Abstract

In recent years, there has been a significant increase in social awareness of environmental problems related to high waste generation, oil scarcity and the growing need to reduce the carbon footprint. In this context, polymers from renewable sources can successfully reduce the use of fossil resources. This research work presents the study of polymer matrix composites from high density polyethylene of renewable origin (bioHPDE) and fibers extracted from the strobili of the common pine (Pinus halepensis) typical of the Mediterranean area, characterized by its high percentage of cellulose, and for being very abundant in the natural and economic environment. The research has focused on the influence of a compatibilizing agent based on polyethylene grafted with maleic anhydride on the final performance of the composite material. The resulting composites have been processed by extrusion and subsequent injection molding and a characterization focused on mechanical and thermal properties has been carried out. The results have demonstrated the optimization of the performance of the composite by using the compatibilizer, offering a significant improvement of the fiber-matrix interaction and thus validating its use in this type of composites. The result is a wood plastic composite (WPC) with a wide range of properties depending on the filler content used, providing a highly versatile material with applications in various industrial sectors.

Abstract

Under the coordination of AITEX and in collaboration with the partners of the r-LightBioCom project, intensive research, selection, and validation of sustainable reinforcement fibers (natural, recyclable or recycled, and with low environmental impact) have been carried out for use in composites that will be validated in automotive demonstrators (spoiler and trunk floor), infrastructure (tunnel lining), and aeronautics (wing leading edge). In this area, the following achievements stand out:

1. Validation procedure regarding processability and mechanical characteristics of various sustainable reinforcement fibers (recycled carbon and glass fibers, natural fibers, basalt fiber, and recycled aramid fiber).
2. Development of sustainable textile intermediates (fabrics, mats, pre-pregs, honeycombs, and rovings) through the adaptation of textile technologies for processing the selected reinforcement fibers and compatible with bio-based resins.
3. Hybridization of sustainable reinforcement fibers with virgin filaments to improve mechanical properties while maintaining low environmental impact. The results obtained indicate that the selection of alternative and more sustainable fibers than those usually used in the production of composites are suitable for the development of the aforementioned demonstrators in terms of processability and resistance.​

The results obtained indicate that the selection of alternative and more sustanaible fibers than those usually used in the production of composites are suitable for the develpment of the aforementioned demonstrators in terms of processability and resistance.

Abstract

The increasing adoption of natural fibres as composite reinforcement is a promising development in materials science. These fibres have a low carbon footprint and are biodegradable, and they also have remarkable properties such as low density and high specific stiffness and strength. However, the mechanical properties of these composites are influenced by various parameters, which can complicate comparisons due to their diverse internal structures. This study focuses on two key normalised parameters: the Tsai modulus, which represents the trace of the stiffness matrix tensor; and the area of the Omni failure envelope in stress space. Our analysis of published data on unidirectional flax, hemp, jute, and kenaf composites shows that trace-normalised longitudinal Young's modulus can effectively facilitate stiffness comparisons between natural and synthetic fibre composites. A new and innovative way of measuring strength is suggested. This is based on the radius of a circle that matches the area of the Omni stress envelopes. This method is both robust and reliable for quantifying and comparing material strength. Although, extensive mechanical data on natural composites is available, it is difficult to establish design criteria for comparing them. Addressing this gap presents a significant opportunity to unlock the full potential of natural fibres in composite applications, paving the way for a more sustainable future in engineering materials.