Much research and development have been conducted to improve the safety of infrastructure against both manmade and natural hazards. However, there still exists a strong demand for cost-effective and environmentally friendly impact-resistant composites. Hence, the fundamental understanding of multiscale interfacial effects on architected composite responses to impact loading is a research topic of current interests. To effectively simulate the multi-phase (solid-liquid-gas or hard-soft media) interactions involving large deformations and failure evolution, the material point method (MPM) has evolved for about three decades [1, 2]. As a continuum-based particle method that takes advantage of the strengths of both Eulerian and Lagrangian formulations, the MPM has been combined with molecular dynamics (MD) for multiscale simulations of multi-phase interactions. With the use of both MPM and MD, a systematic study is being performed to explore the similarity and difference between the MPM and MD in simulating the interfacial effects on the transient responses of architected composites at the same spatial scale. The objective is to characterize the interplay among multiscale mechanisms in the interfacial domain among different types of constituents for optimizing impact-resistant structural designs. It appears from the preliminary findings that both MPM with constitutive modeling and MD with molecular potentials could produce the consistent computational results at the same spatial scale. Thus, both methods could be employed for mutual verification with respective accuracy and efficiency. REFERENCES [1] D. Sulsky, Z. Chen and H.L. Schreyer, “A Particle Method for History-Dependent Materials,” Computer Methods in Applied Mechanics and Engineering, Vol 118, pp. 179-196, 1994. [2] X. Zhang, Z. Chen and Y. Liu, The Material Point Method – A Continuum-Based Particle Method for Extreme Loading Cases, Elsevier, 2016. [3] Z. Chen, S. Jiang, Y., Gan, H. Liu and T.D. Sewell, “A Particle-Based Multiscale Simulation Procedure within the Material Point Method Framework,” Computational Particle Mechanics, Vol. 1, pp. 147-158, 2014. [4] S. Jiang, Z. Chen, T.D. Sewell and Y. Gan, “Multiscale Simulation of the Responses of Discrete Nanostructures to Extreme Loading Conditions Based on the Material Point Method,” Computer Methods in Applied Mechanics and Engineering, Vol. 297, pp. 219-238, 2015.