# A Numerical Study of Blast Resistance of Carbon Fiber Reinforced Aluminum Alloy Laminates
## 4 Results and Discussion
### Influence of Fiber Layering Direction on CARALL Impact Response of Curved Surfaces  
In planar CARALL structures, the fiber lamination direction is the most important structural characteristic of the fiber structure, and has a decisive effect on the failure mode and impact resistance of the fiber. However, in a curved surface structure, the coupling between the influence of the fiber arrangement direction and the curved surface structure is more complex. In this paper, the impact response of double-layer fibers under different radii of curvature is studied according to the change in the one-way layering angle [0; 30; 45; 90] and orthogonal arrangement (X).  
Figure 21 shows the comparison of CARALL deformation modes of double layers with different fiber layering directions.  
D0 arrangement (along the circumferential direction): under the small radius of curvature (R = 30 mm), the matrix fracture zone along the circumferential direction appears in the fiber layer. With the increase in curvature, the number of fiber fracture zones along the axial direction increases.  
D30 arrangement: under the small radius of curvature (R = 30), the fiber layer is mainly fractured by the clipped edge matrix. With the increase in curvature, the fiber layer appears to be axial and axial fractures occur between the fiber and the matrix.  
Figure 20: The influence of the number of layers on the energy absorption of each structure.  
D45 arrangement: in this arrangement, the fiber layer has more complex fiber failure. Fractures of the fiber and matrix appear along the axial direction and circumferential clamping edges. Multiple fault zones appear in the center. With the increase in curvature radius, the number of fault zones and the degree of fracture increase.  
D90 arrangement (along the axial direction): under the small radius of curvature, there are many obvious matrix fractures along the axial direction. This is because the structural deformation is mainly sagging deformation, and the matrix is subjected to strong shear and tensile stress at the edge of sag. With the increase in the radius of curvature, both the fiber fracture along the circumferential clipping edge and the matrix cracking along the axial direction increase. This is because with the increase in the radius of curvature, the overall bending deformation of the structure is dominant, and the shear stress of the clipped edge material increases.  
The DX arrangement is a bidirectional orthogonal arrangement. Under the small radius of curvature, the fiber layer arranged along the circumference can provide strong bending resistance, and prevent the matrix fracture of the fiber layer arranged along the axial direction. Due to the good anisotropy of the bidirectional arrangement, neat fiber or matrix fracture cannot easily occur in the fiber layer, and only scattered failure occurs.  
The maximum center point displacement and corresponding energy absorption of double-layer CARALL with different layering angles and radii of curvature are shown in Figures 22 and 23.  
Under the same radius of curvature, D0 and DX have the minimum deformation, and D45 has the maximum deformation. With the increase in curvature radius, the difference between the maximum and minimum deformation increases, while the corresponding energy absorption shows the opposite trend or pattern.  
Figure 21: Comparison of deformation modes at the maximum center deformation time of double-layer CARALL with different fiber arrangements.