The duration depends on the input acceleration. At 1G input and a Q of 17 I calculate a metal stress of about 2000 psi,depending on the laminate. Assuming the metal to fail, it depends on the static and fatigue strength. You would need about 20G input dwell at resonance to get the metal to reach 40,000 psi. If that is the metal static strength it will fail right away, but if that is the fatigue strength it may take hours or forever unless you increase the load. However, the failure may be dominated by the laminate matrix and shear failure, so the calculation is complex inthat case. At any rate its going to take a whopping load to fail that beam. What is your acceleration input levcel at resonance?