Glass Fiber-reinforced Plastic Composite Materials Research Articles

Damage Detection Test of GFRP Composite Civil Materials Based on Piezoelectric Ceramic Sensors

The piezoelectric ceramic sensor was fixed on Glass Fiber Reinforced Plastic (GFRP) composite civil materials, using the external paste method for damage detection test. The effect of the depth and number of cracks on the surface of the GFRP specimen on the signal received by the piezoelectric ceramic sensor was studied. The time-domain signal graph and energy graph based on wavelet packet were drawn, combining the active induction method and the energy method based on wavelet packet. It is found that the greater the damage degree of GFRP specimens, the smaller the voltage value of the signal, the smaller the energy of the signal, and the greater the damage index based on wavelet packet. The results showed that the active induction method can be used to collect the data of GFRP specimens by piezoelectric ceramic sensor. The collected data are processed by using the damage index principle based on wavelet packet. The maximum voltage value of the specimen, the energy of wavelet packet, and the damage index based on wavelet packet can all accurately judge the damage change of GFRP specimens. The active induction method based on piezoelectric ceramic sensor can detect the damage change of GFRP specimens in real time. It provides an effective method for damage analysis of GFRP composite civil materials.

Evaluation of Heat Treatment Effect on Impact Strength of Glass Fiber–Reinforced Composite Material Using NDT Technique

Of late, the frequent use of composite materials merits effective inspection techniques to ensure structural integrity after manufacturing as well as during service. The inspection of composite materials is undertaken using various nondestructive testing (NDT) techniques. Ultrasonic testing (UT) is one of the popular NDT techniques used for testing of composites. The aim of the research is to establish a quantitative relationship between UT signal’s features and the mechanical property, i.e., impact toughness of the composite material heat treated at different temperatures. Polyester glass fiber–reinforced composite undergone post-cure heat treatment is the composite used in the research work. The glass fiber–reinforced plastic (GFRP) specimens have been heat treated at different temperatures to mimic different levels of thermal aging. The impact toughness of the composite material is determined using the Charpy impact test. Then, variation in attenuation of UT signals is related to the change in impact toughness of GFRP composite material heat treated at different temperatures. A possible classification of UT signals acquired from GFRP specimens in terms of different level of thermal aging has also been investigated through application of Hilbert–Huang transform (HHT) on the acquired UT signals. Hilbert energy frequency distribution-based feature extraction has been successfully used to analyze the effect of post-cure heat treatment on GFRP composite. An empirical relationship is finally obtained between Charpy impact energy and HHT energy. The proposed technique will be useful in prediction of strength and remaining useful life of GFRP composites through analyses of acquired UT-based NDT signals.

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

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

Designing a phthalonitrile/benzoxazine blend for the advanced GFRP composite materials

High performance resin must be used in the high performance glass fiber-reinforced plastic (GFRP) composites, but it is sometimes difficult to balance the processabilities and the final properties in the design of advanced thermoset GFRP composites. In this study, a phthalonitrile/benzoxazine (PPN/BZ) blend with excellent processability has been designed and applied in the GFRP composite materials. PPN/BZ blend with good solubility, low melt viscosity, appropriate gel condition and low-temperature curing behavior could enable their GFRP composite preparation with the prepreg-laminate method under a relatively mild condition. The resulted PPN/BZ GFRP composites exhibit excellent mechanical properties with flexural strength over 700 MPa and flexural modulus more than 19 GPa. Fracture surface morphologies of the PPN/BZ GFRP composites show that the interfacial adhesion between resin and GF is improved. The temperatures at weight loss 5% (T 5%) and char residue at 800 °C of all PPN/BZ GFRP composites are over 435 °C and 65% respectively. PPN/BZ GFRP composites with high performance characteristics may find applications under some critical circumstances with requirements of high mechanical properties and high service temperatures.

The effect of support on multi-hole drilling for glass fiber-reinforced plastic composite materials

Mechanical joint of fastener is widely used in the assembling and repairing of the modern aircraft composite components, so multi-row holes are needed in jointing, and their quality directly influences the reliability of aircraft structures. So, multi-hole drilling of composite components becomes one of important processes. A large number of researchers have carried on the detailed and thorough research for the drilling process and corresponding damage based on single-hole drilling of composite materials, but none corresponding research was based on multi-hole drilling of composite materials. In the case of a round-hole array backing plate and a square-hollow backing plate as supporting, this paper carried out finite element simulation, theoretical analysis, and experimental research for multi-hole drilling of glass fiber-reinforced plastic (GFRP) composite materials. The study aimed at contrasting and analyzing S33 stresses, thrust forces, and exit delamination damage of multi-hole drilling between the two kinds of support cases and between the internal of each support case. The results showed that S33 stresses, thrust forces, and exit delamination damage existed significant difference between two kinds of support cases. What is more, S33 stresses, thrust forces, and exit delamination damage have no difference with a round-hole array backing plate as supporting; under a square-hollow backing plate as a support, S33 stresses, thrust forces, and exit delamination damage existed significant difference with the changing of straight-line distances from the center of hole to the center of backing framework. On the basis of this study, the analytical results provided corresponding theoretical guidance for the multi-hole drilling in the assembling and repairing for the composite components.

Application of the Taguchi based Desirability Function Analysis to Improve a GFRP Micro-drilling Performance

Drilling on GFRP composite materials in micron level is a complex work due to its heterogeneity and the problems such as delamination, fiber push up/pull out, overcut, dimensional deviation and circularity error which show during the machining process. This work presents optimizing the machining parameters on drilling Glass Fiber Reinforced Plastic (GFRP) composites. Optimization of machining parameters was carry out by an analysis called desirability function analysis (DFA), which is the technique for optimizing multi-response problems. In this work, as per the design of experiment, drilling processes were carrying out on GFRP composite using solid carbide drill. The cutting speed and feed are optimized by multi-response considerations namely hole size, delamination factor and circularity error. Based on analysis, the optimum levels of factors have been identified and significant contribution of parameters is determined by analysis of variance.

Effect of Drilling Parameters for the Assessment of Roughness of Drilled Holes in Glass Fiber Reinforced Plastic (GFRP)

Now a day, Glass Fibre-Reinforced Plastics (GFRP) are being widely used in diversity of engineering applications in many different areas such as aerospace, automotive and aircraft industries due to their light weight, high modulus, high specific strength and high fracture toughness. Drilling or Milling of GFRP composite material is a rather complex task owing to its heterogeneity and the number of problems, such as surface accuracy and delamination of drilled holes, which appear during the machining process, associated with the characteristics of the material and the cutting parameters. Current paper focuses the investigational details to find out roughness on drilled hole in GFRP composite laminates by using Taguchi's DOE L9 orthogonal array. The main objective of the present work is to optimize the process parameters in the drilling of GFRP composite using Taguchi DOE and to find the significance of each process parameter using ANOVA. As far as the effect of input factors are considered, the factor spindle speed is having significant and dominating effect on GFRP composite material.

Effect of Cutting Parameters on Delamination of Glass Fiber Reinforced Plastic (GFRP) in CNC Milling

Now-a-days glass fiber-reinforced plastics (GFRP) are always applicable in variety of engineering applications. It is used in aerospace, automotive and aircraft industries due to their well known properties. Milling of GFRP composite materials is very difficult due to its heterogeneity and the number of troubles like as surface delamination during machining affects uniqueness of the material and the machining parameters. Present paper focuses the experimental details to find out delamination factor on GFRP composite laminates by using Taguchi’s DOE L9 orthogonal array. The main objective of the present work is to optimize the process parameters in the drilling of GFRP composite using Taguchi DOE and to find the significance of each process parameter using ANOVA. As far as the effect of input factors are considered, the factors drilled material and spindle speed both have nearly predominant influence on the delamination factor of drilled holes on GFRP composite by using CNC milling process.

Numerical optimization of hole making in GFRP composite using abrasive water jet machining process

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 abrasive water jet cutting. The results show that the optimum values of cutting feed, fiber density, water jet pressure, standoff distance, and abrasive flow rate upon the response variables are 0.3 m/min, 0.82 g/cm3, 150 MPa, 2 mm, and 100 g/min, respectively.

Experimental Investigation of Buckling of Laminated Composite Cylindrical Shells with &Without Cutouts Subjected To Axial Compression

GFRP (Glass Fiber Reinforced plastic) composite materials are find many applications in engineering fields like mechanical and civil engineering applications. It is because of the properties of these materials like light weight when compared to other materials, durability, rust proof and many more. The composite cylindrical shells are being used very widely in underground pipelines, Aerospace industries, submarines and so on. In present study, the buckling of thin walled glass reinforced polymer cylindrical shells with and without cutouts has been investigated by applying axial load on the shells. The results which were obtained in this experiment will show how the imperfections like cutouts will affect the buckling behavior of the

Effects of Grinding Process Parameters and Coolants on the Grindability of GFRP Laminates

Grinding is one of the mandatory methods for fabrication of precise glass fiber reinforced plastic (GFRP) parts. In this work, grinding studies were carried out on GFRP using a cubic boron nitride (CBN) wheel. The grinding process was performed at different cutting speeds, feed rates, and depth of cuts. Grinding performance was evaluated by measuring forces and surface roughness of the ground GFRP composite laminate material. The effects of coolants in grinding the composite laminate material were investigated. Test results showed that in most cases, dry grinding achieved the greatest material removal rate and the lowest surface area roughness (Sa). Higher speed tends to produce better surface finish in dry grinding. Surface area roughness produced in wet grinding shows random and drastic variations. Surfaces ground in synthetic coolant show clean, hard, and smooth matrix, and are in general of better quality than those ground with emulsion coolant. Optical and electron microscopy was used to evaluate the grinding mechanism of GFRP laminate material. Surface profile waviness is the predominating factor contributing to surface area roughness over surface peaks and valleys.

Tensile strength and fracture of glass fiber-reinforced plastic (GFRP) plate with an eccentrically located circular hole

In this paper, tensile strength and fracture of finite glass fiber-reinforced plastic GFRP (glass/polyester) composite materials with a through-the-thickness eccentrically located circular hole are experimentally studied. The strain response histories near the hole boundary for different eccentrically located holes during the whole damage and fracture process of the notched specimen are recorded. The effects of off-center distance and hole diameter on strength and fracture of the notched specimen are analyzed. The tensile fracture strength of the notched specimen with an eccentrically located hole is determined. Also, the initial stress concentrations in the composite laminate due to the presence of the eccentrically located hole are understood. These results play an important role for predicting strength and evaluating lifetime of laminate composite with complex geometrical cutouts.

Selection of a blast-resistant GRP composite panel design for naval ship structures

Glassfiber Reinforced Plastic (GRP) composites can be used to advantage in ship structures to eliminate fatigue cracking, reduce weight and maintenance costs, and improve fire-resistance. Besides transient sea-wave loads, naval ship structures must be designed to withstand shock loads from air-blasts and underwater explosions. GRP composite materials can be specially formulated and configurations selected for applications to specific naval ship structures. Experimental tests have been conducted to select a cost-effective GRP laminate which can be integrated into conventional steel-frame superstructure designs. Initially, the air-blast resistance of the laminate fabricated from woven roving E-glass in polyester isophthalic resin was determined experimentally in a series of shock-tube tests. Clamping of the plate edge supports was necessary to obtain good blast resistance. The fibre breakage and debonding failure of the laminate were examined. Next, the dynamic response of a half-scale laminate section stiffened with steel I-beams was measured in a second series of shock-tube tests to determine the blast resistance of the UK hybrid GRP/steel panel design. Finally, a full-size panel (2·7 m × 4·9 m) and a quarter-scale panel were fielded at recent large-scale blast trials and data correlated to establish scaling rules and confirm the blast survivability and structural integrity of the panel design for possible application in naval ship structures.