Buckling behavior of laminated composites are entirely depends on the geometry and stacking sequence of layers. The different fiber paths as a result of the stacking sequence can affect the buckling ...properties of laminates. The aim of this paper is to determine the effect of fiber path on the buckling behavior of laminated composites using Yarn Interlacing Matrix (YIM). Different fiber paths were implemented by making hybrid/uniform laminates. Glass woven fabrics with different yarn architectures and epoxy resin were used to fabricate the 8-plies laminated composites in 25 × 25 cm
2
with 25 × 8.5 cm
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aluminum sheet in middle layer by vacuum infusion process (VIP). The buckling test was carried out on the prepared samples using DARTEC testing machine with five replicates. In addition, the buckling behavior of laminates was simulated using ABAQUS software. The novelty of this study is to use the YIM in theoretical model and investigate the critical buckling load of hybrid laminate composite in pattern of weave and understand the effect of geometrical hybridization on critical buckling load. It showed that the critical buckling load for hybrid samples are larger than the uniform ones. Comparison between theoretical and experimental results of the critical buckling load showed a maximum error of 16% in predicting the critical buckling loads. Also, comparison between theoretical and experimental results of the critical buckling load showed a maximum error of 59.7% in predicting the critical buckling loads. The main outcome of this research is that the fiber path has a greater effect on the buckling behavior than the elastic modulus of the laminates; so that despite the lower elastic modulus, the critical buckling load of laminates with hybrid reinforcement is higher than that of laminates with uniform reinforcements.
•This paper reviews various aspects of reinforced hollow fiber membranes (HFMs).•There is a focus on the braid-reinforced hollow fiber membranes.•Advantages and disadvantages of reinforcement methods ...are presented.•Tensile strength and elongation at breaks are the most studied properties of HFMs.•Some crucial issues of reinforced hollow fiber membranes need to be further studied.
Reinforcing the HFMs provides appropriate mechanical and shear strengths and improves break at elongation. This comprehensive review paper first discusses the fundamental concept of HFMs fabrications, advantages and disadvantages of HFMs, fabrication methods and fabrication materials. Then, reinforcement methods are categorized into porous matrix membrane reinforced method, the fibers (use of threads or filament) reinforced method, and the use of tubular braids, and each one is discussed based on the concept of thermochemical compatibility of the supporting material and the base polymer. Such a compatibility leads to homogeneous- and heterogeneous-reinforcement method with different interfacial bonding state. A comparative study on the mentioned reinforcement methods is also presented based on the tabulated and charted tensile strength and elongation at break data. At the end, a brief look is taken into commercialized products and worldwide projects installed or under installation in the field of reinforced HFMs.
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Tee-joints are the weakest links in the composite pipelines under internal pressure. In this paper, the internal pressure behavior of Tee-joint composites reinforced with integrated weft-knitted ...preforms was studied. For this purpose, a multiscale approach was developed on meso-and macro-scales using the homogenized finite element method and ABAQUS Commercial package. Three repetitive unit cells (RUC) of the weft-knitted composite were investigated on the mesoscale. Using the result of the mesoscale simulation, the internal pressure behavior of integrated and non-integrated Tee-joint composites was simulated on the macroscale. A burst pressure test was carried out on the prepared samples. The numerical and experimental results showed that the integrated Tee-shape preforms improve the internal pressure resistance of the Tee-joint composite so that the resistance against internal pressure of integrated Tee-joint composites is at least 40% higher than non-integrated Tee-joints.
Joints are the weakest links in the composite pipes under internal pressure due to the discontinuity of reinforcement in connection area. Weft-knitted integrated preforms can be used to enhance the ...strength of these composite joints. The focus of this study is to develop a geometrical model for the finite element analysis of composite joints reinforced with single jersey weft knitted fabric, which take cylindrical forms. Thus our efforts are concentrated on generating geometrical models for weft-knitted integrated preforms as reinforcement of Tee-joint, and various Wye-joint composites in pipelines. A geometrical model was first developed for loops on the curved surfaces by modifying the offered model for loops on flat surfaces. Then, the joint was divided into two cylinders; main cylinder and joint. Each cylinder was modeled using the generated model for loops on curved surfaces. The modeled cylinders were assembled according to the structure of joints. A python algorithm was proposed to simulate the weft-knitted integrated preforms in Abaqus/CAE 2016 commercial package. By implementing the proposed algorithm, the geometry of reinforcement was modeled for three types of joints based on technical data of ASME-B31. To verify the generated model, T-shape weft knitted integrated preform was produced using glass yarn count of 220 tex, CPC and WPC of 6 and 4, respectively. Comparing the experiment and simulation results shows a maximum error percentage of 10 % in the predicting the structural parameters of joints. It can be concluded that the generated model can well predict the geometry of weft-knitted preforms.
In the present study, the buckling behavior of delaminated plate in woven fabric composite laminates was studied. For this purpose, at first, the structure of woven fabrics was defined as shape ...functions. Then, the continuous analysis was used to study the bucking of delaminated plates. Based on the Rayleigh–Ritz method, the related formulations were developed to predict the critical buckling load of composite laminates. Three types of woven fabrics (viz. Plain, Twill, and Satin architecture) were used as reinforcements for polyester composites. The 8-ply laminated composites were fabricated using Vacuum Infusion Process (VIP). The results of buckling test showed that the critical buckling loads of laminates reinforced with Plain, Twill, and Satin woven fabrics are 1.35, 1.12, and 1.48 kN, respectively. Also, the results of analytical method are compared with experimental results and those achieved by the finite element method of analysis using ABAQUS software. Compared with experimental results, the maximum error of analytical and FE models is about 17% and 10%, respectively.
Sandwich-structured composites are designed to improve through-the-thickness mechanical properties. In this paper, the effect of Z-fiber orientation on the bending behavior of sandwich-structured ...composites reinforced with weft-knitted spacer fabrics was studied numerically and experimentally. A new mathematical model was generated for geometry of pile yarns. Using the generated model, different orientations of Z-fibers were simulated in ABAQUS software. To investigate the effect of Z-fiber orientation, different structures of pile yarns designed using the gaiting and feeding ratio of pile yarns and layers. Composites with different Z-fiber orientations of reinforcement were fabricated. Three-point bending test was carried out on the prepared samples. The results of experimental and numerical investigations showed that the pattern of reinforcements that creates different orientations of Z-fibers with various heights and angles considerably influences the bending behavior of sandwich-structured composites. The maximum von Mises stress occurs in Z-fibers when the composites are bent in the transverse direction, but the maximum von Mises stress is created in the layers when the composites are bent in the longitudinal directions. Consequently, in the transverse direction, Z-fibers play the major role in the bending behavior of sandwich-structured composites, whereas in the longitudinal direction, the layers play the main role.
The first and most important step in the numerical analysis of the mechanical properties of complex structures is to create an accurate geometrical model. This paper aims to generate a mathematical ...model for the geometry of weft-knitted spacer fabrics in order to use in the numerical analysis of the mechanical properties of sandwich composites. For this purpose, the equations of path yarn were derived. A mathematical model was developed for the geometry of 1 × 1-Rib-Gaiting weft-knitted spacer fabric using derived equations. In order to simulate the matrix of the sandwich composite, a novel approach was proposed to apply the matrix to the structure of the generated model. The compressional behavior of sandwich composites reinforced with weft-knitted spacer fabrics was simulated using a generated model in the ABAQUS software. The maximum error of 4.04% and 4.2% were recorded in the prediction of geometry and compression modulus of sandwich composites, respectively. In addition, the results of the numerical and experimental compression test showed that the pile yarns have the main role in the compressional behavior of sandwich structures reinforced with spacer fabrics. The maximum Mises and shear stresses are occurred at the midpoint of pile yarns and connection points between piles and layers, respectively.
The aim of this paper is to develop an analytical model to predict indentations of the impactor on the composites reinforced with weft-knitted spacer fabric using Hertz contact law. For this purpose, ...simply supported rectangular plate with partially load developed by Timoshenko was applied to analyze the deflection of top face, and the concepts of the buckling of initially curved struts were used to find the buckling of Z-fibers. To evaluate the accuracy of the model, the effect of the number of Z-fiber per unit area and elastic modulus of Z-fiber were investigated. The results showed that in the outside the contact area, the impact force bends the layer and causes the Z-fibers to buckle, but no indentation occurs. Inside the contact zone, the indentation has occurred, in addition to the layer deflection and Z-fiber buckling. Also, indentations in both X and Y directions decrease by increasing the Z-fiber density. In addition, the higher the z-fiber modulus leads to fewer indentations. Decreasing the angle coefficient of Z-fibers leads to increase their buckling resistance. Moreover, a reasonable agreement was observed between theoretical and experimental results; so that the maximum error of prediction was less than 20%. Furthermore, the proposed model can give the indentation of different points of sandwich-structured composites according to their coordinates.
The main traditional technique for commercial manufacturing of composite pipes is filament winding in which the winding angle and the discontinuity of the structure (caused by starting and ending ...points of the winding process) are two important matters of concern. In the present study, circular woven fabric with its orthogonal net-shaped continuous structure was produced from polyester yarns. Fabric was wet with epoxy and hand lay-up was used to manufacture the composite pipes. Composite pipes were subjected to internal hydrostatic pressure and their burst strength was recorded. In addition, tensile strength of flat laminas was assessed in the warp and weft directions. We estimated and analysed the failure strength of composite pipes using Tresca’s failure criterion and Finite Element (FE) modeling. The experimental burst strength was almost 23% more than the FE model and 77% more than the theoretical estimate.
This study aims to design and analyze novel fibrous structure with in-plane isotropic properties. A fibrous structure was defined in cylindrical coordinate using Archimedes' spiral. The geometry and ...tensile behavior of designed structure were simulated once in one direction and again in all directions using ABAQUS/CAE. The dynamic explicit analysis was used due to the geometric complexities. The mechanical properties of the structure were modeled once as elastic and again as hyperelastic material. The elastic model was closer to the experimental results. The experimental and numerical results indicated that tensile behavior of fibrous structure is identical in different directions.
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