A preliminary proposal for a test to determine the impact damage resis tance of composite materials and their structures is offered. This test is centered on the utility of contact force as a parameter directly related to the damage that occurs during the event. This is demonstrated through work previously published as well as via new experi ments conducted on various graphite/epoxy material systems and laminates in both mono lithic laminate and sandwich configurations. Static indentation and impact tests were con ducted and show a similarity in regards to the structural response and the damage that occurs. This proposal is discussed in terms of the laminates tested and the results, the test's general applicability and utility, and issues that need to be addressed further. The proposal makes a significant step towards providing a common reference point and language for (impact) damage resistance.

Mesoscale simulation techniques have helped to bridge the length scales and time scales needed to predict the microstructures of cured epoxies, but gaps in computational cost and experimental relevance have limited their impact. In this work, we develop an open-source plugin epoxpy for HOOMD-Blue that enables epoxy crosslinking simulations of millions of particles to be routinely performed on a single modern graphics card. We demonstrate the first implementation of custom temperature-time curing profiles with dissipative particle dynamics and show that reaction kinetics depend sensitively on the stochastic bonding rates. We provide guidelines for modeling first-order reaction dynamics in a classic epoxy/hardener/toughener system and show structural sensitivity to the temperature-time profile during cure. We conclude with a discussion of how these efficient large-scale simulations can be used to evaluate ensembles of epoxy processing protocols to quantify the sensitivity of microstructure on processing.

Construction aggregate particles, fine or coarse, can be scanned by X-ray computed tomography and mathematically characterized using spherical harmonic series, and can then be used to simulate random parking of irregular aggregates to form a virtual mortar or concrete using the Anm model. Any other similar composite system of irregular (star-shaped) particles in a matrix can also be simulated. This paper integrates two new algorithms into the Anm model. The first new algorithm is the extent overlap box (EOB) method that detects interparticle contact, and the second is the capability of adding a uniform-thickness shell to each particle. Parameter analysis has shown that the EOB method leads to a more accurate detection of interparticle contact with a smaller computational cost than the previously used Newton-Raphson method. The uniform-thickness shell provides a customizable tool to control the minimum intersurface distance of particles during the parking process, as well as to simulate processes and microstructure that are dependent on the Euclidean distance from a particle surface. For mortar and concrete, the uniform-thickness shell can represent the observed interfacial transition zone (ITZ) structure. A parallel processing application programming interface (API) was integrated into the Anm model to accelerate the particle placement process by parallel optimization, which results in significant improvements in the packing efficiency on multicore processor systems. This significant speedup as well the improved contact function and new uniform-thickness shell algorithm greatly extend the range, size, and type of particle systems that can be studied