Multi-scale Mechanical Characterization of Palmetto Wood using Digital Image Correlation to Develop a Template for Biologically-Inspired Polymer Composites

Abstract

Palmetto wood is garnering growing interest as a template for creating biologically-inspired polymer composites due to its historical use as an energy absorbing material in protective structures. In this study, quasi-static three-point bend tests have been performed to characterize the mechanical behavior of Palmetto wood. Full-field deformation measurements are obtained using Digital Image Correlation (DIC) to elucidate on the strain fields associated with the mechanical response. By analyzing strain fields at multiple length scales, it is possible to study the more homogeneous mechanical behavior at the macroscale associated with the global load-deformation response; while at the microscale the mechanical behavior is more inhomogeneous due to microstructural failure mechanisms. Thus, it was possible to determine that, despite the presence of discontinuous macro-fiber reinforcement, at the macroscale the response is associated with classical bending and progressive failure processes that are adequately described by Weibull statistics proceeding from the tensile side of the specimen. At the microscale, however, the failure mechanisms giving rise to the macroscopic response consist of both shear-dominated debonding between the fiber and matrix, and inter-fiber matrix failure due to pore collapse.These microscale mechanisms are present in both the compressive and tensile regions of the specimen, most likely due to local macro-fiber bending, which is independent of the global bending state. The pore collapse mechanism observed during mechanical loading appears to improve the energy absorption of the matrix material, thereby, transferring less energy and shear strain to the macro-fibermatrix interface for initiation of debonding. However, the pore collapse mechanism can also accumulate substantial shear strain, which results in matrix shear cracking. Through these complex failure mechanisms, Palmetto wood exhibits a high resistance to catastrophic failure after damage initiation, an observation that can be used as inspiration for creating new polymer composite materials.

Multi-scale model updating of a timber footbridge using experimental vibration data

“…Typically, the MFA of the S 2 layer varies between 0 and 22 o [62]. We note that most of these microstructural features have been exploited further in order to develop new bio-inspired composite materials [28].…”

Multi‐Length Scale Hierarchy in Natural Materials

“…The knowledge of the structure is used to form similar structures artificially [12,13]. Composite materials inspired by wood structure and wood polymer composites are some of the examples.…”

Characterization of dynamic damage mechanisms in Palmetto wood as biological inspiration for impact resistant polymer composites

“…Thus, the indentation energy was only 7 percent of the total 5.35 J, which was insufficient to stop the projectile. Thus, the indentation energy was only half of that of the 20 vol.% macrofibers, which indicates that the macrofiber concentration can also play a critical role in the impact resistance of Palmetto wood through the indentation response.In order to assess the effects of strain rate and macrofiber concentration on the mechanical behavior of the Palmetto Wood, a Weibull-based damage model of the stress-strain response for fiber-reinforced polymer composites was used (Gershon et al, 2010;Haldar et al, 2011). The Weibull model can be seen in Eq.…”