@article{zhang_pai_turicek_snyder_patrick_soghrati_2024, title={An integrated microstructure reconstruction and meshing framework for finite element modeling of woven fiber-composites}, volume={422}, ISSN={["1879-2138"]}, url={https://doi.org/10.1016/j.cma.2024.116797}, DOI={10.1016/j.cma.2024.116797}, abstractNote={Critical to finite element (FE) analysis of fiber-reinforced composites is accurately reproducing microstructural features via high-quality meshes such that the material heterogeneity and anisotropy are properly captured. Here we present an integrated computational framework for generating realistic FE models of woven composites with high fiber volume fractions (>50%). This framework relies on a virtual microstructure reconstruction algorithm that first generates a geometric model of loosely-woven yarns (i.e., bundles of fibers), followed by performing an FE compaction simulation to create the final textile composite microstructure. A non-iterative meshing algorithm, i.e., conforming to interface structured adaptive mesh refinement (CISAMR), has been adapted to automatically transform synthesized microstructures into conforming FE meshes. CISAMR can handle challenging geometrical features such as thin resin interstices and yarn interpenetrations (an artifact of the FE compaction) without the need to reprocess the digital geometry before mesh generation. We show that the homogenized elastic moduli obtained from FE simulations of an 8-harness satin woven composite laminate agree well with experimental measurements (within 3%), thereby validating the accuracy of the framework. We also present several other mechanical analysis examples, including a nonlinear damage simulation, that further demonstrate the ability of this framework to construct high-fidelity FE models of intricate woven composites with varying 2D and 3D woven architectures.}, journal={COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING}, author={Zhang, Pengfei and Pai, Salil and Turicek, Jack S. and Snyder, Alexander D. and Patrick, Jason F. and Soghrati, Soheil}, year={2024}, month={Mar} }
 @article{snyder_turicek_diesendruck_varley_patrick_2024, title={Unraveling chemical and rheological mechanisms of self-healing with EMAA thermoplastics in fiber-reinforced epoxy composites}, volume={185}, ISSN={["1878-5840"]}, url={https://doi.org/10.1016/j.compositesa.2024.108271}, DOI={10.1016/j.compositesa.2024.108271}, abstractNote={Interlaminar delamination is a prevalent and insidious damage mode limiting the mechanical integrity and lifetime of fiber-reinforced composites. Conventional resolution involves over-design, laborious inspection, and repair/replacement at cost to the economy and environment. Self-healing via in situ thermal remending of thermoplastic interlayers offers a promising solution. However, better understanding of the healing agent and related mechanisms is necessary to tailor healing performance. Here, we compare non-neutralized (copolymer) and metallic-ion neutralized (ionomer) poly(ethylene-co-methacrylic acid) (EMAA) thermoplastics for healing interlaminar fracture. We reveal (i) how EMAA chemistry affects the interfacial reactions driving healing and (ii) the influence of molten viscosity on repair efficiency. At fixed viscosity, higher methacrylic acid content, chain mobility, and lower neutralization positively influence healing, where lower melt viscosity at fixed temperature improves delamination recovery. Thus, this study deepens scientific understanding of key variables for healing interlaminar fracture with EMAA, providing new insight for the design of multifunctional composites.}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Snyder, Alexander D. and Turicek, Jack S. and Diesendruck, Charles E. and Varley, Russell J. and Patrick, Jason F.}, year={2024}, month={Oct} }
 @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{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={AbstractMicrowave 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 ZrB2/ZrO2. The fabricated ceramic composites have a crystallized t-ZrO2 interface between ZrB2 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 ZrB2/ZrO2. Crystallized t-ZrO2 serve as nanoscale dielectric interfaces between ZrB2 and SiOC, which are favorable for EM wave introduction for enhancing polarization loss and absorption. Existence of t-ZrO2 interface also changes the temperature-dependent DC conductivity of ZrB2/SiOC ceramic composites when compared to that of ZrB2 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{turicek_snyder_nakshatrala_patrick_2023, title={Topological effects of 3D-printed copolymer interlayers on toughening and in situ self-healing in laminated fiber-composites}, volume={240}, ISSN={["1879-1050"]}, url={https://doi.org/10.1016/j.compscitech.2023.110073}, DOI={10.1016/j.compscitech.2023.110073}, abstractNote={Interlaminar delamination in fiber-reinforced composites limits structural capacity and service life. Delaminations, which occur subsurface and can lead to catastrophic failures, are hard to detect and repair. Contrasting traditional mitigation strategies (e.g., inspection, over-design), proactive toughening and responsive self-healing of damaged interfaces offer practical, cost-effective solutions. Our recently developed strategy to address interlaminar damage—3D-printed thermoplastic interlayers and structurally integrated heaters—has been shown to achieve composite toughening and in situ self-healing via thermal remending, abetting repeated repair and improved delamination resistance. Here, we leverage this latest thermal remending strategy to investigate the effects of 3D-printed pattern topology on damage resistance and self-healing response. The chief attributes are: (i) realizing up to 450% increase in mode-I fracture resistance, (ii) restoring up to 100% of the increased fracture resistance for ten consecutive healing cycles, and (iii) achieving in situ self-healing below the thermoset-matrix glass transition temperature, thereby preserving structural integrity during repair. The proposed damage mitigation strategy fosters structural reliability, reduces failure risk, and increases service lifetime—three essential attributes in meeting the multifaceted demands of modern composite infrastructure.}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Turicek, Jack S. and Snyder, Alexander D. and Nakshatrala, Kalyana B. and Patrick, Jason F.}, year={2023}, month={Jul} }
 @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"]}, url={https://doi.org/10.1016/j.compscitech.2022.109850}, DOI={10.1016/j.compscitech.2022.109850}, abstractNote={Structural health monitoring (SHM) of safety-critical composite components is essential to ensure mechanical stasis and detect local damage before it can produce global failure. SHM technologies must also adapt to ever-evolving materials and geometries, but traditional piezoresistive strain sensors lack the ability for end-user customization and modifications throughout service-life. Additive manufacturing via fused filament fabrication (FFF) provides a practical pathway to overcome such sensor shortcomings. However, the electrical conductivity of conventional polymer feedstock is not sufficient for accurate strain measurements without compromise to melt viscosity and thus printability. Here we report the development of a new 3D-printable and electrically responsive nanocomposite by melt-mixing poly(ethylene-co-methacrylic acid) (EMAA) with multi-walled carbon nanotubes (MWCNT). Bulk electrical conductivity of 43.9 S m−1 is achieved at only 5 wt% loading – higher than comparable materials – where the nano-dispersion heterogeneity of MWCNT in EMAA is linked to the favorable conductivity while retaining molten flowability. FFF is employed to print thin (150μm) serpentine strain sensors onto the surface of a glass fiber-reinforced polymer composite, which exhibit strong adhesion and accurate piezoresistive sensing under cyclic flexural loading. Twenty consecutive cycles with converged sensor readings (i.e., < 1% variation in measured resistance) demonstrates reliable performance across a relevant service strain range (0.4 – 0.8 %) for such fiber-composites. This rapid fabrication and transferable sensing strategy, suitable for new and existing structures, thus provides a crosscutting SHM solution.}, 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{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"]}, url={http://dx.doi.org/10.1038/s41467-022-33936-z}, DOI={10.1038/s41467-022-33936-z}, abstractNote={AbstractNatural 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}, publisher={Springer Science and Business Media LLC}, author={Snyder, Alexander D. and Phillips, Zachary J. and Turicek, Jack S. and Diesendruck, Charles E. and Nakshatrala, Kalyana B. and Patrick, Jason F.}, editor={Turicek, Jack S.Editor}, 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} }