Complex sentence: Studies of various projectile types have been crucial in overturning the prior theory that spallation occurs at a threshold of pressure, independent of time: instead, experiments show that longer-lasting shocks of a given magnitude produce more material damage.
Split into simpler sentences: Studies of various projectile types have been crucial in overturning a prior theory that spallation occurs at a threshold of pressure, independent of time. Instead, experiments show longer-lasting shocks of a given magnitude produce more material damage.