scholarly journals Effect of Hydrothermal Exposure on Interfacial Stress Transfer in Graphite/Epoxy Composites loaded in Compression

1996 ◽  
Vol 5 (6) ◽  
pp. 096369359600500 ◽  
Author(s):  
Maher S. Amer ◽  
Linda S. Schadler
Keyword(s):  
Fragment Length ◽  
Stress Transfer ◽  
Interfacial Stress ◽  
Epoxy Composites ◽  
Shear Stresses ◽  
Interfacial Behavior ◽  
The Impact

The effect of hydrothermal exposure on the ability of the interface to transfer shear stresses in graphite/epoxy composites under compression is reported. Hydrothermal exposure caused a drop in the ability of the interface to transfer shear stresses from 130 to 15 MPa and increase in the average fragment length from 80 to 1000 μm. The impact of hydrothermal exposure on the composite interfacial behavior is compared with that for composites loaded in tension. The results showed that the interfacial degradation is more severe for composites loaded in compression.

scholarly journals A process-based method for predicting lateral erosion rates

2021 ◽  
Author(s):  
Myron van Damme
Keyword(s):  
Soil Mechanics ◽  
High Surface ◽  
Shear Stresses ◽  
Empirical Equations ◽  
Predictive Capability ◽  
Surface Shear ◽  
Erosion Rates ◽  
Material Texture ◽  
Empirical Coefficients ◽  
The Impact

AbstractAn accurate means of predicting erosion rates is essential to improve the predictive capability of breach models. During breach growth, erosion rates are often determined with empirical equations. The predictive capability of empirical equations is governed by the range for which they have been validated and the accuracy with which empirical coefficients can be established. Most empirical equations thereby do not account for the impact of material texture, moisture content, and compaction energy on the erosion rates. The method presented in this paper acknowledges the impact of these parameters by accounting for the process of dilation during erosion. The paper shows how, given high surface shear stresses, the erosion rate can be quantified by applying the principles of soil mechanics. Key is thereby to identify that stress balance situation for which the dilatency induced inflow gives a maximum averaged shear resistance. The effectiveness of the model in predicting erosion rates is indicated by means of three validation test cases. A sensitivity analysis of the method is also provided to show that the predictions lie within the range of inaccuracy of the input parameters.

scholarly journals Impact Resistance of Epoxy Composites Reinforced with Amazon Guaruman Fiber: A Brief Report

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2264
Author(s):  
Raphael H. M. Reis ◽  
Fabio C. Garcia Filho ◽  
Larissa F. Nunes ◽  
Veronica S. Candido ◽  
Alisson C. R. Silva ◽  
...  
Keyword(s):  
Fiber Composite ◽  
Impact Resistance ◽  
Fiber Composites ◽  
Epoxy Composites ◽  
Impact Performance ◽  
Electron Microscopy Analysis ◽  
Ballistic Properties ◽  
Microscopy Analysis ◽  
Izod Impact ◽  
The Impact

Fibers extracted from Amazonian plants that have traditionally been used by local communities to produce simple items such as ropes, nets, and rugs, are now recognized as promising composite reinforcements. This is the case for guaruman (Ischinosiphon körn) fiber, which was recently found to present potential mechanical and ballistic properties as 30 vol% reinforcement of epoxy composites. To complement these properties, Izod impact tests are now communicated in this brief report for similar composites with up to 30 vol% of guaruman fibers. A substantial increase in impact resistance, with over than 20 times the absorbed energy for the 30 vol% guaruman fiber composite, was obtained in comparison to neat epoxy. These results were statistically validated by Weibull analysis, ANOVA, and Tukey’s test. Scanning electron microscopy analysis disclosed the mechanisms responsible for the impact performance of the guaruman fiber composites.

Effect of toughened polyamide-coated carbon fiber fabric on the mechanical performance and fracture toughness of CFRP

2021 ◽  
pp. 002199832199945
Author(s):  
Jong H Eun ◽  
Bo K Choi ◽  
Sun M Sung ◽  
Min S Kim ◽  
Joon S Lee
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Photoelectron Spectroscopy ◽  
Mechanical Performance ◽  
Epoxy Composites ◽  
Scanning Calorimetry ◽  
Internal Damage ◽  
Impact Tests ◽  
Flexural Tests ◽  
The Impact

In this study, carbon/epoxy composites were manufactured by coating with a polyamide at different weight percentages (5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.%) to improve their impact resistance and fracture toughness. The chemical reaction between the polyamide and epoxy resin were examined by fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray photoelectron spectroscopy. The mechanical properties and fracture toughness of the carbon/epoxy composites were analyzed. The mechanical properties of the carbon/epoxy composites, such as transverse flexural tests, longitudinal flexural tests, and impact tests, were investigated. After the impact tests, an ultrasonic C-scan was performed to reveal the internal damage area. The interlaminar fracture toughness of the carbon/epoxy composites was measured using a mode I test. The critical energy release rates were increased by 77% compared to the virgin carbon/epoxy composites. The surface morphology of the fractured surface was observed. The toughening mechanism of the carbon/epoxy composites was suggested based on the confirmed experimental data.

scholarly journals Insulation Characteristics of Sisal Fibre/Epoxy Composites

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
A. Shalwan ◽  
M. Alajmi ◽  
A. Alajmi
Keyword(s):  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Thermal Characteristics ◽  
Fibre Volume ◽  
Point Of View ◽  
Natural Fibres ◽  
Epoxy Composites ◽  
Ongoing Research ◽  
Sisal Fibre ◽  
The Impact

Using natural fibres in civil engineering is the aim of many industrial and academics sectors to overcome the impact of synthetic fibres on environments. One of the potential applications of natural fibres composites is to be implemented in insulation components. Thermal behaviour of polymer composites based on natural fibres is recent ongoing research. In this article, thermal characteristics of sisal fibre reinforced epoxy composites are evaluated for treated and untreated fibres considering different volume fractions of 0–30%. The results revealed that the increase in the fibre volume fraction increased the insulation performance of the composites for both treated and untreated fibres. More than 200% insulation rate was achieved at the volume fraction of 20% of treated sisal fibres. Untreated fibres showed about 400% insulation rate; however, it is not recommended to use untreated fibres from mechanical point of view. The results indicated that there is potential of using the developed composites for insulation purposes.

Numerical Simulation of the Impact between the Front-End-Coated Projectile and the Substrate Coated by Ceramic Film

2012 ◽  
Vol 226-228 ◽  
pp. 2198-2202
Author(s):  
Zhi Lin Wu ◽  
Xiao Mei Wang
Keyword(s):  
Normal Stress ◽  
Tangential Stress ◽  
Stress Wave ◽  
Acoustic Impedance ◽  
Axial Direction ◽  
Interfacial Stress ◽  
Ceramic Film ◽  
Front End ◽  
Ceramic Films ◽  
The Impact

The propagation of the stress wave in axial direction during the impact between the front-end-coated projectile and the substrate coated by ceramic films is described by the stress wave theorem. The impact process is numerically simulated by ANSYS/LS-DYNA, where the shell unit is used for precision. The effects of thickness of the front-end coating on the interfacial stress are discussed in detail. Dependence of different ceramic films are also considered. Simulation results show that interfacial normal stress is much greater than tangential stress. The interfacial normal stress is greatest when the thickness of the projectile coating is 0.2 mm. The interfacial tangential stress increases slightly as the thickness of coating increases. Similar stress history in the interface occurs when the acoustic impedance of the films are close. Greater acoustic impedance results in smaller stress.

Photoelastic Determination of Interfacial Shear Stresses in Model Composites

2007 ◽  
Vol 334-335 ◽  
pp. 289-292 ◽  
Author(s):  
F.M. Zhao ◽  
Z. Liu ◽  
F.R. Jones
Keyword(s):  
Glass Fibre ◽  
Mechanical Response ◽  
Interfacial Shear Stress ◽  
Stress Transfer ◽  
Interfacial Shear ◽  
Shear Stresses ◽  
Contour Maps ◽  
Phase Stepping ◽  
Fibre Matrix

Phase-stepping photoelasticity has been used to study the fragmentation of an E-glass fibre in epoxy resin and examine quantitatively the effect of a transverse matrix crack on the stress transfer at an interphase. Unsized glass fibre was coated by plasma polymerisation with a crosslinked conformal film of 90% acrylic acid and 10% 1,7-octadiene. The micro-mechanical response at the fibre-matrix interphase and in the adjacent matrix has been described in detail using contour maps of fringe order. From these, the interfacial shear stress profiles at fibre-break have been calculated.

scholarly journals Numerical and Experimental Investigations of the Interactions between Hydraulic and Natural Fractures in Shale Formations

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2541 ◽  
Author(s):  
Xin Chang ◽  
Yintong Guo ◽  
Jun Zhou ◽  
Xuehang Song ◽  
Chunhe Yang
Keyword(s):  
Hydraulic Fracture ◽  
Interaction Mechanism ◽  
Stress Transfer ◽  
Displacement Discontinuity ◽  
Tensile Fracture ◽  
Experimental Investigations ◽  
Shear Stresses ◽  
Natural Fractures ◽  
Stick Slip ◽  
Joint Element

Natural fractures (NFs) have been recognized as the dominant factors that increase hydraulic fracture complexity and reservoir productivity. However, the interactions between hydraulic and natural fractures are far from being fully understood. In this study, a two-dimensional numerical model based on the displacement discontinuity method (DDM) has been developed and used to investigate the interaction between hydraulic and pre-existing natural fractures. The inelastic deformation, e.g., stick, slip and separation, of the geologic discontinuities is captured by a special friction joint element called Mohr-Coulomb joint element. The dynamic stress transfer mechanisms between the two fracture systems and the possible location of secondary tensile fracture that reinitiates along the opposite sides of the NF are discussed. Furthermore, the model results are validated by a series of large tri-axial hydraulic fracture (HF) tests. Both experimental and numerical results showed that the displacements and stresses along the NFs are all in highly dynamic changes. When the HF is approaching the NF, the HF tip can exert remote compressional and shear stresses on the NF interface, which results in the debonding of the NF. The location and value of the evoked stress is a function of the far-field horizontal differential stress, inclination angle of the NF, and the net pressure used in fracturing. For a small approaching angle, the stress peak is located farther away from the intersection point, so an offset fracture is more likely to be generated. The cemented strength of the NF also has an important influence on the interaction mechanism. Weakly bonded NF surfaces increase the occurrence of a shear slippage, but for a moderate strength NF, the hybrid failure model with both tensile and shear failures, and conversion may appear.

Design and Optimization of Biopolyester Bagasse Fiber Composites

2007 ◽  
Vol 1 (1) ◽  
pp. 46-55 ◽  
Author(s):  
Alma Hodzic ◽  
Richard Coakley ◽  
Ray Curro ◽  
Christopher C. Berndt ◽  
Robert A. Shanks
Keyword(s):  
Stress Transfer ◽  
Soxhlet Extraction ◽  
Interfacial Stress ◽  
Fiber Volume ◽  
Mechanical Reinforcement ◽  
Xylem Structure ◽  
Design And Optimization ◽  
The Matrix ◽  
Packaging Industry ◽  
Bagasse Fiber

Bagasse fiber, a by-product of the sugar making process, maintains a coherent xylem structure and can offer mechanical reinforcement to composite materials. Biopolyester bagasse composites were prepared with biodegradable matrices polyhydroxylbutyrate (PHB) and its copolymer containing polyhydroxyvalerate (PHBV). Both biopolymers were reinforced with treated and untreated bagasse fibers, as well as fiber volume fractions involving two fiber lengths. Optimized properties were achieved with PHB-bagasse composite surpassing the PHB flexural strength by 50% and achieving higher strength and modulus than the standard thermoplastics. The bagasse fibers were cleaned with boiling water and acetone soxhlet extraction to avoid using adhesive chemicals and, therefore, comply with biosafety standards in the packaging industry. A significant improvement in the interfacial stress transfer between the fiber and the matrix was achieved with the fibers subjected to both washing and acetone treatment. While the crystallization of PHBV was shown to be controllable by processing conditions, it was concluded that no transcrystalline region was formed with this particular resin in any of the composites. Bagasse was shown to be an effective filler for PHBV; although the results varied somewhat due to the surface treatment of the bagasse fibers. On average, long fiber bagasse composites displayed flexural moduli 33% higher than those of PHBV. Overall, the results demonstrated the positive potential of bagasse to reinforce both biopolyester matrices.

Characterization of interfacial stress transfer ability in acetylation-treated wood fibre composites using X-ray microtomography

2017 ◽  
Vol 95 ◽  
pp. 43-49 ◽  
Author(s):  
Thomas Joffre ◽  
Kristoffer Segerholm ◽  
Cecilia Persson ◽  
Stig L. Bardage ◽  
Cris L. Luengo Hendriks ◽  
...  
Keyword(s):  
Treated Wood ◽  
Stress Transfer ◽  
Wood Fibre ◽  
Interfacial Stress ◽  
X Ray ◽  
Fibre Composites

scholarly journals Influence of layering pattern of modified kenaf fiber on thermomechanical properties of epoxy composites

2019 ◽  
Vol 36 (1) ◽  
pp. 47-62
Author(s):  
AR Mohammed ◽  
MS Nurul Atiqah ◽  
Deepu A Gopakumar ◽  
MR Fazita ◽  
Samsul Rizal ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Modification ◽  
Epoxy Matrix ◽  
Epoxy Composites ◽  
Woven Composites ◽  
Fiber Reinforced ◽  
Kenaf Fiber ◽  
Kenaf Fibers ◽  
The Impact ◽  
Woven Kenaf

Natural fiber-reinforced composites gained considerable interest in the scientific community due to their eco-friendly nature, cost-effective, and excellent mechanical properties. Here, we reported a chemical modification of kenaf fiber using propionic anhydride to enhance the compatibility with the epoxy matrix. The incorporation of the modified woven and nonwoven kenaf fibers into the epoxy matrix resulted in the improvement of the thermal and mechanical properties of the composite. The thermal stability of the epoxy composites was enhanced from 403°C to 677°C by incorporating modified woven kenaf fibers into the epoxy matrix. The modified and unmodified woven kenaf fiber-reinforced epoxy composites had a tensile strength of 64.11 and 58.82 MPa, respectively. The modified woven composites had highest flexural strength, which was 89.4 MPa, whereas, for unmodified composites, it was 86.8 MPa. The modified woven fiber-reinforced epoxy composites showed the highest value of flexural modulus, which was 6.0 GPa compared to unmodified woven composites (5.51 GPa). The impact strength of the epoxy composites was enhanced to 9.43 kJ m−2 by the incarnation of modified woven kenaf fibers into epoxy matrix. This study will be an effective platform to design the chemical modification strategy on natural fibers for enhancing the compatibility toward the hydrophobic polymer matrices.

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