Purpose The purpose of this paper is to present the mechanical and morphological characterization of new multifunctional carbon fibre-reinforced composites (CFRCs) that are able to overcome two of the main drawbacks of aeronautical composite materials: reduced electrical conductivity and poor flame resistance. Multiwall carbon nanotubes and glycidyl POSS (GPOSS) were used to simultaneously enhance electrical conductivity and flame resistance. The effect of these two combined components on the mechanical and morphological properties of the manufactured CFRCs was analysed. Design/methodology/approach This paper describes the mechanical test results obtained for interlaminar shear strength, three-point bending, and tensile and fracture toughness in mode I tests. Carbon fibre-reinforced epoxy resin plates were manufactured in two series with blank resin and CNT+flame retardant GPOSS-enhanced resin. Findings The mechanical properties were decreased by no more than 10 per cent by combined influence of CNTs and GPOSS. Agglomerates of CNTs were observed using scanning electron microscopy. The agglomerates were large enough to be visible to the naked eye as black spots on the delaminated fracture surface. The decrease of the mechanical properties could be caused by these agglomerates or by a changed fibre volume content that was affected by the difficult infusion procedure due to high resin viscosity. Originality/value If we consider the benefit of CNTs as a nanofiller to increase electrical conductivity and the GPOSS as a component to increase the flame resistance of the resin, the decrease of strength seems to be insignificant.

The application of thermoplastic composites (TPCs) in aircraft construction is growing. This paper presents a study of the effect of an applied methodology (standards) on out-of-plane interlaminar strength characterization. Additionally, the mechanical behaviour of three carbon fibre-reinforced thermoplastic composites was compared using the curved beam strength test. Data evaluated using different standards gave statistically significantly different results. The study also showed that the relatively new polyaryletherketone (PAEK) composite had significantly better performance than the older and commonly used polyphenylensulfid (PPS) and polyetheretherketone (PEEK). Furthermore, considering the lower processing temperature of PAEK than PEEK, the former material has good potential to be used in serial aerospace production.

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The interlaminar properties of a bond joint of stacked layers in a carbon fibre-reinforced composite with a thermoplastic matrix were evaluated under static loading. The un-precracked tension specimen with an external reinforcing layer was analysed in detail in the area of a bond joint. A detailed finite element method (FEM) analysis was performed to evaluate the influence of the bond joint shape on the interlaminar cohesive forces, which are simulated using the cohesive zone model (CZM). Simple lap and tapered joints were analysed. Continuum and shell elements were utilized in the FEM analysis, and the delamination results obtained using both solutions were compared to each other; however, no significant influence of the bond joint shape on the delamination onset was observed. The FEM analysis was supported using an experimental test on an un-precracked specimen made from prepreg with a carbon fibre fabric and a polyphenylene sulphide (PPS) matrix.

Abstract. Polymer based resin is presently the most used resin for preparing of composites constructions, because of its undisputable benefits; however, there are some limits. The aircraft industry has especially strict requirements for fire, smoke and toxicity (FST) properties which are limited when using organic polymers. Conventional polymer resins resist to temperatures usually up to 120 °C and then they lose stiffness and strength. However, geopolymer matrix is a new type of resin with high potential for cost-efficient applications dealing with temperatures up to 1 200 °C.This paper presents compressive properties of a new geopolymer resin and a fibre reinforced composite with the geopolymer matrix (geocomposite). The effect of a harsh environment exposition on the strength was also evaluated, specifically the impact of the exposure in hot-wet and salt mist conditions. Samples were tested in accordance with ASTM D695 in case of pure resin and in accordance with ASTM D6641 in case of the geocomposite. All tests were performed at room temperature and additionally, pure geopolymer resin was tested at 400 °C. The high temperature caused 35 % decrease of the compressive strength in comparison with the room temperature. Geopolymers behaves like a ceramic and have some unique properties such as high thermal stability, non-flammability and do not generate toxic smoke and fumes.