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The global composite industry generates large quantities of waste which mostly ends up in landfills due to a lack of established end-use applications for multiple waste streams. The scrap from end-of-life (EoL) includes manufacturing waste such as dry chopped fiber tows, loose fibers, shredded fibers from fabric textile operations, cured/semi-cured prepregs, and fully cured composite structure waste from aircraft, automobiles, wind blades, boats, and pressure vessels. In this work, different composite waste streams were reduced to shredded intermediates, followed by simple blending, and subjected to wet compression molding to produce composite panels. The panels/plaques were tested for mechanical properties (flexure and impact), fiber-matrix wet-out, and property bounds. It was found that wet-compression molding was a viable and scaleable approach to produce recycled panels from EoL composites shredded scrap. Furthermore, full-scale size panels for use in truck bodies and intermodal shipping container flooring were manufactured and their impact resistance was tested using a drop weight impact test. They were tested both for high- and low-velocity load. In the case of high-velocity load, the average impact load was 14,673 N; the average absorbed energy was 101.6 J; the average elastic energy was 11.7 J and the impact resistance was 1065 J/m. In the case of the low-velocity drop weight impact test, it was found that the average impact load was 7877.358 N; the average absorbed energy was 9.718 J; the average elastic energy was 9.14 J, and the impact resistance was 184.1 J/m. The shredded composite was shown to be a candidate material for the manufacture of truck bodies and intermodal containers' flooring panels. Highlights • By using shredded intermediates from different composite waste streams, it is possible to manufacture composite panels. • Wet-compression process is an appropriate technique for manufacturing recycled fiber composite panels. • Regardless of the source of scrap, the mechanical properties of the produced composite panels were improved. • The recycling process technology can be transformed to commercial scale to produce full-size transportation flooring panels. • A product pathway is established in consideration of lower cost and improved recyclability. [ABSTRACT FROM AUTHOR]

The trend of using natural fiber composites is increasing rapidly due to the growing environmental concerns and increased awareness on sustainability. However, due to the lower strength of natural fibers (95-1600MPa) compared to synthetic fibers (2000-4000 MPa), high moisture absorption rate, variation in the fiber properties, and lower processing temperature range limit its applications. This study advances the concept of overmolding of bamboo fiber-polypropylene (BF-PP) composites with unidirectional and 0/90 textile grade carbon fiber (TCF) tape. BF-PP composites were processed using extrusion compression molding (ECM) technique. TCF tape was produced on a thermoplastic polymer impregnation line. Mechanical and morphological properties of overmolded hybrid composites were studied. These studies attempted to evaluate the interface between the BF-PP and the TCF thermoplastic tape. Flexural strength and flexural modulus of BF-PP composites increased by ~152% and ~164% respectively by overmolding BF-PP with unidirectional TCF tape; and by ~53% and ~54% respectively on overmolding 0/90 TCF thermoplastic tape. Scanning electron microscopic (SEM) images of the TCF tape overmolded BF-PP composites exhibited good interfacial bonding. [ABSTRACT FROM AUTHOR]

Abstract: The wear of C/C composites has been studied using a subscale aircraft brake dynamometer linked with a mass spectrometer. A disc-on-disc configuration allowed for simulation of various aircraft landing energy conditions (12.5%, 25%, 50%, and 100% of normal landing energy of a Boeing 737 aircraft) performed at 50% and 90% relative humidity levels. The microstructure of composite brakes was altered by applying three different heat treatment temperatures: 1800, 2100, and 2400°C, respectively. A mass spectrometer linked to an environmental chamber of the subscale dynamometer was utilized to measure the in situ CO2 release during the wear tests. The relationships between microstructure, hardness of individual components of composites and wear performance at varied conditions are presented. Carbons obtained at higher heat treatment temperatures are most vulnerable to abrasive wear, while the less ordered carbons, typical for samples heat treated at lower temperatures, showed significant amount of oxidative wear. Oxidative wear was related to excessive heating of materials. Optimization of wear behavior of C/C composite is only possible by understanding the mechanisms of the microstructural changes of materials, corresponding mechanical properties and the nature of wear under various environmental conditions. [Copyright &y& Elsevier]

• Recycling of natural fiber reinforced polymer composites to new composites. • Impact of recycling/reprocessing on material properties of natural fiber composites. • Thermomechanical property, hygroscopicity, viscoelasticity, degradation, durability. • Discussing mechanism behind property changes: polymer degradation or fiber breakage. • Mitigating material property degradation with functional additive or virgin plastic. Natural fibers have been widely used for reinforcing polymers attributed to their sustainable nature, excellent stiffness to weight ratio, biodegradability, and low cost compared with synthetic fibers like carbon or glass fibers. Thermoplastic composites offer an advantage of recyclability after their service life, but challenges and opportunities remain in the recycling of natural fiber reinforced polymer composites (NFRPCs). This article summarized the effects of reprocessing/recycling on the material properties of NFRPCs. The material properties considered include mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability. NFRPCs can generally be recycled approximately 4–6 times until their thermomechanical properties change. After recycling 7 times, the tensile strength of NFRPCs can decrease by 17%, and the tensile modulus can decrease by 28%. The mitigation approaches to overcome degradation of material properties of NFRPCs such as adding functional additives and virgin plastics are also discussed. The main challenges in these approaches such as degradation and incompatibility are discussed, and an effort is made to provide a rationale for reprocessing/recyclability assessment. Future applications of NFRPCs such as additive manufacturing and automotive part use are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Past decades have seen an increasing prevalence of natural fiber-reinforced composites (NFRCs) due to growing conscientiousness around sustainability and a push towards vehicle lightweighting. The environmentally friendly and sustainable claims of NFRCs need to be validated due to their large variability and variety, particularly where material substitutions are concerned, such as in substituting glass fiber with natural fiber. The objective of this work is to determine the cumulative energy demand (CED) and greenhouse gas emissions (GHG) associated with an automotive part (of volume 0.001 m3) made from 40 wt% coir fiber-reinforced polypropylene (PP) and compared with a similar part made from 40 wt% glass fiber reinforced PP. SimaPro v. 9.0.0.49 was used for the analysis, whereas inventory data were collected from databases, such as Ecoinvent 3, Transportation Energy Databook, Greet model 2022, and published papers. The results showed that CED and GHG associated with the coir fiber-reinforced composite part were lower than the glass fiber-reinforced composite part for both cradle-to-gate (∼34–40%) and cradle-to-grave (excluding end-of-life) (∼24%) analysis. • Coir fiber composites have a lower environmental impact compared to glass fiber composites. • Transportation of materials and parts has minimal impact on CED and GHG emissions of the composites. • Hybrid composites can have a balance of environmental and mechanical performance. • The extent of energy and GHG savings on lightweighting varies based on vehicle technology and category. [ABSTRACT FROM AUTHOR]

Demands for reducing energy consumption and environmental impacts are the major driving factors for the development of natural fiber–reinforced composites (NFRCs) in many sectors. Compared with synthesized fiber, natural fiber provides several advantages in terms of biodegradability, light weight, low price, life-cycle superiority, and satisfactory mechanical properties. However, the inherent features of plant-based natural fibers have presented challenges to the development and application of NFRCs, such as variable fiber quality, limited mechanical properties, water absorption, low thermal stability, incompatibility with hydrophobic matrices, and propensity to agglomeration. Substantial research has recently been conducted to address these challenges for improved performance of NFRCs and their applications. This article reviews the recent advancements of plant-based NFRCs, focusing on strategies and breakthroughs in enhancing the NFRCs' performance, including fiber modification, fiber hybridization, lignocellulosic fillers incorporation, conventional processing techniques, additive manufacturing (3D printing), and new fiber source exploration. The sustainability of plant-based NFRCs using life-cycle assessment and the burgeoning applications of NFRCs with emphasis on the automotive industry are also discussed. [ABSTRACT FROM AUTHOR]