author contributions: Zhicheng Liu: methodology, software, writing – original draft; Shiying Lu: formal analysis, data curation; Ruyi Ji: visualization, investigation; Yuxuan Zhu: writing – review and editing, visualization, conceptualization; Ruizhi Zhang: software, methodology; Jiuxiao Sun: supervision, conceptualization, funding acquisition; Guoqiang Luo: supervision, funding acquisition; Peng Cao: software, methodology; Yubin Ma: formal analysis; Ming Yang: project administration.

  3. Conflict of interest: The authors state no conflict of interest.

  4. Data availability statement: The data presented in this article are available on request from the corresponding author.

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Received: 2025-05-12
Revised: 2025-07-14
Accepted: 2025-07-31
Published Online: 2025-09-16

© 2025 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/epoly-2025-0035
Schlagwörter für diesen Artikel
fiber-reinforced composites; ballistic performance; multi-scale simulation; damage mechanism
Creative Commons
BY 4.0

Artikel in diesem Heft

  1. Research Articles
  2. Flow-induced fiber orientation in gas-powered projectile-assisted injection molded parts
  3. Research on thermal aging characteristics of silicone rubber composite materials for dry-type distribution transformers
  4. Kinetics of acryloyloxyethyl trimethyl ammonium chloride polymerization in aqueous solutions
  5. Influence of siloxane content on the material performance and functional properties of polydimethylsiloxane copolymers containing naphthalene moieties
  6. Enhancement effect of electron beam irradiation on acrylonitrile–butadiene–styrene (ABS) copolymers from waste electrical and electronic equipment by adding 1,3-PBO: A potential way for waste ABS reuse
  7. Model construction and property study of poly(ether-ether-ketone) by molecular dynamics simulation with meta-modeling methods
  8. Zinc–gallic acid–polylysine nanocomplexes with enhanced bactericidal activity for the treatment of bacterial keratitis
  9. Effect of pyrogallol compounds dosage on mechanical properties of epoxy coating
  10. Preparation of in situ polymerized polypyrrole-modified braided cord and its electrical conductivity investigation under varied mechanical conditions
  11. Hydrophobicity, UV resistance, and antioxidant properties of carnauba wax-reinforced CG bio-polymer film
  12. Janus nanofiber membrane films loading with bioactive calcium silicate for the promotion of burn wound healing
  13. Synthesis of migration-resistant antioxidant and its application in natural rubber composites
  14. Influence of the flow rate on the die swell for polymer micro coextrusion process
  15. Fatty acid filled polyaniline nanofibres with dual electrical conductivity and thermo-regulatory characteristics: Futuristic material for thermal energy storage
  16. Hydrolytic depolymerization of major fibrous wastes
  17. Performance of epoxy hexagonal boron nitrate underfill materials: Single and mixed systems
  18. Blend electrospinning of citronella or thyme oil-loaded polyurethane nanofibers and evaluating their release behaviors
  19. Efficiency of flexible shielding materials against gamma rays: Silicon rubber with different sizes of Bi2O3 and SnO
  20. A comprehensive approach for the production of carbon fibre-reinforced polylactic acid filaments with enhanced wear and mechanical behaviour
  21. Electret melt-blown nonwovens with charge stability for high-performance PM0.3 purification under extreme environmental conditions
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  23. Experimental testing and finite element analysis of polyurethane adhesive joints under Mode I loading and degradation conditions
  24. Optimizing recycled PET 3D printing using Taguchi method for improved mechanical properties and dimensional precision
  25. Effect of stacking sequence of the hybrid composite armor on ballistic performance and damage mechanism
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  28. Corrigendum
  29. Corrigendum to “High-strength polyvinyl alcohol-based hydrogel by vermiculite and lignocellulosic nanofibrils for electronic sensing”
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