Continuous fiber reinforced thermoplastic composites are increasingly valued in automotive, aerospace,
and renewable energy applications for their superior mechanical properties, cost efficiency, and
excellent recyclability. However, with growing environmental regulations urging sustainable waste
management, the development of effective recycling methods and understanding the mechanical behavior
of recycled composites have become critical. This study investigates the mechanical response of
mechanically recycled glass fiber reinforced polyamide 6 composites, emphasizing their nonlinear and
time-dependent behavior under complex loading conditions. The recycling process induces unique
microstructural features, including significant anisotropy and variability in fiber orientation and strand
distribution [3]. These characteristics stem from mechanical recycling and are critical to understanding
the material's performance. Our research combines detailed experimental testing and advanced
numerical modeling to bridge the gap between the microstructural properties and macroscopic mechanical
response of recycled composites. Cyclic loading-unloading tests, creep recovery experiments,
and controlled relative humidity conditions were used to assess the material's damping properties,
energy absorption capacities, and inelastic behaviors. A novel multiscale modeling framework was
developed to predict the composite's nonlinear response. This approach incorporates the viscoelastic
and viscoplastic behavior of the polymer matrix, coupled with anisotropic damage modeling for the
strands [1, 2]. The model successfully captured key aspects of the material's behavior, including high
dissipation levels observed in hysteresis loops and the anisotropic response attributed to recyclinginduced
fiber o rientation. To a ccount for experimental variability, multiple Representative Volume
Elements (RVEs) were generated, enabling the study of strand position and orientation effects on the
mechanical response. The results demonstrate that while the model effectively p redicts monotonic
loading responses and general trends in cyclic and creep behaviors, challenges remain in fully capturing
the extent of viscous effects and damage accumulation in certain orientations. Experimental
observations revealed variability in mechanical performance, with some specimens showing strain
accumulation and reduced recovery during creep recovery tests, underscoring the influence o f the
complex microstructure. Figure 1 provides a comprehensive depiction of the study's methodology and
key outcomes.