PSI - Issue 69

Stefano Rodinò et al. / Procedia Structural Integrity 69 (2025) 20–25

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deflection magnitude demonstrated systematic variation with increasing flow velocity, as detailed in Table 3. The relationship between flow velocity and maximum deflection demonstrated consistent behavior across multiple measurement cycles. Fig. 3 illustrates this relationship, presenting the evolution of maximum deflection as a function of flow velocity. The observed reduction in deflection magnitude with increasing flow velocity follows a nonlinear trend, with more pronounced effects at higher velocities. Of particular significance is the maintenance of substantial shape morphing capability even under maximum flow conditions. At v = 125 km/h, the composite retained approximately 60% of its zero-flow deflection capacity. This retained morphing capability remains within the functional requirements typically specified for automotive applications, where deflections of 30 mm or greater are generally sufficient for active aerodynamic components as mentioned recently by Riccio et. al. (2024). The experimental characterization demonstrates that the multi-material composite architecture maintains stable shape morphing functionality across the investigated flow velocity range (0-125 km/h). Analysis of the deformation profiles reveals a nonlinear relationship between flow velocity and morphing response, characterized by progressive reduction in maximum deflection with increasing aerodynamic loading. The baseline configuration achieves 52 mm tip deflection under controlled thermal activation, establishing the system's maximum morphing capability. This performance systematically transitions through intermediate states, retaining 91.4% of baseline deflection at 50 km/h, 79.6% at 75 km/h, and 68% at 100 km/h, ultimately maintaining 60% (31.6 mm) deflection capability at maximum test velocity. Of particular significance is the preservation of consistent deformation profiles across all velocity conditions, indicating stable actuation behavior despite increasing aerodynamic loads. This characteristic can be attributed to the strategic multi-material design approach, where the compliant silicone layer effectively accommodates shape recovery strains while the PC/ABS component provides requisite structural support. The maintained functionality at elevated velocities validates the effectiveness of this architectural strategy in addressing interface challenges previously documented in the literature (Zhou et al., 2018; Lacasse et al., 2014).

Fig. 5. Maximum deflection vs. flow velocity.

Table 3. Maximum measured deflections under various flow conditions.

Flow Velocity (km/h)

Maximum Deflection (mm) Relative Change (%)

0

52.4 47.9 41.7 35.6

0

50 75

8.6

20.4

100

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