Exploratory Flexural and Compressive Response of Hot-Pressed Composites Made from Source-Sorted Recycled Plastic and Eucalyptus Wood Particles

This exploratory study investigated hot-pressed composites prepared from source-sorted, nominally HDPE-designated post-consumer plastic and screened Eucalyptus wood-processing particles at 0, 10, 20, and 30 wt.% wood content. Polymer identity was assigned from collection/sorting records, not confirmed by spectroscopy or thermal analysis. Three flexural subspecimens were sectioned from one plate for each composition; independent compression-batch replication was not established. The recorded peak nominal flexural stress decreased from 23.30 ± 1.55 MPa for the unfilled control to 21.92 ± 1.73, 18.30 ± 2.78, and 11.81 ± 0.52 MPa, respectively. Peak nominal compressive stresses were 15.78 ± 1.55, 9.16 ± 0.56, 13.05 ± 2.78, and 11.48 ± 0.91 MPa, giving a non-monotonic descriptive pattern. Relative to the unfilled control, the 10 wt.% mixture retained 94.1% of peak nominal flexural stress and 58.0% of peak nominal compressive stress; the corresponding values at 20 wt.% were 78.5% and 82.7%. A weighting sensitivity analysis shows that the preferred composition depends on the relative importance of the two loading modes. Original modulus estimates based on a fixed 10–20 N load window were excluded from engineering conclusions. The measurements describe within-campaign, specimen-level performance and do not establish standardized strength, batch reproducibility, or product suitability.