arXiv subjects

Saujatya Mandal

Publications and source records attributed to Saujatya Mandal.

3 recordsLinked to original sources

arXiv2026

Convective Preheating Enhances Front Propagation in DCPD Frontal Polymerization

Frontal polymerization (FP) enables rapid curing of thermosets via a self-sustaining thermal wave, but its propagation mechanism can shift dramatically depending on processing conditions. In this study, we investigate the effect of trigger direction and monomer viscosity - controlled via hold time - on the front velocity in frontal ring-opening metathesis polymerization (FROMP) of dicyclopentadiene (DCPD). Our experiments reveal that at low viscosities, bottom-triggered FP fronts propagate significantly faster, ~50% faster front speed compared to top-triggered ones, driven by buoyancy-enhanced convection that preheats the unreacted monomer ahead of the front, that can have important implications for manufacturing applications. However, with increasing hold time, the monomer viscosity rises steeply, suppressing convection and causing the front velocity for top and bottom triggering to converge. This behavior reflects a convection-to-conduction (thermal-diffusion) transition in heat transport during FP. Complementary simulations incorporating buoyancy-driven advection reproduce the observed trends and highlight the importance of fluid flow in front dynamics. These results provide new insight into the coupled thermo-fluid-chemical mechanisms in FP offer strategies to tailor front behavior through viscosity and initiation geometry.

cond-mat.soft↗

arXiv2025

Twist-Free Enhancement of Strength and Modulus in Electrospun Yarns via Liquid-Assisted Capillary Densification

Electrospun yarns often fall short of the strength and stiffness of their constituent nanofibers because of loose packing and inter-fiber slip. We report a simple, twist-free route to close this gap by liquid-assisted rolling: yarns are briefly wetted (water or ethanol) and subjected to gentle rolling action (mechanical strokes perpendicular and parallel to the yarn axis), then dried under controlled conditions so that meniscus forces compact the assembly into tightly bound bundles. The treatment yields large gains in tensile strength and modulus, and as yarn diameter decreases the properties of liquid-treated yarns approach single-fiber limits, indicating more efficient load transfer. Dry-rolling controls produce negligible changes compared to as-spun yarns, confirming that capillarity-driven consolidation, rather than mechanical pressing, dominates the improvement. Water consistently outperforms ethanol, reflecting its larger elastocapillary driving term gamma*(1 + cos theta) on PAN and thus stronger capillary compaction; a short post-treatment anneal near Tg further increases stiffness with a corresponding reduction in ductility. To rationalize these trends, we quantify microstructure via SEM-derived alignment and packing density and show that these complementary descriptors jointly explain variability in mechanical response. A compact constitutive framework, grounded in distributed fiber recruitment and adhesion/frictional contact, captures the observed strengthening-ductility trade-off across processing routes. The results establish capillarity-driven consolidation as a scalable pathway to engineer processing-structure-property relationships in hierarchical polymer fiber assemblies and provide practical guidance for upgrading electrospun yarns, alone or as precursors to twisted and composite architectures.

cond-mat.soft↗

arXiv2025

Texture- and Stress-Dependent Electromechanical Response in Ferroelectric PZT: Insights from a Micromechanical Model

The electromechanical response of PbZr0.52Ti0.48O3 (PZT) near the morphotropic phase boundary (MPB) is strongly influenced by crystallographic texture and residual stress, both of which affect domain switching behavior. While these effects are critical for optimizing sensors, actuators, and MEMS devices, their combined influence remains poorly understood. We present a computational micromechanical model that captures texture- and stress-dependent polarization switching in MPB PZT. The framework incorporates both tetragonal and rhombohedral domain switching, along with interphase transformations, enabling accurate simulation of nonlinear electromechanical behavior. The model reproduces key experimental trends, including enhanced piezoelectric response in (001)-textured ceramics, and degradation under high in-plane stress. The implementation, provided as open-source MATLAB code, offers an accessible platform for experimentalists and materials designers to explore and interpret electromechanical behavior. By linking microstructural orientation and stress state to macroscopic response, this work provides a practical tool for understanding and designing next-generation piezoelectric materials.

cond-mat.mtrl-sci↗