@article{snyder_salehinia_2023, title={Effect of Pore Defects on Uniaxial Mechanical Properties of Bulk Hexagonal Hydroxyapatite: A Molecular Dynamics Study}, volume={24}, ISSN={["1422-0067"]}, DOI={10.3390/ijms24021535}, abstractNote={Hydroxyapatite (HAP) is a calcium apatite bioceramic used in various naturally-derived and synthetic forms for bone repair and regeneration. While useful for the regrowth of osseus tissue, the poor load-bearing capacity of this material relative to other biomaterials is worsened by the propensity for pore formation during the synthetic processing of scaffolds, blocks, and granules. Here we use molecular dynamics (MD) simulations to improve the current understanding of the defect-altered uniaxial mechanical response in hexagonal HAP single crystals relative to defect-free structures. The inclusion of a central spherical pore within a repeated lattice was found to reduce both the failure stress and failure strain in uniaxial tension and compression, with up to a 30% reduction in maximum stress at the point of failure compared to a perfect crystalline structure observed when a 30 Å diameter pore was included. The Z axis ([0 0 0 1] crystalline direction) was found to be the least susceptible to pore defects in tension but the most sensitive to pore inclusion in compression. The deformation mechanisms are discussed to explain the observed mechanical responses, for which charge imbalances and geometric stress concentration factor effects caused by pore inclusion play a significant role.}, number={2}, journal={INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES}, author={Snyder, Alexander D. and Salehinia, Iman}, year={2023}, month={Jan} }
 @article{hia_snyder_turicek_blanc_patrick_therriault_2023, title={Electrically conductive and 3D-printable copolymer/MWCNT nanocomposites for strain sensing}, volume={232}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2022.109850}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Hia, Iee Lee and Snyder, Alexander D. and Turicek, Jack S. and Blanc, Fernanda and Patrick, Jason F. and Therriault, Daniel}, year={2023}, month={Feb} }
 @article{jia_yang_xu_snyder_patrick_kumar_zhang_xu_2023, title={Polymer-derived SiOC reinforced with core-shell nanophase structure of ZrB2/ZrO2 for excellent and stable high-temperature microwave absorption (up to 900 degrees C)}, volume={13}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-023-27541-3}, abstractNote={Abstract Microwave absorbing materials for high-temperature harsh environments are highly desirable for aerodynamically heated parts and engine combustion induced hot spots of aircrafts. This study reports ceramic composites with excellent and stable high-temperature microwave absorption in air, which are made of polymer-derived SiOC reinforced with core–shell nanophase structure of ZrB 2 /ZrO 2 . The fabricated ceramic composites have a crystallized t-ZrO 2 interface between ZrB 2 and SiOC domains. The ceramic composites exhibit stable dielectric properties, which are relatively insensitive to temperature change from room temperature to 900 °C. The return loss exceeds − 10 dB, especially between 28 and 40 GHz, at the elevated temperatures. The stable high-temperature electromagnetic (EM) absorption properties are attributed to the stable dielectric and electrical properties induced by the core–shell nanophase structure of ZrB 2 /ZrO 2 . Crystallized t-ZrO 2 serve as nanoscale dielectric interfaces between ZrB 2 and SiOC, which are favorable for EM wave introduction for enhancing polarization loss and absorption. Existence of t-ZrO 2 interface also changes the temperature-dependent DC conductivity of ZrB 2 /SiOC ceramic composites when compared to that of ZrB 2 and SiOC alone. Experimental results from thermomechanical, jet flow, thermal shock, and water vapor tests demonstrate that the developed ceramic composites have high stability in harsh environments, and can be used as high-temperature wide-band microwave absorbing structural materials.}, number={1}, journal={SCIENTIFIC REPORTS}, author={Jia, Yujun and Yang, Ni and Xu, Shaofan and Snyder, Alexander D. D. and Patrick, Jason F. F. and Kumar, Rajan and Zhang, Dajie and Xu, Chengying}, year={2023}, month={Jan} }
 @article{snyder_phillips_turicek_diesendruck_nakshatrala_patrick_2022, title={Prolonged in situ self-healing in structural composites via thermo-reversible entanglement}, volume={13}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-022-33936-z}, abstractNote={Abstract Natural processes continuously degrade a material’s performance throughout its life cycle. An emerging class of synthetic self-healing polymers and composites possess property-retaining functions with the promise of longer lifetimes. But sustained in-service repair of structural fiber-reinforced composites remains unfulfilled due to material heterogeneity and thermodynamic barriers in commonly cross-linked polymer-matrix constituents. Overcoming these inherent challenges for mechanical self-recovery is vital to extend in-service operation and attain widespread adoption of such bioinspired structural materials. Here we transcend existing obstacles and report a fiber-composite capable of minute-scale and prolonged in situ healing — 100 cycles: an order of magnitude higher than prior studies. By 3D printing a mendable thermoplastic onto woven glass/carbon fiber reinforcement and co-laminating with electrically resistive heater interlayers, we achieve in situ thermal remending of internal delamination via dynamic bond re-association. Full fracture recovery occurs below the glass-transition temperature of the thermoset epoxy-matrix composite, thus preserving stiffness during and after repair. A discovery of chemically driven improvement in thermal remending of glass- over carbon-fiber composites is also revealed. The marked lifetime extension offered by this self-healing strategy mitigates costly maintenance, facilitates repair of difficult-to-access structures (e.g., wind-turbine blades), and reduces part replacement, thereby benefiting economy and environment.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Snyder, Alexander D. and Phillips, Zachary J. and Turicek, Jack S. and Diesendruck, Charles E. and Nakshatrala, Kalyana B. and Patrick, Jason F.}, year={2022}, month={Oct} }
 @article{snyder_salehinia_2020, title={Study of nanoscale deformation mechanisms in bulk hexagonal hydroxyapatite under uniaxial loading using molecular dynamics}, volume={110}, ISSN={["1878-0180"]}, DOI={10.1016/j.jmbbm.2020.103894}, abstractNote={Hydroxyapatite (HAP) is a natural bioceramic which is currently used in scaffolds and coatings for the regrowth of osseous tissue but offers poor load-bearing capacity compared to other biomaterials. The deformation mechanisms responsible for the mechanical behavior of HAP are not well understood, although the advent of multiscale modeling offers the promise of improvements in many materials through computational materials science. This work utilizes molecular dynamics to study the nanoscale deformation mechanisms of HAP in uniaxial tension and compression. It was found that deformation mechanisms vary with loading direction in tension and compression leading to significant compression/tension asymmetry and crystal anisotropy. Bond orientation and geometry relative to the loading direction was found to be an indicator of whether a specific bond was involved in the deformation of HAP in each loading case. Tensile failure mechanisms were attributed to stretching and failure in loading case-specific ionic bond groups. The compressive failure mechanisms were attributed to coulombic repulsion in each case, although loading case-specific bond group rotation and displacement were found to affect specific failure modes. The elastic modulus was the highest for both tension and compression along the Z direction (i.e. normal to the basal plane), followed by Y and X.}, journal={JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS}, author={Snyder, Alexander D. and Salehinia, Iman}, year={2020}, month={Oct} }