Read Microsoft Word - Complete_Proceedings_version3.doc text version

Alcock et al.

ID #50

A Comparison of Fibre Characteristics between Linseed Flax, Canadian Grown Linen Flax and European Linen Flax with Respect to Performance as a Composite Reinforcement

ID number: 50 Mercedes Alcocka; Michael Fuquab, Chad Ulvenb, Eric Kerr-Andersonb, Jonn Foulkc a Composites Innovation Centre, 301-78 Innovation Drive, Winnipeg, Manitoba R3T6C2 b North Dakota State University, Department of Mechanical Engineering, Dolve Hall 111, Fargo, ND 58105 c USDA ARS CQRS, Ravenel Center room 10, McGregor Road, Clemson, SC 29634 Abstract

This paper describes the fibre character differences that may influence the fibre's potential as a composite reinforcement. Fourteen linseed samples were tested. Twelve of the sample groups were produced using hammer mill technology and straw from the years 2000, 2006 and 2007 with ranges in cleanliness and level of ret. Three samples were decorticated by scutching to optimize length and straightness of the fibres. In the total fourteen linseed flax specimens, different levels of retting were selected with one linseed specimen processed green, another was water retted and a third was spring baled. The linen straw grown in Canada was from a test plot and was processed by scutching. Three samples of European linen flax and one Canadian sourced linen flax sample were tested to identify factors that might be unique to linen varieties. The fibre characterization test program was extensive, identifying differences in colour, strength, diameter, degree of ret, degree of kink, fibre content, and elongation, to name a few. In addition to these tests, some component tests were conducted to determine the pectin, lignin, wax and cuticle content of the fibres. The fibre characteristics that are determined to be the most influential in composite performance will be discussed along with the implications that their characteristics have for composite applications.

Keywords: flax fiber, linseed, linen, composite, thermoset, vinyl ester, resin infusion INTRODUCTION

One of the main concerns for the composite industry in incorporating biofibres into production parts is the variability of the biofibres due to different crop and retting conditions as well as processing techniques. At present, data on the impact of certain fibre characteristics on thermoset composite performance and the range of variability of those characteristics within different sample sets is not available. Some fibre characterization studies have been performed which have created preliminary testing procedures for analysing natural fibre (1-3) and testing procedures have been used to assess biofibre performance in thermoplastic materials, by examining factors such as surface treatments and other interfacial bonding components (4-5). Investigatory work on the role of certain fibre characteristics on thermoplastic composite properties and developing methods to measure them has been performed (6), but the work has not been exhaustively pursued. As the market for composites in North America is primarily thermoset based, this is a

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

258

Alcock et al.

ID #50

sector still requiring further research. It remains important to develop a strong characterization of natural fibre properties and their effects upon thermoset resin systems. A standardized method to assess biofibres' composite performance would facilitate premiums for high quality fibres, assist in maintaining quality control from crop to crop and provide a means to assess the performance of different processing techniques. An understanding of the fibre characteristics that influence composite performance could also lead to the development of additives, coatings, binders or sizing suitable for natural fibre and thermosetting materials. Further understandings of desired fibre characteristics could lead to ASTM International standardized test methods for the marketing of flax fibres to various industries. The efforts discussed in this paper are the preliminary steps towards identifying the key flax fibre characteristics influencing composite performance and recognizing the differences and similarities between fibres from different crop and processing sources.

FLAX FIBRE SOURCE

Flax fibres were collected from diverse sources with the intention to provide characteristically different physical and chemical properties. Some variables between the sample sets where known and documented, these included processing and cleaning methods, linseed or linen crop source, and crop year. Additional variables without known details which might also influence the sample set are: variety of linseed or linen crop, growing conditions, and location of crop production. In some cases, samples were commissioned to generate specific attributes to provide extremes or baselines in testing. These special cases included degree of ret and preservation of the length and straightness of the fibre. Table 1 illustrates the known attributes of the fibres' sources. It should be noted that details on the hammer milling parameters are not available, however it is known that 3 different hammer mill facilities were used to decorticate the samples and Table 1 indicates which fibres were processed using the same machinery (hammer mill 1, 2 or 3). Similar unknowns surrounded the cleaning processes with different lines or combination of lines for cleaning being used. As the Line 1 and Line 2 cleaning processes significantly altered the fibres through mechanical means, the fibres which underwent those processes have been identified in Table 1.

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

259

Alcock et al.

ID #50

TABLE 1: Known Variables Included in Sample Set

Sample 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Harvest Year 2006 2005 2006 2006 2006 2006 2007 2006 2006 2006 2000 2000 2007 2007 2007 2006 2006 2006

Processing Method Hammer mill 1 Hammer mill 1 Hammer mill 1 Hammer mill 2 Hammer mill 2 Hammer mill 2 Hammer mill 2 Hammer mill 2 Hammer mill 2 Hammer mill 2 Hammer mill 3 Hammer mill 3 Scutching Scutching Scutching Unknown Unknown Unknown

Cleaning Process Used Screening Screening Screening Screening Line 1 + Line 2 Screening Screening Line 1 Screening Line 1 Line 1 Line 1 + Line 2 Shaking Shaking Shaking Unknown Unknown Unknown

Degree of Ret Unknown Unknown Unknown Spring Baled Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown No Retting (green) well-retted Unknown Unknown Unknown Unknown

Country of Origin Canada Canada Canada Canada Canada Canada Canada Canada Canada Canada Canada Canada Canada Canada Canada Belgium Lithuania Eastern Europe

Linseed / Linen Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linseed Linen Linen Linen Linen

FIBRE CHARACTERIZATION

A series of tests were conducted on the fibre character properties. Where multiple methods for testing a fibre property were available or in development, the fibre property was tested by more than one method because the variation in results between test methods and the influence of those variations on being able to identify attributes that could affect composite performance were unknown. Table 2 identifies the different tests performed and where more than one method was used. In cases where the test adhered to or was based on an ASTM standard, the standard is indicated.

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

260

Alcock et al.

ID #50

TABLE 2: Fibre Charaterization Tests And Methods Measured Variable Average Kink Angle Bacteria Content a* b* X Y Z x y Color L* Test Average Kink Angle Bacteria Content Colour Testing Colour Testing Colour Testing Colour Testing Colour Testing Colour Testing Colour Testing Colour Testing Colour Testing Method/Apparatus Optest Fibre Quality Analyzer Viable bacteria counts Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Jasco V-670 Spectrophotometer Myron L Company Model EP conductivity meter

Conductivity Degree of Ret Density Dispersive Component Staple LiUHM LiMEAN LiUI LiSFC Fibre Length (cm) Fibre Elastic Modulus (Gpa) Fibre Strength (MPa) MTS Elongation (%) MTS Strength (g/tex) Stelometer Elongation (%) Stelometer Strength (g/tex) Crimp/Fibre Kink/Fibre Curvature Rectangularity S Number Curvature (USDA Derived)

Conductivity Organoleptic Testing Methods Density Dispersive Component Fibre Length Fibre Length Fibre Length Fibre Length Fibre Length Fibre Length Fibre Strength Fibre Strength Fibre Strength Fibre Strength Fibre Strength Fibre Strength Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis

ASTM D3800 Using Canola Oil Inverse Gas Chromatography Isotester Isotester Isotester Isotester Isotester Modified Astm D519-04 LEX And The MTT675 Tensile Tester LEXAnd The MTT675 Tensile Tester MTS MTS Stelometer (ASTM D1445) Stelometer (ASTM D1445) Flat Bed Scanner Flat Bed Scanner Flat Bed Scanner Flat Bed Scanner Flat Bed Scanner Slide Scanner

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

261

Alcock et al.

ID #50

Rectangularity (USDA Derived) MEAND/Grey SieveEll Shapefactor2 FERETRATIO TauLike/Deg Rectangleshape Complexity Shapefactorc Convexity CircDiam Area Fungus Content Glucose Content Hollowness Zeta Potential Ka (Acid) Kb (Base) Ca Content Fe Content K Content Mg Content Na Content Zn Content Moisture Content Openness pH Raw Sec (Polarity Static Decay) Shirley Sec (Polarity Static Decay) Fibre Processing Fibre Year Linen/Linseed % Shive SSI Wax Content

Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fibreshape Analysis Fungus Content Glucose Content Hollowness Hydrophobicity Ka (Acid) Kb (Base) Metals Content Metals Content Metals Content Metals Content Metals Content Metals Content Moisture Content Openness pH Polarity Static Decay Polarity Static Decay Reported Reported Reported Shive Content Specific Surface Index Wax Content

Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Slide Scanner Viable fungal counts YSI Glucose Analyzer Visual SEM Electro Kinetic Analyzer Inverse Gas Chromatography Inverse Gas Chromatography Fibre Digestion/ Wet Chemistry Fibre Digestion/ Wet Chemistry Fibre Digestion/ Wet Chemistry Fibre Digestion/ Wet Chemistry Fibre Digestion/ Wet Chemistry Fibre Digestion/ Wet Chemistry ASTM D2495-07 Visual SEM Orion model 310 pH meter Static Decay Meter Static Decay Meter

Jasco V-670 Spectrophotometer (ASTM D7076) ASTM D7025-04 Wax Extraction Using Wet Chemistry

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

262

Alcock et al.

ID #50

It is understood that the sample set described in Table 1 are too few in number to conclusively prove that any of the variables mentioned in Table 2 influence composite performance to a specific degree. To do so, without reducing the number of characterization variables, would require an infeasible number of samples with controlled variations in properties. The approach taken instead was to maintain the number characterization variables and attempt to identify possible trends that could be investigated in subsequent research. This approach allowed for a more holistic review of factors affecting performance and the ability to identify properties or test methods that could lead to standardized testing.

COMPOSITE CHARACTERIZATION

The composite characterization test methods were selected to isolate certain fibre variables or variable groups in order to identify aspects that might play a significant role in the composite performance. Table 3 lists the composite tests that were performed and the variables that were artificially controlled to provide results (controlled), those that were kept constant between test samples (constant) and those that could not be controlled and may have varied between samples (variable). It should be noted that the fibre properties listed in Table 3 may vary to some degree within each sample; however, it is assumed that their average would be constant, controlled, variable or not applicable. In all the composite tests, the resin used was Hydropel R037-YDF-40 vinyl ester resin, a low viscosity thermoset resin suitable for resin infusion processing.

TABLE 3: Influence of Fibre Properties on Composite Testing Design Composite Test

Effect Of Fibre Fineness ASTM 3039

Fibre Property Degree Of Ret Fibre Fineness Degree Of Kink Fibre Length Dispersive Forces Acid/Base Properties Surface Topography Hydrophobicity Hollowness Moisture Content Stem Wax Constituents

Effect Of Shive Size And Quantity ASTM 3039 Constant Constant Constant Constant Constant Constant Constant Constant Constant Constant Constant

Constant Controlled Constant Constant Constant Constant Variable Constant Variable Constant Constant

Fibre Pullout (Interfacial Shear Impact Interlaminar Shear Strength) Strength Strength Non Standard ASTM ASTM D2334/DD4812 2344 Variable Variable Variable Variable Variable Variable Variable Variable Variable Constant N/A N/A Variable Variable Variable Variable Variable Variable Variable Constant Variable Variable Variable Variable Variable Constant Variable Variable Variable Variable Variable Constant Variable

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

263

Alcock et al.

ID #50

Conductivity For Soluble Salts pH Of Fibres Glucose Level Stem Pectin Constituents Metal Content Fibre Surface Polarity Colour Shive Content Cuticle Content Bacterial Populations Fungal Populations Fibre Strength And Elongation

RESULTS

Constant Constant Constant Constant Constant Constant Constant Constant Constant Constant Constant Variable

Constant Constant Constant Constant Constant Constant Constant Controlled Constant Constant Constant Constant

Variable Variable Variable Variable Variable Variable Variable N/A Variable Variable Variable N/A

Variable Variable Variable Variable Variable Variable Variable N/A Variable Variable Variable Variable

Variable Variable Variable Variable Variable Variable Variable N/A Variable Variable Variable Variable

The effect of fibre fineness and shive size and quantity were the only tests which went to great lengths to isolate the respective variables. These two qualities were specifically chosen as they were identified either through previous research or common opinion as being strong influences as compared to other variables (6,7,8). The results from these two test programs show a much lower influence on composite performance than originally expected. In respect to the shive size and quantity data, it appeared that only large shive played an obvious detrimental role in composite strength, whereas small or medium sized shive or pedicles did not seem to influence composite strength. The affect on the elastic modulus was less determinable without further testing, but initial results indicate medium to small shive may affect modulus detrimentally. It was found that varying the average fibre fineness in a composite specimen did not influence the strength or elastic modulus of the composite in the range of fibre diameters investigated. An interlaminar shear strength (ILSS) test was conducted as a possible alternative to the fibre pullout test. ILSS is less arduous to perform than the fibre pullout and due to the larger amount of fibres used in specimen preparation, it is a better representative of actual composite performance parameters than fibre pullout. ILSS has been proven in synthetic fibre composite testing (9-11). The ILSS was not used to test the full sample set of fibres and thus can not be used in the statistical analysis of performance variables, but the few sample sets that were tested showed a possible correlation between ILSS and fibre pullout existed. Ideally, an analysis would be made on the full range of factors through direct comparison, so that a statistical analysis could be made stating that certain data showed a true statistical trend, such as an increase in tensile strength with increased loading of some constituent. However, the number of factors studied, coupled with the nature of the testing procedures and variety of

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

264

Alcock et al.

ID #50

unknowns, did not lend itself to this analysis. As such, a secondary characterization and comparison method was developed to perform analysis of factor effects on the mechanical fibre characteristics. Due to the nature of the analysis, it must be stressed that the trends produced through this work do not show true statistical meaning within some confidence interval. However, the analysis was performed in such a manner that the factor effects found to be important should serve as a useful guideline for pursuit in future work. In this secondary characterization method, properties were checked for their correlation to the interfacial shear strength (fibre pullout) and the affect on fibre strength and elongation properties that were measured in the fibre characterization process. Five of the fibre factors showed some mechanical effects or correlations that can be considered mainly of use as an inspection factor to qualify the characteristics of a fibre, and most likely do not hold causation in the actual mechanical performance. While not a direct cause of performance differences, these inspection factors could be of great importance in reducing the specific testing of multiple variables, which could lead to cost effective fibre grading systems. The factors are Y, X, L*, b*, and MEAND/grey; are all values obtained by colour and light testing. As shown in Figure 1, it appears increased values of Y, X, L*, and b* show a decreasing trend in the mechanical strength of the fibres, as observed in the MTS fibre bundle strength. It should be noted that X and L*, while consisting of different values, show the same general trend when mapped through four ranges.

(a)

(b)

(c)

(d)

Figure 1: Color correlation trends upon MTS fibre bundle tensile strength

2008 International Conference on Flax and Other Bast Plants (ISBN #978-0-9809664-0-4) 265

Alcock et al.

ID #50

Figure 2 shows that there is a correlation between increasing values of MEAND/grey and a decreasing ability for fibre elongation. Figure 3 shows a relationship between increasing values of b* and decreasing interfacial bonding strength between the fibres and the vinyl ester resin system.

Figure 2: MEAND/grey correlation with decreasing elongation

Figure 3: Correlation between increasing b* and decreasing interfacial bonding strength

Overall, it was observed that fungus concentration (Figure 4) had the most noticeable effect upon the flax fibre mechanical properties, causing significant change in strength and interfacial bonding strength with variation in concentration. The dispersive component (Figure 5) and the S number (Figure 6) were both found to have an effect on both strength and elongation, but no significant effect upon fibre pullout. Furthermore, fibre curvature (Figure 7) was found to effect both elongation and interfacial bonding strength, but not the fibre strength, while b* was also found to act in correlation with this pattern.

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

266

Alcock et al.

ID #50

(a)

(b)

Figure 4: Correlation of Fungus Concentration and Effects on Properties

(a)

(b)

Figure 5: Correlation of Dispersive Component on Fibre Strength and Elongation

(a)

(b)

Figure 6: Correlation of S Number on Fibre Strength and Elongation

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

267

Alcock et al.

ID #50

(a)

(b)

Figure 7: Correlation of Curvature on Interfacial Bond Strength and Fibre Elongation

It should be noted that while the preceding results are those which were determined to have significant correlation, there also exist five factors which can not reasonably be included within theses results, but still hold potential for being influential. There exclusion is based upon a lack of data samples to properly create averages. Due to this lack of averages, the trends that are observed are not confirmable, however if further work were to yield more samples to meet the analysis's requirements in order to have multiple data points in each range, the current trends would be significant. In that guise, the following trends are possible, but not confirmable from the data collected in this study: increased wax concentration and Mg concentration appear to both cause decreases in fibre pullout strength and fibre elongation; increases in fibre crimp occurrence appear to cause an increase in fibre strength; increase in raw sec potentially causes a decrease in strength; and higher a* levels appear to correlate with increases in fibre elongation. These first attempts at correlating flax fibre quality and biofibre composites contain the initial steps towards identifying key flax fibre characteristics that influence composite performance and recognizing the differences and similarities between fibres from different crop and processing sources. This study determined that among the fibre and composite qualities considered the fibre quality measurements (fungal populations, L*, b*, MTS fiber strength, rectangularity, degree of fiber curvature, Ca, Stelometer elongation, wax, Mg, fiber crimp, polarity decay, and a*) appear to affect biofibre composites. An understanding of these fibre characteristics that influence composite performance could lead to the development of additives, coatings, binders or sizing suitable for natural fibre and thermosetting materials. Further understandings of these desired fibre characteristics could lead to ASTM International standardized test methods for the marketing of flax fibres to various industries and a marketing system for flax fibres.

ACKNOWLEDGEMENTS

The results of this project could not have been achieved without the direct support of many partners. The following groups should be acknowledged for their contributions to the success of this endeavour: The University of Toronto, Biolin Research Incorporated, Dia-stron Limited, The United States Department of Agriculture, Agricultural Research Service, North Dakota State

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

268

Alcock et al.

ID #50

University, Schweitzer-Mauduit Canada Inc,. and the Department of Agriculture and Agri-Food Canada.

REFERENCES

1. A. Pietak, S. Korte, E. Tan, A. Downard, M.P. Staiger, Applied Surface Science, 253, 3627 (2007). 2. M. Sain, S. Panthapulakkal, Industrial Crops and Products, 23, 1 (2006). 3. A. Nechwatal, K.P. Mieck, T. Reußmann, Composites Science and Technology, 63, 1273 (2003). 4. A. Valadez-Gonzalez, J. M. Cervantes-Uc, R. Olayo, P. J. Herrera-Franco, Composites Part B: Engineering, 30, 309 (1999). 5. N. E. Zafeiropoulos, D. R. Williams, C. A. Baillie, F. L. Matthews, Composites Part A: Applied Science and Manufacturing, 33, 1083 (2002). 6. J. Müssig, M. Karus, R. R. Frank, "Bast and Leaf Fibre Composite Materials" in Bast and Other Plant Fibres, R. R. Frank, Ed., Woodhead Publishing Limited, Cambridge, pp. 352367 (2005). 7. D.A. Akin, R.B. Dodd, J.A. Foulk, Industrial Crops and Products, 21, 369 (2005). 8. T. Stuart, Q. Liu, M. Hughes, R.D. McCall, H.S.S. Sharma, A. Norton, Composites: Part A: Applied Science and Manufacturing, 37, 393 (2006). 9. C. Marieta, E. Schulz, L. Irusta, N. Gabilondo, A. Tercjak, I. Mondragon, Composites Science and Technology, 65, 2189 (2005). 10. P. Polacek, J. Jancar, Composites Science and Technology, 68, 251 (2008). 11. J. Li, H. Ma, Y. Huang, Materials Chemistry and Physics, 89, 367 (2005).

2008 International Conference on Flax and Other Bast Plants

(ISBN #978-0-9809664-0-4)

269

Information

Microsoft Word - Complete_Proceedings_version3.doc

12 pages

Find more like this

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate

149264


You might also be interested in

BETA
Microsoft Word - Complete_Proceedings_version3.doc