The fracture toughness of the leaf of the dicotyledon
            <i>Calophyllum inophyllum</i>
            L. (Guttiferae)

Lucas, Peter W.; Choong, M. F.; Tan, Hugh Tiang Wah; Turner, I. M.; Berrick, A. J.

doi:10.1098/rstb.1991.0099

Cited by 87 publications

(37 citation statements)

References 31 publications

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“…Only the cellulosic strands in the S2 layer have a preferred orientation ; they must be responsible. This result has been found before for cuts across secondary and tertiary veins of aloph llum inoph llum leaves (Lucas et al 1991).…”

Section: Discussionsupporting

confidence: 73%

“…Woody tissue in any plant material should behave very similarly. There is some evidence for this from the behaviour of veins (probably the fibres) in aloph llum inoph llum leaves (Lucas et al 1991) and also from seed shells (Lucas et al 1995). In particular, seed shells are worth exploring in considerable detail because they are more homogeneous than wood in cell type and vary a great deal in the layup of fibres.…”

Section: Discussionmentioning

confidence: 99%

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The toughness of secondary cell wall and woody tissue

Lucas

Tan

Cheng

1997

Phil. Trans. R. Soc. Lond. B

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SUMMARYThe ' across grain ' toughness of 51 woods has been determined on thin wet sections using scissors. The moisture content of sections and the varying sharpness of the scissor blades had little effect on the results. In thin sections ( 0.6 mm), toughness rose linearly with section thickness. The intercept toughness at zero thickness, estimated from regression analysis, was proportional to relative density, consistent with values reported for non-woody plant tissues. Extrapolation of the intercept toughness of these woods and other plant tissues\materials to a relative density of 1.0 predicted a toughness of 3.45 kJ m −# , which we identify with the intrinsic toughness of the cell wall. This quantity appears to predict published results from IC tests on woods and is related to the propensity for crack deflection. The slope of the relationship between section thickness and toughness, describing the work of plastic buckling of cells, was not proportional to relative density, the lightest (balsa) and heaviest (lignum vitae) woods fracturing with less plastic work than predicted. The size of the plastic zone around the crack tip was estimated to be 0.5 mm in size. From this, the hypothetical overall toughness of a thick ( 1 mm) block of solid cell wall material was calculated as 39.35 kJ m −# , due to both cell wall resistance (10 %) and the plastic buckling of cells (90 %). This value successfully predicts the toughness of most commercial woods (of relative densities between 0.2 and 0.8) from ' work area ' tests in tension and bending. Though density was the most important factor, both fibre width\fibre length (in hardwoods) and lignin\cellulose ratios were negatively correlated with the work of plastic buckling, after correcting for density. At low densities, the work of plastic buckling in the longitudinal radial (LR) direction exceeded that in longitudinal tangential (LT), but the reverse was true for relative densities above 0.25. This could be attributed to the direction of rays. Density for density, the toughness of temperate hardwoods tested was about 20 % lower than that of tropical hardwoods. This is probably due to the much greater number of vessels in temperate hardwoods. Vessels appear either not to display buckling behaviour during fracture at all or to collapse cheaply. These general results have applications to other plant tissues.

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Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

The toughness of secondary cell wall and woody tissue

Lucas

Tan

Cheng

1997

Phil. Trans. R. Soc. Lond. B

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“…The magnitudes of these parameters are often not reported in the literature, suggesting that the potential of these factors to affect test results has not been recognized. Studies that do mention these parameters indicate that their magnitudes vary, both within and between studies (Lucas et al, 1991 ;Choong et al, 1992 ;Vincent, 1992c ;Choong, 1996). At present, no data on the effect of these parameters on test results are available, so it is difficult to determine suitable parameter settings for conducting mechanical tests.…”

Section: mentioning

confidence: 99%

“…Trials followed the basic protocol described earlier, with modifications to both speed and clearance. Using a punch of area 2.06 mm#, three dies were made allowing clearances of 0.05, 0.10 and 0.15 mm, respectively, reflecting clearances reported in the literature (Feeny, 1970 ;Lucas et al, 1991 ;Choong et al, 1992). The low-speed treatment was 0.84 mm s −" , corresponding to speeds recommended by Vincent (1992c), and the high-speed treatment was 2.98 mm s −" .…”

Section: Standardizing the Position Of Testsmentioning

confidence: 99%

“…These tests are sometimes constrained both by biological aspects of the leaf and by the physics of fracture. For example, Lucas et al (1991) derived the Poisson ratio of Calophyllum inophyllum leaves from tearing tests. This ratio indicates a material's ability to resist changes in shape or volume, but it may be less reliable for biomaterials, as they are nonisotropic (Wainwright et al, 1982).…”

Section: mentioning

confidence: 99%

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Methods of assessing leaf‐fracture properties

1999

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Numerous authors have attempted to quantify the physical properties of leaves in relation to aspects of leaf ecology, including decomposition, sclerophylly, herbivory, and leaf function and longevity. This paper examines the relative merits of the punch-and-die, tearing and shearing tests for assessing leaf physical properties. We conducted a series of these three mechanical tests on leaves of Solanum laciniatum, and determined the effect of various test parameters on the measurement of fracture properties. For the punch-and-die test, the parameters considered were machine speed, clearance between the punch and the die, edge definition of the punch, and area of the punch. Aspects of the tearing test examined were notch length, end effects, and length-to-width requirements of test strips, and for shearing tests the effects of blade proximity, angle and sharpness were investigated. All the test parameters investigated were found significantly to affect the assessment of leaf-fracture properties. In addition, fracture properties were found to vary significantly within leaves. Some general principles for designing and implementing tests are outlined. This study suggests that while punching and shearing tests are useful means of quantifying leaf fracture properties, the value of the tearing test may be reduced as it is most constrained by the biological nature of the test material.

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Functional dental correlates of food properties in five Malagasy lemur species

Yamashita

1998

Am. J. Phys. Anthropol.

112

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Biomechanical explanations are fundamental to studies of functional dental morphology. Until recently foods were not classified in mechanical categories amenable to a rigorous examination of the fundamental physical relationship between teeth and foods. Fruit, insect and leaf categories, although descriptive, are mechanically heterogeneous. The diets of five Malagasy lemur taxa were described in terms of two mechanical properties, hardness and shear strength, in an earlier study (Yamashita, 1996b). In the present study, correlations between these two physical food properties and second molar tooth features of two lemur families are examined. Several relationships are hypothesized: 1) crest length is expected to be positively correlated with food shear strength; 2) the radius of curvature (r) of cusps is expected to be positively correlated with food hardness; and 3) basin area should increase relative to cusp radius as food hardness increases, and cusp-to-basin ratios should decrease with increasing food hardness. Two additional hypotheses address the debate concerning the relative influences of the most frequently eaten foods versus the most stressful foods in determining tooth form. The results of the predicted relationships are equivocal. 1) Crest length is negatively instead of positively correlated with strong foods. Crest lengths are correlated with quantities of leaf consumption, which are related to leaf shape more than to material composition. 2) As expected, r is positively correlated with food hardness and negatively with shear strength, but this applies to upper molar cusps only. Lower molar cusps complicate simple generalizations of relationships. 3) Hard foods are correlated with a tight fit of occluding cusps and basins instead of the expected loose fit. The most stressful foods eaten (hardest and strongest) have higher correlations with tooth features than the most frequently eaten foods. Several functional complexes can be identified. Hard food items are correlated with short cusps in lemurids, tight occlusal fit, small trigon and large talonid areas, and deep, acute basins. Large, shallow trigons, shallow, unrestricted talonids, and large upper molar basins are indicative of a diet of strong foods. These results demonstrate that some variation in tooth features is explicable with reference to mechanical properties of diet, although the relationships are complex.

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The fracture toughness of the leaf of the dicotyledon Calophyllum inophyllum L. (Guttiferae)

Cited by 87 publications

References 31 publications

The toughness of secondary cell wall and woody tissue

The toughness of secondary cell wall and woody tissue

Methods of assessing leaf‐fracture properties

Functional dental correlates of food properties in five Malagasy lemur species

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