The present investigation aimed to understand the physicochemical properties of the new cellulosic fiber extracted from the bark of Silybum marianum (SM), in view of using it as a potential reinforcement for polymer composites. The morphological and anatomy, physical, thermal and mechanical properties of fibers were firstly discussed in this paper. The Silybum marianum fibers (SMF) were characterized by scanning electron microscopy, Fourier transform infrared, thermogravimetric analysis (TGA), optical microscope, X-ray diffraction (XRD), and single fiber tensile test. The average Young’s modulus and the breaking stress data presented by the fibers are 15.97 GPa and 201.16 MPa, respectively. XRD reveals the presence of cellulose with a crystallinity index of 45%. Thermal stability (250°C) and maximum degradation temperature (357.72°C) of the SMF are established by the thermogravimetric analysis. An analysis of the mechanical properties was carried out on a population of 35 samples using Weibull statistics with two and three parameters.

The main goal of this study is to characterize natural lignocellulosic fibers extracted from Malva Sylvestris. The experimental approach used is consisted to analyze the morphological, physical, chemical, thermal and mechanical characteristics of Malva sylvistris fibers. The stem anatomy showed that the bark of Malva is rich in fiber cells. Based on ATR-FTIR and X-ray analysis, the obtained results illustrated that the fiber contained mainly cellulose, hemicellulose and lignin. The crystallinity index of fiber is about 55.12 %, which indicated a high cellulose content. The Thermo-gravimetric analysis (TGA) analysis test point out that Malva Sylvestris fibers are thermally stable until 225°C and an apparent activation energy about of 111 kJ.mol−1 was recorded. Tensile strength of Malva fibers is about of 236.64 ± 93.33 MPa whilst its young’s modulus is about of 26.07 ± 5.14 GPa. In view of the dispersion in the obtained experimental results, the latter were analyzed using the Weibull statistical laws with two parameters.

No abstract

No abstract

The welds are the site of high residual stresses, localized in the vicinity of the weld cracks. Their presence caused many type of damage mode as stress corrosion, fatigue, sudden failure and increasing the temperature of ductile/brittle transition. Residual stresses in restrained welds and weld repairs are very complex. The heat treatment affects the value and distribution of residual stress in the specimen. This peak stress in all three samples occurred not at the toe, but in the middle of the weld bead, where the yield stress is higher. The use of the neutron diffraction (ND) technique for residual stress measurements is described. In addition, studies of macrostructure and hardness were conducted. The results of different tests conclude the influence of heat treatment on Residual stresses in welds.