Carbon fibre reinforced polymers are widely used in industrial applications due to their excellent properties. However, the weak matrix-dominated interlaminar properties limit its further application. With their unique properties, carbon nanotubes (CNTs) have great potential to improve the mechanical properties of composite materials. In this paper, carbon nanotube-modified carbon fibre/polyimide (CF/CNTs/PI) multi-scale composites were prepared by introducing amino-functionalized multi-walled CNTs into a PI resin matrix using an ultrasonic dispersion method. The interlaminar properties of the prepared composites were comprehensively evaluated by double cantilever beam (DCB), end-notched flexure (ENF), and short seam shear (SBS) tests. It is shown that the addition of 0.5wt.% CNTs increased the Mode I and Mode II interlaminar fracture toughness of the material by 50.21% and 61.74%, respectively, and the interlaminar shear strength (ILSS) by 42.85%. The CNTs bridging the crack tip and enhancing the fibre/matrix interface bonding ability were the dominating mechanisms for the improvement of interlaminar properties.
Glass fiber reinforced plastic (GFRP) has become one of the most commonly used materials in the structure of aero engines in the last decades. In this study, GFRP was fabricated by molding with phenolic resin as the matrix. Specimens were prepared along horizontal and vertical directions. Fiber distribution, tensile properties, long‐term creep performance, and damage mechanism were systematically investigated. Experimental results shows that horizontal specimens have better tensile properties, lower viscoelasticity, and excellent creep resistance. The fibers inside the cylindrical material exhibit a 3D core‐shell morphology with transverse isotropy in the core region. Load is carried by the fibers and the damage is in the form of fiber fracture and pull‐out in horizontal specimens. Random distribution and interweaving leads to double fracture sections of fibers. Load is carried by the interface and resin, and the damage is in the form of fiber pull‐out laterally and interfacial debonding in vertical specimens. High viscoelasticity of the resin and the weak interfacial bonding ability lead to large creep deformation of vertical specimens. In addition, the creep strain under different loads can be accurately predicted by Modified Time Hardening model.
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