Abstract
Laminated composites based on polyetheretherketone (PEEK) and polyimide (PI) matrices were fabricated by hot compression. Reinforcing materials (unidirectional carbon-fiber (CF) tapes or carbon fabric) and their layout patterns were varied. Stress–strain diagrams after three-point flexural tests were analyzed, and both lateral faces of the fractured specimens and fractured surfaces (obtained by optical and scanning electron microscopy, respectively) were studied. It was shown that the laminated composites possessed the maximum mechanical properties (flexural elastic modulus and strength) in the case of the unidirectional CF (0°/0°) layout. These composites were also not subjected to catastrophic failure during the tests. The PEEK-based composites showed twice the flexural strength of the PI-based ones (0.4 and 0.2 GPa, respectively), while the flexural modulus was four times higher (60 and 15 GPa, correspondently). The reason was associated with different melt flowability of the used polymer matrices and varied inter- (intra)layer adhesion levels. The effect of adhesion was additionally studied by computer simulation using a developed two-dimensional FE-model. It considered initial defects between the binder and CF, as well as subsequent delamination and failure under loads. Based on the developed FE-model, the influence of defects and delamination on the strength properties of the composites was shown at different stress states, and the corresponding quantitative estimates were reported. Moreover, another model was developed to determine the three-point flexural properties of the composites reinforced with CF and carbon fabric, taking into account different fiber layouts. It was shown within this model framework that the flexural strength of the studied composites could be increased by an order of magnitude by enhancing the adhesion level (considered through the contact area between CF and the binder).
Highlights
Introduction published maps and institutional affilThe design of structural composite materials based on thermoplastic polymers reinforced with carbon fibers (CF) and fabrics is a major trend in advanced manufacturing around the world
The following boundary conditions were assigned for shear along CF: displacements along the y (v) and x (u) axes were equal to zero at the lower boundary of the computational domain (Figure 10a); on the upper boundary, step-by-step displacements along the x (u) axis were set, but displacements along the x (v) axis were zero; normal and shear stresses were equal to zero on the right and left boundaries
The flexural stress–strain curves are shown in Figure 19 for the PEEK- (a) and PI-based (b) composites with changing the CF layouts and adhesion levels (100% corresponded to ultimate stresses equal to the yield point)
Summary
2000’ (Victrex (Victrex Plc, Thorton-Cleveleys, Thorton-Cleveleys, UK), UK), PEEK powder powder‘PEEK ‘PEEK450. Russia) with a surface of 230 g/m modulus of 245 GPa, and GPa, and a tensile strength of more than. COMPOSIT, Moscow, Russia) were loaded the reinforcement purpose. Russia)forwere loaded for the reinforcement purpose.ofThe thicktapes and thecarbon biaxialtapes fabrics were andfabrics. PEEK-film ones, ones, while while the the samples. After packing in a mold (Figure 2a), the composite samples were fabricated by hot compressing. The 70 × 65 × 3.5 mm composite plates (blanks) were obtained (Figure 2c), from which specimens for mechanical tests were cut. The specimens for the mechanical tests were 70 × 10 × 3.5 mm in size (Figure 2d). 2. The step-by-step diagram of process the process of fabricating laminated composite samples: stacking layers (a); hot
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
