Characterization of Cure and Temperature Dependent Properties of Filament Wound Composite Structures

Residual stress development in filament wound composites presents a critical challenge for the fabrication of thick composite structures exposed to elevated temperatures during operation. This study focused on determining temperature and cure dependent material properties to aid in understanding the residual stress build-up during the cure. Material characterization of a filament wound composite materials was performed by investigating thermo-chemical shrinkages in resin, lamina, and bi-lamina configurations. The coefficient of thermal expansion (CTE) of both the neat resin and the fiber was measured, and the gel point and chemical shrinkage of the neat resin were investigated. A filament wound unidirectional laminate was then constructed, and its CTE was characterized and compared to various material homogenization schemes. The constitutive material data and knowledge of the proper CTE homogenization scheme was then used as inputs to self-consistent field equations to calculate the temperature and cure dependent properties of the filament wound lamina, which were calibrated using a bi-lamina experiment. This calibration was successful, and future work on examining the development of residual stress in filament wound lamina can be carried out. To determine the limits of through thickness residual stresses, interlaminar tensile strength testing was conducted on filament wound specimens. Overall, this work provides a validated constitutive material model during cure, and establishes a foundation for improved residual stress modeling in filament wound composite structures.