Glass Reinforced Epoxy Pipes Research Articles

A Novel Investigation on Microstructural Analysis of a Rupture GRE Composite Pipe for Underground Fire Water System

This study investigates how underground fire water systems using Glass Reinforced Epoxy (GRE) pipes are affected by aging. Over time, GRE pipes can degrade, potentially reducing their expected lifespan. The study compared damaged and undamaged areas of pipes to assess how damage impacts their structural integrity. Microscopic and chemical analyses (SEM and EDX) were performed on pipe samples from different locations of the pipe. Mechanical testing (following ASTM standards) was conducted beforehand. Analyses revealed that as damage increased (closer to damaged area), the levels of carbon (C) and oxygen (O) changed significantly with the weight percentage exposed 45.62% difference and 11.62% difference, respectively, as compared with the undamaged area. This suggests that the epoxy resin degrades with age, releasing these elements. Additionally, the presence of foreign objects around the pipes can affect how they bear loads. These findings highlight the importance of understanding how aging and surrounding conditions can influence the performance of GRE pipes in real-world fire water systems.

Fire exposure, impact responses, and burst tests of glass-reinforced epoxy (GRE) composite pipes

The paper presents the fire exposure, impact responses, and burst tests of glass-reinforced epoxy (GRE) composites pipes. Fire responses of three different fire exposure times (10 s, 20 s and 30 s) were conducted, followed by impact loadings. Three different energy levels (5 J, 7.5 J, and 10 J) were applied for impact responses and followed by monotonic burst tests. Monotonic burst tests were conducted on GRE samples using hydrostatic pressure testing equipment in accordance with ASTM D1599. The result shows that the longer the time of fire exposure towards GRE pipes, the higher the impact energy applied to the pipes, the lower the burst strength of the pipes. The maximum burst strength found decreased with an increase in the fire exposure time. The results also indicated that the strength of the GRE pipes significantly decreases with an increase in impact energy level.

Microwave Non-destructive Evaluation of Glass Reinforced Epoxy and High Density Polyethylene Pipes

Owing to their inherent advantages, non-metallic structures such as glass reinforced epoxy (GRE) pipes and high-density polyethylene (HDPE) pipes are rapidly replacing their steel counterparts in pipeline infrastructures. However, non-metallic pipes are vulnerable to a variety of defects which compromise their structural integrity. Hence, periodic inspection of these structures is incumbent to ensure their structural integrity and avoid catastrophic in-service failures. Microwave and millimeter wave non-destructive evaluation techniques have shown great potential for inspecting non-metallic structures due to their high sensitivity, resolution, and cost-effectiveness. However, most of the previous investigations performed on microwave non-destructive testing (NDT) of these particular structures are deemed limited since these investigations considered one probe type and often conducted over narrow frequency band. Furthermore, many of the previous microwave NDT investigations considered unrealistically large defects which renders the reported conclusions about the performance envelope of microwave NDT of non-metallic pipes rather inaccurate. Consequently, an uncertainty still exists in the domain with regards to detection capability of the method when the defects in the pipes are actually small in size. Unlike all previous investigations, a comprehensive and realistic microwave imaging of GRE and HDPE pipes with embedded defects of practical importance is demonstrated in this paper. In order to image these defects, various near-field probes operating at wide range of frequencies are employed and compared herein. The relative performance and the effectiveness of microwave NDT for non-metallic pipe inspection using these probes are quantitatively reported. Furthermore, the images of the HDPE pipe produced by microwave probes are benchmarked to phased array ultrasonic testing.

Influence of a reactive diluent on curing kinetics, Internal Curing Process, and Mechanical Performance of Filament Wound Glass Fiber‐Reinforced Epoxy Composite Pipes

Nowadays, glass reinforced epoxy (GRE) pipes are industrially manufactured by the filament winding process using internal heating technology. This study deals with the comprehensive evaluation of a strategy aimed to improve the plant productivity by means of physical experiments, mechanical tests, and numerical simulations of the curing process. The reactive system is composed by diglycidyl ether of bisphenol A (DGEBA), methyltetrahydrophtalic anhydride (MTHPA), and benzyltriethyl ammonium chloride (BTEAC) used as initiator. An increase in BTEAC concentration in system formulation leads to a reduction in curing times of GRE pipes. The processing problems associated with this increment are proposed to be solved by the incorporation of a reactive diluent (RD) together with the optimization of the curing cycle. The effects that different amounts of 1,4‐butanedioldiglycidyl ether (DGEBD) added as RD exerts on system viscosity, copolymerization kinetics mechanism, curing process and properties of matrix, laminated composites and GRE pipes are deeply analyzed. Results demonstrate that if a 10 wt% RD is used, not only the strategy turns out to be feasible but also GRE pipes performance is improved. POLYM. ENG. SCI., 59:344–354, 2019. © 2018 Society of Plastics Engineers

Impact responses, compressive and burst tests of glass/epoxy (GRE) composite pipes

The paper presents the impact responses, compression and burst tests of glass reinforced epoxy (GRE) composites pipes. Impact loadings of three different energy levels (5 J, 7.5 J, and 10 J) were applied, followed by monotonic burst tests. Uniaxial compressive tests were conducted GRE samples using a universal testing machine in accordance with ASTM D695-10. In addition, the tests were also repeated with samples of different winding angles of ±45 ° and ±55 ° and tested at room temperature, and elevated temperatures of 45 °C and 65 °C. The result shows that the higher the impact energy applied to the pipes, the lower the burst strength of the pipes. The maximum burst strength found decreased with an increase in the impact energy level. The results also indicate that the strength of the GRE pipes significantly decreases with increase in temperature though, they are also found to increase as the winding angles decrease.

A Comparison of the Polymer Matrix Behavior and Mechanical Properties of the Glass Reinforced Plastics and Glass Reinforced Epoxy Pipes under Different Oil Field Chemicals

Fiber reinforced composite material is used widely in oil fields for its high specific strength and resistance to corrosion. Glass reinforced plastics (GRP) and Glass reinforced epoxy (GRE) pipe samples were investigated under oil field conditions. The samples were subjected to ultraviolet radiation, moisture and elevated temperature using accelerating weathering machine and then aged in different environments encountered in oil well streams and characterized by using Scanning Electron Microscopy (SEM). The surface morphology was analyzed and the images produced from wet crude and effluent water has shown different degree of deformation of the glass fiber and debonding with the polymer matrix. The tensile and modulus properties were also evaluated and effect of ageing found to be more pronounced in the case of wet crude especially for the GRE. The study revealed some tendency of GRP samples to reform the polymer matrix interface with the glass fiber after weathering. The assessment of physical properties provided information about the structural stability of composite pipes under harsh environments, which in turn can impact their overall performance and service life.

Effects of elevated temperatures on glass-reinforced epoxy pipes under multi-axial loadings

The effects of elevated temperatures on the performance of glass-reinforced epoxy (GRE) pipes under multi-axial loadings were investigated. Finite element software was used to develop the layers of the winding angle on GRE composite pipes. The simulations of the closed-ended pipes’ performance under internal pressure loadings of various hoop to axial stress interactions were observed, then the failure strength was illustrated in the form of a failure envelope. Five different stress ratios ranging from pure axial loading 0:1, 1:1, 2:1, 4:1 and pure hoop 1:0 were tested at elevated temperatures (room temperature (RT), 65°C and 95°C) respectively. The first ply failure (FPF) for GRE pipes was predicted based on Tsai–Wu failure criteria. The results show that the highest temperature reduced the strength of the GRE pipes since the hoop and axial stress decreased with increasing temperature and thus the mechanical properties of the GRE pipes were degraded with the increase of temperature. Both showed a strong dependence on the stress ratio and test temperatures. Moreover, as the temperature increases, the glass fibres become more ductile and cause the failure envelopes to shrink towards the origin and become slightly narrower to accommodate the increase in strength of the composite pipes. It is shown that the initial failure stress based failure envelope at elevated temperatures generally degraded, except for the 2:1 loading where the initial failure stress increased.

Effect of Geopolymer filler in Glass Reinforced Epoxy (GRE) Pipe for Piping Application: Mechanical Properties

The present work is aimed to carry out the effect of geopolymer material which is fly ash as filler in the glass reinforced epoxy pipe on the micro structure of fly ash geopolymer, compression properties, and bulk density using the filament winding method. Conventional glass reinforced epoxy pipes has its own disadvantages such as high corrosion resistance at acidic environment and low strength which can be replaced by the composite pipes. Geopolymer is a type of amorphous alumino-silicate and can be synthesized by geopolymerization process. A series of glass reinforced epoxy pipe and glass reinforced epoxy pipe filled with 10 - 40 weight percentage geopolymer filler which is fly ash with 4 Molarity were prepared. Morphology of the raw material fly ash and fly ash based-geopolymer surface was characterized using scanning electron microscopy. It was found that the additions of fly ash at the beginning with 10 wt% are showing higher compressive strength than glass reinforced epoxy pipe without fly ash geopolymer filler. The compressive test of these series of samples was determined using Instron Universal Testing under compression mode. It was found that compressive strength for samples fly ash based-geopolymer filler are higher as compared to glass reinforced epoxy pipe without geopolymer filler. However, the compressive strength of glass reinforced epoxy pipe with fly ash geopolymer filler continues to decline when added to 20 wt% - 40 wt% of geopolymer filler loading. The results showed that the mixing of geopolymer materials in epoxy system can be obtained in this study.

Numerical modeling of internal heating curing of glass reinforced epoxy pipes

A dynamic one‐dimensional model is developed to simulate the novel internal heating curing process in the manufacturing of glass reinforced epoxy pipes by filament winding. The model combines the energy balance with a mechanistic kinetic approach and it is experimentally validated using industrial plant data. The efficiency of a specific curing cycle at different operating conditions is analyzed. In particular, the influence of ambient temperature, initial mandrel temperature, glass fiber content, initiator concentration and pipe wall thickness on temperature, and degree of cure profiles within the pipe wall thickness is discussed. This study attempts to dispel current industrial myths and to propose practical strategies to improve the internal heating curing process. POLYM. ENG. SCI., 55:2626–2635, 2015. © 2015 Society of Plastics Engineers

Lifetime estimation of glass reinforced epoxy pipes in acidic and alkaline environment using accelerated test methodology

Accelerated ageing test methodology is valid and widely accepted procedure for estimating the lifetime of isotropic homogeneous polymeric materials. However for non-isotropic and heterogeneous polymeric compounds such as glass reinforced epoxy (GRE) pipes, accelerated ageing test methodology has not been much investigated. Various standards such as ASTM D 3681, ASTM D 5365 are being used to estimate the lifetime of GRE pipes using regression analysis which is time consuming, and requires large number of test specimens and fixtures specific to pipe dimensions. Accelerated ageing test methodology can be a viable method for estimating the lifetime. The research on accelerated test methodology as a vital tool to determine the lifetime of GRE pipes has been limited. The major concern for using accelerated ageing test methodology is primarily due to the degradation kinetics of the anisotropic composite materials which may not be governed by the Arrhenius principle. The present study on the estimation of lifetime of GRE pipes in extreme acidic and alkaline medium reveals that degradation of the composite pipe follows the Arrhenius principle and the degradation mechanism can be described by first order reaction kinetics. The degradation rate, the temperature dependence of the degradation rate and lifetime of the glass reinforced epoxy pipes in extreme acidic and alkaline medium as found in the current study are presented here, along with the morphological study of aged and un-aged GRE pipes.

English

This paper presents the modelling of stress strain response of glass fibre reinforced epoxy (GRE) composite pipes subjected to multiaxial loadings at room temperature (RT). This particular modelling work was developed to predict the non-linear stress strain response caused by the fatigue cyclic and static loading in the multiaxial ultimate elastic wall stress (UEWS) tests by considering the effects of matrix cracking within the laminates. The UEWS test, whilst not yet standardized, appears to offer an attractive alternative to existing procedures of qualifying GRE pipes. The ply properties initially expressed as a function of crack density was computed as a function of increasing stress and strain using shear lag approximation. The predictions are found to be in good agreement with the data from multiaxial UEWS tests on ±55° filament wound glassreinforced epoxy pipes.

Short-Term Test of ±55 ̊ Filament Wound GRE Composite Pipes under Multiaxial Stress Ratios

This paper discusses the the development of an automated pressure testing rig to perform a short term test; Ultimate Elastic Wall Stress (UEWS) for ±55 ̊ glass fibre reinforced epoxy (GRE) composite pipe under various stress ratios. The prototype is capable of determining the stress-strain response caused by the static and cyclic pressure. This developed rig is to provide an alternative solution for the current qualification procedure explained in ISO14692 through ASTM 2992. As part of the work, an automated testing rig powered by labview program is developed with the aid of pressure sensors, solenoid valves and strain gauges which are interfaced through hardware modules from National Instruments. The UEWS test for the five stress ratios namely pure hydrostatic (2H:1A), pure hoop (1H:0A), pure axial (0H:1A), hoop to axial (1H:1A) and quad hoop to axial loading (4H:1A) were performed upon the ±55° filament wound glass-reinforced epoxy pipes. The changes in the stress strain response are captured from the strain gauge measurements and the UEWS failure points are calculated for all the loading conditions. The failure envelope developed from the failure points can be used to predict the long term performance of the GRE pipes and provide the benchmark for the design of composite pipes under various stress ratios.

Ageing Studies of Glass-Reinforced Epoxy Pipes in Oil Well Streams under the Harsh Environments

Fibre reinforced epoxy composite material is used widely in oil fields by utilizing its high specific strength and resistance to corrosion. The composite pipes were aged in different environments encountered in oil well streams and structural features were evaluated. The samples were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). The surface morphology was analyzed using Scanning Electron Microscopy and the images showed clear pattern of glass fibers without any fragmentation in the epoxy matrix. The tensile properties were evaluated for the aged in comparison with the control pipe samples (unaged). The assessment of physical properties provides technical information about the structural stability of composite pipes under harsh environments.

Modelling of Multi-Axial Ultimate Elastic Wall Stress (UEWS) Test for Glass Fibre Reinforced Epoxy (GRE) Composite Pipes

This paper describes the modeling of multiaxial ultimate elastic wall stress (UEWS) at room temperature for glass fibre reinforced epoxy (GRE) composite pipes. The model developed, predicts the stress-strain response caused by the combined, static and cyclic of UEWS loading taking into effects of transverse matrix cracking within the laminates. The procedure, although not a standard method, seems to provide a good alternative to the current raw materials' re-qualification procedure delineated in ISO 14692 through ASTM D2992. The effective transverse and shear modulus of the lamina due to increasing presence of transverse matrix cracking were estimated. Classical laminate analysis was then applied to compute the corresponding ply properties as a function of increasing stress and strain. The model shows a good agreement with the experimental results of multiaxial UEWS tests on ±55° filament wound glass-reinforced epoxy pipes.

Qualification and lifetime modelling of fibreglass pipe

Procedures for qualifying fibreglass pipes are discussed here in relation to industry needs. The ultimate elastic wall stress (UEWS) test appears to provide an efficient means of rating pressure pipe, and indeed vessels, for the case where weepage failure occurs resulting from the accumulation of matrix cracks. The principle behind the UEWS test is to identify, from the pressure–strain response, a pressure level below which damage growth is either negligible or at least sufficiently low to avoid failure within the design life. The version of the UEWS test most often used involves the application of groups of 10 one‐minute pressure cycles at increasing pressure values, recording the hoop or axial strain. The onset of non‐linearity in the pressure–strain relationship can be accurately determined and enables a safe long term pressure level to be identified. The UEWS test appears to provide a desirable alternative to the currently used procedure laid down in ISO 14692, which involves an expensive series of long term constant pressure tests, as described in ASTM 2992, running for a period in excess of 10 000 h. It is shown here that the UEWS test reflects the cyclic fatigue behaviour of fibreglass pipe, but further work on the relationship between cyclic and static behaviour would be desirable. It has been shown that a Miner's law approach is effective in modelling damage due to combined static and cyclic effects, and that damage can be directly related to matrix crack growth. This approach could form the basis of a future procedure for describing lifetime behaviour of glass reinforced epoxy pipes under any required combination of static, fatigue, hydrostatic and non‐hydrostatic (multiaxial) loading.

The Effect of Matrix Microcracks on the Stress-Strain Relationship in Fiber Composite Tubes

A model for the stress-strain behavior of fiber composites with matrix cracks is presented and applied to the deformation of fiber reinforced composite pipes under different combinations of hoop and axial stress. The model provides a good description of the nonlinear stress-strain relationship that develops in composites when the matrix is damaged by the progressive nucleation of microcracks during loading. Ply properties are expressed as a function of crack density, calculated as a function of increasing stress using the shear-lag approximation. The predictions are in very good agreement with data from multiaxial tests on ±55° filament wound glass-reinforced epoxy pipes.