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The small city of Bocholt owns a former industrial area of 25 ha which will be restructured to an urban and cultural district for people to work, live and explore. As part of the new urban development four footbridges with a span of up to 47 m have been designed to connect the two parts of this area which are separated by the river Aa. The bridges form the starting point for the future development and spaces for public events. The connecting bridges are not only an architectural statement, but also show the transition from the former industrial origin to the new cultural urban district. The design of the bridges was chosen because it combines the future and the past. Three of the four bridges are newly designed whereas one former railroad bridge will be refurbished for the use as a pedestrian bridge. This paper will focus on the client's requirements to build architectural icons which will drive the development of the new quarter but to also design structures with low maintenance effort and long durability. Especially smaller cities often lack a dedicated bridge department; they require therefore good guidance by the engineer and would typically prefer low-maintenance materials. This has been achieved by utilizing weathering steel as well as GFRP decks. Even though the initial costs as well as the public approval process for this innovative construction are higher compared to conventional materials, it will be cost-beneficial for the client through reduced maintenance costs in the long run.

Application of GFRP composites in civil engineering is still not large but already noticeable. Advantages ofthis material, such as: low volume weight, relatively high stiffness and strength, well fatigue resistance, easiness inshaping, high material damping and high environmental resistance, make it attractive for bridge and in particular footbridgedesigners. It is estimated that nowadays in the world there are realized hundreds of bridges, the construction ofwhich, whole or in part is made of GFRP. Most of them are small span structures. However, it is possible to find someinteresting designs. The paper presents an overview of the most spectacular examples of footbridge structures, in whichthe GFRP materials plays a key role. The few examples are: Aberfeldy Footbridge in Scotland, the world's largeststructure of this kind; Lleida Pedestrian Bridge, the longest arch bridge made out standard GFRP pultruded profiles orEXPO Footbridge in Lisbon, truss bridge of 30 m span length. The last example is the footbridge designed and constructedby polish consortium Fobridge. The footbridge, which arose as a result of scientific project was studied in agreat details taking into account, among others: material testing, validation studies and load tests. DOI: https://doi.org/10.3846/enviro.2017.143

Under the premise of maximum connection intensity, the composites plate and metal plate connected through three ways using adhesive bonding, bolt connection and mixed connection, comparing and analysing the joint strength of these two, the result of the research showed that mixed connection's strength is the largest, the second one is adhesive bonding. The composite-metal's connection strength is significantly higher than the composite-composite's under the different connection ways, but its ductility is slightly worse than that of the latter.

In this study, the strength of magnesium-GFRP/epoxy single-lap bonded joints are experimentally evaluated with different end shapes. In order to achieve this, four different single-lap joints with different end shapes are fabricated and the failure load is measured under tensile loading tests. From the test results, the single-lap joint with a square end exhibits the lowest failure load while the single-lap joint with reverse tapering and a spew fillet has the highest stress values. It has 11.1% higher failure strength than the single-lap joint with a square end.

In this work, a finite element model is developed to predict the progressive fatigue damage and the life of the composite laminate with different layup Sequence on the composite laminates subjected to various loadings and gets the best ply design for the materials considered in this investigation. Finite element models are created with ABAQUS software. These models are used to simulate for glass epoxy materials with different ply angles, as well as different loads. Graphs are plotted to compare the failure index of glass epoxy materials, the best ply design for the composites are investigated in this project.

The aim of the present paper is to evaluate the residual strength of GFRP laminates following a low-velocity impact event under cyclic loading. The residual strength is calculated using a linear fatigue damage model. According to an investigation into the effect of low-velocity impact on the fatigue behavior of laminates, it seems laminate fatigue life decreases after impact. By normalizing the fatigue stress against undamaged static strength, the Fatigue Damage parameter “FD” is presented with a linear relationship as its slope which is a linear function of the initial impact energy; meanwhile, the constants were attained from experimental data. FD is implemented into a plane-stress continuum damage mechanics based model for GFRP composite laminates, in order to predict damage threshold in composite structures. An S–N curve is implemented to indicate the fatigue behavior for 2 mm thickness encompassing both undamaged and impacted samples. A decline in lifespan is evident when the impact energy level increases. Finally, the FD is intended to capture the unique GFRP composite characteristics.

Machining of composite materials for the production of bolt holes is essential in the assembly of the structural frames in many industrial applications of glass fiber-reinforced plastic (GFRP). Abrasive water jet cutting technology has been used in industry for such purposes. This technology has procured many overlapping applications and as the life of the joint in the assembled structure can be critically affected by the quality of the holes, so it is important for the industry to understand the application of the abrasive water jet cutting process on GFRP composite materials. The aim of the present work is to assess the influence of abrasive water jet machining parameters on the hole making process of woven-laminated GFRP material and to find the optimum values of the process parameters. Statistical approach was used to understand the effects of the predicted variables on the response variables. Analysis of variance was performed to isolate the effects of the parameters affecting the hole making in abra...

Glass Fiber Reinforced Plastic (GFRP) structures are primarily manufactured using hand lay-up or vacuum infusion techniques, which are cost-effective for the construction of marine vessels. This paper aims to investigate the mechanical properties and failure mechanisms of the hybrid GFRP composites, formed by applying the hand lay-up processed exterior and the vacuum infusion processed interior layups, providing benefits for structural performance and ease of manufacturing. The hybrid GFRP composites contain one, two, and three vacuum infusion processed layer sets with consistent sets of hand lay-up processed layers. Mechanical properties assessed in this study include tensile, compressive and in-plane shear properties. Hybrid composites with three sets of vacuum infusion layers showed the highest tensile mechanical properties while those with two sets had the highest mechanical properties in compression. The batch homogeneity, for the GFRP fabrication processes, is evaluated using the experimentally obtained mechanical properties.

This investigation is about the study of efficiency of GFRP (Glass Fibre Reinforced Polymer) composites in strengthening and retrofitting of seismically deficient reinforced concrete frames. Twelve numbers of single bay two storey two dimensional RC frames were cast and Six frames were tested for effectiveness of externally bonded GFRP composites to strengthen the RC frame, Six frames were loaded up to yield load and these yielded frames were wrapped with GFRP and tested for the effectiveness of retrofitting the yielded frames. A preliminary study on RC elements strengthened and retrofitted with GFRP composites were carried out as: Group (I): Six numbers of normal beam elements, Group (II): Twelve beams each addressing influence of strengthening, retrofitting the flexure zone and to compare their flexural capacity. Group (III) six beams each addressing the influence of strengthening, retrofitting the shear zones and to compare shear capacity. Group (IV) three columns each tested under axial load with and without wrapping and for retrofitting. The results indicate that there is an increase in the load carrying capacity of RC frame strengthened with GFRP composites wrapping to the extent of 16.07% and the retrofitted yielded RC frame regain its structural capacity to the extent of 10.02%.

Plain GFRP, copper wire embedded GFRP and SMA short fibres included copper wires embedded GFRP laminates have been prepared by hand lay-up method. The mechanical properties like flexural and tensile strength were investigated. To study the impact properties of the laminates an experimental set up was designed and the impact strength of the laminates was studied by drop weight method. Three point bend method was adopted for flexural studies and the tensile strength was found by Instron Machine. It is found that the inclusion of SMA short fibres significantly improved the mechanical properties of the composites.

In recent years, Glass Fiber-reinforced plastic (GFRP) composite materials have been increasingly replacing conventional metallic materials in structural applications, due their excellent specific strength and stiffness properties. However, GFRP laminate having weak interfaces in normal to loading direction and they are very susceptible to impact loading. The damage of composite structures to impact events is one of the most important aspects of study to uncover the significance and the more dominant damage characteristics in terms of impactor mass, impact velocity, impact energy and different stacking orientations. This paper presents the effect of stacking sequence on low velocity impact behavior of GFRP composite laminate.

The glass fiber reinforced plastics (GFRP) composite material is a low carbon emission, low life cycle cost, and sustainable material. In this paper, the structural behavior of the lateral force resistant performance of GFRP composite material frames with steel joints was presented, and the energy dissipation and failure modes of the GFRP frames were discussed. A total of six GFRP frames, including single-span and double-span frames with and without diagonal bracing members, were tested by pushover tests to obtain the lateral load-displacement relationships of the GFRP frames. The force-displacement relationship and the energy dissipation of the GFRP frames were examined in the pushover test. In addition, the numerical analysis was performed to obtain the lateral load-displacement relationships of the GFRP frames under pushover tests. When the numerical analysis results and the experimental results were compared, the absolute average errors of the maximum loads were less than 4%, and the lateral load-displacement relationships were close to each other. The numerical analysis results can predict the experimental force-displacement relationships of the GFRP frames.

In the present work, an attempt has been made to investigate the strength of bolted fasteners and hybrid fasteners under tensile loading for unfilled, TiO 2 and ZnS filled Glass Fabric Reinforced Polymer Matrix Composites (GFRP). Bolt configurations were chosen as 2, 3 and 4, in order to analyze the effect of number of bolts on the strength aspect. For filled GFRP composites, the volume fractions in the matrix were chosen as 1%, 2% and 3%. The result obtained shows that, the static tensile strength of the GFRP composites increases with increase in number of bolts. Specimens with 4 bolt configurations have shown significantly more absorption of load before failure of the joint. Hybrid fasteners are more sustainable to failure than bolted fasteners. Also it is noticed that, the strength of the composites increases with raise in TiO 2 and ZnS fillers content up to 2 vol.%. In comparison with TiO 2 and ZnS filled composites, it was found that ZnS filled composites bears more load.

In the present work an attempt has been made in order to investigate the bending strength and flextural strength of the TiO2 and ZnS filled Glass Fabric Reinforced Polymer (GFRP) composites. The volume fractions in the matrix were chosen as 1, 2 and 3%. The effect of notch orientation on interlaminar and translaminar bending characteristics has been evaluated and Bending strength has been evaluated for specimens with edge cracks with varied crack lengths. The results have showed that, the addition of filler up to 2 vol% has increased the strength of the composite and ZnS as filler is preferred over TiO2.

Defects that occur during the manufacturing process or operation of a wind turbine blade have a great influence on its life and safety. Typically, defects such as delamination, pore, wrinkle and matrix crack are found in a blade. In this study, the detectability of the pores, a type of defect that frequently occur during manufacturing, was examined from the full field strain distribution determined with the image correlation technique. Pore defects were artificially introduced in four-ply laminated GFRP composites with fiber direction. The artificial pores were introduced in consideration of their size and location. Three different-sized pores with diameter of 1, 2 and 3 mm were located on the top and bottom surface and embedded. By applying static loads of 0-200 MPa, the strain distributions over the specimen with the pore defects were determined using image correlation technique. It was found the pores with diameter exceeding 2 mm can be detected in diameter.

To replace a traditional steel bogie with a composite one, this study designed and manufactured a composite bogie frame made of glass fiber-reinforced plastics to be applied to the bogie of an urban subway train. To evaluate its structural behavior, the composite bogie frame was tested under critical load conditions encompassing vertical loads and a twisting load. The test revealed that the maximum strain measured under the vertical load corresponded to 16.3% of the failure strain of the GEP224 glass fabric/epoxy sample. According to a durability evaluation using Goodman diagrams, both the measured and the calculated stress data were within the endurance limit. Therefore, the composite bogie frame satisfied the structural safety requirements. The evaluation of the contribution of each load case clearly showed that the vertical and braking loads were the most critical load cases. Adding the braking load cases led to movement of the critical point from the inner joint to the outer joint due to the increased torsion.

The behaviour of Glass Fibre Reinforced Composites (GFRPs) under single and multi-impact events of the same total energy was analysed. Experimental tests were performed considering circular simple supported plates impacted on its centre. The analyses of the results issuing from load–time, load–displacement and energy–time curves have shown that the sole impact of 3 J is more detrimental for the plate, relative to the other cases of cumulative damage (1 J + 2 J and 1 J + 1 J + 1 J). A fine-tune analysis of damage evolution between subsequent impacts using a numerical procedure including a cohesive mixed-mode damage model was also performed. This analysis permits to verify the evolution of the projected delaminated area as well as the fracture process zone in the vicinity of delaminations. It was verified that a negligible evolution of damage occurs in the case of three consecutive impacts of the same energy. Additionally, it was concluded that the cumulative damage in the case of (1 J + 2 J) is inferior to the one propitiated by the sole impact of maximum energy (3 J).

The fatigue strength and life of a GFRP composite bogie frame for urban subway trains were evaluated in this study. The GEP224 glass fabric/epoxy was selected as the structural material of a composite bogie frame to save its weight. In order to obtain the fatigue characteristics of the GEP224 glass/epoxy composite material, the tension–compression fatigue test was done with three different stacking sequences of warp direction, fill direction, and warp/fill direction, respectively. A fatigue test was conducted with a stress ratio, R of 0.1 and −1, and up to endurance limit of 107 with frequency of 5 Hz. The fatigue strength of the GFRP composite bogie frame was evaluated on the basis of the S-N curve and Goodman diagrams obtained from GEP224 glass/epoxy composites according to the JIS E 4207 and UIC 515/615-4. The result shows that fatigue strength of the GFRP composite bogie has satisfied the design requirements. Also, the GFRP composite bogie frame had a good fatigue performance in comparison with conven...

Fiber reinforced plastics (FRPs) have replaced conventional engineering materials in many areas, especially in the field of automobiles and household applications. With the increasing demand, various modifications are being incorporated in the conventional FRPs for specific applications in order to reduce costs and achieve the quality standards. The present research endeavor is an attempt to study the effect of natural fillers on the mechanical characteristics of FRPs. Rice husk, wheat husk, and coconut coir have been used as natural fillers in glass fiber reinforced plastics (GFRPs). In order to study the effect of matrix on the properties of GFRPs, polyester and epoxy resins have been used. It has been found that natural fillers provide better results in polyester-based composites. Amongst the natural fillers, in general, the composites with coconut coir have better mechanical properties as compared to the other fillers in glass/epoxy composites.

Machining of composite materials for the production of bolt holes is essential in the assembly of the structural frames of many industrial applications of GFRP. Abrasive water jet cutting technology has been used in industry for such purposes. This technology has procured many overlapping applications and as the life of the joint in the assemble structure can be critically affected by the quality of the holes, it is thus important for the industry to understand the application of abrasive water jet cutting process on GFRP composite materials. The aim of the present work is to to assess the influence of abrasive water jet machining parameters on hole making process of woven laminated GFRP material. Statistical approach was used to understand the effects of the predicted variables on the response variables. Analysis of variance (ANOVA) was performed to isolate the effects of the parameters affecting the hole making in abrasive water jet. The result shows that cutting feed, water jet pressure, standoff distance and abrasive flow rate are influential parameters upon the response variables of the abrasive water jet cutting process of GFRP composite, type 3240.

A multi-scale numerical fatigue modelling methodology is proposed for the characterization of axial tension–tension fatigue behaviour of unidirectional Glass Fibre Reinforced Polymer (GFRP) composites. The methodology is developed to link the dominant fibre failure mechanism to composite fatigue properties, by a three-step geometrical up-scaling process. This study aims to provide composite fatigue predictions by only using the material properties of fibres and matrix. Compared to the experimental results, the fatigue model over-predicts fatigue lives and gives reasonable estimations of axial stiffness degradation curves of the unidirectional GFRP composite dog-bone specimens.

In this chapter we propose a new methodology for CFRP and GFRP composite testing. One of the most important factors describing such materials is the shear modulus. The test we have carried out included a shear test with digital image correlation and acoustic emission. We proposed to use the acoustic emission method to determine degradation of fiber-reinforced composites.

Composites in Compression Molding J.W. Kim, H.S. Kim and D.G. Leec,∗ NGV R&D Center, Gwangju Technopark, Chum-Dan Gwagiro 333, Buk-gu Gwangju 500-706, South Korea Department of Advanced Parts and Materials Engineering, Chosun University Graduate School 375 Seosuk-dong, Dong-gu, Gwangju 501-750, South Korea Department of Mechatronics Engineering, Chosun University, 375 Seosuk-dong, Dong-gu Gwangju 501-750, South Korea

Beams located at the perimeter of buildings, which carry loads from slabs, joists and beams from one side of the member generates torsional forces that are transferred from the beams to the columns. The beams deficient in resisting torsion can be strengthened using Fiber-Reinforced Polymer (FRP) composites. An experimental study for the improvement of the torsional resistance of reinforced concrete beams using FRP is presented in this paper. Total 14 beams of 150mm × 150mm × 1700mm are cast. Two beams are designated as control specimens and eight beams are strengthened by Glass Fiber Reinforced Polymer (GFRP) wrapping of different configuration. All beams are subjected to combined effect of torsion and bending. A loading frame and test set up are fabricated for applying combined torsion and bending. Angle of twist at interval of torque, torque at first crack, ultimate torque are compared for control and strengthened beams.

Nonlaminated composites having superior mechanical properties than laminated composites is widely used in ballistic applications. Since literature on the machinability of nonlaminated composites is scarce, an investigation was carried out to study the hole quality in drilling thick nonlaminated Glass Fiber Reinforced Plastic (GFRP) composite rods using coated tungsten carbide twist drill. The GFRP composite rods were made by pultrusion method with high fiber weight fraction. The surface roughness of the drilled holes was measured using surface roughness tester. Taguchi’s orthogonal array and analysis of variance (ANOVA) were employed to study the influence of process parameters such as feed and spindle speed on surface roughness. The optimum level of process parameters towards minimum surface roughness of the drilled hole walls was obtained to achieve defect controlled drilling of pultruded GFRP composite rods. Correlation for surface roughness with process parameters was established using a statistical software MINITAB 16. The influence of feed and speed on surface roughness was insignificant. The optimal process parameter levels within the range examined was identified as 0.15 mm/rev feed and 750 rpm speed for drilling pultruded GFRP composite rods using 10 mm diameter twist drill. The influence of process parameters on hole quality in nonlaminated composite rods differs with drill geometry and also differs from the influence of process parameters on hole quality in laminated composites.

Objectives: Evaluation of three important delamination factor models and compare their values with varying spindle speeds and feed rates in drilling GFRP composites. Methods: Digital image analysis is adopted for measurement of the dimensions of delamination damage. Accurate assessment of delamination damage is essential for the analysis and design of optimum drilling parameters. Experiments were conducted on GFRP composite materials with feed rates ranging from 100-400 mm/min and spindle speeds ranging from 1000-2500 rpm. Findings: These experiments reveal that delamination reduces with increase in the spindle speed and reduction in the feed rate, but higher spindle speeds may increase the delamination damage. Results also reveal the consideration of area of delamination damage in the assessment of delamination is more important than the maximum damage diameter. Applications: The good mechanical properties of GFRP composites allow their use in compartment panels and doors. Digital image analysis improves the accuracy in measurement of delamination damage.

Conventional procedures and methods used for evaluating the fatigue performance of materials require time consuming tests with high number of specimens. In the last years different methods have been developed with the aim to reduce the testing time and then the cost of the experimental campaign. In this regard, thermographic methods represent a useful tool for rapid evaluating the fatigue damage and the fatigue limit.

This paper addresses the sensitivity of the elementary wear mechanisms of UD-GFRP composite to the tribological parameters. A scanning electron microscope (SEM) was used to assess the wear mechanisms on the scratched UD-GFRP composite for different test conditions. A 3D FE micromechanical models was developed using ABAQUS/Explicit to simulate single indenter scratch test (SST). Both material behavior and damage of fibers and matrix are described using Johnson Cook behavior law. However, the fiber/matrix interface was modeled using the cohesive zone approach by the mean of the cohesive elements. The numerical results show a good agreement with the experimental wear mechanisms.

Steel and concrete bridge structures that serve as the backbone of U.S. transportation and navigational infrastructure systems have been exhibiting moderate to severe deterioration within a few years of service. The focus of this paper is on the rehabilitation of water-submerged bridge steel piles using precured glass-fiber-reinforced polymer (GFRP) shells wrapped with water-curable GFRP prepreg fabrics. The GFRP shells were placed around the corroded steel piles of the East Lynn Lake Campground Bridge in Wayne County, West Virginia, and wrapped with GFRP fabrics. The space between GFRP shells and steel piles was filled with self-consolidating concrete to strengthen and protect the piles from further deterioration. Prior to field implementation, experiments were conducted on concrete cylinders embedded with steel I-sections that were encased by a polymeric shell and FRP wrap system to evaluate the load transfer mechanisms and increase in concrete strength as a result of confinement. To increase th...

Pomimo wielu przewag w stosunku do konwencjonalnych materiałów budowlanych, współczesny rozwój zastosowań kompozytów FRP w budownictwie mostowym jest ograniczony ze względu na wysoki koszt początkowy oraz zbyt małą sztywność elementów konstrukcyjnych. W celu redukcji tych ograniczeń od blisko 20 lat w wielu krajach testuje się rozwiązania mieszane (hybrydowe), łączące kompozyty FRP z konwencjonalnymi materiałami budowlanymi, w tym głównie z betonem. Kształtowanie konstrukcji hybrydowej, bazujące na właściwościach poszczególnych materiałów składowych, ma na celu zwiększenie sztywności i redukcję kosztów, bez utraty nośności, lekkości i łatwości budowy mostów z takich dźwigarów. W artykule przedstawiono ewolucję w kształtowaniu hybrydowych dźwigarów mostowych typu „kompozyty FRP – beton” na przestrzeni ponad 20 lat. Podano także podstawowe zasady kształtowania dźwigarów hybrydowych, wynikające z przeprowadzonej analizy, a także wskazano kierunki dalszych badań, niezbędnych w celu upowszechnienia tych innowacyjnych konstrukcji mostowych.

This article describes an experimental investigation on end milling of glass fiber reinforced polymer (GFRP) composites using uncoated tungsten carbide tool. A series of experiments were carried out to evaluate the machinability of GFRP composites in terms of tool wear, tool useful life, machining quality, and machining forces. Machinability data were evaluated in the form of Taylor's equation in order to predict the tool performance while machining this composite material. The useful life of the cutting tool was found to be well described by the Taylor's equations. The cutting speed was identified as the key parameter in influencing the tool life followed by feed rate and fiber orientation. Machining force variations were constantly monitored during end milling tests, which are mainly attributed to the growth of tool wear and fiber orientation.

KARA, Fuat/0000-0002-3811-3081; ERKAN, Omer/0000-0002-9428-4299 WOS: 000322706000012 Glass fibre reinforced plastic (GFRP) composites are an economic alternative to engineering materials because of their superior properties. Some damages on the surface occur due to their complex cutting mechanics in cutting process. Minimisation of the damages is fairly important in terms of product quality. In this study, a GFRP composite material was milled to experimentally minimise the damages on the machined surfaces, using two, three and four flute end mills at different combinations of cutting parameters. Experimental results showed that the damage factor increased with increasing cutting speed and feed rate, on the other hand, it was found that the damage factor decreased with increasing depth of cut and number of the flutes. In addition, analysis of variance (ANOVA) results clearly revealed that the feed rate was the most influential parameter affecting the damage factor in end milling of GFRP composites. Also, in present study, Artificial Neural Network (ANN) models with five learning algorithms were used in predicting the damage factor to reduce number of expensive and time-consuming experiments. The highest performance was obtained by 4-10-1 network structure with LM learning algorithm. ANN was notably successful in predicting the damage factor due to higher R-2 and lower RMSE and MEP.

In the present work an attempt has been made to investigate the bearing strength of the TiO2 and ZnS filled glass fabric reinforced polymer matrix composites (GFRP). The volume fractions in the matrix were chosen as 1, 2 and 3%. Single-hole-pin-loaded specimens of each composite material were tested in tension. The result showed that the bearing strength of the glass fabric reinforced polymer matrix composites joints is associated with the filler content and the geometrical parameters. The increase of the filler content in the matrix has increased the bearing strength of the composites. The height bearing strength was obtained in case of composites with 2 volume% of filler content, and it was found that ZnS filled composites bears more load than the TiO2 filled composites.

Fatigue life of GFRP (glass-fiber reinforced plastic) composites used in wind turbine rotor blades has been evaluated considering the glass fiber orientations. Three different laminate composites with the respective laminating orientation of 0°, ±45°, and 0°±45° were prepared using vacuum infusion method. Tensile properties and S-N curves for these composites were experimentally determined at room temperature. From the tensile tests, it was found that tensile properties were greatly dependent upon the fiber orientation and the tensile strength of unidirectional composite was the largest and bidirectional (45°) composite was the weakest among three composites. The fatigue properties were determined under constant amplitude load control at different stress ratios, R, of 0.5, 0.1 and −0.2. The properties also show the dependency of stress ratios and fiber orientation. The fatigue life diagrams of these three composite were relatively well presented with the double logarithmic S-N curve. The linear slopes of the respective S-N curves for three composite were not greatly different. The fatigue limits for the composites were evaluated and predicted with linear Goodman and Gerber diagrams.

The impact behavior of glass fibers reinforced polyester (GFRP) was experimentally investigated using notched Izod impact test specimen. The experimental program was carried out on unidirectional laminate of GFRP in directions 0°, 45° and 90° in addition to cross-ply laminate ( 0 / 90 / 0 ¯ ) s . The effect of fiber volume fraction, V f % (16%, 23.2% and 34.9%) was considered. The impact specimens were tested after exposure to temperatures of −10 °C, 20 °C, 50 °C and 80 °C for exposure time of 1 h and 3 h. Test results showed that the effect of exposure temperature and fiber volume fraction on impact strength of GFRP composite depends on the parameter controlling the mode of failure, i.e. matrix or fiber. The failure characteristic changed from fiber pull-out to fiber breakage with increasing the exposure temperature.

An impact fatigue study has been conducted for GFRP composite laminates to investigate failure mechanisms. A nylon bead with diameter of 4 mm was used as an impactor to simulate raindrop impact. Various specimen thicknesses of 3.0, 4.0 and 5.0 mm were used during experiment. Incident impact velocity of nylon bead ranged between 100 to 220 m/s. Optical microscopic observations were conducted to evaluate the damage at specimen center part of front and back surfaces. SEM investigations were made on the cross-section of damaged specimen. In conclusion, there are three damage modes were found to appear: debonding, matrix cracking, and delamination. Debonding occurred inside specimen at an early stage. Matrix cracking at front speciemens surface was ring crack, and that at back specimen surface was star crack. Delamination was resulted by repeated impacts. Initiation life for each damage mode depends on incident impact energy expressed as an (E–N) diagram of impact fatigue.

Nowadays composite materials are used in many industrial areas. The main application of these is the aircraft industry. Problematic points with machining of composite materials are tool wear, tool life and temperature during machining of polymer composite materials. In the first part of this investigation, the tool wear of sintered carbide (SC) with AlTiN coat milling tools in various cutting conditions has been studied. The second part deals with the problem of cutting temperature during machining of GFRP composite materials in different cutting conditions. In the end, the results illustrated in graphs and figures were evaluated.

In order to select the optimal dimension GFRP cloth for composite wood of timberwork, the mechanics of experimental samples made by China southern plantation were analyzed. The results showed that: GFRP reinforced the wood mechanical properties and the strength was affected by GFRP reinforcement ratio. However, it reduced the strength of internal bonding strength in a low range. As a result, the best dimension GFRP cloth was 145g/m2 grid cloth with grid size 5mm×5mm. moreover. The eucalyptus was fit to make for timberwork.

In this article, influence of drill geometry on thrust force in drilling GFRP composites is analyzed. Glass fiber-reinforced composite materials are finding increased application in different fields such as automobile, ship building, sport goods, etc., due to their excellent properties. Drilling is indispensable process and it cannot be avoided for joining composite structures. In this study, drilling experiments are conducted on these composite materials using CNC drilling machine. Three different drill bits are used for the experimentation. The response analyzed is thrust force. The influence of drill geometry on thrust force in drilling of composite materials is carried out using three different drill bits, namely, ‘Brad and Spur’ drill, ‘multifaceted’ drill, and ‘step’ drill. The analyses of the results are carried out using effect graphs and three-dimensional graphs. The results indicated that the step drills are performing better than the other drills considered.

The effect of multiple/repeated impacts on a repaired composite was investigated using a low-velocity impact test. The composite samples were fabricated through a vacuum resin infusion method (VARI) and repaired by a scarf repair technique. Later, a repeated low-velocity impact test was performed on the original and repaired composites samples. Performance of the multi-impacted repaired and original samples was evaluated and compared by measuring maximum contact force, maximum displacement, maximum time duration, absorbed energy and damage area. Photographs of the post-impacted samples were taken to observe the multi-impact damage progression through visual inspection. The results showed that each repeated impact subjected the samples to more damage. Tensile tests revealed that the scarf repair restored 81.23% strength. It was also observed that the sample obtained the highest damage dent in the low-velocity impact test that failed early during a tensile test and carried the lowest ultimate load.

We have investigated the unexpected phenomena on the surface of molded GFRP composites. The major cause of the unevenness, as a result of which the surface becomes rough, is a shrinking of the matrix in the process of holding pressure and cooling temperature. The higher holding pressure load in a molding process and the lower demolding temperature in an annealing experiment, the better GFRP composites moldings improved its appearance. In addition, by taking the holding pressure and demolding temperature into consideration, we evaluate the process that causes the surface unevenness and the variation in the fiber projection height.

The purpose of this article is to investigate the influence of the cutting parameters, such as cutting speed and feed rate, and point angle on delamination and surface roughness produced when drilling a glass fiber-reinforced plastic composite. All tests were run without coolant at cutting speeds of 5, 10, 15, 20, and 25 m/min and feed rates of 0.1, 0.2, 0.3, and 0.4 mm/rev and point angle of 118° and 135°. The damage generated associated with drilling GFRP composites was observed, both at the entrance and the exit during the drilling process. It was observed that the delamination on drilled holes increased with increasing cutting speed and feed rate. The best results of the delamination are obtained at lower cutting speed and feed rates. For minimum damage on drilled holes, glass fiber-reinforced plastic composite must be drilled at a lower feed rate. It is shown that the point angle of drill is an important parameter on delamination and surface roughness.

The consolidation technology of prestressed hybrid fibre CFRP/GFRP sheet takes full advantages of the initiative of the prestressed reinforcement and force transferring of the composite materials features, which belongs to relatively advanced reinforcement strategies in reinforcement area. This paper derives nonlinear composite element and shell element to simulate concrete beam and the prestressed hybrid fibre CFRP/GFRP sheet. Besides, the characters of nonlinear concrete beams are described by the Owen yielding criterion and the Hinton crushing criterion. Meanwhile, the three-dimensional prestressing effects of the composite CFRP/GFRP materials have been realized and the nonlinear finite element computer program of reinforced system has been compiled. In order to determine the best stress condition of prestressed hybrid fibre CFRP/GFRP composite materials, the optimal hybrid CFRP/GFRP ratio is achieved through the systematic calculation based on two main properties which take the strength and ductility properties into consideration. The results show that the optimal CFRP/GFRP hybrid ratio is one of the major factors to impact its mechanical properties of the reinforced structure which has been strengthened by the prestressed hybrid fibre CFRP/GFRP sheet. And the theoretical method and calculation model that determine the optimal hybrid CFRP/GFRP ratio in this paper is reasonable and reliable. The research conclusions can be used as a reference in practice construction design.