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U.S. FOREST SERVICE RESEARCH PAPER FPL 65 AUGUST 1966 U. S. DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY MADISON, WISCONSIN PHYSICAL AND MECHANICAL PROPERTIES OF BLACKBUTT EUCALYPTUS GROWN IN HAWAII SUMMARY Physical and mechanical properties of blackbutt eucalyptus (Eucalyptus pilularia Sm.) grown in Hawaii were determined because of the interest in the species for forestation in Hawaii, Based on the property evaluations in this study, the wood is heavy, very strong in bending and compression, hard and exceed- ingly stiff, and its shrinkage is very large. It is not as dense nor as strong and hard as the wood native to Australia, but it essentially has the same stiffness and shearing strength. The results of this research will aid in forestation planning in Hawaii and contrib- ute to efficient utilization of the species. ACKNOWLEDGEMENT Prepared in cooperation with the Pacific Southwest Forest and Range Experiment Station, U.S. Forest Service, and the Forestry Division, Hawaii Depart- ment of Land and Natural Resources. PHYSICAL AND MECHANICAL PROPERTIES OF BLACKBUTT EUCALYPTUS GROWN IN HAWAII1 BY C. C. GERHARDS, Engineer Forest Products Laboratory2 Forest Service U. S. Department of Agriculture warping occur occasionally, but this is remedied INTRODUCTION by reconditioning. The wood is widely used in general construction and for flooring and has Blackbutt eucalyptus (Eucalyptus pilularis Sm.), been used successfully in glued-laminated mem- a hardwood species native to Australia, has bers.5 been introduced to all islands of Hawaii, although South Africa plantations of blackbutt euca- extensive plantings have mainly been confined to lyptus. Air-dry wood from the plantations was the Island of Oahu. The Forestry Division, Hawaii found to be somewhat lower in density and strength Department of Land and Natural Resources, than the native wood of Australia.6 which is currently planting this species, is No systematic evaluations of the wood grown interested in properties of the wood from the in Hawaii have been made, although it has been standpoint of forestation planning. used there as flooring and in heavy construction. The native wood of Australia, according to Therefore, research was undertaken by this evaluations,3 is very heavy, exceedingly strong, Laboratory in collaboration with the Pacific and exceedingly stiff.4 Heartwood is a pale Southwest Forest and Range Experiment Station grayish-brown color with a pinkish tinge. Sap- and the Forestry Division of the Hawaii Depart- wood is less than 1 inch wide. The wood is ment of Land and Natural Resources to deter- moderately textured straight, though mine the physical and mechanical properties of occasionally wavy grained. It may be worked by blackbutt eucalyptus grown in Hawaii. This paper hand or machine. In drying, some collapse and presents results and evaluation 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 Hawaii Forestry Research Center, Pacific Southwest Forest and Range Experiment Station, who selected the sample material and provided background information on the description of the material and uses of the wood; to Hawaiian Fern-Wood, Ltd., for logging and milling; and to Honokaa Sugar Co. for providing the trees. 2 Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 3 Bolza, E., and Kloot, N. H. The mechanical properties of 174 Australian timbers. Div. of Forest Prod. Tech. Pap. No. 25. CSIRO, Australia. 1953. 4 Classified according to "Standard terms for describing wood," U.S. Forest Serv., Forest Prod. Lab. Rep. 1169. 1956. 5 Division of Wood Technology, Forestry Commission of New South Wales. Technical Notes, Vol. 5(3): 3-7. 1951. 6 Banks, C. H. Notes on the properties of the timber of South African grown Eucalyptus pilularis Sm. J. of the South African Forestry Ass. 29:56-59. 1957. DESCRIPTION OF MATERIAL Five representative trees were selected for sampling. These ranged from 22 to 29 inches in Sample trees came from an even-aged stand diameter at breast height and 163 to 178 feet of mixed blackbutt and robusta eucalyptus (E. high with merchantable lengths of to 117 feet, robusta Sm.), estimated at about 42 or 43 years All log ends showed splits after felling and old and located on the land of Waikoekoe near bucking. A 6-inch-thick, north-south flitch con- the lower edge of the Hamakua Forest Reserve, taining the pith was cut from the 9- to 17-foot about 2 miles south of town of Kukuihaele on height of each sample tree. Similar flitches were the Island of Hawaii. Pertinent conditions at the cut from the 1- to 9-foot and 97- to 105-foot- site are: 1,700 feet elevation, undulating slope. height of one of the trees. All flitches were generally moist soil with good natural drainage, brush coated with a 5 percent solution of penta- and about 80 inches average annual rainfall. chlorophenol, then bare surfaces were coated About percent of the stand was blackbutt with a wax-emulsion-type end sealer. eucalyptus which was described as being in good Representative pictures of the standing trees to medium pathological condition Incipient decay are shown in figure 1. Flitch sections are was common to the pith area at the butt of most shown in figures 2 and 3. trees. Figure 1.--Blackbutt eucalyptus trees: (A) light-barked trees are blackbutt and dark- Figure 2.--Cross sections of blackbutt euca­ barked trees are robusta eucalyptus; (B) lyptus flitches from sample tree No. 1. closeup of sample tree No. 1. M 125 891 M 130 971 FPL 65 Figure 3.--Crosssections of blackbutt eucalyptus flitches from sample trees Nos. 2, 3, 4, and 5. green wood and another four sticks fox strength PROCEDURES tests of air-dry wood. Each stick selected was cut into specimens for evaluation in static bend- In general, standard procedures were followed ing, shear, compression parallel to the grain, in determining physical and mechanical properties and for toughness and hardness. Four longitudinal fer this species.7 Departures from the shrinkage specimens, 1 inch square by 10 inches were mainly concerned with methods of sampling long, were also obtained from each bolt. As and the number of properties evaluated. suspected from the splits on the log ends, some Three 1-inch-thick cross sections were cut of the material in the pith area contained pre- from near the top end of each flitch. Radial and existing compression failures, a condition known tangential shrinkage specimens were obtained as brittleheart.8 Specimens were cut to avoid from one of the disks; another disk was used as these failures or to minimize their influence. a volumetric shrinkage specimen; and the third Shrinkages, except for volumetric, were meas- disk was used for identification purposes. The ured at 80, 65, and 30 percent relative humidity remainder of each flitch was then ripped into at 80° F. and at the ovendry condition. Volumetric 2-1/2-inch-square sticks. By random selection, shrinkage was measured only at the ovendry four were chosen for strength tests of condition. 7 American Society for Testing end Materials. Standard methods of testing small clear specimens of timber. ASTM D 143-52. 1952. 8 Skolmen, R. G., and Gerhards, C. Brittleheart in Eucalyptus robusta grown in Hawaii. Forest Prod. J. 14(12): 549-554. 3 4 PRESENTATION OF RESULTS eucalyptus into the heavy wood classification along with two other eucalypts, robusta and Data on physical properties are presented in saligna, grown in Hawaii and many of the table 1 and data on mechanical properties in grown on the Mainland. It is not as heavy as the table 2. Data concerning variations of the physical wood grown in its native habitat-Australia. and mechanical properties are presented in Overall shrinkage from green to ovendry is table 3. Information on other species is included very large, which is comparable to the shrinkage in each table for comparison. Average shrinkage- for many of the hickories. Overall shrinkage of moisture content relationships are given in fig- blackbutt is slightly lower than previously found ure 4. for robusta eucalyptus and somewhat lower than found for saligna eucalyptus (E. saligna Sm.). DISCUSSION OF RESULTS Based on extrapolation of curves in figure 4, the fiber saturation point for radial shrinkage is The average specific gravity of 0.59 for green about 26 percent moisture content and for tan- wood and 0.66 for air-dry wood places blackbutt gential shrinkage is about 32 percent. The nor- Table 1.--Shrinkage of blackbutt eucalyptus grown in Hawaii FPL 65 4 9 mally expected value is 30 percent. and saligna) previously evaluated, although spe- Volumetric shrinkages of some disks (flitch cific gravity averages for all three species are cross sections) are high in comparison to over- practically identical. In other properties, black- all in radial, tangential, and longitu- butt eucalyptus has about the same shock resis- dinal directions. For example, total volumetric tance (based on values for toughness and work shrinkage for the disk from tree No. 2 was static bending), hardness, and shear strength 21.9 percent, whereas, the sum of shrinkages as saligna eucalyptus, and Et has practically the for the three different directions (a close approx- same hardness as robusta eucalyptus but higher imation of volumetric shrinkage) amounts to shock resistance. 14.8 percent. The larger estimate of volumetric The higher stiffness and strength In bending shrinkage is probably a reflection of some and compression parallel to grain of blackbutt collapse of wood structure that occurred during eucalyptus are probably a reflection of grain. drying, since this is one of the known character- The grain in the blackbutt eucalyptus specimens istics of the species.

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