Structural health monitoring using nuclear quadrupole resonance is disclosed. For example, in one embodiment, a method of monitoring stress is provided. The method includes scanning a composite using an NQR spectrometer, the composite having a polymer matrix and a microcrystalline material disposed in the matrix. The microcrystalline material includes molecules having nuclei with respective nuclear quadrupole moments. The method also includes determining microscopic strain distribution indices of the composite from the NQR scans to quantify stress and identify precursors to failure in the composite.