Modeling the Mechanical Behavior of P3HT/Fullerene Blends For Photovoltaic Applications

ABSTRACTOrganic solar cells, comprised of P3HT-fullerene blends, have the potential for photovoltaic energy applications. However, there is limited understanding of the mechanical behavior of these devices, and how this behavior can be tailored for optimal organic solar cell performance and device reliability. Therefore, a recently developed computational approach that is based on a constitutive representation of semi-crystalline polymers and fullerenes is used to identify the dominant morphological and microstructural characteristics that would affect the mechanical behavior of the active layer. The predictions indicate that stress and dislocation-density accumulation in interfacial regions and tie molecules play a significant role on the overall behavior.

High-Speed Biaxial Tissue Properties of the Human Cadaver Aorta

Traumatic rupture of the aorta (TRA) is one of the leading causes of mortality in automobile crashes. Finite element (FE) modeling, used in conjunction with laboratory experiments, has emerged as increasingly important tool to understand the mechanisms of TRA. Appropriate material modeling of the aorta is a key aspect of such efforts. The current study focuses on obtaining biaxial mechanical properties of aorta tissue at strain rates typically experienced during automotive crashes. Five descending thoracic aorta samples from human cadavers were harvested in a cruciate shape. The samples were subjected to equibiaxial stretch at a strain rate of 44 s−1 using a new biaxial tissue-testing device. Inertially compensated loads were measured. High-speed videography was used to track ink dots marked on the center of each sample to obtain strain. The aorta tissue exhibited anisotropic and nonlinear behavior. The tissue was stiffer in the circumferential direction with a modulus of 10.64 MPa compared to 7.94 MPa in longitudinal direction. The peak stresses along the circumferential and longitudinal directions were found to be 1.89 MPa and 1.76 MPa, respectively. The tissue behavior can be used to develop a better constitutive representation of the aorta, which can be incorporated into FE models of the aorta.