This review critically examines the effects of moisture absorption on the mechanical and fatigue properties of natural fiber composites (NFCs), with a focus on tensile strength, elastic modulus, and long-term durability. Moisture uptake can cause reductions in tensile strength of up to 40% and in elastic modulus by 20–30% depending on fiber type, mass fraction (typically in the range of 30–60%), and surface treatments. The review highlights Ithat while surface modifications (e.g., alkaline and silane treatments) significantly mitigate moisture-induced degradation, their effectiveness is highly sensitive to the processing conditions. Additionally, hybridization strategies and optimized fiber orientations show promise in enhancing fatigue resistance under humid environments. Despite substantial progress, major challenges remain, including the lack of standardized testing protocols and the limited understanding of multiscale aging mechanisms. Future research directions include developing predictive models that couple moisture diffusion and mechanical deterioration, implementing advanced in situ monitoring of damage evolution, and exploring novel bio-based treatments. By addressing these gaps, NFCs can become more reliable and widely adopted as sustainable alternatives in structural applications.

Modelling and simulating complex systems, such as forestry equipment, are often the only way for their full analysis and design. This problem may lead to a stiff set of equations that are followed by numerical problems. In this paper two alternative approaches are investigated. The first one refers to the use of a variable step of integration by continuous models adjusted to the fastest processes. The second one refers to the approximation of fast transitions by ideal instantaneous mode-transitions and hybrid models. These two approaches are analysed in the framework of bond graph. The classical bond graph is adopted for description of the continuous models, and the switched bond graph is preferred for description of the hybrid models. The model of check valve is used as a working example for illustration of results. Matlab/Simulink tools are used for modelling and simulation.