Polymer nanocomposites are expected to enhance structural integrity and induce smart sensing capability in ways critical to next-generation materials. However, an understanding of the nature of the fracture and subsequent prediction of material properties is still very premature, owing to a lack of a) characterization techniques to capture the mechanics at sub-100 nm scale and b) accurate models for the estimation of failure modes. Current models based on linear fracture mechanics fail to capture sub-nanometer crack-tip formation or describe the role of nanoinclusion on the fracture toughness of the material. This study incorporates the crack-tip stress field in molecular dynamics simulations to evaluate fracture toughness using MoS2-epoxy composites as a model system. This allows direct measurement of the near-tip strain field, enabling an understanding of the mechanism of toughness enhancement by nanoparticles. A systematic processing technique was developed to ensure proper dispersion of the nanocomposites of high weight percentage of MoS2 in DGEBA epoxy polymer matrix. The detailed characterization using FT-IR, DSC, DMA, AFM-IR enabled insights into the nanosheet-polymer network system. High-resolution TEM, SEM, and AFM as well as nano-X-ray computed tomography provided an understanding of 3D dispersion status of these nanosheets. Experiments associated with nanoscale visualization of fracture in the composite are conducted using in-house in situ tensile testing stages placed within SEM and AFM. These experiments provide in-depth knowledge of the influence of flaw size, and platelet size, thickness, and dispersion of nanoparticles on fracture toughness and will be indispensable in guiding the refinement of multi-scale models.

Nanoscale toughening mechanism in MoS<sub>2</sub> dispersed epoxy composite system

253rd National Meeting (2017)

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Nanoscale toughening mechanism in MoS2 dispersed epoxy composite system

Nanoscale toughening mechanism in MoS₂ dispersed epoxy composite system