Punch shear damage of unidirectional (UD) composite is an important damage mode during the penetration and perforation of fiber-reinforced composites. A rate dependent progressive composite continuum damage model MAT1...
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(纸本)9781510872073
Punch shear damage of unidirectional (UD) composite is an important damage mode during the penetration and perforation of fiber-reinforced composites. A rate dependent progressive composite continuum damage model MAT162 in LS-Dyna® requires the punch shear strength and progressive damage softening parameters as input. A micro punch shear experimental test method has been developed for UD composite at sub-millimeter length scale for determining the punch shear properties and parameters. S Glass/DER353 epoxy UD composite ribbon specimens have been fabricated using the VARTM process. The samples have an nominal cross-sectional dimensions of 1000 × 57~70 , with about six (6) through-thickness fibers. The UD ribbon is adhesively bonded onto the specimen holder and a transverse load is applied across the width of the sample. Localized transverse shear loading is created within a narrow gap (153 ) between the punch and fixture support. Punch shear load-displacement data is reduced to engineering punch shear stress-strain. A large number of replicates are tested to quantify the stochastic non-linear progressive damage behavior. In order to identify the micromechanical damage mechanisms and quantify the fiber-matrix debonding length, fracture surfaces of micro punch shear __________ specimens have been thoroughly investigated using SEM and confocal microscopy. SEM micrographs clearly shows the initiation and propagation of mode II dominated fiber fracture, fiber-matrix debonding and matrix cracking. Confocal microscopy has been used to quantify the probability distribution functions associated with fiber-matrix debonding and pull-out. The experimental methodology using the micro punch shear test developed in this study can be used to study the effects of composite constituents (fiber, resin and interphase properties and FVF) on the non-linear progressive punch shear behavior of unidirectional composite punch shear strength. The statistical results and failure modes can also
The applicability of high entropy alloys (HEAs) as useful structural components is limited due to our lack of systematic understanding of the role of micro- and sub-structural features on their deformation and fractur...
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The applicability of high entropy alloys (HEAs) as useful structural components is limited due to our lack of systematic understanding of the role of micro- and sub-structural features on their deformation and fracture behaviour. Synergistic assessment of fracture toughness (FT) and activation volume (V) for plastic deformation of typical BCC and FCC HEAs containing Al-Cr-Co-Cu-Fe-Ni by standard practices have been made to throw some light in this direction; these assessments are supplemented by micro- and sub-structural examinations using electron microscopy together with measurements of conventional mechanical properties. The major results indicate that the BCC alloy exhibits higher hardness and strength with inferior FT compared to the FCC alloy. This observation has been explained using the estimated magnitudes of V which is governed by the operative deformation mechanisms controlled by the nature of dislocations in the concerned microstructural constituents.
A novel phase field model has been developed to study the effect of coherent precipitate on the Zener pinning of matrix grain boundaries. The model accounts for misfit strain between precipitate and matrix as well as ...
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It is well known that the presence of hydrogen in ferrous materials promotes both static fracture and affect the material fatigue crack growth rates. The latter is often referred to as Hydrogen Enhanced Fatigue Crack ...
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It is well known that the presence of hydrogen in ferrous materials promotes both static fracture and affect the material fatigue crack growth rates. The latter is often referred to as Hydrogen Enhanced Fatigue Crack Growth Rate (HE-FCGR) which defines the reduction of crack growth resistance of the material under cyclic stresses when hydrogen is present. When it comes to the determination of the life of components exposed to hydrogen it is therefore of paramount importance to establish such hydrogen induced variation in crack speed in the material in order to avoid unexpected catastrophic failures. In this study the fatigue crack growth rate was determined for a Fe-3wt%Si alloy. Compact tension specimens were used to determine the Paris regime of the fatigue crack growth rate curve of the material. Two environmental conditions were investigated: laboratory air and in-situ electrochemically charged hydrogen. Different mechanical conditions, in terms of load ratio (R=0.1 and R=0.5) and test frequency (f=0.1 Hz, 1 Hz and 10 Hz), were used under electrochemically charged hydrogen conditions. The results show that compared to the specimens tested in air, there is a clear detrimental effect of H for the specimens tested in hydrogen, in terms of accelerated crack growth. The strength of the impact of hydrogen in enhancing the fatigue crack growth rates of the Fe-3wt%Si alloy clearly depends on the test conditions. Fractographic investigations were also used to unveil the mechanisms involved in the process leading to accelerate crack growth in presence of hydrogen.
This paper describes the ground effect aerodynamics of a wing with both slit and no slit Gurney flap. For this purpose, FX73-CL3-152 wing with two different shapes of Gurney flaps is considered. Computational results ...
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Thermal protection systems (TPS) materials are fundamentally important to the aerospace and defense industry. These TPS materials have the unique ability to withstand the high heat flux generated during entry into a p...
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We report a first exploration of High-angular-Resolution Electron Backscatter Diffraction, without using simulated Electron Backscatter Diffraction patterns as a reference, for absolute stress and orientation measurem...
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