Natural composites can be fabricated through reinforcing either synthetic or bio-based polymers with hydrophilic natural fibers. Ultimate moisture absorption resistance at the fiber–matrix interface can be achieved when hydrophilic natural fibers are used to reinforce biopolymers due to the high degree of compatibility between them. However, the cost of biopolymers is several times higher than that of their synthetic counterparts, which hinders their dissemination in various industries. In order to produce economically feasible natural composites, synthetic resins are frequently reinforced with hydrophilic fibers, which increases the incompatibility issues such as the creation of voids and delamination at fiber–matrix interfaces. Therefore, applying chemical and/or physical treatments to eliminate the aforementioned drawbacks is of primary importance. However, it is demonstrated through this review study that these treatments do not guarantee a sufficient improvement of the moisture absorption properties of natural composites, and the moisture treatments should be applied under the consideration of the following parameters: (i) type of hosting matrix; (ii) type of natural fiber; (iii) loading of natural fiber; (iv) the hybridization of natural fibers with mineral/synthetic counterparts; (v) implantation of nanofillers. Complete discussion about each of these parameters is developed through this study.

The main target of the present study is to preserve the structural integrity of the composite pressure vessels (PVs) used in the seawater reverse osmosis (SWRO) desalination plants under internal pressure loading when moisture effects are taken into consideration. Different composite material lay-ups and fiber orientations are considered. In each case, the optimum safe thickness of the PV is found based on the appropriate failure criterion. The PVs are made of carbon/epoxy C/E IM7/977-3 with (±θ)ns lay-up. For verification purposes, PVs made from stainless steel SST 316L and carbon/epoxy C/E AS4/3501-6 are considered and their available results are compared with the predictions of the MATLAB code developed in this study. The study consists of three main cases. The first case considered the PVs materials SST 316L steel and C/E AS4/3501-6 carbon/epoxy composite, without moisturizing effect, with the purpose to verify the results of the developed MATLAB code by comparing with results from the available literature. The second case is concerned with the composite material C/E IM7/977-3, without moisture effects, while the third case included moisture effects on the same material (C/E IM7/977-3). The optimum angles found for C/E AS4/3501-6 is (±55.1)ns and for C/E IM7/977-3 with and without moisture are (±55.8)ns and (±54.0)ns, respectively. The best weight saving of the composite PV, when compared to the steel PV, reached 95.2%.

In the design and analysis of bolted connections, it is essential to determine the stiffness of each element in the connection: the bolt and the members. While the stiffness of the bolt is easily computed as a bar in simple tension, the members stiffness, however, is much more complex. In this work, finite element analysis is used to compute the member stiffness in bolted connections. Two- and three-dimensional models are constructed and analyzed. Analyses are performed for joints containing members made of steel, aluminum, copper, and cast iron. In each case, the material is assumed to be linearly elastic and isotropic. The effect of the joint geometry on the member stiffness is investigated by constructing models with different aspect ratios that contain the most reasonable design values. Comparison with existing previous works and analytical models is performed. Empirical functional relationship is determined for the dimensionless stiffness.

Functionally graded materials (FGMs) have variable volume fractions in different directions, making structural analysis challenging due to shear deformation. This study investigates the behavior of a two-directional functionally graded material (TDFGM) Timoshenko beam under thermomechanical loads. Varied material properties in both axial and transverse directions are analyzed using a mathematical approach and a finite element model. The mathematical approach involves transforming the system of two ordinary differential equations to a single fourth-order differential equation to determine deflection and rotation. Additionally, a bilinear quadrilateral element is used to validate the mathematical solution. The results show that increasing grading parameters reduced transverse deflection, with a maximum reduction of 38.97% for CF beams and 39.26% for SS beams when the gradation index a z increased from 0 to 1 under mechanical loading. Under combined mechanical and thermal loading, higher temperatures on the beam’s hot side lead to increased deflection, with notable increases at higher gradation indices. Moreover, increased maximum deflection by 6.29% for CF beams and 4.05% for SS beams when considering temperature-dependent properties. It was observed that when TDFGM Timoshenko beams were heated for thermal loading, the SS beam deflected in the opposite direction of the applied mechanical load. The results agree with previous research and indicate alignment between mathematical and finite element solutions. The impact of boundary conditions on the deflection of Timoshenko beams made of TDFGM is discussed. The introduced methodology enhances TDFGM beam bending analysis, allowing control over behavior through grading parameters and boundary conditions selection.