Viscoelastic characteristics of carbon fiber-reinforced epoxy filament wound laminates

The mechanical properties of fiber-reinforced composites are time-dependent due to the viscoelastic nature of polymers. This study covers the creep/recovery and dynamic mechanical properties of high-performance composites under low-stress loading. Flat unidirectional 6-layer laminates are manufactured by dry-filament winding and cured under hot compression. Four different laminates are studied: [0] ₆, [30] ₆, [60] ₆, and [90] ₆. Dynamic mechanical curves and creep behavior are highly dependent on the ply angle up to 60°. The fiber orientation does not influence significantly the glass transition temperature, except for the [0] ₆ laminate, which has a higher T _g compared to the other samples. Normalized dynamic mechanical curves are plotted aiming to study the behavior of the material passing through the glass transition temperature (T _g). The modulus decreases for fiber angles toward the transverse direction, but the energy dissipation occurs in a broader temperature range. Creep/recovery also demonstrates a dependency on the fiber orientation, in which the sample [0] ₆ (highest storage modulus) has the lowest strain, leading to higher molecular hindrance compared to the other laminates.