Glass Fiber Reinforced Plastic Pipes Research Articles

Stress relaxation experimental research and prediction of GFRP pipes under ring deflection condition

Abstract Glass fiber-reinforced plastic (GFRP) pipes are widely used as buried pipes in petrochemical and other industries. At present, in-depth studies have been conducted on GFRP pipes in terms of internal hydrostatic pressure, axial compression, and cyclic internal pressure, especially limited research has been carried out on transverse load, especially stress relaxation behavior. In this study, GFRP pipes with three different component contents were subjected to different initial deflections at different temperatures and subjected to stress relaxation tests for 1000 h. The findings demonstrate that the stress relaxation behavior of GFRP pipes is not affected by the initial deflection. Rather, it is primarily influenced by temperature and sand entrapment content, which are identified as the key factors determining the stress relaxation behavior of GFRP pipes. In addition, the time-temperature superposition principle (TTSP) was used to pass the test results to obtain a smooth master curve and verify the applicability of TTSP on GFRP pipes. Subsequently, the relaxation performance of GFRP pipes was predicted after 50 years. This research result contributes to a more comprehensive understanding of the stress relaxation behavior of GFRP through accelerated testing and offers crucial insights into the application of GFRP pipes.

A Sustainable Solution with Improved Chemical Resilience Using Repurposed Glass Fibers for Sewage Rehabilitation Pipes

This paper introduces a sustainable sewage rehabilitation solution, utilizing repurposed glass fibers for enhanced chemical resilience and environmental conservation. The approach involves dividing a unitary pipe into segments, assembled during commissioning, aiming to reduce installation and transportation costs, particularly in less accessible areas. Each pipe segment comprises a multi-layered glass fiber composite sandwich, joined by an adhesive reinforced with recycled glass fibers. The glass fiber-reinforced plastic (GFRP) pipe features a core of blended sand impregnated with resin, an outer layer for impact resistance, and an inner layer to prevent corrosion. Chemical resilience is assessed through a 10,000 h strain corrosion study exposing both unitary and two-piece circular GFRP pipes to sulfuric acid in a deflected condition. An apparent hoop tensile test evaluates mechanical integrity before and after exposure. The experimental results reveal that the two-piece pipe with a tongue and groove joint (TGJ) with recycled glass fiber adhesive exhibits superior long-term bending stress and failure strain % compared to unitary pipes. This enhancement is attributed to the TGJ’s improved load-bearing capability and chemical resistance. The failure strain % of the two-piece pipe (1.697%) is higher compared to the unitary pipe (1.2613%). The long-term bending stress of the two-piece pipe obtained is 119.94 MPa whereas the unitary pipe reaches 93.48 MPa at the 50-year mark. The cost analysis supports the adoption of the two-piece pipe over unitary pipes due to a 40% reduction in carbon emissions and transportation cost. The novelty lies in the utilization of multi-piece pipes with enhanced chemical resilience, achieved through the incorporation of milled fiberglass reinforcements in the TGJ. Strain corrosion tests take a long time to perform; hence, an accelerated test is needed to improve the current recommended testing standard.

Experimental Study of the Effect of Temperature on the Circumferential Bending Performance of GFRP Pipes

Glass Fiber Reinforced Plastic (GFRP) pipes are widely used as polymer-based composite pipes in various engineering fields where the temperature influences their performance. This paper investigated the circumferential bending properties of GFRP pipes with different continuous fiber contents at 30 °C, 50 °C and 70 °C. GFRP pipes are classified into three types according to their component content: type I, type II and type III. The results show that the bending performance of GFRP pipes tends to decrease with increasing temperature, with the retention of circumferential stiffness being 80-85% and the retention of bending strength and damage displacement being about 25-40% from 30 °C to 70 °C. The rate of decay of ring stiffness, bending strength and damage displacement is significantly higher from 30 °C to 50 °C than from 50 °C to 70 °C. Both temperature and continuous fiber content greatly influenced the damage pattern. At 30 °C, delamination damage occurred at the top and bottom of the Type I GFRP pipe before fracture damage happened at the left and right ends and fracture damage occurred at both the left and right ends of Type II and Type III GFRP pipes. Delamination damage happened at the upper and lower ends of the GFRP pipes at 50 °C and 70 °C. In addition, the paper analyses the mechanisms of the associated effects.

Effect of cutting parameters on surface roughness of waste-filled composite at milling

Industrial waste is a problem for companies as well as for the environment. In recent years, an alternative solution to this problem has been found – the use of waste in the production of new composite materials. It is not enough to produce only the composite. The machinability of the composite produced should also be investigated. This study obtained the new composite material using industrial waste produced by glass fibre-reinforced plastic pipes. The terephthalic resin was used as a matrix material. The waste powder was used as a filling material in the ratio of 30, 40 and 50% by weight compared to the matrix material. The machinability of produced composites was investigated according to three parameters with three levels. According to the experimental results, the optimum cutting parameters are obtained, depending on surface roughness.

NUMERICAL INVESTIGATION OF GLASS-FIBER REINFORCED PLASTIC MORTAR PIPES CULVERT RESPONSE TO HEAVY TRUCK LOADS


 
 
 The main objective of this paper is to investigate the dynamic performance and behaviour of glass-fiber reinforced plastic (GRP) mortar pipes under heavy truck loads. According to the field conditions, a finite element dynamic analysis (FEDA) model of GRP pipe culverts was established. Modal analysis of the vibration system was carried out, and the main natural frequencies with 26.6Hz,32Hz,35.7Hz and corresponding mode shapes were obtained. On the basis of modal analysis, dynamic response of GRP pipe culverts under vehicle loads was simulated through random vibration. Based on the measured vibration velocity time histories, the modal and random vibration responses of the vibration system were analyzed. The results show that the spectral response value of pipeline to vehicle load decreases with the increase of buried depth. When the depth of GRP pipe culverts buried is greater than 0.8m, the influence of ground vehicle dynamic loads on the vibration of GRP pipe culverts cannot be taken into consideration. It can provide the basis for the design of GRP pipe culverts, especially under heavy loads.
 
 

Thermal characteristics of epoxy as a bonding material in a low temperature vessel

One of the main sources of heat leakage in a low temperature vessel is the thermal conduction of the vessel wall between room temperature and the low temperature. The material of the vessel is generally stainless-steel, and it is fabricated by welding. To reduce the amount of the thermal conduction, materials having low thermal conductivity are chosen. Glass fiber reinforced plastic (GFRP) is one of the adequate candidate materials because it has low thermal conductivity and high mechanical strength. We use GFRP pipe instead of stainless-steel pipe, as a neck in a liquid nitrogen vessel (or Dewar). Epoxy, as a bonding material, is inserted between the GFRP neck and the main body of the vessel. Therefore, the thermal characteristics, especially the thermal expansion, are very important because the vessel is cooled and warmed periodically. The experimental results of thermal expansion between room temperature and the low temperature are presented in the paper. Leakage in a vacuum environment is incurred because of different linear thermal expansion coefficients of various materials. The leakage is investigated using a vacuum-level checking method during the thermal cycle. In addition, the amount of boil-off in a low temperature vessel is discussed in terms of the thermal characteristics of the neck’s material.

Adiabatic heating and damage onset in a pultruded glass fiber reinforced composite under compressive loading at different strain rates.

Damage onset and adiabatic heating of a pultruded Glass Fiber-Reinforced Plastic (GFRP) composite was investigated using compression tests at low, intermediate and high strain rates (10−3 s−1, 1 s−1 and 103 s−1). Optical and infrared (IR) cameras monitored the specimens during testing, so that the mechanical response, damage onset, and damage evolution were obtained along with the adiabatic heating of the specimen due to plastic deformation and fracture. The results revealed clear strain rate effects on stiffness, strain softening and damage initiation. The simultaneous optical and IR imaging allowed quantitative description of thermomechanical response of the material and studying the formation and propagation of shear localizations and their temperature history. The maximum temperatures in the fracture zones exceed 80 °C at the strain rate of 103 s−1. Scanning Electron Microscopy (SEM) was used to identify the micro-scale crack paths at different strain rates. The findings allow more exact numerical predictions and design of tubular GFRP pipes for impact applications.

Stress characteristics of double-row glass fiber-reinforced plastic pipe culvert with sand and optimization of load reduction parameters under adverse conditions

In this study, the stress and deformation rules of the double-row fiber-reinforced plastic sand pipes under the two loading methods of single-pipe and double-pipe loading were discussed. First, the indoor full-scale test was used to analyze the single-tube pipe top loading. The 90° measurement point of the loaded pipe and the 270° measurement point of the adjacent pipe were the most unfavorable positions for the stress of the pipeline. Through investigating the influence of cover soil height, load level, and compaction on the mechanical index of the most unfavorable load-bearing measuring point of the pipeline, the height of the overburden is found to be the most significant factor affecting the double-pipe stress system. Second, the numerical calculation model of the stress of the double-row pipeline was established to analyze the stress and deformation of the pipe culvert when the spacing of the double pipe was changed. The results indicated the critical spacing equivalent to the stress of the single pipe was 2.5D. Finally, the numerical method was also used to optimize the parameter of the geogrid at the top of the pipe in the most unfavorable stress state of the double pipe with 550-mm pipe spacing and double-loaded mode.

Optimization of water distribution networks using developed binary genetic algorithm and hydraulic model software

The optimal design of urban water distribution networks is a significant issue that has been of critical interest in the water industry for many years. The optimal design of the distribution network aims to find the best solution for transferring water from the reservoir to consumers at the lowest cost. In this study, optimization of the water distribution network (ZONE 1 of Ilam city, Iran) was performed using the fast messy genetic algorithms (FMGA) tool in the hydraulic model for three different pipe networks. Also, these networks were optimized by using a combination of EPANET and an in-house developed binary genetic algorithm in MATLAB. The costs of the optimized hydraulic networks of polyethylene and polypropylene pipes were lower, respectively, by 20.56 % and 52.94 % compared to the consulting company's original designs, while for the glass fiber reinforced plastic pipe (GRP) pipe network the cost increased by 12.61 %. Also, the results of a developed algorithm for polyethylene pipe decreased by 22.13 %.

Effects of the Number of Fatigue Cycles on the Hoop Tensile Strength of Glass Fiber/Epoxy Composite Pipes

Glass fiber-reinforced plastics (GFRPs) composite materials are widely used in many areas due to their superior properties such as high strength, corrosion resistance against many chemicals, duplicate production, the possibility of production in very large dimensions, and lighter weight than metals and alloys. As the use of GFRP pipes increases, many test methods are performed to determine their mechanical properties. Hoop tensile strength of GFRP pipes was determined by hoop tensile strength test according to ASTM D 2290 standard, and fatigue tests of GFRP pipes were carried out by applying internal hydraulic pressure according to ASTM D 2992 standard. In this study, six-layered E-glass epoxy composite pipes which were manufactured by the filament wound method for winding angle ± 55° were subjected to fatigue tests at the different number of cycles, and hoop tensile strength of fatigued pipes was determined. The samples were subjected to a fatigue test at a stress ratio of 0.05 and a frequency of 0.42 Hz according to ASTM D 2992 standard. Fatigue tests were performed on samples with a stress value of 35% static burst pressure. As a result of experiments, the effects of the number of fatigue cycles on the hoop tensile strength of the GFRP pipes were investigated, and the damage occurred in the GFRP pipes was evaluated. The increase in the number of cycles from the fatigue tests applied to the samples resulted in a reduction in the tensile strength of the samples.

An experimental study on the effects of various drill types on drilling performance of GFRP composite pipes and damage formation

Drilling is the most commonly used machining operation among others for assembly applications. The necessity of this operation has come to the forefront in composite materials that are becoming widespread nowadays. In this study, drilling performance of glass fiber reinforced plastic (GFRP) composite pipes used in many sectors such as natural gas transmission lines, pressurized sewer lines, industrial waste transmission, defense industry, and construction industry was investigated. The GFRP pipe was produced by filament winding method with a winding angle of ±55°. Different drill types (conventional twist drill, brad and spur drill, and brad center drill) with a drill diameter of 4 mm were utilized for drilling the pipe and the effect of drill type on the drilling performance was investigated. Drilling tests were performed at a constant 5000 rpm spindle speed and six different feed rate parameters (25, 75, 125, 175, 225, and 275 mm/min). Thrust forces generated during drilling were recorded and after the drilling operations, hole exit surface damage, and borehole surface damage were examined by a digital microscope and scanning electron microscope (SEM). Results showed that the brad center drill produced lower thrust forces while the twist drill generated higher thrust forces. The severity of damages could vary depending on the tool geometry and feed rate. Especially, at lower feed rates, conventional twist drill results with increased delamination and uncut fibers as compared with other drills. The brad center drill presents better performance since it generates fewer damages. Also, it is observed that these damages formed in the winding angle direction (orientation).

Evaluation and comparison of GRP and FRP applications on the behavior of RCCs made of NC and HSC

This paper presents the results of axial pressure testing on reinforced concrete columns (RCCs) filled with confined normal concrete (NC) and high-strength concrete (HSC) using glass-fiber reinforced plastic pipes (GRP) casing as well as fiber reinforced polymer (FRP). This study aims to evaluate the behavior and mechanical properties of columns confined with GRP casing and FRP wrapping under pressure loads. The major parameters in the experiments were the type of concrete, the effect of GRP casing and FRP wrapping, as well as the number of FRP layers. 12 cylindrical RCCs (150*600) mm were prepared and divided into two groups, NC and HSC, and each group was divided into two parts. In each part, one column was without FRP strengthening layer, a column was wrapped with one FRP layer and another column with two FRP layers. All columns were tested under concentrated compression load. The results of the study showed that the utilization of FRP wrapping and GRP casing improved compression capacity and ductility of RCCs. The addition of one and two layers-FRP wrapping increased compression capacity in the NC group to an average of 18.5% and 26.5% and to an average of 10.2% and 24.8% in the HSC group. Meanwhile, the utilization of GRP casing increased the compression capacity of the columns by 4 times in the NC group and 3.38 times in the HSC group. The results indicated that although both FRP wrapping and GRP casing result in confinement, the GRP casing resulted in increased compression capacity and ductility of the RCCs due to higher confinement. Furthermore, the confinement effect was higher on columns made with NC.

Axial Compressive Strength Experimental and Numerical Studies of Full-Scale Specimens Simulating GFRP Composite Bushing Column

To study the axial compressive performance of glass fiber-reinforced plastic (GFRP) composite structure, a full-scale axial compression experiment was conducted on GFRP composite bushing (GFRP-CB) column specimens. The axial compressive mechanical properties, failure mode, and load–displacement curves were obtained and analyzed. It is found that brittle fracture occurs in the GFRP-CB column specimens. Diagonal cracks as the main failure mode appear in the upper part of the GFRP pipe. Moreover, the maximum stress in specimens is less than the compressive strength of the GFRP composite material. The steel casing remains in the elastic state during the entire loading process. Based on the strength theory of transversely orthotropic material, the finite element method was used to scrutinize the influence of eccentricity and diameter–thickness ratios on strength of specimens. Numerical results prove that the ultimate bearing capacity of the eccentric compression specimens decreases with the eccentricity ratio. Reduction in diameter–thickness ratio can improve the ultimate bearing capacity of the specimens. As the diameter–thickness ratio decreases by 20%, the ultimate bearing capacity increases by 20%. Finally, an equation for calculating the ultimate bearing capacity of the GFRP-CB column is proposed according to test results. The calculated and test results are fairly consistent, which indicates the effectiveness and accuracy of the proposed equation.

Stiffness degradation of GFRP pipes under fatigue loading

Abstract This research on the stiffness of glass fiber reinforced plastics (GFRP) pipes constructed according to various types of winding patterns and under varied loading conditions, proposes a model of stiffness degradation for GFRP pipes and the parameters for a model of stiffness degradation. Based on a hoop winding GFRP pipe fatigue test, it was found that the stiffness reduction rate of the first half a million cycles is 0.67 times that of the last 500,000 cycles when maximum alternating displacement is 5 % of the diameter of the GFRP pipe. For the same type of winding GFRP pipe, the stiffness reduction rate at a maximum alternating displacement of its diameter'of 10 % and 15 % yields 1.34 and 1.59 times the stiffness reduction rate of a GFRP pipe with an alternating displacement maximum of its diameter of 5 %, respectively. For GFRP pipes of varied types of winding modes, when the maximum alternating displacement is 5 % of the diameter of a GFRP pipe, the rate of stiffness degradation of the helical winding GFRP pipe and hoop-helical combined winding GFRP pipe is 1.50 and 1.28 times that of a hoop winding GFRP pipe, respectively.

Behavior study of NC and HSC RCCs confined by GRP casing and CFRP wrapping

This paper presents the results of axial compression testing and numerical modeling on reinforced concrete columns (RCC) with normal concrete (NC) and high-strength concrete (HSC), RCC confined by glass-fiber reinforced plastic pipes (GRP) casing as well as carbon fiber reinforced polymer (CFRP), The major parameters evaluated in the experiments were the effects of concrete type, GRP casing and CFRP wrapping, as well as the number of CFRP layers. 12 cylindrical RCC (150×600 mm) were prepared and divided into two groups, NC and HSC. Each group was divided into two parts; with and without GRP casing. In each part, one column was without CFRP strengthening layer, a column was wrapped with one CFRP layer and another column with two CFRP layers. All columns were tested under concentrated compression load. Numerical modeling was performed using ABAQUS software and the results of which were compared with experimental findings. A good agreement was found between the results. Results indicated that the utilization of CFRP wrapping and GRP casing improved compression capacity and ductility of RCC. The addition of one and two layer-FRP wrapping increased capacity in the NC group to an average of 18.5% and 26.5% and in the HSC group to an average of 10.2% and 24.8%. Meanwhile, the utilization of GRP casing increased the capacity of the columns by 3 times in the NC group and 2.38 times in the HSC group. The results indicated that although both CFRP wrapping and GRP casing increased confinement, the GRP casing gave more increase capacity and ductility of the RCC due to higher confinement. Furthermore, the confinement effect was higher on NC group.

Ultraviolet Radiation and Elevated Temperature Impact on Flexural and Swelling Properties of Glass Fiber Reinforced Plastic Pipes

The aim of this paper is to investigate whether ultraviolet radiation and elevated temperature influence the flexural strength, flexural modulus and swelling of glass fiber reinforced plastic pipes (GRP) over different aging periods. The degree of resistance to breaking on impact, and its measurement, is of practical importance in the selection and comparison of composite materials. Prepared samples from unused GRP pipe were subjected to ultraviolet radiation, humidity and elevated temperature prior to aging for 3, 6, 9, and 12 months in two different media, aquifer water and crude oil with high water cut. Flexural strength and modulus were obtained through a three-point bending test, results show that flexural strength noticeably decreases for samples aged in aquifer water when subjected to ultraviolet radiation. The exposed wet crude samples of composites to ultraviolet environment showed better flexural strength and modulus when compared to the unexposed samples. Maximum value of flexural strength (208 MPa) and flexural modulus (14.2 GPa) was observed for non UV aquifer water samples. In addition, swelling tests indicated that the pipe polymer matrix has a great resistance to solvent uptake which synergize with flexural modulus results for aquifer and wet crude samples. It can be found from this study that the combination of flowing chemicals in the pipe with the external factors such as elevated temperature and ultraviolet radiation have a notable impact over the polymer matrix and consequently on the composite physical properties .

Evaluating mechanical performance of GFRP pipes subjected to transverse loading

The main objective of this research is to investigate the damage progression and the failure mechanism of Glass-Fiber Reinforced-Plastic (GFRP) pipes subjected to compressive transverse loading. An experimental study is performed to observe the level of diametric deflection where failure takes place under transverse loading and also to monitor experienced failure mode. Then, conducted experimental study is simulated in commercial finite element software taking into account both interlaminar and intralaminar failure modes, simultaneously.The degree to which the pipe can withstand diametric deflection without experiencing any failure mode is extracted. Then, appropriate in-plane failure criteria are chosen for identifying the onset of in-plane failure mode while cohesive approach is employed for identifying the initiation of delamination as the out-of-plane failure mode. Results of numerical simulation reveal that the liner is debonded from its adjacent hoop layer at 27% diametric deflection which is in a reasonable agreement with experimentally observed 31%. Moreover, the magnitude of the reaction force at 5% diametric deflection is obtained as 1242 N which is in a good agreement with experimentally measured 1225 N. Therefore, a satisfactory level of accuracy is achieved in constructed model implying on the appropriate modeling of damage progression. Finally, a parametric study is conducted to investigate the influence of various effective parameters on the pipe resistance level against transverse loading wherein neither in-plane nor out-of-plane failure is experienced.

Evaluating long-term performance of Glass Fiber Reinforced Plastic pipes subjected to internal pressure

A computational modeling procedure is developed for simulating long-term creep behavior of Glass Fiber Reinforced Plastic (GFRP) mortar pipes subjected to internal pressure. The modeling procedure includes creep evaluation, stress analysis, failure evaluation and degradation of mechanical properties. Different levels of internal pressure are examined to obtain sufficient data point on failure-pressure versus time-to-failure graph up to 100,000min. At each specific pressure level, the modeling procedure continues till the functional failure is distinguished implying on weepage phenomenon. Obtained data are extended to 50years using extrapolation technique for predicting the remaining strength of investigated GFRP pipe after 50years.

Sensitivity Analysis of the Crack Compliance and Layer Removal Methods for Residual Stress Measurement in GFRP Pipes

A comparison is presented between the sensitivity to measurement error of the crack compliance and layer removal methods of residual stress measurement when applied to glass fiber reinforced plastic (GFRP) pipes. This is done by adding random scatter to the exact strain distribution associated with a known stress distribution. This defines strain data that simulate experimental measurements. These data are used to determine the corresponding residual stress distributions. The error in the residual stress distribution when scatter is included can thereby be determined. It is shown that the layer removal and crack compliance methods are equally suitable for the measurement of axial and circumferential stresses in a pipe wound at only ±55 deg. The layer removal method, however, is shown to have significantly lower sensitivity to measurement error when the axial residual stresses in layered GFRP pipes are considered.

Simulation of the long-term hydrostatic tests on Glass Fiber Reinforced Plastic pipes

The main objective of this paper is to simulate long-term hydrostatic tests on Glass Fiber Reinforced Plastic (GFRP) pipes. An experimental procedure for obtaining pressure class of GFRP pipes on the basis of long-term behavior is very time consuming and costly that sometimes take about 2years for collecting required data. Then, obtained results are extrapolated to 50years. In this work, a theoretical modeling procedure is developed to obtain residual strength of pipes after 50years taking into account creep phenomenon. Developed progressive modeling consists of creep modeling, stress analysis and failure evaluation. An integrated modeling procedure is developed reporting time-to-failure at any desired internal pressure. As a case study and also validation purpose, the developed modeling procedure is conducted for predicting long-term behavior of a specific GFRP pipe subjected to internal pressure. A comparison between real experimental data and theoretical modeling is presented. A very good agreement between predicted 50-year hydrostatic pressure and experimental data implies on the proficiency of the developed modeling. Since the developed modeling is just in need of short-term experimental data on pure resin, it could be used as an appropriate engineering tool for industrial centers.