Glass Fiber Reinforced Polymer Plates Research Articles

Investigation on fatigue behavior of GFRP hybrid bonded/bolted joint under shear loading based on nondestructive monitoring test and numerical modeling

The GFRP (Glass Fiber Reinforced Polymer) is prospective in bridge and building engineering for its advantageous material property. The connection configuration of hybrid bonded/bolted joint of GFRP is thought superior in mechanical performance compared with the traditional bonded and bolted joints. However, the fatigue issue of this type of joint remains unclear which impedes its engineering applications. The presented work experimentally and numerically investigated the fatigue behavior of the GFRP hybrid bonded/bolted single-lap joints under shear loading. High-cycle fatigue tests on single-bolt, four-bolt, and nine-bolt specimens were conducted to study the failure process, rigidity degradation, failure mode, and fatigue life of the hybrid joints, where the nondestructive monitoring techniques of AE (Acoustic Emission) and 3D-DIC (Three-Dimensional Digital Image Correlation) were adopted, respectively to detect the material damages and overall deformation of specimens. Finite element modelling was further carried out to reveal the fatigue failure mechanism of hybrid joints, in which the property degradation of GFRP plates and adhesive layer were considered. Results showed that the failure process of GFRP hybrid single-lap joints under fatigue shear loading can be divided into four stages: (1) steady and (2) rapid development of adhesive damage, (3) steady and (4) rapid development of GFRP damage, of which the (2) and (4) stages account for less than 3% of the total fatigue life of joint, respectively. Stiffness degradation of 14–35% were read for the tested joints before final failure, and the joints with more bolts performed a superior degradation resistance compared to the less ones. Besides debonding and bolt inclination, the single-bolt joints failed with bearing failure of GFRP material, while the failure mode of multi-bolt joints were dominated by shear failure in GFRP plate with Y-shaped zone. The simulation results well supported the observations in experimental test. Based on the experimental results, the S-N curve of the GFRP hybrid single-lap joints is proposed, which can provide support for the engineering design of this type of joints.

Enhancing Damage Localization in GFRP Composite Plates: A Novel Approach Using Feedback Optimization and Multi-Label Classification

Damage localization in GFRP (glass-fiber-reinforced polymer) composite plates is a crucial research area in marine engineering. This study introduces a feedback-based damage index (DI) combined with multi-label classification to enhance the accuracy of damage localization and address scenarios involving multiple damages. The research begins with the creation of a modal database for yachts’ GFRP composite plates using finite element modeling (FEM). A method for deriving a feedback-weighted matrix, based on the accuracy of the DI, is then developed. Sensitivity analysis reveals that the feedback DI is 50% more sensitive than the traditional DI, reducing false positives and missed detections. The associated feedback-weighted matrix depends solely on the structural shape, ensuring its transferability. To address the challenge for localizing multiple damages, a multi-label classification approach is proposed. The synergy between the feedback optimization and multi-label classification enables the rapid and precise localization of multiple damages in GFRP composite plates. Modal testing on damaged GFRP plates confirms the enhanced accuracy for combining the feedback DI with multi-label classification for pinpointing damage locations. Compared with traditional methods, this feedback DI method improves sensitivity, while multi-label classification effectively handles multiple damage scenarios, enhancing the overall efficiency of the damage diagnosis. The effectiveness of the proposed methods is validated through experimentation, offering robust theoretical support for composite plate damage diagnostics.

Experimental and numerical investigation on failure behavior of hybrid bonded/bolted GFRP single-lap joints under static shear loading

The mechanical performance of the GFRP (Glass Fiber Reinforced Polymer) hybrid bonded/bolted single-lap joints under static shear loading is investigated. Static loading tests considering the hybrid joints with one bolt, four bolts, and nine bolts were first conducted to study the failure mechanism of hybrid joints, where failure process, rigidity, failure load, and failure modes were focused. Finite element (FE) analysis involving the material degradation and failure laws was also carried out for exploring the internal mechanism of joints’ failure. Based on the verified FE model, the effects of plate thickness and bolt edge distance on the failure capacity and strength of the hybrid joints were further investigated by performing a numerical parametric analysis. Results show that, the failure process of the hybrid joints can be divided into two stages which correspond to the failures of adhesive layer and GFRP plates, respectively. The joint rigidity of joints increases by 98.9 %∼133.1 % comparing the second loading stage to the first stage, and it is found that the rigidity in the first stage is hardly affected by the number of fasten bolts, while it decreases with more bolts in the second stage due to the severe incompleteness of GFRP plates. The failure patterns of the hybrid joints mainly include the slippage between connected plates, the compressive failure and shear failure of GFRP material, and the inclination of bolts. A proper arrangement of bolts can lead to shear failure of GFRP which makes full use of the material property. The final failure loads of four-bolt and nine-bolt joints are respectively 14.5 % and 22.9 % higher than the single-bolt specimen. As the plate thickness getting greater, the shear bearing capacity of hybrid joint increases almost linearly, while it would increase first and then descend with increasing bolt edge distance. In general, the achievement of this work can provide references for the design and further study of the GFRP hybrid joints.

Fracture research of adhesive-bonded joints for GFRP laminates under mixed-mode loading condition

Abstract The mixed-mode fracture characterization of adhesively bonded glass fiber-reinforced polymer (GFRP) plate joints is studied based on theoretical and experimental techniques. An improved beam model is used to estimate the compliance and the mixed-mode energy release rate (ERR) for GFRP four-point mixed-mode bending specimens. In this model, the deformation of the upper and lower GFRP plates is mutually independent, and the deformable adhesive is considered to satisfy the displacement compatibility conditions on the bonding interface. The explicit theoretical solutions of the compliance and ERR using the compliance method are reduced. The present theoretical solutions fit well with the finite element solutions by comparison with the rigid joint model. From the critical loads in experiment, the variation in fracture toughness on mixed-mode I/II has been determined by modifying the stiffness of the composite GFRP/GFRP substrate.

Energy absorption of polyurethane filled Al 6061 honey comb sandwiched structure

The energy absorption characteristics of composites are developed for applications likely to be subjected to sudden or prolonged impacts. In lightweight applications, the possibilities of Al 6061 composites are being explored with various known materials with similar properties. Three materials of low densities but high strength was combined: hexagonal honeycomb Al 6061 core was sandwiched with polyurethane foam and embedded within two glass fiber-reinforced polymer plates. L-9 orthogonal array Taguchi DOE was adopted for the design of the experiment varying the polyurethane mixture, core height, and face sheet thickness using the three-factor method. From the output of the Taguchi DOE, twenty-seven samples were fabricated. In order to determine the force-displacement relationship for each of the test samples, a three-point bending test was performed on a universal testing machine. Energy absorption (EA) and crushing force (CF) were determined from the force and displacement values. These values were then optimized to minimize the PCF while maximizing EA. Numerical analysis performed correlated with the results from experimental samples after testing. Since energy absorption is a measure of applied force and the resulting displacement on a material, the energy absorption characteristics were discussed.

MWCNT and nano-silica hybrids effect on mechanical and fracture characterization of single lap joints of GFRP plates

The current study aimed to explore the effects of nanoparticle hybridization on the shear and flexural performance of single lap joints (SLJs) of glass fiber reinforced polymer (GFRP) substrates. To this end, the hybridizations of multi-walled carbon nanotubes (MWCNT) and silica nanoparticles at various concentration rates were incorporated into the epoxy adhesive. Three-point bending tests and single-lap shear tests were performed to analyze in detail the effects of hybrid nanoparticle inclusions on adhesion performance under different loads. The maximum values for both shear and flexural strengths were achieved from the samples containing the combination of 0.5 wt.% MWCNT and 0.25 wt.% Nano-silica particles. The enhancements in shear strength and flexural strength were 45.4% and 63.2%, respectively, compared to pure samples. Furthermore, damage surfaces were examined via scanning electron microscopy (SEM) to investigate fracture mechanisms and failure modes. The findings demonstrated that almost all nanoparticle-doped samples, regardless of hybrid or single nanoparticle, exhibited higher load-bearing capability by increasing the adhesion ability of the additive and the adhesive. It was observed that the failure mechanisms such as crack deviation, crack pinning, pull out, bridging, etc. occurred in the nanoparticle doped adhesive joints as seen in SEM images.

Optimal slope angles of the air-coupled transducer from viewpoint of the effective Lamb waves propagation in different materials

Air-coupled transducers (ACT) allow for non-contact generation of acoustic waves which can be later transferred into elastic waves due to interactions with the solid specimen. Proper slope of the ACT in relation to the investigated specimen surface during acoustic waves generation is important as it leads to the possibility of generation of desired Lamb wave modes in the form of elastic waves with selected propagation velocity values. Effective generation of these modes ease the analysis of elastic waves propagation in specimens, simultaneously helping in detection of material defects if they exist. The attempt to determine optimal slope angles was undertaken in case of aluminum (Al), carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) plate-like structure. Due to relatively low excitation frequency of the used ACT (40 kHz) the investigation was focused on the slope angles referred to the generation of zero-order modes - antisymmetric A0 and symmetric S0. In CFRP plate case the issue of efficient generation of shear horizontal (SH0) wave mode was additionally considered. In Al and CFRP plate case optimal slope angles were considered numerically (Comsol, Matlab) and experimentally (lab investigations, Matlab) while in GFRP plate case they were estimated experimentally. Although not all of the slope angles were successfully determined within different approaches, the results helped to form some interesting conclusions. After determination of the slope angles the performance of sloped/non-sloped ACT was compared in full wavefield measurements (comparison of signal energy maps calculated with the usage of root mean square (RMS) formula). Recommendations for further work were depicted within the summary section.

Experimental and numerical investigation on dynamic behaviors of glass fiber reinforced polymer plates under explosion loadings

In this paper, field blast tests and numerical simulations were conducted to investigate the damage mechanism of glass fiber reinforced polymer plates under explosion loadings. Six specimens were fabricated and tested, and the effects of explosive mass and standoff distance on the failure mode of glass fiber reinforced polymer plates were studied. The experimental result showed that the damage mode of the glass fiber reinforced polymer plates under near-field explosion was mainly scabbing on the top surface, tensile crack on the back surface, accompanied by a small amount of spalling. Crater damage occurred on the top surface of plates, the bottom surface generates spalling damage, and a through hole was formed in the center of the plate under contact explosions. Furthermore, the finite element (FE) model of glass fiber reinforced polymer plates under contact explosion was established using the Arbitrary-Lagrangian-Eulerian (ALE) method. The effects of explosive mass on the damage mechanism of the glass fiber reinforced polymer plates were investigated. Thereafter, the dimensional analysis was used to analyze this physical model to obtain the functional relationship between explosion equivalent, plate thickness and fracture diameter. The present work can provide helpful references for the blast-resistant design of protective structures.

Structural performance evaluation of UHPC/conventional concrete cast on new Y-shape FRP stay-in-place formwork for concrete bridge decks

Overthe pastfewyears, there has been a rise in the use of Stay-In-Place (SIP) structural formworks made of fibre reinforced polymer (FRP). This study investigates the performance of decks made of FRP SIP structural formworks with an improved configuration using conventional and ultra-high performance concrete under static loadings. The proposed new composite deck consisted of a glass fibre reinforced polymer plate stiffened with Y-shape ribs for resisting tensile and shear stresses while reinforcements was placed on the compressive side of the deck. The new composite deck was compared with conventional reinforced concrete solid decks and a composite deck consisting of square hollow section (SHS) stiffeners. Results showed that the deck made of Y-shape stiffeners failed in punching shear, and the use of Y-shape stiffeners significantly enhanced the ultimate strength and shear capacity of the proposed deck. It was also concluded that the voids in the concrete deck with SHS stiffeners resulted in lightweight structures but had a negative influence on the ultimate strength of the deck cast on FRP SIP formwork. Increasing the concrete strength from 34 MPa to 140 MPa resulted in a 71% enhancement in the maximum load-carrying capacity but did not considerably influence their stiffness.

Structural performance of sandwich wall made of concrete cast in between GFRP facings

The structural performance of concrete walls reinforced with pultruded glass fibre-reinforced polymer (GFRP) ribbed plates on either side has been experimentally investigated. The GFRP plates were used as a stay-in-place (SIP) structural formwork replacing internal steel reinforcement. The pultruded flat plates incorporated 51 mm deep T-shape ribs on one side, spaced at 100 mm, which provided interlocking with concrete. Six 3000 × 616 mm panels, either 150 or 200 mm thick, were tested in bending ( M), under axial compression ( N) and under combined loads to establish the completed ( M- N) failure envelope of the wall. The effect of surface treatment of the GFRP forms was also investigated. It resulted in full composite action with no concrete slip, reaching 30% higher flexural strength than untreated panels. The effect of reinforcement ratio was studied by varying wall thickness. In all panel tests, diagonal concrete shear cracking occurred and propagated into a horizontal delamination above the GFRP ribs. Slenderness effect and secondary moments were accounted for in developing the ( M- N) interaction curve. Initially, M increased by 25% as N increased from zero to 17% of pure axial strength. Then, M reduced linearly to zero at pure N as concrete crushing occurred when the GFRP compression plate separated from the ribs and buckled outwards at midspan. A simplified design approach is also presented.

Influence of Loading Direction on Impact Strength and Small Span Length Variation on Flexural Strength in GFRP Laminate

Abstract This experimental work focuses on the two aspects of glass fiber–reinforced polymer (GFRP) laminate. The first is the effect of GFRP plate thickness and impact loading direction on impact strength, and the second is the effect of GFRP panel thickness and small span length variation on flexure strength. The GFRP laminate thicknesses considered for experimentation were 2, 3, and 4 mm. Both Izod and Charpy impact tests were conducted by considering edgewise (lateral impact) and flatwise (normal impact) impact loading directions. The quasistatic flexural tests were conducted using a three-point bend method for two small span length variations, viz., 50.8 and 56 mm. Impact strength of 2-mm-thick GFRP laminate under the edgewise loading condition showed 13 and 134.1 % more for Charpy and Izod, respectively, compared with 4-mm GFRP samples. In contrast, under the flatwise loading condition, 2-mm-thick specimens showed 14 and 54 % more impact strength when compared with 4-mm-thick GFRP specimens. GFRP samples with 2-mm thickness showed 59.85 and 59.6 % enhancement in flexural strength for span lengths of 56 and 50.8 mm, respectively, when compared with 4-mm-thick GFRP panels. Improvement in flexural strength between span lengths 50.8 and 56 mm for thicknesses 4 and 2 mm is 26 and 42 MPa, respectively, which is a 10 % improvement. Analysis of variance statistical analysis showed that the loading conditions and thickness of GFRP panels in the case of impact and small span length variation, and thicknesses in the case of flexural strength, is the significantly influencing parameters.

Glass fiber reinforced Polymer (GFRP) retrofitting of timber I-Joists with opening and notch

In this experimental study, Glass Fiber Reinforced Polymer (GFRP) plates were used to retrofit timber I-joists having a top flange-notch or a web-hole. Three types of GFRP reinforcing plates were used to retrofit and test 27 flange-notched and 27 web-holed I-joists for 3.65 m and 6.1 m span lengths. Another 200 I-joists were also tested to compare the performance improvement of the GFRP retrofitted I-joists. These I-joists had two different sizes of flange notch (100 mm × 100 mm and 100 mm × 150 mm) and two different diameters (150 mm and 200 mm) of web-hole located at different locations from the support. Although North American codes do not allow any form of a notch in the flange of I-joist, the current study shows that full capacity restoration can be achieved with proper retrofitting. From the four-point bending test of the I-joists, it is observed that GFRP plates can improve the structural capacity of retrofitted flange-notched or web-holed I-joists up to 605% and 106%, respectively, compared to the capacity of I-joists with a flange notch or a web hole, respectively. Two prediction models proposed here can predict the structural capacity of the retrofitted flange-notched and web-holed I-joists with different GFRP reinforcements with reasonable accuracy.

Graphene nanoparticle effect on flexural and shear behaviors of adhesively bonded single lap joints of GFRP composites

Adhesive bonded joints of fiber-reinforced polymer structural components provide countless benefits; these include great strength and large hardness-to-weight ratios, good fatigue and corrosion resistance, and high energy absorption capability, all of which make them more influential in comparison with other types of fasteners. In this study, the effect of various contents of graphene nanoparticle (GNP) in the epoxy adhesive on the shear and flexural behaviors of glass fiber-reinforced polymer plates (GFRP) bonded joints are investigated. Based on the weight content of epoxy graphene, nanoparticles were added by 0.1, 0.2, 0.3, 0.4, and 0.5 wt.%. GFRP were used as adherents. Failure mechanisms were analyzed by taking photos over the front and rear sides of the samples after tests. The obtained results showed that 0.3 wt.% graphene nanoparticle addition exhibiting the better load transferring between adherents had 145% improvements in shear strength. Furthermore, the samples containing 0.2 wt.% GNP resulted in an increase in flexural strength by 100%.

Experimental and analytical study on continuous GFRP-concrete decks with steel bars

A hybrid bridge deck is proposed, which includes steel bars, concrete and glass-fiber-reinforced-polymer (GFRP) plates with channel sections. The steel bar in the negative moment region can increase the flexural stiffness, improve the ductility, and reduce the GFRP ratio. Three continuous decks with different steel bar ratios and a simply supported deck were fabricated and tested to study the mechanical performance. The failure mode, deflection, strain distribution, cracks and support reaction were tested and discussed. The steel bar improves the mechanical performance of continuous decks, and a theoretical method is proposed to predict the deformation and the shear capacity. The experimental results show that all specimens failed with shear failure in the positive moment region. The increase of steel bar ratio in the negative moment region can achieve an enhancement in the flexural stiffness and reduce the deflection without increasing GFRP. Moreover, the continuous deck can achieve a yield load, and the negative moment can be carried by GFRP plates after the steel bar yields. Finally, a nonlinear analytical method for the deflection calculation was proposed and verified, with considering the moment redistribution, non-cracked sections and nonlinearity of material. In addition, a simplified calculation method was proposed to predict the shear capacity of GFRP-concrete decks.

Evaluation of the compression strength performance of fiber-reinforced polymer (FRP) and steel-reinforced laminated timber composed of small-diameter timber

Laminated timber composed of small-diameter timbers reinforced with a steel bar and fiber-reinforced polymer (FRP) were fabricated to satisfy the seismic design performance level of wooden columns, and their compression strength performance was evaluated. The experimental results showed that the average compression strength of the specimen reinforced with a CFRP (Carbon FRP) bar increased by approximately 7% compared to that of the control. The average compression strengths of the specimens reinforced with a GFRP (Glass FRP) bar and a steel bar increased by 38 and 37% compared to that of the control, respectively. The unreinforced control column specimens showed a diagonal failure tendency due to the fiber slope angle, and the wood part of the reinforced specimens showed a failure mode with suppressed diagonal fracture. The average strength of the column reinforced with a CFRP plate increased by approximately 6%, but the average strength of the column reinforced with a GFRP plate decreased by approximately 5%. A comparison of the measured and predicted compression strengths of the specimens showed that the strength differences of all the specimens except the specimen reinforced with a GFRP plate were good (2 to 10.4%).

Elevated thermal conditioning effect on flexural strength of GFRP laminates: An experimental and statistical approach

This study aims to investigate the flexural strength and damage formation in glass fibre reinforced polymer (GFRP) laminates for different thicknesses (2, 3 and 4 mm), small span length variations (50.8 and 56 mm), crosshead speeds (1 and 10 mm/min), thermal conditioning duration (3 and 6 h) and thermal conditioning temperatures (27 °C (room temperature), 50 °C, 100 °C and 150 °C). A closed muffle furnace used for thermal conditioning of GFRP specimens. A quasi-static transverse load applied using four-point bend method. GFRP plates are translucent; hence high-intensity background light is used to observe the formed damage and its extent after four-point bend test. The most effectively influencing parameters among GFRP laminate thickness, span length, thermal conditioning temperature, thermal conditioning time and crosshead speeds on the flexure strength of GFRP plates analysed by adopting the two-parameter Weibull distribution statistical method. Flexural strength of the GFRP laminates severely degraded when the exposed elevated temperature approached the glass transition temperature (Tg) 100 °C. Exposure duration affected the flexural strength. GFRP composites exposed for 6 h showed comparatively better flexural strength regain than those GFRP specimens exposed for 3 h. GFRP laminate thickness showed a more significant influence on the flexural strength compared to small span length variation. GFRP laminate with 2 mm thickness showed highest flexural strength compared to 3 mm and 4 mm thick GFRP specimens while the span length 50.8 mm showed higher flexural strength compared to GFRP laminates with 56 mm span length. Crosshead speed also affected the flexural strength and GFRP specimens tested at 10 mm/min showed higher flexural strength compared to specimens tested at 1 mm/min. For specimens tested at room temperature the cumulative failure probability curves agglomerated at a single region in the graph. However, as the temperature and laminate thickness increased these curves dispersed over the entire graph. Experimental flexural strength showed good agreement with the theoretical flexural strength calculated from gamma function.

Damage process in glass fiber reinforced polymer specimens using acoustic emission technique with low frequency acquisition

The damage process in fiber-reinforced polymers (FRP) has been the subject of continuous studies in recent decades using different approaches. In particular, the acoustic emission technique has been proved to be a powerful tool in the monitoring of structures of this type of material due to the large acoustic activity captured when this material is loaded to rupture. The present work explores several indexes that were calculated from the experimental recording of acoustic emission signals, and their efficiency in describing the failure process in structures. One of these indexes, called c value, is originally proposed, and its sensibility it is compared with other classical parameters that are usually employed in the Acoustic Emission analysis. A 3-point bending test has been performed on a glass fiber reinforced polymer plate. Our own methodology was proposed to identify AE signals in semi-automatic manner. This methodology also allowed a faster analysis of the global parameters during the process data of the AE test. The global parameter evolution obtained from the acoustic emission data during the damage process could be considered as precursors of the more meaningful event and as an aid to understand in which way the structure is going to the collapse.

Wavelet-aided guided wavefield imaging of delaminations in laminated composite plates

Delamination is a commonly encountered type of damage in composite structures, which may lead to degraded performance and even failure of structures. Thus, detection of delaminations is considered a vital task to maintain structural integrity and reliability. This paper presents a delamination imaging method based on the analysis of guided wavefields. The method relies on the fact that delaminations in a structure will cause wavefield anomalies, which in turn can be utilized for the indication of delamination zones. Such anomalies, however, could be easily masked by the major components of the wavefield signals including incident waves from actuators and reflected waves from structural boundaries. To address the problem, one-dimensional wavelet transform (WT) is used to process the wavefields leading to WT wavefields. The WT wavefields can highlight signal anomalies associated with delaminations. A WT wavefield imaging algorithm is first constructed step by step in detecting multiple delaminations in a glass fiber reinforced polymer (GFRP) plate. The algorithm is then successfully used in the imaging of a single delamination zone in a carbon fiber reinforced polymer (CFRP) plate. The locations, sizes, and shapes of the delamination zones in the GFRP and CFRP plates are clearly visualized in the ultimate damage maps.

A Variable Data Fusion Approach for Electromechanical Impedance-Based Damage Detection.

There is continuing research in the area of structural health monitoring (SHM) as it may allow a reduction in maintenance costs as well as lifetime extension. The search for a low-cost health monitoring system that is able to detect small levels of damage is still on-going. The present study is one more step in this direction. This paper describes a data fusion technique by combining the information for robust damage detection using the electromechanical impedance (EMI) method. The EMI method is commonly used for damage detection due to its sensitivity to low levels of damage. In this paper, the information of resistance (R) and conductance (G) is studied in a selected frequency band and a novel data fusion approach is proposed. A novel fused parameter (F) is developed by combining the information from G and R. The difference in the new metric under different damage conditions is then quantified using established indices such as the root mean square deviation (RMSD) index, mean absolute percentage deviation (MAPD), and root mean square deviation using k-th state as the reference (RMSDk). The paper presents an application of the new metric for detection of damage in three structures, namely, a thin aluminum (Al) plate with increasing damage severity (simulated with a drilled hole of increasing size), a glass fiber reinforced polymer (GFRP) composite beam with increasing delamination and another GFRP plate with impact-induced damage scenarios. Based on the experimental results, it is apparent that the variable F increases the robustness of the damage detection as compared to the quantities R and G.

Experimental study on the interfacial bond behavior of FRP plate-high-strength concrete under seawater immersion

The excellent bonding performance of the glass fiber-reinforced polymer (GFRP) profile-high-strength concrete interface is the key to ensuring the safety, reliability and durability of a composite structure. Therefore, it is necessary to study the durability of the composite interface. In this paper, a total of 48 GFRP plate-high-strength concrete double-lap joints were tested to investigate the effect of the epoxy resin type, interfacial type and artificial seawater immersion time on the bonded interfaces. The main properties of the bonded joints were examined, including the failure mode, ultimate load, load-slip curve, typical strain and shear stress distributions along GFRP plates. The results showed that the ultimate loads of each type of interface gradually decreased with increasing immersion time. After 360 days of artificial seawater immersion at a constant temperature, the ultimate load of the wet bond (WB) interface had the largest reduction, and the ultimate load of the dry bond (DB) interface showed a minimal decrease. The ultimate load of the shear key combined with wet bond (SK-WB) interface was significantly greater than that of the other three interfaces under different immersion ages. In general, the durability of the interface with the CFSR type (B-type) epoxy resin was superior to that of the Sanyu L-500 type (A-type) epoxy resin. The strain and interfacial shear stress distributions along GFRP plates of the DB interface specimens were different from that of the SK-WB interface specimens under different immersion ages.