PHYSICAL AND MECHANICAL PROPERTIES OF NORFOLK-ISLAND-PINE GROWN IN HAWAII

Transcription

1 U.S. FOREST SERVICE RESEARCH PAPER FPL 73 JANUARY U.S. DEPARTMENT OF AGRICULTURE. * FOREST SERVICE * FOREST PRODUCTS LABORATORY * MADISON, WISCONSIN PHYSICAL AND MECHANICAL PROPERTIES OF NORFOLK-ISLAND-PINE GROWN IN HAWAII

2 SUMMARY Physical and mechanical properties of the wood of Norfolk-Island-pine grown in Hawaii were determined as an aid to forestation planning. Evaluations of those properties show that the wood is moderately heavy, moderately strong in both bending and compressive strength, stiff, and moderately hard; its shrinkage is small. These results will serve as a guide along with other factors to forestation planning in Hawaii. ACKNOWLEDGMENT Prepared in cooperation with the Pacific Southwest Forest and Range Experiment Station, U.S. Forest Service; the Forestry Division, Hawaii Department of Land and Natural Resources; and the Kahului Development Company of Kahului, Maui, Hawaii.

3 PHYSICAL AND MECHANICAL PROPERTIES OF NORFOLK-ISLAND-PINE GROWN IN HAWAII 1 by C. C. GERHARDS, Engineer FOREST PRODUCTS LABORATORY FOREST SERVICE US. DEPARTMENT OF AGRICULTURE INTRODUCTION Several Araucaria species have been introduced into Hawaii. Two of these species (A. columnaris (Forst.) Hook. (=A. cookii R. Br.) and A. heterophylla (Salisb.) Franco (=A. excelsa R. Br.)), collectively known in Hawaii as Norfolk-Islandpine, have b en planted in small stands on all of the Islands. 3 This Norfolk-Island-pine has grown well at most sites but is not plentiful. No record could be found of any evaluation of strength for either species other than for airdry wood of A. columnaris, but this was very limited in scope and not in readily comparable form (7). 4, 5 In contrast. more or less complete evaluations have been made for the more important species of the genus that grow Australia (2), 6 New Guinea (6), and South (5). As an to forestry planning, this Laboratory, in collaboration with the Pacific Southwest Forest and Range Experiment Station and the Forestry Division of the Hawaii Department of and Natural Resources, undertook research to evaluate the more important strength properties of Norfolk-Island-pine grown in Hawaii. This paper presents the results of that research. 1 Appreciation is extended to the Forestry Division. Hawaii Department of Land and Natural Resources, for providing financial support for the study; to R. G. Skolmen of the U.S. Forest Service research staff in Honolulu who selected and provided background information on the description of material; and to Kahului Development Company of Kahului, Maui, Hawaii, for donating the trees. 2 Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 3 A. columnaris is usually called Cook's pine, Cook's araucaria, pin colonnaire or columnar araucaria, while A. heterophyila is the true Norfolk-Island-pine. A. columnaris is native to New Caledonia and nearby islands and A. heterophyila to Norfolk Island (4). The species evaluated here is the more common of the two in Hawaii, but its identity could not be established from either the wood or the herbarium material received. 4 Underlined numbers in parentheses refer to Literature Cited at the end of this report. 5 See under A. cookii in Sallenave's "Proprietes Physiques et Mecaniques des Bios Tropicaux de l'union Francaise" (7). 6 See under A. bidwilli Hook. and A. cunninghamii Ait. in Bolza and Kloot's "The Mechanical Properties of 174 AustraIian Timbers'' (2).

4 DESCRIPTION OF MATERIAL pine." When sample trees were cut down in May of 1964, the stand spacing was 12 by 12 feet and the stand was 96 percent "Norfolk-Island-pine. Five trees of Norfolk-Island-pine were sam- Range in diameter at breast height was 14 to pled from a plantation located about 1-1/2 miles 24 inches for Norfolk-Island-pine and 2 to south-southwest of Haiku on the island of Maui, 8 inches for silk-oak. The plantation was in good Hawaii. The plantation, believed to have been pathological condition. planted between 1910 and 1915, is on a slope in The Norfolk- Island-pine trees sampled for hilly terrain at about 900 to 1,200 feet elevation. this study were of good form. They ranged in Rainfall at the site amounts to about 70 inches height from 111 to 133 feet and in diameter at annually. Temperature is moderate--ranging breast height from 19 to 22 inches. Merchantable from a low of 50 to a high of 85 F. Humidity is lengths ranged from 83 to 91 feet based on a top high throughout the year. The plantation was diameter inside bark of 8.0 inches. originally a row-by-row mixture of Norfolk- An 8-foot log was bucked from the 9- to 17-foot Island-pine and silk-oak (Grevillea robusta) (c-d) portion of each tree. Two additional 8-foot spaced 6 by 6 feet. Almost all of the silk-oak logs were bucked from one of the trees--at the died out when overtopped by the "Norfolk-Island- 1- to 9-foot (a-b) portion and at the 50- to 58-foot. Figure 1.--"Norfolk-Island-pine."A, a plantation on the island of Maul, Hawaii; B, a slabbed flitch; and C, flitches prepared for shipment. (M ) FPL 73 2

5 (m-n) portion. Slabs were cut from the logs on two opposite sides yielding a flitch of 6 to 8 inches thick containing the pith. Remaining bark was removed from the flitches which were then brushed with a preservative solution and coated with asphalt roofing cement. They were strapped to a pallet and shipped to this Laboratory. Illustrations showing plantation trees, a slabbed flitch, and all flitches readied for shipment are: in figure 1. When the flitches were cut into sticks at this Laboratory, it became obvious that considerable cross grain was present--as high as 1 in 4 slope in some sticks. The cause of this cross grain was mostly due to spiral grain in the tree, which ran as high as 14 degrees relative to the pith. An indication of the variation in grain angle across each flitch near the top end is given in figure 6 of the Appendix It was also noted that the wood was more or less cream-colored except for the central core of one tree which was tan. A sample of the tan core was examined for fungi, but none was found. Apparently, the one tree contained heartwood. PROCEDURES Standard methods (1) were followed in determining properties of Norfolk-Island-pine that a random method of selecting specimens for strength tests and a 1-inch-thick volumetric shrinkage specimen were used. Three 1-inch-thick cross sections were cut from near the tup end of each flitch as positioned in the tree. One cross section of each flitch was used as the volumetric shrinkage specimen (figs. 2 and 3), another for radial and tangential shrinkage specimens, and the third for species identification purposes. The remainder of each flitch was ripped into 2-1/2-inch square sticks. From each flitch, sticks were randomly chosen to provide four green and four air-dry specimens for static bending, compression parallel to grain, hardness, shear, and toughness tests as well as four longitudinal shrinkage specimens. Sizes of greenwood specimens corresponded to those given in the secondary methods of the standard (1). Shrinkages in radial. tangential, and longitudinal directions were measured at about 14, 7, and 0 percent moisture content. Shrinkage in volume was measured from green to ovendry only. Figure 2.--Cross sections of the "Norfolk- Isrand-pine" flitches from sample trees Nos. 1, 2, 4, and 5. (M 656) 3

6 PRESENTATION OF RESULTS Data on physical properties are presented in table 1 and data on mechanical properties in table 2. Average shrinkage-moisture relationships are shown in figure 4. Data on variations of physical and mechanical properties for green wood are presented in table 3. Tables 1 and 2 contain published data on various species for comparison. DISCUSSION OF RESULTS Figure 3.--Cross sections of the Norfolk- Island-pine flitches from sample tree No. 3. (M ) Specific gravity of the Norfolk-Island-pine evaluated in this study averaged 0.42 for green wood and 0.44 for air-dry wood. The wood is thus classified as moderately heavy (9), a category which includes mainland Douglas-fir. The standard deviation of specific gravity values for green specimens amounted to about 7 percent of the specific gravity, which is lower than the average of 10 percent for many mainland species as given in table 3. Average shrinkage of Norfolk-Island-pine from green to ovendry is small (9). It is substantially lower than shrinkages for many mainland species when specific gravities are compared. Although average shrinkage was small, shrinkage values for individual specimens were somewhat more variable than might be expected. This may be seen by comparing the coefficients of variation for Norfolk-Island-pine with those for the mainland species as given in table 3. A shrinkage fiber-saturation point may be estimated for Norfolk-Island-pine from the shrinkage-moisture relationships shown in figure 4 by extrapolation to zero shrinkage. The fiber-saturation point thus estimated is about 25 percent moisture content for radial shrinkage and about 28 percent moisture content for tangential shrinkage. The mechanical properties of Norfolk-Islandpine given in table 2 reflect the properties of wood having some cross grain, since so much of the wood in the sample flitches was spiral grained. Most of the cross grain was removed from static bending and compression parallel specimens of green wood by using the secondary standard size of 1-inch- square cross section. FPL 73 4

7 Figure 4. --Average shrinkage-moisture reiationships for "NorfoIk-Island-pine" grown in Hawaii. (M ) The small size was also used to eliminate as many knots from the specimens as possible. When specimens were cut from air-dry wood, almost all were prepared with the 2-inch cross section because the grain did not appear to be crossed. (Grain on the planed tangential surface of the air-dry wood was difficult to see with the unaided eye, and the wood could be scribed at any angle to the grain about as easily as with the grain.) As a result, a number of tests of air-dry wood had to be culled because of excessive cross grain. Blank spaces in table 2 for trees 1 and 5 result from culling all the specimens for the particular type of test. There was nothing unusual about the tests of greenwood. In the air-dry wood, however, failures in bending specimens and in some shear specimens were different than normally encountered for mainland species. Bending specimens of air-dry wood failed in simple tension, but the failure tended to be about 40 to 50 degrees with the grain rather than straight across as is common for lower density woods. Figure 5 shows the type of failure. In air-dry shear specimens, normal failures occurred when the plane to be sheared was oriented essentially either normal or tangent to the growth rings, but atypical failures occurred when orientations were lacking. For the latter, failure was partly shear parallel to grain and partly tension into the shear at an angle to the grain; the tension failure was particularly prominent when cross grain extended out of the block into the sheared section. This peculiar failure was also noted in shear specimens of Araucaria angustifolia (Bert.) O. Kuntze, the Parana pine of Brazil (5). Aside from the unusual failures, mechanical properties of Norfolk-Island-pine tend to be about as expected for a species of its density. The wood is stiff, moderately strong in both bending and compressive strength, and moderately hard. Its density and mechanical properties are 5

8 ff more or less comparable with those of Douglasfir of the intermediate type. 7 Compressive strength a little lower for Norfolk-Islandpine, but end and shear strength are higher. Shear strength is probably somewhat high and compressive strength a little low because of cross grain. Because there was so much spiral grain in the sample material. the prevalence of spiral grain in other trees should be studied to see if this is a dominant characteristic of Norfolk-Islandpine. This is an important factor to consider, since structural utilization will depend upon the extent of cross grain as well as other characteristics that affect strength in lumber. CONCLUSIONS The wood of Norfolk-Island-pine is moderately heavy, moderately in bending and compression, stiff, and moderately hard. Its shrinkage is small. It is roughly comparable to intermediate type Douglas-fir in density and mechanical properties. Utilization of the wood will depend upon the prevalence of spiral grain in the tree. Figure 5.--Tension side of air-dried bending specimens of Norfolk-Island-pine grown in Hawaii, showing the angle of fracture. A portion was removed from each specimen for a moisture sample. The white spots appearing on the surface of the specimens are planer chip marks and the lines show the direction of the grain. (M ) 7 This classification of Douglas-fir has been used for many years and appears In the Wood Handbook (8). A different classification, based on newer data, is shown in the Western Wood Density Survey, Report No. 1 " (10). FPL 73 6

9 LITERATURE CITED (1) American Society for Testing and Materials Standard method for testing small clear specimens of timber. ASTM D Philadelphia. Pa. (2) Bolza, E., and Kloot, N.H The mechanical properties of 174 Australian timbers. Commonwealth Sci. Ind. Res. Organ., Div. Forest Prod. Tech. Pap. 25. Melbourne, Australia. (3) Bryan, L.W., and Walker, C.M A provisional check list of some common native and introduced forest plants in Hawaii. U.S. Forest Serv., Pacific Southwest Forest and Range Exp. Sta. Misc. Pap. No. 69. Berkeley, Calif. (4) Dallimore, W., and Jackson, A.B A handbook of coniferae. Edward Arnold and Co., London, England. (5) Dohr, A.W Mechanical properties of Brazilian Parana pine, Southern Lumberman 186:39-40, 42. (6) Ryan, Anne The mechanical properties of Klinki and Parana pines. Commonwealth Sci. Ind. Res. Organ.. Div. Forest Prod. Tech. Pap. 5. Melbourne, Australia. (7) Sallenave, P Proprietes physiques et mecaniques des bois tropicaux de l'union Francaise. Centre Tech. Forest Trop. No. 8. Nogent-sur-Marne (Seine), France. (8) U.S. Forest Products Laboratory Wood handbook. U.S. Dep. Agr., Agr. Handb. 72. (9) Standard terms for describing wood. U.S. Forest Serv., Forest Prod. Lab. Rep (10) Forest Service Western wood density survey, Report No, 1. U.S. Forest Serv. Res. Pap. FPL Forest Prod. Lab., Madison, Wis. Table 1.--Shrinkage of "Norfolk-Island-pine" grown in Hawaii and of other species for comparison 7

10 Table 2.--Mechanicalproperties of "Norfolk-Island-pine" grown in Hawaii and of other species for comparison Table 3.--Variation of data on strength and related properties of "Norfold-Island-pine" grown in Hawaii (green condition) 1 FPL

11 APPENDIX The angles of the grain given in figure 6 are relative to the pith. They were measured on the specimens used for volumetric shrinkage and were 1-inch-thick cross sections of each flitch. After ovendrying, the cross sections were split along a radius and the angle of the grain, usually the split surface, was measured relative to the face of the cross section at the pith and at 1-inch intervals from the pith, using a machinist's protractor. Because of the method of determining angles, the graphs shown should only be taken as indicative of the presence of spiral grain. Except for trees 2 and 5, the grain angles lack symmetry for the two sides of each tree. This is mostly because of a lack of symmetrical growth about the pith, but differences in shrinkage along the radii and visual judgments of the grain direction are also partially responsible. All spiral grain was right-handed, that is, the grain appeared to traverse up and around the tree in a right-hand thread manner. Figure 6.--Angle of grain vs. distance from pith in "Norfolk-Island-pine" specimens used for voiumetric shrinkage determinations. M