The thermal effect of CO₂high-power laser cutting on cut surface of steel plates is investigated. The effect of the input laser cutting parameters on the melted zone depth (MZ), the heat affected zone depth (HAZ), and the microhardness beneath the cut surface is analyzed. A mathematical model is developed to relate the output process parameters to the input laser cutting parameters. Three input process parameters such as laser beam diameter, cutting speed, and laser power are investigated. Mathematical models for the melted zone and the heat affected zone depth are developed by using design of experiment approach (DOE). The results indicate that the input laser cutting parameters have major effect on melted zone, heat affected zone, and microhardness beneath cut surface. The MZ depth, the HAZ depth, and the microhardness beneath cut surface increase as laser power increases, but they decrease with increasing cutting speed. Laser beam diameter has a negligible effect on HAZ depth but it has a remarkable effect on MZ depth and HAZ microhardness. The melted zone depth and the heat affected zone depth can be reduced by increasing laser cutting speed and decreasing laser power and laser beam diameter.

This paper focuses mainly on investigating the mechanical properties of mortar reinforced with long-unidirectional vegetable fibers such as palm fibers and sisal fibers. The mechanical properties of fibers are also studied by considering fiber tensile test and fiber coupling test to analyze the twist-extension coupling and the tensile strength. Fibers were manually extracted from palm and sisal leaves. Laminated mortar specimens with fibers volume fraction ranging between 0% and 1.95% were prepared. The long unidirectional oriented fibers were placed on the lower part of the mortar. The influence of curing conditions on flexural strength of laminated mortar specimens was analyzed by considering two curing conditions: WCCC (wet chamber curing condition) and LCC (laboratory curing condition). Results confirm that the optimum fiber volume fraction was evaluated as 1.4% for Palm fiber-reinforced mortar. Better mechanical performance was accorded to the Palm fiber reinforced mortar in WCCC case due to the availability of water which is necessary to cement hydratation. Long Sisal fiber submitted to a tensile load shows coupling phenomenon between twist and extension which has a mechanical effect on the matrix behavior.

Composite materials reinforced with vegetal fibers appear to be a good alternative for engineering applications. The objective of this work was to develop a 2D mechanical model for the vegetal fibers-reinforced composite materials. This approach gives more possibilities for combining the two different materials without any more experimental tests for each kind of composition and position of the fibers. It's a two-dimensional theory taking into account the one-dimensional behavior of the fibers, but considered, geometrically, as a two-dimensional system. The vegetal fibers are considered as simple cords and they are represented by an equivalent geometrical surface having the mechanical characteristics, including bending property and the coupling between twist-extension. The analytical solutions can be used to determine the optimization parameters leading to maximize the stress in the vegetal fibers and minimize it in the matrix

During laser cutting, the heat caused by cutting has thermal effects on the cutting surface. This results in a hardening zone directly at the cut edge and an adjacent tempering zone. These zones are often associated with undesirable effects such as surface cracking and fatigue resistance. In the present study, high-power CO₂ laser cutting of steel sheets is considered and the thermal influence of laser cutting and its main operating parameter, laser power, on the microhardness beneath the cutting section is examined using Vickers microhardness tester. The microstructure changes of the cut edge surface and of the cut surface are investigated using optical and electron scanning microscopes. The results show that laser cutting has a thermal effect on the surface microstructure and on the microhardness beneath the cut section. The microstructure and microhardness of the cut edge are affected by the main input laser cutting parameter, the laser power. Also the microhardness of the affected zone depends on the value of laser power. Microstructure analysis shows that high-power laser cutting leads to the formation of cracks and the average size of grains of the heat affected zone increases with laser power.