# A Numerical Study of Blast Resistance of Carbon Fiber Reinforced Aluminum Alloy Laminates
## 4 Results and Discussion  
### Influence of Curvature on CARALL Impact Response  
#### 4.1.1 Influence of Curvature on Failure Modes of CARALL Deformation  
As the most important structural parameter of the surface structure, the curvature has the most direct effect on structural deformation. Figure 12 compares the deformation history of double-layer CARALL (layering along the circumferential direction) with different curvature radii, and Figure 13 shows its corresponding deformation history at the center point and deformation cloud diagram at the maximum deformation time. Figure 11: Comparison between the experimental and numerical predicted maximum central deflection of aluminum panel. Figure 12: Deformation–time history diagram of double-layer CARALL structures with different radii of curvature. As shown in Figure 13, structural deformation can be divided into three stages: (a) rapid deformation and bending under the action of explosion load to reach the maximum deformation; (b) spring back with the weakening of the explosion load; and (c) the structure undergoes a long period of vibration until energy dissipates. As shown in Figure 12, when the radius of curvature is small, R30_N2_D90 has a small deformation area and deformation value, and the overall deformation mode of the R30_N2_D90 structure is the central sag deformation. In the fiber part, the failure of lamination between fiber layers and between the fiber layer and aluminum plate is the main failure. The structure has strong shape recovery ability and small residual permanent deformation. With the increase in curvature radius, the deformation area and the deformation amount of R60_N2_D90 increase. The overall deformation mode of the R60_N2_D90 structure is the central sag deformation mode and the overall bending deformation mode. The delamination failure between the fiber and the aluminum plate and the delamination failure between fiber layers both increases. When the radius of curvature continues to increase, R90_N2_D90 and R120_N2_D90 show obvious overall bending deformation, the deformation amount and deformation area both increase, and  
Figure 13: Comparison of deformation history and maximum deformation of CARALL center with different radii of curvature: (**a**) central point displacement-time; (**b**) cloud diagram of backplane. there are obvious axial fractures in the center of the fiber layer, as well as along the clamping edge. The number and width of fractures increase with the radius of curvature. In order to analyze the specific influence of curvature on the deformation failure of the fiber layer, the typical failure characteristics of R30_N2_D90 and R60_N2_D90 are shown in Figure 14 as a structural contour diagram. In the x, y plane and the sectional drawing of R30_N2_D90 fiber fracture, fiber drape is not obvious. Fiber in the center uplift and the fiber layer between layers, and layered between the fiber and aluminum plate, due to the large circumferential curvature of the clamping side in the center of the circumferential form stress concentration of the substrate under high tensile and shear stress, suffer matrix fracture. In R60_N2_D90, the degree of fiber fold is strengthened, and the fiber and aluminum plate are seriously stratified in the central uplift. Fiber fracture begins to occur at the fold, and there are many obvious fiber fracture zones on the whole. The above analysis shows that the double-layer CARALL structure with a small radius of curvature has strong impact deformation resistance, which is because the structure with a small radius of curvature has greater bending stiffness. In addition, the incident shock wave on the structure surface has a large incident angle, the transmitted shock wave energy is small, and the overall impulse of the structure is small. Figure 15 shows the typical failure characteristics of R90_N2_D90 and R120_N2_D90 in structural contours.