Engineering topics

Chen, Weinong

Publications and source records attributed to Chen, Weinong.

10 records

DOE OSTI2023

In-Situ X-Ray Imaging High Strain Rate Compression of Laminate Al-Graphene Composite and Mechanical Property Characterization

Owing to the opaque nature of the laminated structures, traditional high-speed optical camera cannot be used to detect the dynamic process of sub-surface deformation. In this article, we report a study of using high speed X-ray imaging to study the high strain rate deformation in laminated Al structures. We used a Kolsky bar apparatus to apply dynamic compression and a high-speed synchrotron X-ray phase contrast imaging (PCI) setup to conduct the in situ X-ray imaging study. The in situ X-ray imaging captures the shock wave propagation in the laminated structures. After shock compression, we characterized the microstructures by using transmission electron microscopy (TEM), which demonstrates an increase of dislocation density. In conclusion, the micro-pillar compression tests show that the yield strength at 0.2% offset of laminated Al-graphene composite has a significant increase of 67%, from 30 to 50 MPa, compared to laminate Al after shock loading.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Resolving the Martensitic Transformation in Q&P Steels In-Situ at Dynamic Strain Rates Using Synchrotron X-ray Diffraction

Herein the dynamic deformation response of two quenching and partitioning (Q&P) steels was investigated using a high strain rate tension pressure bar and in-situ synchrotron radiography and diffraction. This allowed for concurrent measurements of the martensitic transformation, the elastic strains/stresses on the martensite and ferrite, and the bulk mechanical behavior. The steel with the greater fraction of ferrite exhibited greater ductility and lower strength, suggesting that dislocation slip in ferrite enhanced the deformability. Meanwhile, the kinetics of the martensitic transformation appeared similar for both steels, although the steel with a greater ferrite fraction retained more austenite in the neck after fracture.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Multiscale dynamic experiments on fiber-reinforced composites with damage assessment using high-speed synchrotron X-ray phase-contrast imaging

We report fiber-reinforced composites (FRCs) have been widely used as protection materials to replace heavier metals. However, predictive capabilities for the impact-induced failure of FRCs have not been well-developed. In this work, we introduced an integrated technique to visualize the dynamic failure of FRCs, with the modified Kolsky bar loading and the high-speed synchrotron X-ray phase-contrast imaging (PCI). We summarize our experimental studies across the FRCs’ structural levels by using this integrated technique, including single-fiber tensile experiments, fiber/matrix debonding experiments, and single-edge notched bending experiments on composite laminates. It is revealed that the high-speed synchrotron X-ray PCI technique possesses sufficient spatial resolution to identify the failure behavior of a single fiber in the 10-μm scale level, as well as temporal resolution to identify the time sequence of internal dynamic damage evolution. The technique can penetrate through the opaque composite sample and provide real-time visualization of small-scale damaging mechanisms such as the embedded fiber’s sliding in the matrix and the fiber’s transverse debonding with the matrix. At an expanding scale, the technique can identify the crack initiation and track the cracking behavior inside a single ply or between different plies of a composite laminate. High-speed visualization inside the material by this integrated technique provides critical deformation and failure information to develop physical understanding of the damage inside composites under impact.

47 OTHER INSTRUMENTATION↗

DOE OSTI2022

Dynamic fracture of glass fiber-reinforced ductile polymer matrix composites and loading rate effect

Here, the dynamic fracture of S-2 glass fiber-reinforced polymer matrix composites (FRPMCs) was investigated in this study. The matrix ductility was improved by a recently developed network topology modification technique via mixing partially reacted substructures (mPRS). The composite material was manufactured and characterized by micro-CT scanning and scanning electron microscopy (SEM). Dynamic single-edge notched bending (d-SENB) experiments were performed on the composites by using a modified split-Hopkinson pressure bar. Each specimen’s fracture process was visualized by ultrafast X-ray imaging. Such in-situ radiography enabled identifying the damage initiation below 50-micron scale and inspecting its propagation through the internal structures of opaque composites, thereby accurately quantifying the composites’ mechanical properties. Furthermore, the identical d-SENB experiments were designed and the digital image correlation (DIC) was employed to monitor the stress wave propagation on the composite specimens. The force and deflection measurements were modified and correlated to the physical damage processes. Besides, quasi-static SENB experiments were conducted to identify the loading rate effects on the composites’ fracture behaviors. The force and deflection history, bending stiffness, energy dissipation, and fracture toughness at different loading rates were quantified and compared. Finally, post-fracture analysis by micro-CT scanning and SEM provided physical observations on the variation of the fracture morphology by different loading rates.

42 ENGINEERING↗

DOE OSTI2021

High-speed synchrotron X-ray phase-contrast imaging for evaluating microscale damage mechanisms and tracking cracking behaviors inside cross-ply GFRCs

In this study, we integrated the high-speed synchrotron X-ray phase-contrast imaging (PCI) with a modified Kolsky compression bar loading platform to visualize the dynamic failure processes of cross-ply glass fiber reinforced composites (GFRCs). Four S-2 glass/SC-15 composite specimens were prepared, having similar thicknesses but different stacking sequences, namely as [0 12 /90 12 ], [90 12 /0 12 ], [0 8 /90 8 /0 8 ], and [90 8 /0 8 /90 8 ]. Three-dimensional synchrotron X-ray computed tomography and scanning electron microscopy (SEM) were employed to examine the microstructures and quantify the fiber volume fractions. Each specimen was notched and subjected to a dynamic three-point flexural loading. The onset of cracking close to the notch tip, crack propagation in 0° or 90° plies and their interface, crack opening, and ultimately failure of the specimen were captured by high-speed synchrotron X-ray PCI. Additional dynamic experiments were performed to determine the average time when the stress wave propagated through the specimen and correlate the X-ray images with the specimen's force-deflection response. Finally, the surface morphology of each specimen after the dynamic loading was imaged by SEM. Comparison between real-time X-ray images and post-fracture SEM images demonstrated the capability of the X-ray method to record damage evolution inside composites. Furthermore, the high spatial and temporal resolutions of the X-ray setup and edge enhancement by PCI enabled the identification of microscale damage features within 1 μs. Two damaging processes were identified, crack growth was quantified, and fracture toughness of the composites was evaluated. The method is deemed useful to reveal microscale damage mechanisms and track cracking behaviors inside cross-ply GFRCs under dynamic loading in real time.

42 ENGINEERING↗

DOE OSTI2021

Transverse impact by RCCs on S-glass and Kevlar® FRC strips

This study aims to isolate interactions between plies and tows and reveal fundamental physics involved in transverse impact on fiber-reinforced composite (FRC) structures. Composite strips were sectioned from large panels and characterized by optical photography, three-dimensional synchrotron X-ray computed tomography, and scanning electron microscopy (SEM). Each strip was impacted perpendicularly by a right circular cylinder (RCC) projectile at a velocity ranging from ~ 150 to 600 m/s. The global strip behavior, as well as localized deformation and failure of the strip near the projectile corner, were both captured by high-speed optical imaging. S-Glass FRC strips were observed to fail in tension ahead of the RCC projectiles’ flat surfaces while Kevlar® FRC strips fractured at the projectile corners. The concept of critical velocity region previously used for impact on yarns was introduced to define different failure modes of each composite strip type. The strip damage extent was found to increase with the impact velocity and reach the maximum at the upper limit of the critical velocity region. Above the critical velocity region, the damage extent decreased with impact velocity. Wave propagations and load histories in the composite strips during impact were quantified and compared with Smith’s theory. Finally, critical velocities of single fibers, yarns, and composite strips and ballistic limits of single-ply and multi-ply composite panels were compared to provide insight into the design of impact-resistant fabrics and composites.

42 ENGINEERING↗

DOE OSTI2020

Real-time damage characterization for GFRCs using high-speed synchrotron X-ray phase contrast imaging

Here, we report the application of high-speed synchrotron X-ray phase contrast imaging (PCI) in real-time damage characterization for glass fiber reinforced composites (GFRCs) subjected to dynamic loading. Dynamic single-edge notched bending (DSENB) experiments on pre-notched S-2 GFRCs were performed on a modified Kolsky compression bar. During loading, the synchrotron X-ray beam penetrated through the composite specimen from the side to detect damage evolution inside the material. Entire dynamic events were recorded by a high-speed camera as image sequences.0° and 90° unidirectional and cross-ply composites were investigated. An optical imaging technique was also employed to capture similar dynamic events in comparison with the radiographic imaging. It is demonstrated that high-speed X-ray PCI had sufficient phase contrast to characterize a crack initiation at a 20-μm spatial resolution within 920 ns and track the crack geometry during propagation, thereby providing reliable data to quantify the dynamic damage resistance of GFRCs. Furthermore, being capable of recognizing microscopic damage-related features at a sub-10-μm resolution, high-speed X-ray PCI provided fundamental material failure mechanisms to reveal the essential of macroscale structural failure of composites. It can also track the damage evolution inside and between individual plies of laminated composites. However, current high-speed X-ray PCI technique only supports in-situ observation and the high timing and spatial resolutions are limited within a field of view of ~2.5 mm in square, preventing its application in the three-dimensional and larger-area damage detection for GFRC structures.

42 ENGINEERING↗

DOE OSTI2020

A method for characterization of multiple dynamic constitutive parameters of FRCs

We propose a method to measure multiple dynamic material constitutive parameters of unidirectional fiber reinforced composites (FRCs) in a single experiment. Dynamic short-beam shear (DSBS) experiments were performed on a modified Kolsky compression bar, with integration of high-speed imaging and digital image correlation (DIC). The unidirectional FRCs investigated were S-2 glass fiber reinforced matrix of TGDDM-Jeffamine® D230 with monoamine functionalized partially reacted substructures (mPRS) and commercially available SC-15. Analytical solutions of normal and shear strains of a composite beam were derived based on Timoshenko beam theory, assuming material to be transversely isotropic and have different moduli in tension and compression in each principle material orientation. Tensile and compressive moduli were inversely computed through monitoring normal strain slope when specimen was constantly loaded at a speed of ~7.3 m/s within a small deflection. Non-linear shear stress-strain behavior of the composite was described via Ramberg–Osgood equation. Finite element (FE) analysis was conducted in ABAQUS, simultaneously defining via user subroutine UMAT the transverse isotropy of material, bi-modulus constitutive model, and non-linear shear stress-strain relation. The method proposed in this work was validated by comparing strain distributions computed by FE model and DIC measurements. Comparing with traditional dynamic tensile, compressive, and shear experiments on FRCs, this method significantly simplifies the specimen preparation and design of complicated gripping fixtures for multiple experiments. Here, systematic errors resulting from variations of specimen geometry and dimension, loading direction, and instrumentation are reduced, thereby providing compatible data for numerical studies on impact behavior of composites.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Real-time visualization of impact damage in monolithic silicon carbide and fibrous silicon carbide ceramic composite

Impact resistance from foreign debris is a critical requirement for brittle ceramic and ceramic composite materials intended for use in the hot-section of gas turbine engines. A design to mitigate against such impact failures necessitates a detailed understanding of the driving failure mechanisms. The present study introduces a unique time-resolved experimental method which advances the latter effort. Specifically, a pulsed synchrotron X-ray source, in phase contrast imaging (PCI) configuration, is used as a medium, to visually characterize the evolution of damage inside the target materials during impact. As a proof of concept, two types of ceramic materials were tested: monolithic silicon carbide and fibrous silicon carbide composite. Impact was performed using a light-gas gun and 1.5 mm diameter spheres of partially stabilized zirconia (PSZ) and silicon nitride (Si 3 N 4 ). The retrieved dynamic X-ray image sequences provided clear outlines of the damage features. In the case of the monolithic ceramic, the impact by a PSZ projectile initially produced a cone crack and complete failure resulted by extension of a median crack. By contrast, the fibrous composite deformed readily prior to cone crack formation. Nearly identical damage features were observed in the monolith for the Si 3 N 4 projectile, with the exception of the added vertical tensile crack. For this same projectile, the fibrous ceramic showed very limited surface deformation and enhanced cone cracking and kinking of laminates along the crack path. The latter response is attributed to the change in projectile properties. Some of the target materials were recovered, and post-mortem analysis via scanning electron microscopy (SEM) showed correlation with observed X-ray damage profiles. Furthermore, simple Hertzian contact was used to estimate damage for the elastic portion of impact. This approach was found to yield a reasonable match with experimental results for the surface displacement near the contact interface.

36 MATERIALS SCIENCE↗

NASA NTRS2007

Sub-diffraction limit resolution in microscopy

A method and apparatus for visualizing sub-micron size particles employs a polarizing microscope wherein a focused beam of polarized light is projected onto a target, and a portion of the illuminating light is blocked from reaching the specimen, whereby to produce a shadow region, and projecting diffracted light from the target onto the shadow region.

Cheng, Ming↗