Many trees in tropical rain forest exhibit interlocked grain. This phenomenon was observed, using a splitting method on 10 genus from 8 families in French Guiana. There were rather strong variations between trees and inside of each tree. Different index were used to describe this interlocked grain.
MOE was measured on selected trees, using different type of specimen: thin long samples (2x12x150mm, RTL) both parallel to local grain or to log axis in successive radial position, standard rods (20x20x360mm, RTL) parallel to log axis and big rods (50x25x1000mm, RTL) parallel to log axis, large enough to present a full wave of interlocked grain). A mechanical model based on classical wood anisotropy fits well to the experimental data for prediction of massive wood MOE from local information.
MOE of massive wood show a clear decrease when interlocked grain index grow, but usually not more than 10% decrease was observed.
Former results have shown that rupture energy necessary to create a radial-longitudinal surface by wood splitting grows more than 50% with interlocked grain occurrence.
Moreover, radial splitting of large tropical trees with high density wood is more prone to appear due to the decrease of the ratio rupture energy/MOE when wood density grows.
Finally the long lasting high level of maturation stress in tropical trees growing in primary forest means a very high level of stored elastic energy in the trunk that could be dangerous for the living tree.
Interlocked grain can be a good solution to prevent the risk of radial splitting for these adult trees.