Effect of thickness of carbon fiber backplane on penetration resistance of aluminum composite plate

As a typical advanced lightweight material, Carbon fiber reinforced (CFRP) composites are widely used in lightweight protection fields such as the aviation industry. A common way to improve the protection performance of fiberboard is to add more layers in different arrangements, but it also affects the total weight and flexibility of the target plate, so how to measure the relationship between thickness and protection performance is the focus of research. In this paper, the influence of CF backplane thickness on the impact resistance of Al/CF composite plate and the damage properties of the fiber layer is studied through the mutual verification of experiment and numerical simulation.

The experiments were carried out on Al/CF composite plates with 8 mm tungsten alloy spherical fragments fired by a musket. Projectiles with different speeds were used to penetrate Al/CF composite plates with different thicknesses. The strain dynamic response and internal damage of Al/CF composite plates were obtained through DIC and CT scanning analysis. Based on the Johnson-Cook material model and the Abaqus Explicit/Dynamic User-defined Materia Mechanical Behavior (VUMAT) constitutive model, the influence of the interaction between Al plate and fiber layer and fiber layer on energy absorption was analyzed under different CF plate thicknesses, and numerical simulation of spherical fragmentation penetration process of Al/CF composite plate under different CF plate thicknesses was carried out to study the influence of CF plate thickness (0.7~ 12.6mm) on energy absorption performance of Al/CF composite plate.

The error between the numerical simulation results and the experimental results is less than 5%, and the damage morphology of the numerical simulation Al plate and carbon fiber plate is similar to the experimental results. Combining the experimental and numerical simulation results, it can be found that: (1) The influence of the thickness of the CF plate on the mechanical support of Al plate increases nonlinearly. After the CF plate increases to a certain thickness (4.2mm, 5.6mm, 5.6mm), the energy absorption of fragments (1000 m/s, 1250 m/s, 1500 m/s) penetrating Al plate does not increase significantly. The impact kinetic energy of Al plate is 1008.02J, 2061.84J, and 2868.61J, respectively. (2) The impact strength of the metal fiber bonding layer is greater than that of other fiber layers, and the Al plate shows obvious convex deformation under the impact of the projectile, resulting in a large degree of deformation of the metal layer and the fiber layer bonding surface. Due to the limitation of adjacent fibers and aluminum plates, the fiber layer located in the middle of the fiber plate cannot absorb energy through sufficient deformation, resulting in the smallest area of fiber damage. With the decrease of the interlayer shear strength, the deformation degree of the fiber layer under the action of tensile stress increases, the fiber failure crack extends along the fiber direction, and the fiber damage area increases slowly along the thickness direction. Therefore, along the direction of fiber thickness, the damage area of fiber decreases first and then increases. (3) The Circular shape factor(CSF) of the fiber layer damage shape decreased along the thickness direction. Under the constraint of the fiber layer and the metal layer, the damage shape of the inner fiber tended to be elliptical, while the interlayer shear strength on the outer fiber layer gradually decreased, resulting in a large relative displacement of the outermost fiber. The damage shape of fibers tends to be elongated. (4) The range of diffusion impact energy of CF plate is restricted by the diffusion of epoxy resin matrix, the local fibers are damaged, and the overall anti-penetration effect of the fiber layer cannot be played. The specific energy absorption of the Al/CF composite plate shows a linear decline trend with the increase of surface density.Conclusions: The numerical simulation results are consistent with the experimental results of 8 mm tungsten alloy spherical fragment impacting the Al/CF composite plate. The User-defined Materia Mechanical Behavior based on the Johnson-Cook material model and Abaqus Explicit/Dynamic solver The constitutive model written by VUMAT can well simulate the damage morphology and energy absorption properties of carbon fiber under high-speed impact. The influence of the thickness of the CF plate on the mechanical support of the Al plate increases nonlinearly, indicating that the appropriate thickness of the backplane stack can limit the main damage to the elastic attack surface. The convex deformation of the aluminum plate and the restriction of adjacent fiber layers have an impact on the deformation degree of the fiber layer, resulting in the fiber damage area decreasing first and then increasing along the fiber thickness direction, and the fiber damage shape changing from oval to elongated along the thickness direction. Moreover, the specific energy absorption of the composite plate decreases linearly with the increase of surface density, which makes the overall penetration resistance of the Al/CF composite plate increase when the fiber thickness is thicker, it cannot give full play to the penetration resistance of the Al/CF composite plate, and the energy absorption efficiency decreases with the increase of the thickness.