SUMMARY

In the design of many advanced composite materials, the goal is to fabricate lightweight, strong, and tough materials by reinforcing soft materials such as polymers. There is considerable ongoing research into how such composites achieve better properties than the constituents. To investigate this property amplification we have to understand the mechanical properties at the scale in which the separate constituents interact and not the average property of the composites. To understand the physics of this property amplification, we propose to develop novel experimental protocols to map mechanical behavior of constituents and interfaces at the meso-scale. The challenge encountered when investigating their mechanical properties is the lack of rigorous analysis techniques for information collected at that scale. One method that has been successfully applied to characterize mechanical properties of hard materials is nanoindentation. Current methods that are used for viscoelastic materials are usually applied after the material has experienced some significant deformation. This does not give us an accurate representation of the material properties of the undeformed sample. We propose to develop analysis protocols to extract mechanical properties from the load-displacement data generated from nanoindentation on soft materials in the initial viscoelastic segment. Once these protocols are developed they can then be applied to study interface properties of different composite material systems. This will be useful in eventually developing a tool that can quickly and efficiently characterize such materials at the meso-scale. We plan to use our protocols to study a range of composites such as polymers, polymer blends, nacre-like natural materials, and novel hybrid thin films with highly aligned microstructures that we have recently fabricated to mimic natural materials.