Research Projects

Residual stresses—the internal stresses that persist in materials without external loads—are crucial in determining the mechanical responses of biological tissues and engineered soft materials. They influence various mechanical phenomena, including wrinkling, bulging, and buckling, and are increasingly seen as indicators of disease progression in organs that undergo growth or remodeling. Accurate measurements of these stresses may help detect diseases such as arterial aneurysms, diabetes, and cancers at various stages. We plan to demonstrate this through the use structures built with biomimetic materials. However, measuring residual stresses is challenging, particularly in amorphous, soft, anisotropic, or viscoelastic materials, where traditional methods fall short. This proposal aims to address this challenge by developing a cost effective, mechanics-based approach for non-destructive measurement of residual stresses in soft materials. The approach will utilize the exact models of residually stressed soft materials recently developed by the investigators. Our method will integrate theoretical modeling and both static and shear-wave elastographic experiments, along with a finite element-like analysis of the results to accurately measure residual stresses. We will conduct measurements on biomimetic polymers. The central hypothesis is that the residual stress field can be accurately captured by analyzing the response of residually stressed materials in static and shear wave elastographic tests, aided by numerical inverse analysis. The developed models will be further implemented to investigate residual stress-induced patterns creation in biological materials (including wrinkling, folding, creasing, etc.). The project has five key objectives: 1. Develop constitutive models for soft materials that consider residual stress, elasticity, viscoelasticity, and anisotropy. 2. Use inverse methods to accurately measure residual stress from static responses and shear wave propagation in biomimetic polymers. For certain models unique inversion may not be possible. However this gives an opportunity to investigate the stability of the residually stressed reference state and to study instabilities in these materials. 3. Fabricate and characterize biomimetic polymers with tunable stiffness, anisotropy, and residual stress states similar to those found in biological systems. 4. Conduct experiments to measure residual stresses in healthy or diseased biomimetic structures, demonstrating the role of residual stress measurement in disease detection. 5. Employing the developed models to investigate instability patterns, including wrinkling wavelengths, bulging profiles, and bifurcation points through numerical computations. This project will provide accurate non-destructive tools for detecting residual stress in soft materials—a presently unmet need in biomechanics, materials science, and biomedical engineering. It will have significant implications for early diagnosis of diseases (e.g., aneurysms, tumors) and in the design of smart materials and soft robotic systems where tuning residual stress is vital. From a broader perspective, the work proposes to integrate continuum models with applied material science and is of significant biomedical relevance. It will likely enhance understanding of stress-driven pattern formation in biological systems and offer practical pathways for measurable diagnostics.