What is the primary risk associated with prolonged exposure of wood to sunlight?

Prolonged exposure of wood to sunlight primarily leads to structural weakening. This weakening occurs because ultraviolet (UV) radiation from the sun breaks down the lignin and cellulose within the wood. Over time, this breakdown can significantly reduce the integrity and strength of the material. As a result, wood may become brittle and more susceptible to damage, making it less reliable in applications such as aviation, where strength and durability are critical.

While color change is a noticeable effect of sunlight exposure, it primarily involves aesthetic aspects rather than structural integrity. Fungal growth and insect infestation are also concerns related to wood but are typically more linked to moisture and environmental conditions rather than direct sunlight exposure. Therefore, understanding the impact of UV radiation on wood's structural properties helps highlight why this is the primary risk associated with prolonged sunlight exposure.