Abstract In this study, a biodegradable and sustainable piezoelectric–triboelectric hybrid nanogenerator (HENG) was designed and fabricated using cellulose nanofibrils (CNFs) as a nucleating agent and phycocyanin (PC), an algae-derived protein from Spirulina platensis, as the tribo-positive layer paired with poly(vinylidene fluoride) (PVDF) films. The investigation was conducted in two parts to investigate the effect of CNF incorporation into different layers. In the first part, CNFs were incorporated into the PVDF layer, whereas in second part incorporated into the PC layer. Electromechanical performance was characterized under periodic contact–separation motion. Even in the absence of nanofillers, the PVDF–PC pair exhibited efficient electromechanical behavior, generating an open-circuit voltage (V oc ) of 84 V and a short-circuit current (I sc ) of 87 µA. Upon CNF incorporation, the output was significantly enhanced. The highest performance was observed when CNFs were added to the PVDF layer (at 20 wt.% CNFs loading) with V oc and I sc values of 228 V and 199 µA, respectively. On the other hand, when CNFs were incorporated into the PC layer and paired with neat PVDF, the maximum output reached 128 V and 126 µA (at 5 wt.% CNFs). This outcome highlights that CNFs contribute more effectively to performance improvement in PVDF than in PC.

Abstract The spatial arrangement of crystalline cellulose nanofibers and amorphous hemicellulose in the coconut endocarp remains unclear. Inspired by the hierarchical structures of nacre and bone, we proposed a brick-and-mortar model in which cellulose bundles are arranged in a staggered pattern and then fully embedded within the hemicellulose matrix. Such complex, high-dimensional biopolymer composite systems pose a significant challenge for all-atom molecular dynamics (AAMD) simulations to study microstructure-property relationships and reveal the underlying deformation mechanisms. Therefore, in this work, we developed a coarse-grained (CG) potential model that explicitly incorporates hydrogen bonding, the key interfacial interaction in cellulose-hemicellulose composites. The CG model parameters were carefully fitted and validated against AAMD simulations, ensuring accurate predictions of stiffness, strength, toughness, and failure mechanisms. It was proven that the CG model enables efficient simulations of large-scale 3D systems with millions of atoms, providing crucial insights into mechanical behavior while maintaining computational efficiency. The staggered 3D distribution of long cellulose bundles was found to optimize the reinforcement effect by maximizing strain energy absorption during deformation. Given the vital role of hydrogen bonding, we modified the rule of mixture (ROM) to quantify their contributions across different models by incorporating an interphase term to account for interfacial interactions, facilitated by comprehensive data from MD simulations. This integrated approach of CGMD and ROM analysis not only enhances our understanding of the mechanical behavior of cellulose-hemicellulose composites but also provides a generalizable framework for studying and optimizing natural and bioinspired materials at large scale.

Abstract This study investigates the synthesis and characterization of polymer matrix composites reinforced with eucalyptus cellulose fibers, using epoxy and vinyl ester resin as matrices. Composites were produced with 5 and 10 wt.% of eucalyptus fibers, denominated EC/EF (Epoxy Composite reinforced with Eucalyptus Fibers) and VEC/EF (Vinyl Ester Composite reinforced with Eucalyptus Fibers), respectively, for each concentration. The materials characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM/EDS), Shore D hardness testing and Tensile Test. FTIR analyses confirmed the preservation of functional groups and highlighted interactions between the fiber and polymer matrices, while TG results demonstrated improved thermal stability in the composites, with epoxy-based systems showing higher degradation temperatures and char residue compared to vinyl ester. DSC analysis revealed a reduction in glass transition temperature with fiber incorporation, attributed to increased chain mobility and possible agglomeration. XRD confirmed composite formation and cellulose phase presence, particularly in 10 wt.% samples. SEM images showed rougher surfaces and better fiber dispersion at higher loadings, especially for EC/10EF, while EDS showed a uniform distribution of carbon and oxygen across all samples. Shore D hardness increased with fiber content, from 73.1 ± 0.2 for neat vinyl ester to 77.8 ± 0.2 for VEC/10EF. Conversely, tensile strength decreased with fiber incorporation in both matrices (e.g., from 23.4 to 15.4 MPa for EC/10EF, corresponding to a 34.2% reduction), which is attributed to fiber agglomeration and increased chain rigidity. However, the Young’s modulus of the epoxy composites showed an enhancement from 464.8 (pure epoxy) to 608.0 MPa (EC/10EF), representing a 30.8% increase. The results highlight the reinforcing potential of eucalyptus fibers in thermosetting matrices and support their application in structural and sustainable materials. Epoxy composites, in particular, exhibited superior thermal resistance and mechanical performance, suggesting greater suitability for applications requiring durability under thermal stress.