Environmental Effects on Flexural Over-Strength Factor of Epoxy Resin Materials

2013 ◽  
Author(s):  
Masoud Yekani Fard ◽  
Aditi Chattopadhyay ◽  
Brian Raji
Keyword(s):  
Epoxy Resin ◽  
Environmental Effects ◽  
Composite Structures ◽  
Stress Gradient ◽  
Polymeric Materials ◽  
Image Correlation ◽  
Flexural Behavior ◽  
Strength Factor ◽  
Loading System ◽  
Tension And Compression

Polymer composite structures are usually subjected to large flexural loadings during their life-span of the structures, so the flexural behavior of these structures and their constituents in different environmental conditions are critical to their use. A novel analytical approach for epoxy resin semi-brittle materials with strain softening model in tension and compression has been developed to investigate the flexural behavior of these materials. The value of the flexural over-strength factor which is the ratio of the flexural strength to the strength obtained from tension and compression stress strain models depends on stress gradient, size and loading system and it has already been evaluated at the laboratory condition. The mechanical properties of epoxy resin materials are sensitive to environmental effects at which they are loaded. The influence of temperature 60°C and humidity 90% Rh on tension, compression and flexural behavior of epoxy resin polymeric materials PRI and PR 520 have been investigated. Digital image correlation system was used for material characterization. The effects of heat and humidity on softening localization in flexural response were considered. The influence of heat and humidity on the flexural over-strength factor was evaluated.

Nonlinear Flexural Modeling for Epoxy Resin Materials

2011 ◽  
Author(s):  
Masoud Yekani Fard ◽  
Yingtao Liu ◽  
Aditi Chattopadhyay
Keyword(s):  
Composite Structures ◽  
Strain Softening ◽  
Constitutive Models ◽  
Polymeric Materials ◽  
Local Stress ◽  
Image Correlation ◽  
Flexural Behavior ◽  
Peak Strain ◽  
Stress Strain ◽  
Tension And Compression

Polymer composite structures are usually subjected to large flexural loadings, so the flexural behavior of these structures and their constituents are critical to their use. A novel approach for polymeric materials with strain softening model in tension and compression is developed to investigate the flexural behavior of Epon E 863. The tension and compression model consists of a bilinear ascending curve in pre-peak, strain softening followed by constant plastic flow in the post-peak response. The effects of softening localization on flexural response are considered. Local stress strain tension and compression responses, using digital image correlation system, are used for material characterization. Closed form expressions for flexural behavior are developed. The structural response of beams under three and four point bending and round plate on three symmetrical supports are studied experimentally and analytically. Results show that direct use of uniaxial tension and compression stress strain models underestimates the flexural load carrying capacity. Flexural over-strength factor obtained from inverse analysis of beam under three point bending is conservative and it could be used to modify the constitutive models for analyzing a structural system.

scholarly journals Anti-Inflammatory Properties of Injectable Betamethasone-Loaded Tyramine-Modified Gellan Gum/Silk Fibroin Hydrogels

Biomolecules ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1456
Author(s):  
Isabel Matos Oliveira ◽  
Cristiana Gonçalves ◽  
Myeong Eun Shin ◽  
Sumi Lee ◽  
Rui Luis Reis ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Mechanical Properties ◽  
Silk Fibroin ◽  
Therapeutic Efficacy ◽  
Composite Structures ◽  
Gelation Time ◽  
Polymeric Materials ◽  
Gellan Gum ◽  
Traditional Use

Rheumatoid arthritis is a rheumatic disease for which a healing treatment does not presently exist. Silk fibroin has been extensively studied for use in drug delivery systems due to its uniqueness, versatility and strong clinical track record in medicine. However, in general, natural polymeric materials are not mechanically stable enough, and have high rates of biodegradation. Thus, synthetic materials such as gellan gum can be used to produce composite structures with biological signals to promote tissue-specific interactions while providing the desired mechanical properties. In this work, we aimed to produce hydrogels of tyramine-modified gellan gum with silk fibroin (Ty–GG/SF) via horseradish peroxidase (HRP), with encapsulated betamethasone, to improve the biocompatibility and mechanical properties, and further increase therapeutic efficacy to treat rheumatoid arthritis (RA). The Ty–GG/SF hydrogels presented a β-sheet secondary structure, with gelation time around 2–5 min, good resistance to enzymatic degradation, a suitable injectability profile, viscoelastic capacity with a significant solid component and a betamethasone-controlled release profile over time. In vitro studies showed that Ty–GG/SF hydrogels did not produce a deleterious effect on cellular metabolic activity, morphology or proliferation. Furthermore, Ty–GG/SF hydrogels with encapsulated betamethasone revealed greater therapeutic efficacy than the drug applied alone. Therefore, this strategy can provide an improvement in therapeutic efficacy when compared to the traditional use of drugs for the treatment of rheumatoid arthritis.

Flexural behavior of functionally graded polymeric composite beams

2021 ◽  
pp. 152808372110003
Author(s):  
M Atta ◽  
A Abu-Sinna ◽  
S Mousa ◽  
HEM Sallam ◽  
AA Abd-Elhady
Keyword(s):  
Flexural Strength ◽  
Volume Fraction ◽  
Stress Gradient ◽  
Polymeric Composite ◽  
Composite Beams ◽  
Functionally Graded ◽  
Flexural Behavior ◽  
Bending Test ◽  
Polymeric Composite Material ◽  
Fiber Volume

The bending test is one of the most important tests that demonstrates the advantages of functional gradient (FGM) materials, thanks to the stress gradient across the specimen depth. In this research, the flexural response of functionally graded polymeric composite material (FGM) is investigated both experimentally and numerically. Fabricated by a hand lay-up manufacturing technique, the unidirectional glass fiber reinforced epoxy composite composed of ten layers is used in the present investigation. A 3-D finite element simulation is used to predict the flexural strength based on Hashin’s failure criterion. To produce ten layers of FGM beams with different patterns, the fiber volume fraction ( Vf%) ranges from 10% to 50%. A comparison between FGM beams and conventional composite beams having the same average Vf% is made. The experimental results show that the failure of the FGM beams under three points bending loading (3PB) test is initiated from the tensioned layers, and spread to the upper layer. The spreading is followed by delamination accompanied by shear failures. Finally, the FGM beams fail due to crushing in the compression zone. Furthermore, the delamination failure between the layers has a major effect on the rapidity of the final failure of the FGM beams. The present numerical results show that the gradient pattern of FGM beams is a critical parameter for improving their flexural behavior. Otherwise, Vf% of the outer layers of the FGM beams, i.e. Vf% = 30, 40, or 50%, is responsible for improving their flexural strength.

Optical strain measurements on fast moving fiber reinforced polymer rotors using diffraction gratings

2019 ◽  
Vol 86 (3) ◽  
pp. 175-183
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Robert Kuschmierz ◽  
...  
Keyword(s):  
Rigid Body ◽  
Strain Measurement ◽  
Composite Structures ◽  
Dynamical Behavior ◽  
Image Correlation ◽  
Fiber Reinforced Polymers ◽  
Strain Gauges ◽  
Objective Lens ◽  
Fiber Reinforced ◽  
Body Movements

AbstractIn-situ measurements of the deformation and of the structural dynamical behavior of moving composite structures, such as rotors made of glass fiber reinforced polymers (GFRP), are necessary in order to validate newly developed simulation models. Local methods like strain gauges and fiber Bragg gratings lack spatial resolution, while contactless optical methods like image correlation or speckle interferometry suffer from noise effects in the presence of fast rigid body movements. A novel compact sensor – based on the diffraction grating method – is introduced for spatially and temporally resolved strain measurement. The use of a line camera allows the measurement of vibrations up to several tens of kHz. With a scanning movement, strain fields at submillimeter resolution can be recorded. The use of two diffraction orders and an objective lens reduces cross sensitivities to rigid body movements on the strain measurement by two to three orders of magnitude. A validation on a GFRP probe was conducted in a quasi-static tensile test with an optical extensometer up to 14500 µϵ. Furthermore, a strain measurement on a moving rotor at surface speeds up to 75 m/s was performed and the results were compared with those of strain gauges as a gold standard. The statistical standard deviation was around 10 µϵ and independent of the rotational speed.

Self Healing of Epoxy Composite for Aircraft's Structural Applications

2008 ◽  
Vol 136 ◽  
pp. 39-44 ◽  
Author(s):  
Willy C.K. Tan ◽  
J.C. Kiew ◽  
K.Y. Siow ◽  
Z.R. Sim ◽  
H.S. Poh ◽  
...  
Keyword(s):  
Composite Structures ◽  
Polymeric Materials ◽  
Hollow Fibre ◽  
The Body ◽  
Strength Increase ◽  
Self Healing ◽  
Structural Applications ◽  
Self Repair ◽  
Repair Systems ◽  
Point Bend

When one cut himself, it's amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetric inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Preliminary results based on flexural 3 point bend test on prepared samples have shown the healed hollow fibre laminate has a healed strength increase of 47.6% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft’s composite structures.

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