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Merbau Wood: Characteristics, Strength, and Applications

Introduction
Merbau wood, also known scientifically as Intsia spp., primarily I. palembanica (Leguminosae family), is one of the most recognized woods in Malaysia and across Southeast Asia. Other common names include *merbau ipil* (Peninsular Malaysia) and *ipil laut* (Sabah), particularly for I. bijuga. This highly regarded wood is known for its strong heartwood, which darkens from yellowish to orange-brown when fresh, maturing to a brown or dark red-brown with exposure.

Globally, merbau wood is also referred to as Kwila (Australia), Merbau (Brunei), Vesi (Fiji), Ipil (Philippines), and Lumpha (Thailand), among others. It is also popularly used in regions like Indonesia and Papua New Guinea.

Density
Merbau wood is classified as a *Heavy Hardwood*, with an air-dry density ranging from 515 to 1,040 kg/m³. Its density contributes to its strength and durability, making it ideal for a variety of uses, especially in high-traffic and heavy-duty applications.

Natural Durability
Merbau wood is classified as durable under exposed conditions. Tests conducted by the Forest Research Institute Malaysia (FRIM) indicate that the untreated wood has an average service life of 5.5 to 6 years. However, it is highly susceptible to powder-post beetle attacks, especially in the sapwood.

Preservative Treatment
Merbau wood is notably *very difficult to treat* with preservatives, which is typical of dense and naturally durable hardwoods.

Texture
The wood has a rather coarse but even texture, with interlocked grain that gives it an appealing appearance. Its interlocked grain also contributes to its resilience in both indoor and outdoor applications.

Strength Properties
Merbau is classified under *Strength Group B* or *SG 4* based on Malaysian standards. Its mechanical properties show that it is a strong, durable wood, capable of withstanding substantial stress.

Strength Properties of Merbau Wood
| Condition | Modulus of Elasticity (MPa) | Modulus of Rupture (MPa) | Compression Parallel to Grain (MPa) | Compression Perpendicular to Grain (MPa) | Shear Strength (MPa) |
| --------- | ---------------------------- | -------------------------- | ------------------------------------ | ------------------------------------------ | --------------------- |
| Green     | 13,900                        | 89.0                        | 46.7                                | 6.4                                        | 10.8                   |
| Air Dry   | 15,400                        | 116.0                       | 58.2                                | 9.2                                        | 12.5                   |

Machining Properties
Merbau wood is relatively *easy to resaw and cross-cut* when green, but becomes slightly difficult when dried. It is moderately easy to plane, producing a smooth surface. However, there may be slight grain pickup on the radial face when planed.

Machining Properties of Merbau Wood
| Condition | Sawing                | Planing               | Boring               | Turning              |
| --------- | --------------------- | --------------------- | -------------------- | -------------------- |
| Green     | Moderately easy        | Easy                  | Easy                 | -                    |
| Air Dry   | Slightly difficult     | Slightly difficult     | Slightly difficult    | Smooth               |

Nailing Property
The nailing property of merbau wood is *very poor*, requiring pre-drilling for effective fastening.

Air Drying
Merbau wood seasons slowly and requires time for proper air drying. It takes approximately 4.5 months to air dry 13 mm thick boards, while 38 mm thick boards require around 6 months. The wood generally dries without significant degradation, although some powder-post beetle attacks on the sapwood have been reported.

Shrinkage
Merbau wood exhibits *low shrinkage*, with radial shrinkage averaging 0.9% and tangential shrinkage averaging 1.6%. This characteristic makes it dimensionally stable for various applications, particularly for flooring and joinery.

Defects
While merbau logs are typically free from significant defects, they are vulnerable to powder-post beetle attacks, particularly in the sapwood. Preventative measures are recommended for sapwood portions in furniture and construction applications.

Uses
Merbau wood is celebrated for its attractive grain and color, making it a favorite for *interior finishing, panelling, mouldings, office fittings, and superior joinery. Due to its durability and low shrinkage, it is also widely used in **flooring, particularly for high-traffic areas, and in the manufacturing of **cabinetry, furniture, and musical instruments*.

Beyond decorative applications, merbau is also suitable for *heavy construction, including **power transmission poles, railway sleepers, and marine structures. Its strength and natural resistance to decay make it an excellent material for **tool handles, pallets, decking, and staircase components*.

In summary, merbau wood is versatile and well-suited for both *aesthetic and structural applications* due to its durability, strength, and unique appearance. Its combination of mechanical properties and aesthetic appeal makes it a top choice in the woodworking and construction industries worldwide.