Wood-plastic composites (WPCs) have shown exceptional promise as a building material, especially for outdoor uses. Using renewable wood fiber as the reinforcing filler in WPCs increases the material’s environmental sustainability. While virgin commodity thermoplastics are primarily used in these composites, using post-consumer plastic further contributes to their sustainability. While they are beginning to be used in the Gulf countries, information on their performance, especially durability under harsh desert climates, is sparse. The present investigation on WPCs is based on the two most popularly used thermoplastics in WPCs, virgin high-density polyethylene (HDPE) and polypropylene (PP), with the wood content varying between 0 and 36 wt. %. These were prepared with melt processing from a masterbatch and characterized primarily using thermal methods and tensile properties of their injection molded test pieces. Variations in tensile properties, especially the tensile modulus (MPa), the tensile strength (MPa), and the ultimate extensibility (%) of the composite samples were investigated to determine an optimal wood-fiber loading. For either polymer type, exceeding 27 weight percent of wood fiber resulted in unacceptably low ultimate extensibility of the material.

The natural and laboratory-accelerated weathering of wood–plastic composites (WPCs) based on high-density polyethylene (HDPE) and polypropylene (PP) plastics was investigated in this study. Injection molded samples of WPCs with different loadings of wood fiber ranging from 0 to 36 wt.% of wood were subjected to laboratory-accelerated weathering and natural weathering. The integrity of samples weathered to different extents was tested using a standard tensile test and surface hardness test to investigate the dependence of these properties on the duration of weathering exposure. Tensile data were used to identify the loading of wood fibers in either plastic matrix that afforded superior ultra-violet (UV) stability. Tensile measurements under uniaxial strain yielded average values of tensile strength (TS), low-extension modulus (E), and elongation at break (EB). Both natural weathering outdoors and accelerated weathering in the laboratory showed that the TS and EB decreased while the E increased with the duration of exposure for all samples tested. The change in the average TS of composites with the duration of exposure offers valuable insights. The correlation between the tensile and hardness data for the WPC samples was explored. After naturally weathering at two exposure sites, the hardness of the WPCs was found to decrease between 8% to 12.5%, depending on the composition and exposure location parameters. Furthermore, no marked difference in performance with increasing wood fiber beyond 18 wt.% was observed. WPCs can be a key parameter in environmental sustainability by being used in the building and packaging industries, which reduces carbon emissions and waste generation.

Deformational and breakage behaviors of concrete and cement mortar greatly influence various engineering structures, such as dams, river bridges, ports, tunnels, and offshore rig platforms. The mechanical and petrophysical properties are very sensitive to water content and are controlled by the liquid part in pore spaces to a large extent. The objective of this paper is to investigate the water saturation effect on the strength characteristics and deformability of cement mortar under two loading conditions, static and dynamic compression. A set of cement mortar samples was prepared and tested to study the mechanical behavior in dry and saturated states. The first part of the research incorporates the study of static mechanical properties for dry and brine-saturated cement mortar through uniaxial compressive strength tests (UCS). Second, drop-weight impact experiments were carried out to study the dynamic mechanical properties (impact resistance, deformation pattern, and fracture geometry) for dry and saturated cases. The comparative analysis revealed that water saturation caused substantial changes in compressive strength and other mechanical characteristics. Under static loading, water saturation caused a reduction in strength of 36%, and cement mortar tended to behave in a more ductile manner as compared to dry samples. On the contrary, under dynamic loading conditions, water saturation resulted in higher impact resistance and fracture toughness as compared to dry conditions. In addition, fractures could propagate to smaller depths as compared to dry case. The study will help resolve many civil, mining, and petroleum engineering problems where cement structures undergo static as well as dynamic compression, especially in a hydraulic environment where these structures interact with the water frequently. To the best of our knowledge, the effect of water saturation on the dynamic mechanical properties of cement mortar has not been well understood and reported in the literature.

The natural and laboratory-accelerated weathering of wood-plastic composites (WPCs) based on high-density polyethylene (HDPE) and polypropylene (PP) plastics was investigated. Injection molded samples of the WPCs with different loadings of wood fiber ranging from 0 to 36 wt. percent of wood were subjected to laboratory accelerated weathering and natural weathering. The integrity of samples weathered to different extents was tested using a standard tensile test and surface hardness test to investigate the dependence of these properties on the duration of weathering exposure. Tensile data was used to identify the loading of wood fiber in either plastic matrix that afforded superior ultraviolet (UV) stability. The correlation between the tensile and hardness data for the WPC samples was explored.

Multi-material fused-filament fabrication (FFF) enables the integration of two or more materials within a single printed component, offering significant potential for producing functionally graded and hybrid structures with tailored mechanical properties. However, the effects of processing conditions on interfacial quality and fracture behavior in multi-material FFF remain insufficiently understood. This study investigates the Mode-I interfacial fracture behavior of multi-material FFF using compact-tension (CT) specimens through combined experimental testing and finite-element simulation. CT specimens were fabricated from polylactic acid (PLA), thermoplastic polyurethane (TPU), and polyethylene terephthalate glycol (PETG) using five raster configurations, including rectilinear 0°/90°, ±45° and aligned-rectilinear 0°, 45°, 90° configurations. The load-extension response, peak load (P_max), critical stress-intensity factor (K_IC), and critical strain-energy release rate (G_IC) were evaluated. Two-way ANOVA showed that material pairing was the dominant statistically significant factor affecting peak load, whereas raster orientation and its interaction with material pairing were not statistically significant. The PETG–TPU interface exhibited the highest fracture resistance, with the AR-45 orientation producing an average P_max of 130.90 N, K_IC of 0.761 $\mathrm{MPa}\sqrt{\mathrm{m}}$, and G_IC of 375.5 N/m. Fracture-surface observations supported these findings, revealing greater deformation, material transfer, surface roughness, and mechanical interlocking in the PETG–TPU specimens. The calibrated cohesive-zone model demonstrated the stress contours and the localized interfacial damage patterns. Overall, material pairing primarily governed interfacial fracture resistance, whereas raster orientation showed no statistically significant effect under the tested conditions.