Why were modern composite bows less affected by temperature and humidity than longbows?

The premise that modern composite bows are less affected by environmental conditions than traditional longbows is correct. While traditional longbows were typically crafted from a single material—most famously the English yew—their performance was highly susceptible to fluctuations in temperature and humidity, which could alter the wood's properties and necessitate leaving the bow unstrung when not in use.1

In contrast, the modern composite bow design, which became standard in the mid-20th century, utilizes a laminated construction that provides superior stability. These bows feature a core of wood sandwiched between facing and backing strips of fibreglass, all secured with epoxy glue. This combination of synthetic materials and modern adhesives makes the limbs significantly more resistant to the environmental changes that historically impacted wooden bows, allowing for greater consistency in accuracy, velocity, and distance.1