Experimental study of void evolution in partially impregnated prepregs

Controlling voids to minimize the final porosity level is an important concern when processing advanced composite structures. In this study, the porosity evolution during processing of partially impregnated prepregs is investigated using interrupted cure cycles and optical microscopy. Laminates made of MTM 45-1/5HS carbon/epoxy prepreg subjected to different cure cycles, bagging conditions, and humidity levels were studied. Fiber tow geometry and gas permeability were measured to determine the amount of compaction and the interconnectivity of unsaturated zones in the laminates. Three types of voids were identified: inter-laminar, fiber tow and resin voids, all with different origins and evolution patterns. It is shown that gas transport (both in-plane and through-thickness), fiber bed compaction, and resin infiltration govern void evolution during processing. The results provide insights for development of representative transport models and to optimize processing cycles.

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Gas Permeability and Porosity Evolution of a Porous Sandstone Under Repeated Loading and Unloading Conditions

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-017-1215-1 ◽

2017 ◽

Vol 50 (8) ◽

pp. 2071-2083 ◽

Cited By ~ 19

Author(s):

H. L. Wang ◽

W. Y. Xu ◽

M. Cai ◽

Z. P. Xiang ◽

Q. Kong

Keyword(s):

Gas Permeability ◽

Repeated Loading ◽

Porosity Evolution ◽

Porous Sandstone ◽

Loading And Unloading

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Porosity Reducing Processing Stages of Additive Manufactured Molding (AMM) for Closed-Mold Composite Fabrication

Materials ◽

10.3390/ma13235328 ◽

2020 ◽

Vol 13 (23) ◽

pp. 5328

Author(s):

Marquese Pollard ◽

Phong Tran ◽

Tarik Dickens

Keyword(s):

Additive Manufacturing ◽

Composite Structures ◽

Low Cost ◽

Processing Parameters ◽

Strength Properties ◽

Material Strength ◽

Composite Manufacturing ◽

Layer Height ◽

Porosity Reduction ◽

Final Porosity

This article aims to merge two evolving technologies, namely additive manufacturing and composite manufacturing, to achieve the production of high-quality and low-cost composite structures utilizing additive manufacturing molding technology. This work studied additive manufacturing processing parameters at various processing stages on final printed part performance, specifically how altering featured wall thickness and layer height combine to affect final porosity. Results showed that reducing the layer height yielded a 90% improvement in pristine porosity reduction. Optimal processing parameters were combined and utilized to design and print a closed additive manufacturing molding tool to demonstrate flexible composite manufacturing by fabricating a composite laminate. Non-destructive and destructive methods were used to analyze the composite structures. Compared to the well-established composite manufacturing processes of hand lay-up and vacuum-assisted resin transfer molding methods, additive manufacturing molding composites were shown to have comparable material strength properties.

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INVESTIGATION OF THE ROLE OF PLASTICIZERS IN FILM-FORMING COATS FOR PROTECTING COOLED MEAT

EUREKA Life Sciences ◽

10.21303/2504-5695.2018.00594 ◽

2018 ◽

Vol 2 ◽

pp. 27-34 ◽

Cited By ~ 1

Author(s):

Andrii Kyshenia ◽

Lydmila Vinnikova ◽

Tat’yana Volovik ◽

Evgenii Kotlyar ◽

Kateryna Garbazhiy

Keyword(s):

Sodium Alginate ◽

Gas Permeability ◽

Comparative Characteristic ◽

Theoretical Studies ◽

Film Forming ◽

Interaction Of Components ◽

Rheological Indices ◽

Different Origins ◽

Complex Film

As a result of theoretical studies on problems of protection and prolongation of storage terms of meat, it was revealed, that one of promising directions is to use protecting coats, based on natural biopolymers. The topicality of this study is in studying film-forming coats, based on natural polysaccharides, because they have high mechanical indices, absence of a smell, taste and are subjected to biological destruction. For regulating mechanical properties, the composition of film-creating coats is added with plasticizers of different origins. The aim of this work is in describing characteristics of food films, based on carrageenan, sodium alginate and plasticizers of different origins. There were mechanical, rheological properties of protecting coats. The comparative characteristic of these properties, depending on an added plasticizer, was realized. The type and mechanisms of interaction of components of the film-forming coat and plasticizers were completely described. The viscosity of the film-forming coat with a plasticizer has less values comparing with other solutions. Adding plasticizers resulted in increasing the film elasticity, but at the same time some increase of the firmness was observed. Film-forming coats with adding a plasticizer had a higher limit of fluidity, so they were firmer than complex film-forming coats without a plasticizer. From the other side, deformation values of film-forming coats without adding a plasticizer were higher than ones of complex film-forming coats with adding a plasticizer, because they were firmer. The study of physical properties of developed film-forming coats, based on hydrocolloids, demonstrated that coats with a plasticizer have more gas permeability. According to the results, obtained at experiments it was established, that the film-forming coat, based on sodium alginate, carrageenan and glycerin, has best mechanical, physical and rheological indices.

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Spectroscopic Diagnostics of Tokamaks

International Astronomical Union Colloquium ◽

10.1017/s0252921100107638 ◽

1988 ◽

Vol 102 ◽

pp. 165-174

Author(s):

C. de Michelis

Keyword(s):

Transport Properties ◽

Power Losses ◽

Spectroscopic Diagnostics ◽

Important Concern

AbstractImpurities being an important concern in tokamaks, spectroscopy plays a key role in their understanding. Techniques for the evaluation of concentrations, power losses and transport properties are surveyed, and a few developments are outlined.

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Anisotropy of damage productions in electron irradiated molybdenum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010891x ◽

1978 ◽

Vol 36 (1) ◽

pp. 354-355

Author(s):

K. Izui ◽

S. Furuno ◽

H. Otsu ◽

T. Nishida ◽

H. Maeta

Keyword(s):

Electron Flux ◽

Threshold Energy ◽

High Energy ◽

Voltage Electron ◽

High Voltage Electron Microscope ◽

Displacement Threshold ◽

The Mean ◽

Channeling Effect ◽

Different Origins ◽

Threshold Energies

Anisotropy of damage productions in crystals due to high energy electron bombardment are caused from two different origins. One is an anisotropic displacement threshold energy, and the other is an anisotropic distribution of electron flux near the atomic rows in crystals due to the electron channeling effect. By the n-beam dynamical calculations for germanium and molybdenum we have shown that electron flux at the atomic positions are from ∽4 to ∽7 times larger than the mean incident flux for the principal zone axis directions of incident 1 MeV electron beams, and concluded that such a locally increased electron flux results in an enhanced damage production. The present paper reports the experimental evidence for the enhanced damage production due to the locally increased electron flux and also the results of measurements of the displacement threshold energies for the <100>,<110> and <111> directions in molybdenum crystals by using a high voltage electron microscope.

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In Situ microscopy of the anodic etching of silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137537 ◽

1995 ◽

Vol 53 ◽

pp. 232-233

Author(s):

Frances M. Ross ◽

Peter C. Searson

Keyword(s):

Composite Structures ◽

High Surface ◽

High Surface Area ◽

Chemical Properties ◽

Selective Etching ◽

Silicon On Insulator ◽

Second Phase ◽

Porous Layers ◽

New Class ◽

Porous Semiconductors

Porous semiconductors represent a relatively new class of materials formed by the selective etching of a single or polycrystalline substrate. Although porous silicon has received considerable attention due to its novel optical properties1, porous layers can be formed in other semiconductors such as GaAs and GaP. These materials are characterised by very high surface area and by electrical, optical and chemical properties that may differ considerably from bulk. The properties depend on the pore morphology, which can be controlled by adjusting the processing conditions and the dopant concentration. A number of novel structures can be fabricated using selective etching. For example, self-supporting membranes can be made by growing pores through a wafer, films with modulated pore structure can be fabricated by varying the applied potential during growth, composite structures can be prepared by depositing a second phase into the pores and silicon-on-insulator structures can be formed by oxidising a buried porous layer. In all these applications the ability to grow nanostructures controllably is critical.

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