Effects of PVDF on mechanical and damping properties of co-cured aramid nonwoven fabric/epoxy composite

In order to estimate the effects of thermoplasticity crystalline polymer polyvinylidene fluoride (PVDF) on dynamic mechanical and damping properties of co-cured composites, PVDF was loaded on aramid nonwoven fabric (ANF), and PVDF-ANF/epoxy (EP) structural damping composites were fabricated by co-cured process firstly. Then, the temperature spectra of loss factor, loss modulus and storage modulus were tested through dynamic mechanical analyzer; flexural strength, flexural modulus and interlaminar shear strength were measured to evaluate the static mechanical properties of the composites; the resonant frequencies and decaying curves of free vibration were tested by single cantilever beam vibration experiment and the loss factors were calculated; the fracture toughness and toughening mechanisms were investigated by type I and type II interlaminar fracture toughness experiments as well as the observation of fracture surface micro morphologies. At last, the microstructure of the composites were analyzed to discuss the structural internal reasons for having both mechanical properties and damping properties. The results indicate that the damping properties and interlaminar fracture toughness of PVDF-ANF/EP composites can be improved further more by loading PVDF on the surfaces of ANF without leading to an obvious decrease of mechanical properties of the composite. The loss factor of composite is improved by 33.3%, and the fracture toughness of type I and type II are improved by 168% and 208%, respectively.