Parts made by additive manufacturing are often structural in nature, rather than having functional properties conveyed by a polymer or other component present therein. Printed parts having piezoelectric properties may be formed using compositions that are extrudable and comprise a plurality of piezoelectric particles and a plurality of carbon nanomaterials dispersed in at least a portion of a polymer material. The piezoelectric particles may remain substantially non-agglomerated when combined with the polymer material. The polymer material may comprise at least one thermoplastic polymer, optionally further containing at least one polymer precursor. The compositions may define an extrudable material that is a composite having a form factor such as a composite filament, a composite pellet, a composite powder, or a composite paste. Additive manufacturing processes using the compositions may comprise forming a printed part by depositing the compositions layer-by-layer.