Developing the stress–strain curve to failure using mesoscale models parameterized from molecular models

Using Coarse-Grained Molecular Models (Molecular-Mesoscale) of a Copper Oxide-Epoxy Interface to Obtain Stress–Strain Failure Predictions Which Include Interfacial Roughness, Water and Filler Effects

“…From these examples, it appears that a bond breaking criterion is needed for simulations which qualitatively match expected reality. Previous studies [36][37][38] used perfectly flat copper oxide-epoxy interfaces, however in reality materials, do not exhibit perfect flatness [1,42], so one question that arises is whether the effect of roughness can be captured using the same coarsegraining method. In order to approach the interface roughness question, in relationship to how the polymer may be coupled into the adhesive interface [43][44][45][46][47][48], the polymer structure was fixed at the highest crosslink case studied previously [36][37][38] (all epoxies reacted with a phenolic unit from bisphenol A) and only the copper oxide-polymer interface was considered.…”

“…The entire novolac epoxy plus its' bisphenol A curative represented one bead, as described previously [36]. As before with the perfectly smooth interfaces [36][37][38], the polymer was incrementally compacted onto the Cu 2 O bead surface in order to attain a global minimum before the interfaces were separated by incrementally moving the Cu 2 O layer into the vacuum space.…”

“…In order to look at the effect of silica, the previous vacuum cell models [38] containing the polymer mass optimized on a Cu 2 O layer were thinned down more in order to embed one particle of silica into the polymer without overwhelming the effect of the particle in the model (the epoxy + silica layer size within the vacuum cell was~180 Â 126 Â 65 Å, with a silica particle block the size of~60 Â 37 Â 5 Å).…”

“…So one way in which the initial modulus is increased, is through roughness that grabs a more dense mass with it during shear. More polymer inclusion leads to more cohesive contribution and the cohesive interface has been found to have less energy gain than the adhesive interface [38]. However in the mixed rough/shear case there is almost no energy gain at separation.…”

“…When the maximum yield in the tensile saw tooth models (as determined by the energy at the step in which the maximum number of bonds are broken) is plotted and compared with global yield both show a similar linear relationship in a positive Hall-Petch-like relationship. Previously [38], it was shown that the maximum number of bonds that break occurs close to but after the maximum energy, so there may be another qualitative definition of yield. It is also interesting that there is a more significant trend Fig.…”