Time and temperature dependence of the viscoelastic properties of CFRP by dynamic mechanical analysis

Understanding viscoelastic properties of composite materials is essential for the design and analysis of many advanced structures. Viscoelastic material characterization is critical in designs that incorporate specified levels of damping, and to the understanding of processing problems. However, experimental viscoelastic characterization of anisotropic materials can be complicated because of the number of independent parameters to be evaluated. Recently, an approach leading to the 3-D viscoelastic characterization of transversely isotropic materials using a reduced number of measured parameters has been developed. Based on this recently developed model, the present work evaluates time and temperature effects on the viscoelastic properties of unidirectional carbon fiber reinforced laminae and cross-ply laminates. The experimental investigation is conducted on subscale specimens loaded in flexure, using dynamic mechanical analysis (DMA) equipment. The results presented demonstrate that DMA equipment offers good potential to study changes in viscoelastic properties of transversely isotropic laminae and laminates, related to temperature and frequency. This work provides a means for the study of viscoelastic properties of fiber-reinforced composites, and, therefore, constitutes a valuable contribution to the understanding of time and temperature dependence of these mechanical properties.