Biological materials such and blood vessels, muscles, tendons and ligaments have been known to exhibit non-linear mechanical behavior. These materials are viscoelastic, anisotropic and non-linear and they do not have a simple constitutive response to applied loading.

We probe the fundamental mechanical properties of biological tissues and apply physics and engineering principles to tackle cardiovascular issues such as aortic dissection and aneurysms. We use experimental techniques such as uni-axial and bi-axial tension tests for material characterization, peel testing for fracture property determination and torsional rheometry for viscoelastic property determination.

We additionally use implicit elastic constitutive equations to study the mechanical properties of soft tissues and to guide the development of more robust constitutive theory and experimental techniques.

**Propagation and Initiation of Aortic Dissectio****n.**

Heart disease is the leading cause of death in the United States. Within this category cardiovascular diseases is the most deadly. Aortic dissection has one of the highest mortality and morbidity rates among cardiovascular disease and despite numerous advances in modern preventive and surgical techniques little is understood about this disease. We seek to study the initiation and propagation of aortic dissection through experimental and theoretical mechanics techniques. We are developing mathematical theories for dissection propagation of intimal tears in addition to conducting many mechanical characterization experiments to determine the material properties of aortas.

**Relevant Publications**

**C.C.Benjamin**, Myneni, M., Muliana, A., & Rajagopal, K. R. (2019). Motion of a finite composite cylindrical annulus comprised of nonlinear elastic solids subject to periodic shear.*International Journal of Non-Linear Mechanics*.- Myneni,M., Rao,A.,Jiang,M.,Moreno,M.,Rajagopal,K.R.,
**Benjamin, C.C.**, Peeling energy of rupture for porcine thoracic aorta, (In preparation).

**Publications by Collaborators**

- Alagappan, P., Rajagopal, K. R., & Kannan, K. (2018). A damage initiation criterion for a class of viscoelastic solids.
*Proc. R. Soc. A*,*474*(2214), 20180064. - Alagappan, P., Rajagopal, K. R., & Kannan, K. (2017). Initiation of damage in a class of polymeric materials embedded with multiple localized regions of lower density.
*Mathematics and Mechanics of Solids*, 1081286517692392. - Freed, Alan D., and K. R. Rajagopal. “A promising approach for modeling biological fibers.”
*Acta Mechanica*227.6 (2016): 1609-1619. - Alagappan, P., Kannan, K., & Rajagopal, K. R. (2016). On a possible methodology for identifying the initiation of damage of a class of polymeric materials.
*Proc. R. Soc. A*,*472*(2192), 20160231. - Rajagopal, K., Bridges, C., & Rajagopal, K. R. (2007). Towards an understanding of the mechanics underlying aortic dissection.
*Biomechanics and modeling in mechanobiology*,*6*(5), 345-359.