فهرست مطالب r. eslami farsani

This paper reports the applicability of fuzzy logig (FL) to predict the hardness of melt zone (HMZ) during the gas metal arc welding (GMAW) process, which is affected by the combined effect of ZrO2 nano-particles and welding input parameters. The arc voltage, welding current, welding speed, stick-out, and ZrO2 nano-particles were used as the input parameters and HMZ as the response to develop FL model. The predicted results from FL were compared with the experimental data. The most important input parameter affecting the HMZs was the addition of ZrO2 nanoparticle coatings with a thickness of 1 mm, which increased the hardness from 78 to 84 HRB. The correlation factor value obtained was 99.98% between the measured and predicted values of HMZ. The results showed that FL is an accurate and reliable technique for predicting HMZ because of its low error rate. Also, the presence of ZrO2 nano-particles in the weld pool has increased the penetration up to 2 times.

In this study, the effects of adhesive type (Epon 828 and Araldite EA 1103), the overlapping area (12.5 and 25 mm), and the surface treatment of the polymer composite on the shear behavior of the sandwich panels with a foam core of polyvinyl chloride (PVC) C7075 and a polymer composite skin (glass fibers-vinyl ester) were investigated by finite element simulation and experiment. The results revealed that the sample with Epon adhesive exhibited higher shear strength and lower strain percentage value compared to the sample containing the Araldite adhesive. The samples with an overlapping area of 12.5 mm showed higher shear properties compared to those with a 25 mm overlapping area which is due to the presence of more bubbles and imperfections on the overlapping surface. Due to increased contact area and penetration of the adhesive into the porosities, surface-modified polymer composites with 100-grit sandpapers exhibited higher shear properties in comparison with those surface modified with 60-grit sandpapers. Also, the investigation of the fracture mechanism showed that the two mechanisms of the adhesive fracture and the rupture of the PVC foam led to the destruction of the sandwich panel. Since the foam rupture mechanism overcame the adhesive fracture, the shear properties of the sandwich panel were increased. The results showed that there was a good agreement between the experimental and simulation results.

Using natural hemp fibers to reinforce the tensile characteristics of polymer matrix composites is investigated in this article. The fibers were applied to the epoxy matrix in unidirectional and hybrid tissue forms. After preparation of standard tensile stress test specimens via manual layup, the standard tensile test was done.  Young’s modulus, ultimate tensile stress, and the amount of absorbed energy before fracture were obtained experimentally. A comparison is performed with respect to fibers posture. In all cases, the tissue fiber samples gave a higher strength in comparison with the unidirectional laminated fibers. An analytical model is finally presented to estimate the elasticity modulus of the tissue reinforced composites.