Analysis of measurements of defects in multiaxial warp knitted fabrics for CFRP composites

10.32920/ryerson.14664231.v1 ◽

2021 ◽

Author(s):

Diane Suk-Ching Liu

Keyword(s):

Image Analysis ◽

Standard Deviation ◽

Carbon Fibre ◽

Compression Strength ◽

Cell Model ◽

Unit Cell ◽

Sample Standard Deviation ◽

Cfrp Laminates ◽

Laboratory Results ◽

Out Of Plane

Multiaxial Warp Knitted (MWK) Fabrics are used to create Carbon Fibre Reinforced Plastic (CFRP) laminates. In contrast to Prepregs, CFRP laminates made with MWK fabrics are of interest because they could lower costs and processing time by being already constructed with multiple layers and through the use of a hot air oven instead of an autoclave. Defect in the form of fibre angle orientation plays an important role in the compression strength for laminates made with MWK fabrics. The in-plane and out-of-plane waviness of the fibres were characterised by the standard deviation of the angular waviness: sample Standard deviation of Fibre In-plane (SFI) and the sample Standard deviation of Fibre Out-of-plane (SFO). The SFI value was found in two ways: analysis (Multiple Field Image Analysis (MFIA) technique) software and Fibre Image Analysis software. Measurements of the holes in the carbon fibre textile, colloquially known as “fisheyes,” caused by sewing the textile together were also gathered. The SFI, SFO, and “fisheye” dimensions were together used in the FMB-PMB model and the Unit Cell Model to calculate the compression strength. These predicted compression strengths were compared to the laboratory results. Also, a reliability model was developed to find R, the reliability of each textile, to be used as a textile classification tool. It has been found that the compression strength predictions found using analysis and Fibre Image Analysis yielded similar results, with predictions from analysis closer to the laboratory results. The R value yielded a positive correlation with the results from analysis. A large percentage of difference between the predicted and the actual compression strength was observed for some textiles. This could be attributed to the inherent lack of regularity for some of the examined textiles and variability in determining the SFI and “fisheye” parameters. Improvements would involve devising rules and methods to determine the SFI and “fisheye” parameters, modifying the FMB-PMB and Unit Cell Models, and making the analysis process faster and more applicable for on-line quality process control.

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Elastic constants estimation of stitched NCF CFRP laminates based on a finite element unit-cell model

Composites Science and Technology ◽

10.1016/j.compscitech.2006.05.024 ◽

2007 ◽

Vol 67 (6) ◽

pp. 1081-1095 ◽

Cited By ~ 25

Author(s):

H HES ◽

Y ROTH ◽

N HIMMEL

Keyword(s):

Finite Element ◽

Elastic Constants ◽

Cell Model ◽

Unit Cell ◽

Unit Cell Model ◽

Cfrp Laminates

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A method for the production of carpet plots for notched compression strength of carbon fibre reinforced plastic multidirectional laminates

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1243/0954410971532659 ◽

1997 ◽

Vol 211 (4) ◽

pp. 251-261 ◽

Cited By ~ 7

Author(s):

C Soutis ◽

E C Edge

Keyword(s):

Carbon Fibre ◽

Compression Strength ◽

Room Temperature ◽

Prediction Method ◽

Cfrp Laminates ◽

Reinforced Plastic ◽

Wide Range ◽

Theoretical Predictions ◽

Open Hole ◽

Carbon Fibre Reinforced Plastic

This paper outlines a newly developed method for the calculation of the notched compression strength of carbon fibre reinforced plastic (CFRP) laminates. The BAe-Warton laminate strength prediction method (1) is used to predict the unnotched strength of the laminate and the Soutis et al. model (2) to predict the notch effect. Notched and unnotched strengths are reported for a wide range of T800/924C and T800/5245C carbon fibre—epoxy multidirectional laminates with 0°, ±45° and/or 90° lay-ups; results are compared with theoretical predictions and in most cases the error is less than 10 per cent. Carpet plots of open hole compression strength for different T800/5245C lay-ups tested at room temperature (RT)/dry and 100°C/wet are produced. Finally, the open hole strengths generated by the Soutis et al. (2) model are factored by using appropriate experimental data to allow for plain and countersunk filled holes.

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Nucleic Acid Molecules Prepared by Monolayer Techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100094140 ◽

1972 ◽

Vol 30 ◽

pp. 178-179

Author(s):

Dimitrij Lang

Keyword(s):

Electron Microscopy ◽

Standard Deviation ◽

Nucleic Acid ◽

Cytochrome C ◽

Nucleic Acids ◽

Contour Length ◽

Sample Standard Deviation ◽

Molecular Weights ◽

Length Measurements ◽

Protein Monolayer

The success of the protein monolayer technique for electron microscopy of individual DNA molecules is based on the prevention of aggregation and orientation of the molecules during drying on specimen grids. DNA adsorbs first to a surface-denatured, insoluble cytochrome c monolayer which is then transferred to grids, without major distortion, by touching. Fig. 1 shows three basic procedures which, modified or not, permit the study of various important properties of nucleic acids, either in concert with other methods or exclusively:1) Molecular weights relative to DNA standards as well as number distributions of molecular weights can be obtained from contour length measurements with a sample standard deviation between 1 and 4%.

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Thermo-Viscoelastic Response of 3D Braided Composites Based on a Novel FsMsFE Method

Materials ◽

10.3390/ma14020271 ◽

2021 ◽

Vol 14 (2) ◽

pp. 271

Author(s):

Jun-Jun Zhai ◽

Xiang-Xia Kong ◽

Lu-Chen Wang

Keyword(s):

Finite Element ◽

Cell Model ◽

Structural Parameters ◽

Thermal Relaxation ◽

Viscoelastic Behavior ◽

Unit Cell ◽

Time Dependent ◽

3D Braided Composites ◽

Equivalent Time ◽

Representative Unit Cell

A homogenization-based five-step multi-scale finite element (FsMsFE) simulation framework is developed to describe the time-temperature-dependent viscoelastic behavior of 3D braided four-directional composites. The current analysis was performed via three-scale finite element models, the fiber/matrix (microscopic) representative unit cell (RUC) model, the yarn/matrix (mesoscopic) representative unit cell model, and the macroscopic solid model with homogeneous property. Coupling the time-temperature equivalence principle, multi-phase finite element approach, Laplace transformation and Prony series fitting technology, the character of the stress relaxation behaviors at three scales subject to variation in temperature is investigated, and the equivalent time-dependent thermal expansion coefficients (TTEC), the equivalent time-dependent thermal relaxation modulus (TTRM) under micro-scale and meso-scale were predicted. Furthermore, the impacts of temperature, structural parameters and relaxation time on the time-dependent thermo-viscoelastic properties of 3D braided four-directional composites were studied.

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Extension of Pin-Based Point-Wise Energy Slowing-Down Method for VHTR Fuel with Double Heterogeneity

Energies ◽

10.3390/en14082179 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2179

Author(s):

Tae-Young Han ◽

Jin-Young Cho ◽

Chang-Keun Jo ◽

Hyun-Chul Lee

Keyword(s):

Cross Sections ◽

Cell Model ◽

Unit Cell ◽

Moderation Effect ◽

Slowing Down ◽

Matrix Layer ◽

The Mean ◽

Dancoff Factor ◽

Double Heterogeneity ◽

Very High

For the resonance treatment of a very high temperature reactors (VHTR) fuel with the double heterogeneity, an extension of the pin-based pointwise energy slowing-down method (PSM) was developed and implemented into DeCART. The proposed method, PSM-double heterogeneity (DH), has an improved spherical unit cell model with an explicit tri-structural isotropic (TRISO) model, a matrix layer, and a moderator for reflecting the moderation effect. The moderator volume was analytically derived using the relation of the Dancoff factor and the mean chord length. In the first step, the pointwise homogenized cross-sections for the compact was obtained after solving the slowing down equation for the spherical unit cell. Then, the shielded cross-section for the homogenized fuel compact was generated using the original PSM. The verification calculations were performed for the fuel pins with various packing fractions, compact sizes, TRISO sizes, and fuel temperatures. Additionally, two fuel block problems with very different sizes were examined and the depletion calculation was carried out for investigating the accuracy of the proposed method. They revealed that the PSM-DH has a good performance in the VHTR problems.

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