Journal of Composites Science

Research

22 pages, 40549 KiB

Open AccessArticle

Impact Resistance of Fibre Reinforced Composite Railway Freight Tank Wagons

by George Edward Street, Preetum Jayantilal Mistry and Michael Sylvester Johnson

J. Compos. Sci. 2021, 5(6), 152; https://doi.org/10.3390/jcs5060152 - 4 Jun 2021

Cited by 10 | Viewed by 4281

The use of fibre reinforced composite materials is one method by which the lightweighting of rail vehicles can be achieved. However, the issue of impact damage, amongst other challenges, limits their safety certification. This issue is accentuated by the high levels of loading [...] Read more.

The use of fibre reinforced composite materials is one method by which the lightweighting of rail vehicles can be achieved. However, the issue of impact damage, amongst other challenges, limits their safety certification. This issue is accentuated by the high levels of loading a rail vehicle may be subjected to during service. This paper addresses the significance of pre-tension on large composite structures, specifically for a composite redesign of a pressure vessel for a freight tank wagon. Preloading was determined to be detrimental to the overall impact resistance of a large composite vessel. At 15.71 J of impact energy, there was a 22% increase in mean absorbed energy for a uniaxially loaded panel over an unloaded panel. However, there was only a 4% difference in penetration depth between uniaxial and biaxial loading. A novel finding from these results is that the effects of preloading are more profound if the loading does not act parallel to a principal fibre direction. Matrix cracking and delaminations are the most common failure modes observed for specimens under low-velocity impact and are intensified by preload. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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14 pages, 9350 KiB

Open AccessArticle

Development of a Pultrusion Die for the Production of Thermoplastic Composite Filaments to Be Used in Additive Manufacture

by Filipe Ferreira, Pedro Fernandes, Nuno Correia and António Torres Marques

J. Compos. Sci. 2021, 5(5), 120; https://doi.org/10.3390/jcs5050120 - 1 May 2021

Cited by 6 | Viewed by 3257

Abstract

The use of 3D printing has proven to have significant benefits to manufacture components with complex geometries with several types of materials and reinforcements for a wide variety of uses including structural applications. The focus of this study is to develop and implement [...] Read more.

The use of 3D printing has proven to have significant benefits to manufacture components with complex geometries with several types of materials and reinforcements for a wide variety of uses including structural applications. The focus of this study is to develop and implement a thermoplastic pultrusion process that can obtain a carbon fiber/polypropylene (CF/PP) filament for a 3D printing process. This development process included the design and finite element analysis of the die used to conform the filament, considering the adaptation of a filament-winding setup to achieve adequate production conditions. The finite element model tried to achieve homogeneous heating of the die with the use of a series of resistors controlled by PID controllers monitoring several thermocouples strategically positioned while the use of water circulating channels was responsible for the cooling effect. The die-heating environment is optimized for different scenarios with different initial temperatures, cooling temperatures, and pulling speeds. A series of experiments were performed under different conditions, such as different heating temperatures and pulling speeds to analyze the quality of the filament produced. The obtained filaments presented an average diameter of 1.94 mm, fiber volume fraction of 43.76%, and void content of 6.97%. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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23 pages, 7111 KiB

Open AccessArticle

Experimental Investigation of Instabilities on Different Scales in Compressive Fatigue Testing of Composites

by Andreas Baumann and Joachim Hausmann

J. Compos. Sci. 2021, 5(4), 114; https://doi.org/10.3390/jcs5040114 - 20 Apr 2021

Cited by 3 | Viewed by 2701

Abstract

Compression testing of continuous fiber reinforced materials is challenging, because a great number of competing failure modes and instabilities on different length scales have to be considered. In comparison to tensile testing, the results are more affected by the chosen test set-up. Effects [...] Read more.

Compression testing of continuous fiber reinforced materials is challenging, because a great number of competing failure modes and instabilities on different length scales have to be considered. In comparison to tensile testing, the results are more affected by the chosen test set-up. Effects introduced by the test set-up as well as the type of damage in continuous fiber reinforced materials are mainly investigated for quasi-static loading. This is not the case for cyclic compression loading. Neither standardized methods nor a great deal of literature for reference exists. The aim of this work is to increase the understanding by analyzing the potential effects the set-up in fatigue loading might have on the damage for two common testing strategies by fatigue tests, load increase creep tests and supplementary analytical models. The results show that damage modes can be altered by the testing strategy for the investigated woven glass fiber reinforced polyamide 6. The tools both experimentally and analytically provide the basis to choose the correct set-up in future investigations. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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20 pages, 924 KiB

Open AccessArticle

Comparison of Specimen Geometries for Measuring Through-Thickness Tensile Mechanical Properties of Fibre-Reinforced Polymer Composites

by Rory Pemberton, Louise Crocker, Matthew Poole, Richard Shaw and Michael Gower

J. Compos. Sci. 2021, 5(3), 84; https://doi.org/10.3390/jcs5030084 - 16 Mar 2021

Cited by 2 | Viewed by 2386

Abstract

Engineering design of fibre-reinforced polymer (FRP) composite components requires reliable methods for measuring out-of-plane mechanical properties in the through-thickness (T-T) material direction. Within this work, existing indirect and direct test methods and geometries for measuring T-T tensile properties have been evaluated through experimental [...] Read more.

Engineering design of fibre-reinforced polymer (FRP) composite components requires reliable methods for measuring out-of-plane mechanical properties in the through-thickness (T-T) material direction. Within this work, existing indirect and direct test methods and geometries for measuring T-T tensile properties have been evaluated through experimental testing and finite element analysis (FEA). Experimental testing showed variations, particularly in failure properties, for both indirect (failure strengths from 10–94 MPa) and direct (failure strengths from 48–62 MPa) geometries. Results were shown to be in good agreement with FEA, which also confirmed stress concentration factors. A linear relationship between the magnitude of stress concentration factors and experimentally determined T-T tensile failure strengths was observed for all but one of the direct geometries evaluated. Improved knowledge of stress concentration factors from this work should help instil confidence for industry to use T-T tensile properties determined from these methods. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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12 pages, 3018 KiB

Open AccessArticle

Design of a Lightweight Multifunctional Composite Railway Axle Utilising Coaxial Skins

by Preetum J. Mistry, Michael S. Johnson, Charles A. McRobie and Ivor A. Jones

J. Compos. Sci. 2021, 5(3), 77; https://doi.org/10.3390/jcs5030077 - 7 Mar 2021

Cited by 4 | Viewed by 3947

Abstract

The rising economic and environmental pressures associated with the generation and consumption of energy necessitates the need for lightweighting of railway vehicles. The railway axle is a prime candidate for lightweighting of the unsprung mass. The reduction of unsprung mass correlates to reduced [...] Read more.

The rising economic and environmental pressures associated with the generation and consumption of energy necessitates the need for lightweighting of railway vehicles. The railway axle is a prime candidate for lightweighting of the unsprung mass. The reduction of unsprung mass correlates to reduced track damage, energy consumption and total operating costs. This paper presents the design of a lightweight multifunctional hybrid metallic-composite railway axle utilising coaxial skins. The lightweight axle assembly comprises a carbon fibre reinforced polymer composite tube with steel stub axles bonded into either end. The structural hybrid metallic-composite railway axle is surrounded by coaxial skins each performing a specific function to meet the secondary requirements. A parametric sizing study is conducted to explore the sensitivity of the design parameters of the composite tube and the stub axle interaction through the adhesive joint. The optimised design parameters of the axle consist of a; composite tube outer diameter of 225 mm, composite tube thickness of 7 mm, steel stub axle extension thickness of 10 mm and a bond overlap length of 100 mm. The optimised hybrid metallic-composite railway axle design concept has a mass of 200 kg representing a reduction of 50% over the solid steel version. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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15 pages, 8983 KiB

Open AccessArticle

Numerical Analysis of Filament Wound Cylindrical Composite Pressure Vessels Accounting for Variable Dome Contour

by Kumar C. Jois, Marcus Welsh, Thomas Gries and Johannes Sackmann

J. Compos. Sci. 2021, 5(2), 56; https://doi.org/10.3390/jcs5020056 - 11 Feb 2021

Cited by 20 | Viewed by 6946

Abstract

In this work, the stress distribution along cylindrical composite pressure vessels with different dome geometries is investigated. The dome contours are generated through an integral method based on shell stresses. Here, the influence of each dome contour on the stress distribution at the [...] Read more.

In this work, the stress distribution along cylindrical composite pressure vessels with different dome geometries is investigated. The dome contours are generated through an integral method based on shell stresses. Here, the influence of each dome contour on the stress distribution at the interface of the dome-cylinder is evaluated. At first, the integral formulation for dome curve generation is presented and solved for the different dome contours. An analytical approach for the calculation of the secondary stresses in a cylindrical pressure vessel is introduced. For the analysis, three different cases were investigated: (i) a polymer liner; (ii) a single layer of carbon-epoxy composite wrapped on a polymer liner; and (iii) multilayer carbon-epoxy pressure vessel. Accounting for nonlinear geometry is seen to have an effect on the stress distribution on the pressure vessel, also on the isotropic liner. Significant secondary stresses were observed at the dome-cylinder interface and they reach a maximum at a specific distance from the interface. A discussion on the trend in these stresses is presented. The numerical results are compared with the experimental results of the multilayer pressure vessel. It is observed that the secondary stresses present in the vicinity of the dome-cylinder interface has a significant effect on the failure mechanism, especially for thick walled cylindrical composite pressure vessel. It is critical that these secondary stresses are directly accounted for in the initial design phase. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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18 pages, 4743 KiB

Open AccessArticle

Study of Monitoring Method and Melt Flow Behavior in Compression Molding Process Using Thermoplastic Sheets Reinforced with Discontinuous Long-Fibers

by Masatoshi Kobayashi

J. Compos. Sci. 2021, 5(2), 50; https://doi.org/10.3390/jcs5020050 - 6 Feb 2021

Cited by 1 | Viewed by 3154

Abstract

In compression molding using glass-fiber-mat-reinforced thermoplastic (GMT) sheets, a slightly longer compression waiting time from sheet placement on a lower mold to the start of sheet compression by an upper mold can cause incomplete filling due to a decrease in the sheet temperature. [...] Read more.

In compression molding using glass-fiber-mat-reinforced thermoplastic (GMT) sheets, a slightly longer compression waiting time from sheet placement on a lower mold to the start of sheet compression by an upper mold can cause incomplete filling due to a decrease in the sheet temperature. However, precise measurement techniques for compression waiting time have not been sufficiently established. A monitoring system was produced that includes pressure—temperature sensors mounted in a compression mold that can simultaneously measure the pressure and temperature of one local surface. Two types of distance sensors were also used to measure upper mold motion widely and precisely. Determination of compression waiting time was attempted by measuring the moment when the lower mold temperature slightly increases in response to contact with the melted GMT sheet and the moment when the melt pressure increases in response to compression by an upper mold. The results showed that compression waiting time could be precisely calculated using the profile data obtained. Moreover, it was also possible to observe the melt pressure overshoot that occurs depending on sheet stacking patterns and mold cavity shape, although in some cases, the overshoot was not observed. In conclusion, this study has demonstrated that the system is effective in monitoring the compression molding process widely and precisely. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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11 pages, 3672 KiB

Open AccessArticle

Model Calibration and Data Set Determination Considering the Local Micro-Structure for Short Fiber Reinforced Polymers

by Andreas Primetzhofer, Gabriel Stadler, Gerald Pinter and Florian Grün

J. Compos. Sci. 2021, 5(2), 40; https://doi.org/10.3390/jcs5020040 - 27 Jan 2021

Cited by 2 | Viewed by 2861

Abstract

To ensure the usability of parts made of fiber-reinforced polymers, a lifetime assessment has to be made in an early stage of the development process. To describe the whole life cycle of these parts, continuous simulation chains can be used. From production to [...] Read more.

To ensure the usability of parts made of fiber-reinforced polymers, a lifetime assessment has to be made in an early stage of the development process. To describe the whole life cycle of these parts, continuous simulation chains can be used. From production to the end of the service life, all influences are mapped virtually. The later material strength is already given after the manufacturing process due to the process dependent fiber alignment. To be able to describe this fiber orientation within the lifetime assessment, this paper presents an approach for model calibration and data set determination to consider the local micro-structure. Therefore, quasi-static and cyclic tests were performed on specimens with longitudinal and transversal fiber orientation. A supplementary failure analysis provides additional information about the local micro-structure. The local fiber orientation is determined with µCT (micro computer tomography)-measurements, correlated to the extraction positions of the specimen, and implemented in a dataset. With an attached lifetime calculation on a demonstrator, a major influence of the local micro-structure on the calculation results can be shown. Therefore, it is indispensable to consider the local fiber orientation in the data set determination of short fiber reinforced polymers. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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16 pages, 7674 KiB

Open AccessArticle

Design and Validation of a Modified Compression-After-Impact Testing Device for Thin-Walled Composite Plates

by Markus Linke, Felix Flügge and Aurelio Jose Olivares-Ferrer

J. Compos. Sci. 2020, 4(3), 126; https://doi.org/10.3390/jcs4030126 - 29 Aug 2020

Cited by 10 | Viewed by 3277

Abstract

Thin-walled fibre reinforced composites like carbon fibre reinforced plastics are very susceptible to strength reductions due to low-velocity impact damages. In aerospace engineering, the dominating failure mechanisms of impact damaged composite structures are usually investigated based on the compression after impact (CAI) test [...] Read more.

Thin-walled fibre reinforced composites like carbon fibre reinforced plastics are very susceptible to strength reductions due to low-velocity impact damages. In aerospace engineering, the dominating failure mechanisms of impact damaged composite structures are usually investigated based on the compression after impact (CAI) test procedure. This enables the determination of the influence of impact damages on the static residual compressive strength. CAI testing procedures are typically applicable to composite plates with thicknesses larger than 3–4 mm. If thinner panels are used, they typically fail near one of the loaded edges of the CAI device, in particular the area of the free edge (which is needed for compressing the panel) and not within the free measuring area. As a consequence, the investigated samples cannot be used as valid tests for the evaluation of the residual strength in CAI testing. In order to enable an investigation of the residual strength of thin-walled plates in CAI testing, a CAI testing device is developed based on an available CAI fixture and a standardized one. For comparability reasons, this new device exhibits the same dimensions as standardized fixtures. It shows a significant improvement with respect to standardized devices concerning the measurement of mechanical behaviour during CAI testing. Full article

(This article belongs to the Special Issue Recent Advances in Composite Process Modeling and Characterization)

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