majid Tehrani

The present research aimed to investigate the effect of stitching angle and stacking sequence of stitched layers on high velocity impact behavior of composites reinforced by glass woven fabrics. To study the effect of stitching angle on ballistic impact behavior, six different angles of (0°), (90°), (45°), (0°,90°), (±45°) and (0°,90°,±45°) were chosen as stitching angles. These stitching angles were applied on eight layers of glass woven fabric. To study the effect of stacking sequence of stitched layers, a different number of layers were stitched together with the angle of 0°. Unstitched and stitched composites were exposed to high velocity impact with 180 m/s using a spherical projectile. The residual velocity of projectile and dimensions of damage area on the composites’ front and back sides were measured. It was found that the sample with the 45° stitching angle had the best behavior against ballistic impact and its energy absorption was significantly higher than the other samp...

During recent years, the fabrics made from different yarns have been used for industrial purposes such as composite materials. Given the importance of the shear properties of these fabrics, a mechanical model based on the Grosberg and Park's Model for hybrid plain-woven fabrics is proposed. In this model, using the Energy method, the initial load-shear angle behavior of hybrid fabrics is calculated from the yarn mechanical properties and the fabric structure. To evaluate the proposed model, the experimental results for initial shear modulus obtained from pure and hybrid fabrics of basalt and nylon are compared with the theoretical model results. A comparison of the results shows that there is rather a good agreement between the proposed model predictions and experimental results.

One of the key issues associated with using of composites in various applications is their tensile behavior. The tensile behavior of a composite material is strongly influenced by the properties of its constituents and their distribution. This paper focuses on gaining some insights into the tensile process of pure and hybrid woven composite reinforced with brittle and ductile yarns. For this purpose, mesoscale finite element simulations were performed to detect the tensile response within three types of composites: i.e, a brittle fiber reinforced composite, a ductile fiber reinforced composite and a brittle/ductile fiber reinforced composite. The numerical predictions were then compared with the experimental observations and the results were discussed to give some insights into the reinforcing mechanisms in the composites. Based on the results it can be concluded that this finite element model is a reliable tool in the prediction of the tensile behavior of pure and hybrid composite ...

In the past two decades, worldwide interest in the natural dyes obtained from plants has rapidly increased, and a diversity of health and environmental benefits were found or argued for the practice. Cloves are the aromatic flower buds of a tree in the family Myrtaceae, Syzygium aromaticum, which their chemical compounds makes them suitable for the application in dyeing process. The important essential chemical constituents of clove include acetyl eugenol, beta-caryophyllene, vanillin, crategolic acid, gallotannic acid, and methyl salicylate. In this study, clove as the plant-derived dyestuff was used for dyeing the wool yarns to be investigated the effects of the different dyeing parameters including dyeing methods, acid and mordant type, and concentration and dyeing temperature in the yielded dyeing. The dyeing capability of the samples at different concentrations and temperatures was investigated using the spectrophotometer method and Beer–Lambert law. The results show that apply...

Basalt fiber offers an economic alternative to carbon fiber for the manufacture of composite parts. In this research, homogenous and intra-ply hybrid composites of basalt and nylon fibers have been produced in order to investigate the effects of bending speed and fiber volume ratio on the bending damage of composite structure. Five different types of woven fabric as reinforcement and different volume percentages of nylon including 0, 25, 33.33, 50 and 100% were used. All composites consisted of six-ply laminates were prepared using hand lay-up method. Three-point bending test was used in this research. The residual tensile strength values was employed in order to study the amount of bending damage of samples. The results demonstrated the highest residual tensile strength for the samples containing 33.33, 50 and 100% nylon fiber. Also, with increasing bending speed, the influence of the content of nylon and basalt on the residual tensile strength became more

Basalt and nylon fibers were used to produce both pure and hybrid composites with an epoxy resin. Results are presented regarding to the flexural behavior of both intra-ply and inter-ply hybrid composites, with particular regarding to the effects of the fiber content, plies stacking sequence and loading speed. Four different plies stacking sequences were selected for this study, and composites of different nylon fiber contents (0, 25, 33, 50 and 100 % by volume) in hybrid form with basalt fibers have been studied. In addition, scanning electron microscopy was used to examine the fracture modes of the pure and hybrid composites. The results indicate that by increasing of nylon/basalt fibers ratio the flexural modulus and strength decrease. Furthermore, with a proper choice of plies stacking sequence, the inter-ply hybrid composites can achieve better flexural properties than the intra-ply hybrid composites.

In this study, the tensile and compressive behaviors of pure and hybrid composite laminates reinforced by basalt-nylon bi-woven intra-ply fabrics were experimentally investigated. Epoxy resin was used as the matrix material. The purpose of using this hybrid composite is to obtain superior characteristics by using the good strength property of basalt fiber with the excellent toughness of nylon fiber. Five different types of woven fabric were used as reinforcement with different volume percentages of nylon (0%, 25%, 33.3%, 50% and 100%). The effects of nylon/basalt fiber content on tensile and compressive parameters were studied. In addition, the after failure visual inspection and scanning electron microscopy (SEM) analysis was used to determine the extent and type of damage on tested specimens. The results indicate that the tensile and compressive performances of these composites are strongly affected by the nylon/basalt fiber content. Also, with a proper choice of fiber content, the nylon/basalt hybrid composites can achieve mechanical properties comparable with the pure ones. The stress-strain curves, after failure visual inspection and SEM analysis of tested specimens reveal that hybridization can prevent catastrophic and complete failure. In hybrid composites, the basalt and nylon fibers cannot reach their maximum strength at the same time and the progressive failure of the various fibers therefore occurred

In this research study, anthocyanin pigments were extracted from Hibiscus sabdariffa L pigment using some solvents including distilled water, citric acid, ethanol and sodium hydroxide. Then the effect of the type of solvent used in the pigment extraction stage on the dye parameters and fastness of the dyed silk fabric was investigated. Pre-mordanting, simultaneous and post-mordanting methods were used for dyeing, and potassium aluminum double sulfate metal salt was used as the mordant. The results showed that although the dyeing process for all the samples was carried out in an acidic environment, the use of different solvents and the change in the pH of the pigment extraction environment caused a change in the created hue, the amount and area of a* and b* and the color strength of the examples. The highest color strength was created in the pre-mordanting method by using the pigment extracted in sodium hydroxide environment, while the lowest one was obtained in the post-mordanting method by applying the pigment extracted in distilled water environment. Also, according to the ISO standard, in the pre-mordanting method, the samples dyed with pigment extracted in sodium hydroxide environment and in the post-mordanting method, all samples had acceptable washing and light fastness.

The present research aimed to investigate the effect of stitching angle and stacking sequence of stitched layers on high velocity impact behavior of composites reinforced by glass woven fabrics. To study the effect of stitching angle on ballistic impact behavior, six different angles of (0), (90), (45), (0 ,90), (AE45) and (0 ,90 ,AE45) were chosen as stitching angles. These stitching angles were applied on eight layers of glass woven fabric. To study the effect of stacking sequence of stitched layers, a different number of layers were stitched together with the angle of 0. Unstitched and stitched composites were exposed to high velocity impact with 180 m/s using a spherical projectile. The residual velocity of projectile and dimensions of damage area on the composites' front and back sides were measured. It was found that the sample with the 45 stitching angle had the best behavior against ballistic impact and its energy absorption was significantly higher than the other samples. Stitching also reduces damage area in front and back sides of the composites and inhibits delamination.