Session: 03-02 Wave Propagation, Buckling, and Dynamic Response

Paper Number: 167598

167598 - Stress Wave Propagation in Reconfigurable Kerf Composite Structures 

Kerfing is historically a subtractive manufacturing technique used to create flexible freeform structures out of stiff panels such as wood. By varying the cut pattern and cut density the stiffness of the structure can be altered locally making it easy to form the panels into complex geometries without compromising the strength (Capone and Lanzara 2019, Chen et al., 2020). Kerf structures have been used for indoor panels, pavilion, and building facades. Some of the kerf patterns display topological microstructures of chiral and fractal characteristics, presenting an opportunity to create reconfigurable structures with intriguing load transfer mechanisms and control wave propagation (Shahid et al. 2022). With additive manufacturing, kerf structures can be designed out of various materials, such as polymers, composites, as well as multi-materials (Darnal et al., 2023, 2024), expanding the applications of kerf structures in aerospace structures, robotics, automotive, etc.

This study focuses on understanding the load transfer mechanisms in kerf structures out of carbon fibre reinforced polymer composites. Additive manufacturing techniques such as FDM 3D printing was used to fabricate kerf structures. Two kerf patterns are considered which involve chiral and fractal patterns of slender beams in square and hexagonal unit cells. Nylon Carbon Fibre composite (PA6 - CF) is used for the kerf structures. In addition, Polylactic acid (PLA) material is used to benchmark the mechanical properties and performance of kerf structures.

The purpose of this research is to understand the temporal and spatial responses of flexible and reconfigurable kerf structures subjected to dynamic loading, investigate the interplay of material damping and structural topology in mitigating dynamic stress waves, and create a tuneable kerf structure which can demonstrate the ability to mitigate or redirect the stress wave propagation. Mechanisms such as localized deformation, micro-macro scale reconfigurations, material anisotropy when subjected to dynamic loading will help in altering the vibration response of the overall system and can be used to enhance energy dissipation which will help in shielding certain regions from high amplitude of vibrations.

We present experiments and modelling to study the responses of kerf structures under dynamics loadings. We first study the modal responses of kerf cells and explore the stress wave propagation under impact loadings. We prescribed an impact force from one side of the kerf cells and determined the time when the stress propagated to the furthest side of the kerf cells. The kerf cells have the same side length of 1 inch and thickness of 0.125 inches and are out of carbon/nylon composites. The tortuous or meander path in the kerf cells slows down the overall wave propagation when compared to the wave propagation in solid panel. The kerf topology delays the wave reaching the opposite side of the cells and results in a much smaller stress amplitude when compared to the stress amplitude in the plate. This study highlights the ability of the kerf cells to mitigate imparted energy and stress waves in the structures attributed to the meandering load transfer passage. The hexagon pattern shows more effective wave attenuation compared to the square pattern, resulting in a significantly small stress amplitude. This is attributed to increase in the meander path in the hexagon kerf cells compared to the square kerf cells.

The results demonstrate the ability of the kerf cells to effectively tune the dynamic response according to the application needed. The energy dissipation obtained by such structure will be more when a viscoelastic material model is used to characterize the PA6 – CF composite material. Testing will be performed to validate the stress wave propagation through the kerf unit cells. A large panel will be studied using different kerf densities to effectively manage the stress wave propagation which can be helpful in applications where local isolation is needed from vibrations. 

Presenting Author: Deepashri Prashant Joshi Texas A&M University

Presenting Author Biography: Deepashri Joshi is a PhD candidate at Texas A&M University. She is working with Dr. Anastasia Muliana as a graduate research assistant on developing adaptive kerf structures for mitigating or redirecting stress wave propagation. She has also worked on projects such as Bio-inspired structures for energy absorption, investigating flexural response of sandwich composites. Her areas of research interests are dynamic behavior of structures and modeling, 3D printing and finite element analysis.