Nacre-like composites with superior specific damping performance

Abstract

Biological materials such as nacre have evolved microstructural design principles that result in outstanding mechanical properties. While nacre's design concepts have led to bio-inspired materials with enhanced fracture toughness, the microstructural features underlying the remarkable damping properties of this biological material have not yet been fully explored in synthetic composites. Here, we study the damping behavior of nacre-like composites containing mineral bridges and platelet asperities as nanoscale structural features within its brick-and-mortar architecture. Dynamic mechanical analysis was performed to experimentally elucidate the role of these features on the damping response of the nacre-like composites. By enhancing stress transfer between platelets and at the brick/mortar interface, mineral bridges and nano-asperities were found to improve the damping performance of the composite to levels that surpass many biological and man-made materials. Surprisingly, the improved properties are achieved without reaching the perfect organization of the biological counterparts. Our nacre-like composites display a loss modulus 2.4-fold higher than natural nacre and 1.4-fold more than highly dissipative natural fiber composites. These findings shed light on the role of nanoscale structural features on the dynamic mechanical properties of nacre and offer design concepts for the manufacturing of bio-inspired composites for high-performance damping applications.

Keywords: bio-inspired materials; extreme damping; hierarchical structures; nacre.

Fig. 1.

Manufacturing and structural features of nacre-like composites. (A) Schematics of the VAMA process used to generate brick-and-mortar architectures with high volume fraction of inorganic platelets. (B) Illustration of the structural features formed within the brick-and-mortar architecture upon dewetting of the titania coating from the surface of the alumina platelets.

Fig. 2.

Microstructural analysis of scaffolds used for the manufacturing of nacre-like composites. (A–C) Representative SEM images of scaffolds obtained by hot-pressing assembled platelets under distinct temperatures and pressures. (D–F) Size distribution of titania features obtained by image analysis and used to estimate the fractions of mineral bridges and nano-asperities within the brick-and-mortar structures. (G) Fraction of mineral bridges, nano-asperities, and thin films or coatings of specimens prepared at different temperatures and pressures. (H) Observed experimental correlation between the fraction of mineral bridges and of nanoscale asperities in the investigated composites. The temperature and pressure used to fabricate the scaffolds are provided for each data point.

Fig. 3.

Damping behavior of nacre-like composites. (A) Storage modulus (E′), (B) loss modulus (E″) and (C) dissipation factor (tan (δ)) of specimens processed at different temperatures and pressures. (D–G) Experimental correlations between the (D, E) storage modulus and (F, G) the loss modulus of the nacre-like composites with the fractions of mineral bridges and nano-asperities.

Fig. 4.

Ashby plot displaying the stiffness and damping properties of the nacre-like composites (orange circles) compared to other classes of materials. The dashed lines represent the loss modulus, the damping figure of merit, E″. Data were obtained from Lakes (45), CES EduPack (46) and Woigk et al. (26) The room-temperature mechanical properties of the epoxy used for the preparation of the nacre-like composites studied in this work are also included in the plot (red diamond symbol, E′ = 3.6 GPa, E″ = 59.7 MPa, tan (δ) = 0.017).