## 5 Results and Discussion  
By applying the material-structure integrated optimization algorithm presented in Section 4, we successfully addressed the multiscale optimization design challenges for plain weave, twill, and satin weave composite car doors, considering both scenarios with and without process constraints. The converging Pareto solution sets are shown in Figures 12-14[33]. Overall, it is observed that the sagging stiffness and the mass of the CFRP car doors are two conflicting performance indicators. This means that if a solution with a lower door mass is selected from the solution set, it will inevitably have a larger sagging displacement, i.e., lower sagging stiffness, and vice versa. Furthermore, the solution sets considering process constraints and those not considering them show similar patterns of variation, but their distribution positions are significantly different. Specifically, the solution sets considering process constraints are mostly located in the upper right area of those not considering constraints, with this trend being most evident in the twill composite car door, as shown in Figure 13. The possible reason for this phenomenon is that when process constraints are considered, the feasible domain of design variables decreases. Some designs with lower mass and higher stiffness may not meet the layup process constraints of carbon fiber composites. Therefore, in the Pareto solution set, considering process constraints shifts the set towards the upper right, losing some performance indicators. To clarify this point further, the solution set within the circle in Figure 14 is examined: it was found that the solution set not considering process constraints includes layup designs with four consecutive layers at 0\({}^{\circ}\), whereas the set considering process constraints, although slightly compromising on door mass and sagging stiffness, fully meets the requirements proposed in Section 4.1. In summary, although the performance parameters of the multiscale design of CFRP considering process constraints are slightly deteriorated, the solution set meets layup process requirements, avoiding design flaws due to poor layup design. Figure 12: Pareto solutions for integrated design of plain weave. Although the Pareto solution set offers many feasible alternatives, selecting an appropriate solution for guiding engineering design is crucial in practical applications. To reasonably balance the conflicting performance indicators of door mass and sagging stiffness, this paper employs the minimum distance selection method [34], choosing the best solutions from the sets in Figures 12-14. The optimal solution for the plain weave car door: microscale cell fiber volume fraction of 59.49%, mesoscale cell fiber yarn volume fraction of 49.11%, laminate layup angles of [0\({}^{\circ}\), 45\({}^{\circ}\), \(-\)45\({}^{\circ}\), 0\({}^{\circ}\), 90\({}^{\circ}\), 0\({}^{\circ}\), 0\({}^{\circ}\), 90\({}^{\circ}\), 0\({}^{\circ}\), 45\({}^{\circ}\), \(-\)45\({}^{\circ}\), 0\({}^{\circ}\)]. The optimal solution for the twill weave car door: microscale cell fiber volume fraction of 62.25%, mesoscale cell fiber yarn volume fraction of 49.35%, laminate layup angles of [90\({}^{\circ}\), 45\({}^{\circ}\), 90\({}^{\circ}\), 0\({}^{\circ}\), 90\({}^{\circ}\), 90\({}^{\circ}\), 0\({}^{\circ}\), 90\({}^{\circ}\), -45\({}^{\circ}\), 90\({}^{\circ}\)]. The optimal solution for the satin weave car door: microscale cell fiber volume fraction of 39.37%, mesoscale cell fiber yarn volume fraction of 70.23%, laminate layup angles of [0\({}^{\circ}\), 45\({}^{\circ}\), 0\({}^{\circ}\), 90\({}^{\circ}\), 0\({}^{\circ}\), 90\({}^{\circ}\), 90\({}^{\circ}\), 90\({}^{\circ}\), 0\({}^{\circ}\), -45\({}^{\circ}\), 0\({}^{\circ}\)]. The chosen optimal solutions all meet the process requirements in terms of layup angles.