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Go to Editorial ManagerThe aim of this work is to experimentally study the influence of fiber prestress and curing temperature on the tensile and flexural properties of carbon fiber-epoxy composite. Adaptive Neuro-Fuzzy Inference System model was used to predict the effect of fiber prestress and curing temperature on the tensile strength, tensile modulus, flexural strength and flexural modulus of carbon fiber-epoxy composite. It was found that, the best membership functions for predicting the tensile strength, tensile modulus and flexural modulus are Gaussian membership functions with 4 number of membership function, and for predicting the flexural strength are generalized bell membership functions with 4 number of membership functions. From the comparison between the experimental and predicted results of carbon fiber-epoxy composite properties, it is found that the prediction results of this model show a good agreement with experimental results.
The trend of using natural fibers in geotechnical engineering has become of great interest to improve weak soils due to some of its advantages such as local availability, environmental friendliness, and lower cost. In this study, a set of unconfined compression strength and direct shear tests were conducted to evaluate the performance of Al-Nasiriya clayey soil reinforced with natural fibers. Three different types of natural fibers were investigated as sustainable ones, including wheat straw fiber and palm frond fiber, as well as imperata cylindrica fiber. The effects of various fiber contents (0.25 %, 0.5 %, 0.75 %, and 1 %) and lengths (20 mm, 30 mm, and 40 mm) were experimentally evaluated. The results indicated that the compressive strength increased significantly with the increase of fiber content and length up to an optimum value and then decreased. The optimum fiber content and length were 0.5 % and 30 mm, respectively. Compared to the unreinforced soil, the compressive strength values at the optimum content and length increased by 102 %, 126 %, and 66 % for samples reinforced with wheat straw, palm fronds, and imperata cylindrica fibers, respectively. The shear properties improved due to soil reinforcement with natural fibers. Compared to the unreinforced soil, the internal friction angle of the samples reinforced with wheat straw, palm fronds, and imperata cylindrica fibers increased by 17.7 %, 42 %, and 9 %, respectively. Forever, the cohesion and shear strength are also improved due to inclusion of natural fibers.
This paper presents the effect of fiber orientation angle on the stress intensity factor SIF for carbon epoxy composite plates with single-edge, center, and inclined cracks of varying lengths under tensile load. The stress intensity factor and shape factor were calculated individually for each case, with nine different fiber orientation angles computed using the extended finite element method XFEM concepts. It is found the stress intensity factor increases with increasing crack lengths while the shape factor decreases. In the case of single edge cracks, the SIF increases in the average value reached (173 %) for composite plates with different fiber orientation angles, while in the case of the center crack, the average value of SIF reaches (81 %). It was observed in this study that the increases in stress intensity factor and the decreases in the shape factor with different crack lengths were more stable in the composite plate with a fiber orientation angle of 75°. The higher values of SIF at an angle of 75° are because of the high probability of fiber slippage at 75° due to induced shear stresses in addition to the tensile stresses at the fiber-matrix interface. As a result, the crack tip has a high-stress intensity factor.
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, a finite element method program under domain loading and plain strain conditions is developed and applied in evaluation of the stress intensity factor in opening mode (K1) in two dimensions crack problems. Two types of crack problems analyzed and verified: first, cracked rotating disc made from bi-directional fiber reinforced material composite, second crack blade made from bi-directional fiber reinforced metal matrix composite. It is found that the finite element method under domain loading is a good tool for the analysis of composite material. The simulation is accurate in comparison with that obtained from extrapolation method. The stress intensity factor for fiber reinforced metal matrix composite is larger when obtained from fiber-reinforced material under same condition.
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
In this paper, the influence of thermal residual stress on strength and fracture rotating speed of composite disc is studied and analyzed using finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result the thermal residual stress will reduce radial and tangential stresses in radial fiber reinforced disc, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber reinforced disc. The existing of residual stresses in composite disc will leads to initiation of crack and begins to propagation near the inner diameter compared to case when neglecting residual stress for cases taken in analysis. It is also verified that the finite difference method is a good tool for stress analysis of composite disc under residual stress effec
A large number of RC structures or at least some of their members need strengthening or rehabilitation. Among the typical failure modes, the shear failure is more dangerous and less predictable, because of usually brittle behavior and sudden collapse. Therefore, there are necessities for upgrading the shear capacity and the local ductility of reinforced concrete beams. In this study, four different techniques of concrete jacketing were used to improve the behaviors of the shear deficiencies beams. The four techniques used in this study to enhance the behavior of the beams were by using a Self-Compacted Fiber Reinforced Concrete jacket without stirrups (S.-J. + Steel Fiber), a concrete jacket of Self Compacted Concrete with stirrups (S.-J. + Stirrups), a concrete jacket of ferrocement jacket (S.-J. + Ferrocement), and a concrete jacket of ferrocement jacket with external steel reinforcing bars (S.-J. + Ferrocement + R). These techniques contributed to enhancing the load-carrying capacity and delaying the appearance of the first crack in tested beams compared with the control beam by a percentage of (35, 59, 30, 6) % and (18, 35, 81, 80) %, respectively. The specimen (S.-J. + Stirrups) showed the best performance in comparison with the other used strengthening techniques used in this study in terms of stiffness and the ultimate load-carrying capacity. The ferrocement jacket (S.-J. + Ferrocement) was found to be the most suitable jacketing system used to enhance the shear capacity in terms of cracking load.
This study investigates the effect of the shear span-to-effective depth ratio (a/d) on the behavior of high-strength steel fiber–reinforced concrete deep beams without stirrups containing circular web openings. A circular opening of 12.6 cm diameter was positioned at the center of the shear span, and beam performance was evaluated in terms of crack patterns, load–deflection response, and stress–strain behavior. Four specimens were tested experimentally. The control specimen consisted of a solid deep beam without openings and without steel fibers, while the remaining three specimens were reinforced with 1% steel fibers and included circular openings. All specimens were reinforced with 2Ø12 mm top bars, 3Ø16 mm bottom bars, and two stirrups at the supports to prevent local failure. The beams had different shear span ratios (a/d = 0.75, 1.0, and 1.5) and corresponding total lengths of 1025 mm, 1200 mm, and 1550 mm, respectively. All specimens were simply supported and subjected to two-point loading. The experimental results revealed that the optimal shear span ratio for maximum performance was a/d = 0.75 when combined with 1% steel fiber reinforcement. In addition, the ultimate strength of beams with circular openings decreased as a/d increased, with a strength increase of approximately 5.48% at a/d = 0.75 compared with a/d = 1.0.
The use of fiber-optic links as the connecting media in wireless microcellular networks can be provide uniform radio coverage to spatially distributed mobile users in cost effective manner. This paper investigates theoretically the performance of fiber distribution system for mobile phone networks that uses a single high power Nd:YAG laser in the base station and shared by many microcells. Analytical expressions are derived for the bit-error-rate (BER) floor characteristics and optimum operating conditions. The results indicate clearly that the laser power can be reduced significantly when the modulation index is optimized.
This numerical study aimed to investigate the torsional behaviour of hollow cross section reinforced concrete members strengthened with steel fibers (end hooked and corrugated), subjected to pure torsion. The numerical results were compared with experimental results and show good agreement. The experimental study was conducted on ten steel fiber reinforced concrete specimens with low longitudinal reinforcement ratio to investigate the torsional behavior under pure torsion. For this analysis, a computer program (ANSYS 18.2) was used. The brick elements 8-nodes (SOLID65) were used to concrete simulation, while the steel bars simulated as axial members (link 180). The steel fibre was represented theoretically by the stress-strain relationship. The theoretical results indicated that the adopted smeared crack model is capable of making relatively acceptable estimations of cracking and ultimate torsional capacity of the members.
This study investigates the deep drawing process of carbon fiber-reinforced high-density polyethylene (CF-HDPE) composites through experimental and numerical approaches. The experimental part involved fabricating CF-HDPE sheets and conducting deep drawing operations under controlled parameters (punch speed, temperature, and forming depth) to evaluate material behavior and mechanical properties. Numerically, finite element analysis (FEA) using ABAQUS simulated the forming process, analyzing stress distribution, strain development, and material deformation under varying conditions. Results revealed that increasing forming depth and decreasing forming temperature elevated the required forming force. Comparisons between experimental and numerical outcomes showed consistent trends, though some differences arose due to factors like friction and material nonlinearity. The findings contribute to optimizing deep drawing processes for composite materials, enhancing manufacturing precision, and minimizing material defects.
In this research, the mechanical properties were studied from the experimental, theoretical, and numerical aspects of the sports prosthetic foot for the purpose of providing a sporty prosthetic limb with high performance, easy to use and an appropriate financial cost to use by amputees who have lost their lower limbs (amputation below the knee) in practicing their sports activities and overcoming physical disability. The dimensions of the blades were calculated based on side profiles from European patent specifications. The chosen fibers have high strength, are light in weight, and can be purchased for a lower price than the materials that are used in the production of the sports prosthetic feet that are already on the market and are produced by specialized companies such as Ottobock and Ossur. Six laminates of the composite material consisting of matrix orthocryl lamination 80:20 pro reinforced with different fibers (Kevlar fibers, carbon fibers, glass fibers, and perlon fibers) were fabricated in the form of rectangles using the vacuum system and then cut to the required dimensions using a CNC machine. The density and volume fraction of the samples and the use of the rule of mixtures to calculate the mechanical properties of the laminates were calculated and entered into the ANSYS program. Then the boundary conditions were applied to the athlete's prosthetic foot and the total deformation, and the total strain energy was calculated to find out the best laminates in the athlete's foot industry. It was noticed that the laminates reinforced with carbon fibers were better than the laminates reinforced with glass fibers in terms of Young’s Modulus, as well as deformation. The best laminate obtained is (12 K + 4 C).
In recent decades, the need for strengthening and repairing reinforced concrete structures has increasingly arisen. One common method is the use of concrete jackets. Slurry Infiltrated Fiber Concrete (SIFCON), a newly developed material, offers superior mechanical properties, making it a preferred choice for strengthening and repairing concrete structures. However, there is limited understanding of its bonding performance when used as an overlay on a Normal Strength Concrete (NSC) substrate. This study conducted a direct Shear Test (DST) to evaluate the bond performance using reinforced NSC cubes externally bonded with SIFCON jackets subjected to direct shear. Eighteen reinforced cubes were strengthened with various bonding systems to investigate how different factors affect the bond performance between the NSC substrate and SIFCON overlay. The parameters studied included surface preparation methods, binder types, jacket configurations, bonding conditions (fresh overlay on hardened substrate and hardened overlay on hardened substrate), dowel placement, and bonding mechanisms. The results show that using bonding agents significantly improved bond strength, with epoxy proving more effective than latex. Specimens prepared by chipping showed better bonding performance compared to those prepared through diamond cutting. Chipping increased bond strength by 8.91% to 13.84% over diamond cutting in the case of fresh SIFCON overlay on hardened substrate. Using dowels in the bonding systems also improved bond performance by 10.89% to 16.97%. Applying jackets to three sides instead of two increased the ultimate failure load by 31.76% when dowels were used in both the two-sided and three-sided strengthened samples, and by 35.45% in the absence of dowels in both types of strengthened specimens. The cast-in-situ specimens demonstrated superiority over those strengthened with precast jacket layers.
A series of unconfined compression and direct shear tests were carried out to investigate the compressive strength and shear strength parameters of clay soil reinforced with different contents and lengths of wheat straw and palm frond fibers and by adding different percentages of furnace slag. The bearing capacity and settlement characteristics of the rectangular footing based on a clay soil layer reinforced with wheat straw fibers, palm fronds and furnace slag at different thicknesses were also studied by conducting model footing tests. The results indicated that the compressive strength and shear strength parameters improved significantly when adding 0.5% of natural fibers and 20% of furnace slag. The maximum compressive strength of soil samples reinforced with wheat straw fiber MT1 and palm frond fiber MT2 was 365 and 407 kPa, respectively. Compared to the unreinforced sample, samples reinforced with natural fibers and furnace slag significantly improve the shear strength parameters c and ϕ . The cohesion of soil sample reinforced with wheat straw and palm frond fibers increased by 8% and 43% respectively, while the internal friction angles improved by 19% and 40% respectively. The sample treated with furnace slag MT3 showed improved significantly in cohesion by 76% and less effect in internal friction angle. Compared to unreinforced soil samples, the cohesion of soil samples reinforced with wheat straw and palm fibers and treated with furnace slag MT4 and MT5 increased by 77% and 92% respectively, and less effect in internal friction angle. Moreover, the bearing capacity and settlement characteristics of the rectangular footing improved significantly with the increase in the thickness of the top layer reinforced with natural fibers and treated with furnace slag. The ultimate bearing capacity of layer reinforced with wheat straw fibers MT1 increases to 193.2, 220.15 and 247.5 kPa at thicknesses of 0.5 B, 1.0 B, and 1.5 B respectively, while the settlement decreased by 10.4%, 15% and 20.48% respectively at same thicknesses.
The ultimate objective of this study was to compare the performance of repaired edge cracks in steel plates before and after repair with patches made of steel patch and glass fiber-reinforced polymer composite patches (GFRP) in different shapes: circular, rectangular, and trapezoidal, under two conditions: unsymmetric patch (one patch) and symmetric patch (two patches). A three-dimensional finite element model of the one-sided and two-sided repaired examples is used to study how the steel and composite patch affect the stress intensity factor (SIF). Under uniaxial tensile loads, the use of steel patches and GFRP composite patches to repair cracks was studied. The results showed that the steel patch performs better than the GFRP patch because it significantly lowers the stress intensity factor (SIF). The symmetric patch arrangement (two patches) is better than the un-symmetric patch arrangement (one patch) because it significantly reduces the stress intensity factor (SIF).
In this paper, a universal testing machine and an impact testing apparatus have been upgraded by using a high- accuracy data acquisition and control system interfaced to a personal computer with proper sensors and actuators. The purpose of upgrade is to increase the accuracy of the measurements and to perform advanced material testing procedures that are not possible with the old configuration. The modernization process not only permits the accurate data acquisition and convenient operation but also the ability to study the effect of strain rate on the tensile properties of materials. Also, an experimental study of the response of CFRP (Carbon Fiber Reinforced Plastic) material to low and intermediate strain rates has been carried out.
This research studied the critical load of composite columns theoretical and numerical by using ANSYS14 package depended on experimental tensile properties of composite specimens. The composite specimens were prepared by hand lay-up technique made from unsaturated polyester reinforced with glass fibers with different fiber volume fraction V f , aspect ratio (L/T), and angle of fibers for coarse and fine woven fibers. The critical load that obtained by using program (ANSYS 14) have also shown a good agreement with results that were obtained theoretically and the maximum difference was (0.7%). The results show that the maximum value of the critical load can be observed at V f =11%, L/T = (3.5) and θ = (0 º /90 º ) for fine woven fibers was (622.115N). Also its found the maximum critical load for coarse woven fibers can be observed at V f %=8%, L/T=(3.5) and θ = (0 º /90 º ) was (486.887N). Also the observed values of tensile properties and predicated values are scattered close to the (45 ˚ ) line.