Modeling of the effect of local material imperfection to the structural mechanical property variability of 2D finite-size cellular structures

摘要

Understanding the effect of local material property fluctuation on the overall structural properties of cellular structures is not only important for more effective designs, but also critical for their adoption in load bearing applications. In this work, an analytical modeling approach based on direct stiffness method was adopted, which allows for the implementation of heterogeneous material imperfection at full-scale cellular structure level. Three representative 2D cellular designs including auxetic, diamond and triangular structures were modeled and analyzed. The material property imperfection was represented by 3 levels of variabilities (2%, 5% and 10%) for both elastic modulus and strength, defined at local cellular element level. Experimental verification using Ti6Al4V cellular structures fabricated via laser powder bed fusion additive manufacturing demonstrated the potential of the established model in providing accurate predictions to the mechanical property variability of the cellular structures. In addition, the results also revealed new insights into the topology-material imperfection coupling relationships for the cellular structures. The auxetic structures exhibit the lowest material imperfection tolerance, whereas the stretching-dominated triangular structures exhibit the highest material imperfection sensitivity. The contribution of elastic modulus and ultimate strength imperfections at material level to the overall structural performance were established. Ultimately, this work could help ?re-establishing? the fundamental understanding of design factors for finite-size cellular structures with imperfect material properties.