Bio-epoxy composites were fabricated by casting a resin–hardener–filler mixture into 3D-printed molds, using different sea-originated secondary raw materials: mussel shell powder (MSP) (63–83 μm) and Posidonia oceanica short fibers (POF) (1–2 mm). Monofiller composites were prepared with 5 or 10 wt.% MSP, or 5 or 10 wt.% POF. Hybrid formulations were also produced, containing both MSP and POF in two combinations, where the total amount of filler again summed up at 10 wt.%. A subset of the samples was conditioned by immersion in a 35 ‰ NaCl solution reproducing seawater composition until saturation was reached. Characterization was carried out on unconditioned and conditioned samples by Shore D hardness and Charpy impact tests while performing three-point flexural loading only on unconditioned ones. Fracture morphology was also investigated. Adding MSP slightly enhanced resin hardness, whereas impact absorption exhibited, to a variable extent, a two-phase behavior, reproducing crack initiation and propagation. The MSP6-POF4 hybrid configuration provided the greatest improvement in absorbed energy (25–30% higher), which was retained after conditioning. The introduction of fillers, first separately, then in combination, resulted in a reduction in flexural strength to a similar extent for all unconditioned configurations. Finally, composite panels containing 10 wt.% MSP, 10 wt.% POF, and a 6MSP–4POF hybrid formulation, intended for prospective boat deck applications, were fabricated and compared with neat bio-epoxy, showing satisfactory consolidation. Density and post-molding dimensional shrinkage were measured on the panels.

During the machining processes, surfaces are often contaminated by cutting fluids, metallic debris, and residual films, which may compromise subsequent operations (e.g., coating, bonding, or precision assembly). In the present study, the effectiveness of several cleaning methods applied to machined metallic surfaces was experimentally evaluated. A set of commonly used industrial metals, including stainless steels, alloy steels, aluminum alloys, and brass, was machined under controlled conditions and subjected to various cleaning treatments, including solvent-based cleaning, ultrasonic washing, and aqueous detergent processes. Surface conditions were first assessed through optical microscopy, focusing on machining grooves as preferential sites for contaminant accumulation. Then, scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) was employed to better identify residual contaminants. Optical observations highlighted the progressive removal of debris and lubricant residues, while SEM–EDS analyses revealed the presence of thin organic films and localized carbon-rich contaminants, even on apparently clean surfaces. Results show a consistent trend across all materials, with increasing cleaning effectiveness from solvent-based treatments to ultrasonic cleaning and specific aqueous detergent processes. Ultrasonic cleaning proved particularly effective in removing thin films and contaminants in complex geometries, whereas aqueous detergent treatment demonstrated superior performance in eliminating larger debris and achieving overall surface cleanliness. The findings, combining a broad experimental campaign across multiple materials, cleaning treatments, and characterization techniques, underline the importance of multi-scale characterization for a reliable assessment of cleaning efficiency and suggest that combined cleaning approaches may further enhance surface quality in demanding industrial applications.