Search

This study aims to predict the compression behavior of ultra-high molecular weight polyethylene (UHMWPE) at various temperatures (25, 40, and 55[degrees]C) and strain rates (~[10.sup.-4]/s and ~[10.sup.-2]/s) using a single set of three-network (TN) viscoplastic model parameters. The TN model is made up of three parallel networks: networks A and B use nonlinear springs and dashpots to control the responses of the crystalline phase and confined amorphous phases, respectively, while network C captures the macromolecular amorphous networks using a single nonlinear spring. A single set of TN model parameters captures the yield and post-yield hardening responses of the stress-strain curves at experimental temperatures and strain rates. When these TN model calibrated parameters are used as material property in a commercial finite element tool to simulate UHMWPE compression, the predicted and simulated results match well, showing the model's fidelity. Additionally, the model predicts experiments conducted at 40 and 70[degrees]C with loading rates of ~[10.sup.-3]/s and ~[10.sup.-2]/s, respectively. The study also correlates the deformations of UHMWPE's crystalline structure and macromolecular amorphous networks with its global stress versus strain response by extracting stresses from individual networks of the TN model at different strain rates and temperatures. Highlights * UHMWPE's mechanical behavior predicted by a single set of TN model parameters * TN model predicts mechanical response at various strain rates and temperatures. * TN model explains microstructural crystalline and amorphous phase deformations. KEYWORDS compression properties, numerical simulations, three-network (TN) viscoplastic model, UHMWPE, 1 | INTRODUCTION Ultra-high molecular weight polyethylene (UHMWPE) is one such polymer, which demonstrates an encouraging potential as an impact, chemical, and wear-resistant material. (1) UHMWPE has found diverse applications, [...]

Epoxy resin controls the mechanical behavior of fiber-reinforced epoxy composites, which are extensively deployed in the aerospace and automotive industries. For numerical simulations to accurately predict the mechanical deformations of these components under multi-axial loading, matrix characteristics must account for tension, compression, and shear loads at varying strain rates. The existing literature lacks a comprehensive approach to predicting the experimental outcomes across all three loading conditions in a polymer matrix simultaneously using a unified set of viscoelastic or viscoplastic model parameters. In this study, the Three-Network (TN) viscoplastic model was successfully applied to concurrently predict the tension, compression, and shear experimental data of an epoxy resin, published by Littel et al. (Journal of Aerospace Engg., 2008). The elastic modulus, strain softening-hardening response after yield for tension-compression deformation, and post-yield stress saturation under shear deformation are all accurately predicted by the model at different rates of loading conditions. The predicted and simulated results matched well when the TN viscoplastic model predicted parameters were employed as material property in Abaqus (a commercial finite element software) to simulate the deformation modes. This integrated approach highlights the potential of the TN model in enabling precise predictions for epoxy-based composites, which is crucial for optimizing their performance and reliability in aerospace engineering. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the compression characteristics of the 3D-printed polylactic acid (PLA) samples at temperatures below the glass transition temperature (Tg) with varying strain rates and develop a thermo-mechanical viscoplastic constitutive model to predict the finite strain compression response using a single set of material parameters. Also, the micro-mechanical damage processes are linked to the global stress–strain response at varied strain rates and temperatures through scanning electron microscopy (SEM). Design/methodology/approach: Tg of PLA was determined using a dynamic mechanical analyzer. Compression experiments were conducted at strain rates of 2 × 10–3/s and 2 × 10–2/s at 25°C, 40°C and 50°C. The failure mechanisms were examined using SEM. A finite strain thermo-mechanical viscoplastic constitutive model was developed to analyze the deformations at the considered strain rates and temperatures. Findings: Tg of PLA was determined as 55°C. While the yield and post-yield stresses drop with increasing temperature, their trend reverses with an increased strain rate. SEM imaging indicated plasticizing effects at higher temperatures, while filament fragmentation and twisting at higher strain rates were identified as the dominant failure mechanisms. Using a non-linear regression analysis to predict the experimental data, an overall R2 value of 0.98 was achieved between experimental and model prediction, implying the robustness of the model's calibration. Originality/value: In this study, a viscoplastic constitutive model was developed that considers the combined effect of temperature and strain rate for FDM-printed PLA experiencing extensive compression. Using appropriate temperature-dependent modulus and flow rate properties, a single set of model parameters predicted the rise in the gap between yield stress and degree of softening as strain rates and temperatures increased. [ABSTRACT FROM AUTHOR]

This study aims to predict the compression behavior of ultra‐high molecular weight polyethylene (UHMWPE) at various temperatures (25, 40, and 55°C) and strain rates (~10−4/s and ~10−2/s) using a single set of three‐network (TN) viscoplastic model parameters. The TN model is made up of three parallel networks: networks A and B use nonlinear springs and dashpots to control the responses of the crystalline phase and confined amorphous phases, respectively, while network C captures the macromolecular amorphous networks using a single nonlinear spring. A single set of TN model parameters captures the yield and post‐yield hardening responses of the stress–strain curves at experimental temperatures and strain rates. When these TN model calibrated parameters are used as material property in a commercial finite element tool to simulate UHMWPE compression, the predicted and simulated results match well, showing the model's fidelity. Additionally, the model predicts experiments conducted at 40 and 70°C with loading rates of ~10−3/s and ~10−2/s, respectively. The study also correlates the deformations of UHMWPE's crystalline structure and macromolecular amorphous networks with its global stress versus strain response by extracting stresses from individual networks of the TN model at different strain rates and temperatures. Highlights: UHMWPE's mechanical behavior predicted by a single set of TN model parametersTN model predicts mechanical response at various strain rates and temperatures.TN model explains microstructural crystalline and amorphous phase deformations. [ABSTRACT FROM AUTHOR]

Short or nanofillers‐reinforced composites increase the thermo‐mechanical characteristics of additive manufacturing (AM) base materials. Effective outputs were regulated via parametric optimisation and custom production. One of the most used AM method, Vat photopolymerization (VPP), creates complex and geometrically precise photopolymer parts. This study prepares photopolymer composite (PPC) samples with 2.0, 4.0, 6.0, and 8.0 volume percentages of short glass fiber (SGF) using an inter‐stage stirring method in DLP‐based VPP process. An adequate curing time and formable layer thickness were evaluated for the printability performance of SGF‐photopolymer composite. The 4.0% PPC‐sample showed a 20% higher compressive yield strength than pure photopolymer and other volume fractions. The consequences of increased strength values were assessed by the effect of stirring method and the fractography analysis of PPC specimen. The investigation additionally encompassed numerical simulations that employed an innovative technique for constructing and simulating three‐dimensional representative volume elements (RVEs). The RVEs were designed to replicate the experimental outcomes by randomly situating and orienting fillers within the matrix. The study employs the calibrated Three Network (TN) viscoplastic constitutive material model as the matrix property, and the simulation results demonstrate a margin of error of 5%–10% when compared to the experimental findings. Highlights: Layer‐wise availability of SGFs through inter‐stage stirring methodThe exposure time and layer thickness were determined by Jacob's working curveConcept of RVE is used to combine individual SGF layers into a single layerSEM showed that increasing SGF layer resists cracking better than neat matrixExperimental data and numerical simulations are in good agreement [ABSTRACT FROM AUTHOR]

Highlights This study aims to improve the compressive strength of epoxy at operating temperatures below the glass transition temperature by introducing micron‐sized spherical and milled glass fillers at varying volume fractions. Test specimens were prepared by mixing spherical and milled fillers up to 20% and 15% volume fractions. The room temperature (27°C) results showed that 15% and 10% volume fractions of spherical and milled filler‐reinforced epoxy composites, respectively, exhibited the highest stress‐bearing ability among their respective filler volume fractions and hence were further tested at 45°C and 60°C. 15% spherical and 10% milled fillers enhanced epoxy's yield strength from 103 MPa to 111 MPa and 123 MPa at 27°C and from 67 MPa to 73 MPa and 80 MPa at 60°C. Scanning electron microscopic imaging revealed matrix cracking and filler breakage as the primary failure mechanisms at ambient temperature, while matrix softening at 60°C caused filler‐matrix debonding to dominate. The Three‐Network viscoplastic model was used as matrix property in ABAQUS to simulate the representative volume elements reinforced with milled and spherical fillers at mentioned temperatures. The modulus, yield, and strain softening stresses for both filler‐reinforced epoxy composites are well predicted by the simulations. Simulations revealed that milled fibers endure higher compressive stress than spherical particles at the given temperatures, although matrix stress remains almost the same. Milled fiber epoxy composites exhibit higher yield strength than spherical ones. 10% milled fiber endures the highest strength among all the fillers used. Matrix and filler breakages are witnessed at ambient temperature. Filler‐matrix debonding dominates at elevated temperature. Three‐Network model captures well the milled and spherical epoxy composite's experimental data. [ABSTRACT FROM AUTHOR]