Matrix and Filler Recycling of Carbon and Glass Fiber-Reinforced Polymer Composites: A Review

Abstract

Fiber-reinforced polymers (FRPs) are low-density, high-performance composite materials, which find important applications in the automotive, aerospace, and energy industry, to only cite a few. With the increasing concerns about sustainability and environment risks, the problem of the recycling of such complex composite systems has been emerging in politics, industry, and academia. The issue is exacerbated by the increased use of FRPs in the automotive industry and by the expected decommissioning of airplanes and wind turbines amounting to thousands of metric tons of composite materials. Currently, the recycling of FRPs downcycles the entire composite to some form of reinforcement material (typically for cements) or degrades the polymer matrix to recover the fibers. Following the principles of sustainability, the reuse and recycling of the whole composite—fiber and polymer—should be promoted. In this review paper, we report on recent research works that achieve the recycling of both the fiber and matrix phase of FRP composites, with the polymer being either directly recovered or converted to value-added monomers and oligomers.

Quantitative and Qualitative Aspects of Composite Action of Concrete and Dispersion-Reinforcing Fiber

“…From the point of view of fundamental science, aspects of the operation of fiber in a concrete matrix were previously studied. Thus, in several works, various types of fiber [6][7][8]11,19,20,30,32], as well as different diameters and lengths of fiber [6][7][8]20,30] were investigated, as was the quantitative aspect [6][7][8]11,13,[30][31][32] of the influence of the characteristics of the fiber (glass fiber) and its type on properties of the resulting fiber-reinforced concrete composites. In [10,21,29,31,42], fiber-concrete specimens were studied using high-precision microscopic equipment.…”

“…The strength of polydispersion-reinforced specimens changed in a similar way (Figure 5). An analysis of literary sources made it possible to establish that most often, the volume content of glass fibers in fiber-reinforced concrete is 1.5-3.0% [6][7][8]11,13,[30][31][32][33]. The dependence of the strength of fiber-reinforced concrete on the volume percentage of reinforcement is linear.…”

“…Arbitrary orientation is carried out, as a rule, with short fibers, but in this case, roll materials in the form of canvases, mats, and veils, in which the fibers do not have an organized weave, can also be used. In practice, various types of arbitrary orientation can be implemented in structures [10][11][12][13][14][15]. Plane-arbitrary orientation is characterized by an equiprobable and unlimited (free and chaotic) distribution of fibers in a plane (in two-dimensional space).…”

“…The degree of all these changes in material properties and the structures' characteristics is mainly determined by the type and properties of the fibers and concrete used and the degree of interaction between them. Thus, a close relationship of reinforcing fibers with a concrete matrix, in addition to its activity, is provided by the length of the boundaries, which depends on the degree of saturation of concrete with fibers, their geometric characteristics, and surface energy [7,[10][11][12][13]. Considering this, it is logical to assume that the greatest positive effects in improving the structure and properties of fiber-reinforced concrete can be achieved as a result of polydispersed reinforcement with an optimal combination of two or more types of fibers with different geometric dimensions.…”

Recycled (Bio)Plastics and (Bio)Plastic Composites: A Trade Opportunity in a Green Future

“…The impurities catalyze the thermal degradation, i.e., cleavage reactions, while blending different plastic-types leads to phase separation during the processing because of the chemical incompatibility. These drawbacks mean poor properties of the recycled material, making it necessary to employ antioxidants, stabilizers, compatibilizers, coupling agents, and performance modifying techniques [ 11 , 12 ].…”