###### Abstract  
The increasing use of composite materials in the automotive field requires more attention with regards to the appearance of noise, vibration and harshness (NVH) study in cars construction. However, in car door panels production, impact characteristics need to be evaluated in sandwich laminates. Furthermore, it is important to consider the effect of prolonged environmental aging on crashworthiness properties. The innovative content of the work is the hygothermal effects evaluation on impact performance for two damped CFRP sandwich laminates. In this paper, two damping materials, Kraibon HHZ9578/99 and SUTP609/24, were used as core between two skins of CFRP for sandwich composite production. Freeze-Thaw aging treatment according to IEC 60068, specific for Automotive, was performed to investigate environmental effects on components. Up to 750 h, it was demonstrated that water absorption is regulated by Fick's Law. The low-velocity impact behavior of the damped sandwic has been studied according to ASTM D7136 throughout drop dart test equipment. Both main peak forces and energy absorption characteristics are negatively affected by aging condition. The introduction of damping core inside the composite structure of vehicle components can satisfy NVH constrictions. By contrast, at least same operating conditions must be assured in relation to not-damped components. NVI; CFRP; drop dart test; impact; ageing test; damping; rubber foil; automotive +
Footnote †: journal: Applied Science and Technology Department, Politecnico di Torino, 10129 Torino, Italy
damped composites on tubes, evaluating that the positioning of the rubber in the outer region of the section leads to higher impact absorption energy. [PERSON] et al. [10] proposed a new industrial solution to produce formed composite-metal hybrid laminates, utilizing the rubber layers to soften the deformation in the bended regions. [PERSON] et al. [11; 12] have applied the rubber layer in a multi-material Lower Control Arm (LCA) of a McPherson suspension, obtaining relevant advantages in terms of joining and damping effects from the component hybridization. By contrast, car door panel designer must ensure adequate crashworthiness for passive vehicle safety system. A first approach to crashworthiness evaluation by drop dart test was studied since early 2000 for automotive passive safety system. A drop dart test was used to assess composite laminated structure energy absorption. For example, [PERSON] et al. [13] analyzed the influence of laminates thickness and stacking sequence on energy absorption. The study of laminates thickness is strongly claimed in energy absorption. They defined two quantities for crashworthiness design approach are saturation energy (i.e., the minimum energy values for laminates penetration) and damage degree (i.e., the ratio between the total energy transformed (stored and dissipated) and the dissipated part of it). These two parameters can be useful for passive safety system design. In addition, no strain-rate effect was detected for GFRP. Similar results were discovered for CFRP composites [14]. Moreover, saturation energy value increases with the laminate thickness. The stacking sequence [0/90]i was detected as the best choice for energy absorption. In recent year, [PERSON] et al. [15] investigated laminates thickness influence on energy absorption and fracture behavior for pure thermoplastic composite laminates (i.e., both the matrix and the reinforcement made of thermoplastic). A PP matrix reinforced with PP fiber was analyzed. Samples were composite laminated plates obtained overlaying [0-90]i plain weaves. The experimental results highlighted the influence of the thickness of the laminate on the impact behavior. With the considered low thickness, a perforation of the specimens was observed, whereas a ductile behavior and extended plasticity without a crack tip was obtained with the considered high thickness.