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Fiber reinforced polymers boast exceptional mechanical performance coupled with low material density. Over recent decades, their usage has been steadily increasing and is poised to accelerate in the future. These materials typically have a lifespan of around 25–30 years, so at present time lots of tons of polymer composites are next to their end of life and this volume continues to grow. Currently, a significant portion of these materials is either incinerated or landfilled, resulting in substantial environmental impacts. Numerous studies have aimed to identify optimal recycling approaches, one of which involves solvolysis: the chemical dissolution of the polymer matrix. In this study, a solvolysis method has been devised and refined to effectively recover carbon fibers from composites while minimizing property degradation. The process begins with the identification of a suitable solvolysis fluid, specifically an aqueous sulfuric acid solution. Subsequently, key solvolysis parameters including solution concentration, temperature, residence time, and fluid agitation are meticulously optimized. The chemical and morphological impacts of this process are thoroughly examined using Fourier‐transform infrared spectroscopy analysis and scanning electron microscope observations. [ABSTRACT FROM AUTHOR]

This study investigated the friction and wear properties of high‐strength polyacrylonitrile (HS‐PAN)‐, high‐modulus polyacrylonitrile (HM‐PAN)‐, and high‐modulus pitch (HM‐pitch)‐based carbon fiber‐reinforced polymer matrix composites (CFRPs) with silicon carbide (SiC) nanoparticles. The fiber orientation of the CFRP specimens was set as 8‐ply unidirectional laminates, denoted as [0]8. Ball‐on‐disk (cyclic) wear testing was accompanied by laser, digital, and scanning electron microscope observations. For the HS‐PAN CFRP, the coefficient of friction and wear resistance were the highest among the HM‐PAN and HM‐pitch CFRPs and wear resistance was improved by the addition of SiC‐nanoparticles. Furthermore, there was no significant enhancement of wear resistance for the SiC‐nanoparticle‐filled and nanoparticle‐unfilled HM‐PAN CFRP. The wear resistance was improved by adding SiC‐nanoparticles for the HM‐pitch CFRP. [ABSTRACT FROM AUTHOR]

Delamination is always considered as a threat to the resin matrix composite laminates due to the nonvisibility from the outside. Much effort on the interleaving toughening has been made to improve the interlaminar fracture toughness. The synergistic toughening effect of thermoplastic resin and carbon nanotubes (CNTs) has been the topic in the interleaving toughening. In this study, the influence of the hybrid structure between thermoplastic polyetherketone‐cardo (PEK‐C) and CNTs on the toughening efficiency was investigated. The mode II interlaminar fracture toughness was tested and the fracture surface was examined by scanning electron microscope. The results showed that the interlaminar structure was closely related with the interlayer structure and the synergistic toughening effect depended greatly on the hybrid structure. [ABSTRACT FROM AUTHOR]

In order to improve the poor solvent resistance and poor temperature resistance caused by traditional sizing agents, crystalline poly(ether ether ketone) (PEEK) is introduced to the interfacial phases of carbon fiber (CF) reinforced PEEK composites by a soluble precursor named PEEK‐1,3‐dioxolane. By changing the soluble precursor molecular weight and concentration in the sizing solution, the content of PEEK coated on the CF fiber surface can be controlled and the different interfacial properties of the PEEK composites can be obtained. The results shows that, with this method, crystalline PEEK can be completely coated on the CF surface, and the interfacial shear strength of the PEEK composites increases from 43.42 to 83.13 MPa. Due to none of any soluble compounds in the PEEK composites, the interfacial layer is well preserved under organic solvents and hygrothermal conditions, and the interfacial shear strength (IFSS) of the PEEK composites maintained above 85.4% and 90.44%, respectively. Scanning electron microscope clarifies that the mechanism of interface enhancement comes from a better wetting of crystalline PEEK on the fiber surface. Additionally, the sizing system of this investagation has the potential commercial value because of no toxic reagent (such as 2,4,5‐trichloro‐1‐hydroxy‐benzene or concentrated sulfuric acid) is required during sizing. [ABSTRACT FROM AUTHOR]

ABSTRACT The polyimide (PI) composites reinforced with carbon fibers, glass fibers, and aramid fibers were fabricated by means of a hot-press molding technique and irradiated by electron or proton for a certain time. The friction and wear behavior after irradiation, sliding against GCr15 steel balls, were evaluated in a ground-based simulation facility using ball-on-disk tribosystem. The change of the chemical composition of the radiated surface was examined by X-ray photoelectron spectroscopy. The worn morphologies and radiated surfaces of the materials were observed by scanning electron microscope to reveal the wear mechanism. Experimental analysis indicated that the chemical composition of the materials changed and an irradiated layer was formed at the surface. This irradiation layer had an important effect on the friction and wear behavior of the PI composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40774. [ABSTRACT FROM AUTHOR]