For a statically determinate truss, only the equations of static equilibrium are required to solve for the internal forces. Material properties and displacements need not be considered. See sub-subunit 2.3.1.
Attribution:
Stephanie Redfern, Ranjeet (Ron) Agarwala, and Dr. Steve Gibbs. Mechanics I. The Saylor Academy 2014, http://www.saylor.org/courses/me102/