Effects of material anisotropy on impact mitigation in single column woodpile structures

We studied effects of material anisotropy on impact mitigation in single column woodpile structures. Local vibrations and nonlinear contacts of cylindrical members are key mechanisms of wave modulation in woodpile structures. We numerically obtained wave propagations in single column woodpile structures by changing longitudinal and/or transverse stiffness different from stiffness along the stacking direction. We found that changes in longitudinal and/or transverse stiffness altered wave propagation tendency as well as impact mitigation rate. We observed compact and wide waves propagated through single column woodpile structures with small stiffness ratio, while disintegrated but narrow waves with large stiffness ratio. According to dynamic behavior under impact loadings and frequency responses of woodpiles, bending vibration changed from 3rd to 1st mode and low energy band moved to relatively low frequency region when the single column woodpile structures had small stiffness ratio. This leads to increase impact mitigation characteristics of single column woodpile structures.