Mechanical Properties of Tropical Hardwoods

As the industry continues to navigate the supply chain challenges and reduced availability of Ipe due to its recent listing under CITES Appendix II, finding reliable, high-performance alternatives has become critical. To address this shortage, we initiated a comprehensive comparative study evaluating several other tropical hardwoods against Ipe. Our primary objective was to demonstrate that readily available species—specifically Torem, Bangkirai, and Batu—are statistically equivalent substitutes for structural and decking applications. By subjecting these materials to rigorous physical testing, we aim to show that these alternatives not only provide the strength and durability expected of Ipe but also offer more predictable and consistent material properties.

Scope of Testing

We have concluded our material testing on four tropical hardwood species: Torem (Manilkara kanosiensis), Bangkirai (Shorea laevis), Batu (Shorea guiso), and Ipe (Handroanthus spp.). The materials were systematically evaluated for the following key properties:

• Density
• Moisture Content (MC) at the time of testing
• Hardness
• Bending Strength (Modulus of Rupture - MOR)
• Bending Stiffness (Modulus of Elasticity - MOE)

Methodology & Conditioning

To ensure an accurate and equitable comparison, all boards were stacked and stickered in an environmental conditioning chamber maintained at 20°C and 65% relative humidity (RH) until they reached equilibrium prior to testing.

Density and Moisture Content

The average density and moisture content for the specimens at the time of the test are documented below.

Density Summary:



Moisture Content Summary:

SPECIES	MOISTURE CONTENT (%)	STD. DEV.
TOREM	14.8	0.1
BATU	13.5	0.6
BANGKIRAI	15.6	0.6
IPE	12.4	0.5

• Bending Tests (MOR & MOE): Conducted on 15 specimens per species. The test pieces were milled to 1" x 1" x 18" dimensions and tested across a 16-inch span.
• Density & Moisture Content: Calculated by randomly selecting four bending specimens from each species group. We cut 1-inch-long blocks from these specimens, measured them precisely using digital calipers, and recorded their initial weights. These blocks were then oven-dried for 24 hours and re-weighed to calculate the exact moisture content at the time of testing.
• Hardness: Conducted on specialized specimens milled to 2.5" x 3.5" dimensions.

Test Results

Bending Strength – Modulus of Rupture (MOR)

The table and plot below outlines the average and standard deviation for the bending strength (MOR) of each species.

SPECIES	AVG.MOR (psi)	STD. DEV.
TOREM	23712	2250
BATU	19518	3313
BANGKIRAI	18328	2639
IPE	2633	7917

Bending Stiffness – Modulus of Elasticity (MOE)

The table and plot below illustrates the average and standard deviation for bending stiffness (MOE).

SPECIES	AVG.MOE (X10^6 psi)	STD. DEV.
TOREM	2.65	0.458
BATU	2.62	0.344
BANGKIRAI	2.16	0.260
IPE	2.82	0.647

Key Observation on Bending Variability: While Ipe yielded the highest average values for both MOR and MOE, the variability within the Ipe samples was significantly higher than the alternatives. Specifically, the standard deviation for Ipe's MOR was 2.4 to 3.5 times higher than the other species. Similarly, Ipe’s MOE values varied 1.4 to 2.5 times more than the comparison group.

Hardness

The table below details the average and standard deviation for the hardness of each species.

SPECIES	AVG.HARDNESS (lbs.)	STD. DEV.
TOREM	3257	502
BATU	1878	392
BANGKIRAI	2084	450
IPE	3715	667

Key Observation on Hardness: Consistent with the bending test results, Ipe exhibited the highest average hardness. However, it once again displayed the widest margin of inconsistency, with hardness values varying 1.3 to 2 times more than the other tested species.

Conclusions & Customer Recommendations

The data clearly demonstrates that we have highly viable, statistically equivalent alternatives to Ipe. It is important to emphasize that while Ipe is historically recognized for its high density and peak strength, our testing reveals that its performance values are remarkably inconsistent compared to other tropical hardwoods.

Torem, in particular, emerges as an exceptional substitute. It compares very closely to Ipe in overall physical performance but delivers significantly tighter standard deviations. This means Torem offers structural predictability and consistency that Ipe currently lacks, making it a highly reliable choice for future projects while bypassing CITES-related supply chain hurdles.