A toughening and strengthening technique of hybrid composites with non-woven tissue

The hybrid composite materials with non-woven tissue (NWT) are developed to improve the mechanical properties of conventional fiber reinforced plastic (FRP) composite materials. From the previous works we can see that the interleaving of the non-woven carbon tissue (NWCT) layer largely increases the Mode II interlaminar fracture toughness, while it does not significantly change the Mode I interlaminar fracture toughness. In addition, compared with conventional carbon fiber reinforced plastic (CFRP) composites, the hybrid composites with NWCT have high reliability and high strengthening effect for mechanical properties under tensile static and fatigue loadings. The impact damage mechanism of low-energy range for the hybrid composites with NWCT was also investigated under quasi-static indentation loading. The mechanism of the NWCT interleaving's effect was clarified based on the observation of damage. As the CFRP and hybrid composites with the indentation damage failed by shearing under the compressive fatigue loading, it was effective that the propagation of shear cracks in the hybrid composites were prevented by NWCT located between the CFRP layers. It was found that the Mode II interlaminar fracture is predominant in the delamination by the indentation loads. The purposes of this study of hybrid prepreg with NWT are (i) to increase the interlaminar properties (the fracture toughness and strength), (ii) to improve the mechanical properties (tensile strength and stiffness) and reliability, while maintaining a low cost, (iii) to propose an interlayer hybrid concept with NWT as a "Toughening and Strengthening Technique". Namely, this concept is designed to introduce a tough and strong interlayer at the positions of typical premature composite failure. A production technique to decrease voids in NWT is exhibited by comparing two types of hybrid laminates. The mechanical properties of the hybrid composites were measured, and then the validity of the present technique was confirmed.