The application of Time–Temperature Superposition (TTS) for the determination of isochronous stress–strain diagrams of textile-reinforced thermoplastic composites under compressive load in laminate thickness direction is evaluated. Creep experiments are carried out at various temperature and load levels. The creep curves are assembled to master curves using horizontal and vertical shifting. These curves are compared to long-term creep data and an isochronous stress–strain diagram is determined.