It used to be simple; a bat was one piece of wood, aluminum or composite. How things have changed! Two piece bats are now extremely popular and seem to be the trend for the foreseeable future.
Easton, Demarini and Nike have long championed the two-piece design. Demarini and Nike have held fast to this philosophy while Easton has branched out to make bats in almost all designs in an effort to appeal to everyone. They say the major benefit of a two piece bat is that it gives more flex to the barrel at the point of contact and, therefore, increases the trampoline effect (see photo of bat after the point of contact). This should not be confused with handle flex (or whip action). Handle flex or whip action is supposed to take place before the point of contact with the ball, and the trampoline effect at the point of contact.
The one-piece bat argument long championed by Louisville and recently COMbat. Louisville claims their Triton and H2 are “bonded” together to act more like a true one-piece bat. They say the two-piece design results in weakness at the joint of the handle and barrel thereby reducing the trampoline effect or spring back. They’re essentially saying that it provides very little resistance and therefore will not spring back as quick and hard as a one-piece design.
Before we go any farther, let’s understand what trample effect actual means in the scientific world. The trampoline effect refers to pronounced elasticity in the impacting object (baseball bat, tennis racquet, golf club, etc.) such that it acts like a trampoline. It is also referred to as the spring-like effect because of the degree to which the object depresses, then springs back into shape when striking a ball. Here are the scientific specifics for a baseball bat: