Fiber Reinforced Plastic Composites Research Articles

Evaluation of porosity effects on the mechanical properties of carbon fiber-reinforced plastic unidirectional laminates by X-ray computed tomography and mechanical testing

The effects of porosity on the matrix-dominated mechanical properties of unidirectional carbon fiber-reinforced plastic composites were evaluated using X-ray computed tomography and mechanical testing. Carbon fiber-reinforced plastic plates of four porosity levels were manufactured by implementing different curing cycles. Porosity was detected by X-ray computed tomography tests, conducted on samples taken from the plates, and quantified by analyzing the computed tomography scans using the VGStudio Max software. Four different types of mechanical tests were conducted; namely, transverse tension, V-notched rail shear, three-point bending, and short-beam shear tests. The porosity analysis showed that with increasing the porosity volume fraction, the number of pores decreases, their volume increases while their shape changes from spherical or ellipsoidal to a needle-shape. The results from mechanical tests reveal that the presence of pores reduces all matrix-dominated material properties of the UniDirectional (UD) carbon fiber-reinforced plastic material. The reduction in strength is greater than the reduction in the elastic properties. Moreover, the reduction in the in-plane shear and interlaminar properties is greater than the tensile properties of the UD carbon fiber-reinforced plastic material. Between porosity contents of similar volume fraction, the one with the few large pores proved more severe than the one with the many small pores. The large standard deviation observed for some of the tests is attributed to the non-uniform dispersion of pores.

Characterization of Glass Fibre/Carbon Fibre Hybrid Thermoplastics Composite Laminates Fabricated by Film Stacking Method

The Fibre Reinforced Plastic (FRP) composites are extensively used for a wide variety of applications in automobile, aerospace, chemical, biomedical and civil engineering fields due to their excellent properties. Composite materials offer significant advantages in strength-to-weight ratio and corrosion resistance over metallic materials. Initially FRP composites were based mainly on thermoset polymers because of the ease of manufacturing. But, recently FRP composites using thermoplastics matrices are gaining importance because of their advantages over thermoset composites. In the present work, FRP laminates were fabricated using glass fabric and carbon fabric as reinforcements and thermoplastic polymer (polypropylene) as matrix. Fiber Reinforced Thermoplastics (FRTP) laminates of glass fibre /polypropylene (GF/PP), carbon fibre/ polypropylene (CF/PP) and glass-carbon fibre /polypropylene (GF/CF/PP) hybrid composite laminates were fabricated by film stacking method using hot compression molding press under optimum process parameters (pressure, temperature and dwell time). The fabricated FRTP laminates were tested for various mechanical and physical properties viz., tensile strength/modulus, flexural strength/modulus, izod impact strength, moisture absorption, barcol hardness and density as per relevant ASTM standards. The results of the tests carried out on three materials were compared. It was observed that hybrid laminate (GF/CF/PP) is superior in flexural strength/modulus as compared to GF/PP but the little lower mechanical properties compared to CF/PP laminates. But use of hybrid laminates has great cost advantage compared to CF/PP.

Fabrication of superhydrophobic surfaces on FRP composites: from rose petal effect to lotus effect

A simple method is reported for the preparation of superhydrophobic fiber reinforced plastic (FRP) surfaces with controlled adhesion. By simply adjusting the content of CaCO3 and SiO2 of surface coating, after surface treatment, we can obtain the different FRP surfaces with diverse morphologies. The results confirm that the FRP samples not only could achieve superhydrophobicity but also present huge differences in adhesive abilities. The microlens surface presents a strong sticky performance which can hold a 10-μL water droplet even tilted vertically or turned upside down. Such a property is very similar to the rose petal effect. In comparison, the microbowls surface presents a slippery property which can be regarded as a lotus effect. The water roll-off angle is as low as of approximately 9°. At the same time, the adhesion work of the surfaces is decreased from extreme high (34.7 mN/m) to very low (7.9 mN/m). Noticeably, the heat resistance and antifriction of the microbowls surface are better than that of the microlens.

Improvement of impact-resistant property of glass fiber-reinforced composites by carbon nanotube-modified epoxy and pre-stretched fiber fabrics

Glass fiber-reinforced plastic composites (GFRPs) are often suffered to impact loadings; it is essential to improve its damage-resistant properties and understand the energy absorption mechanisms. In this work, the low-velocity impact behaviors of GFRPs were investigated in consideration of epoxy resins modified with 0, 0.4, and 0.75 % multi-walled carbon nanotubes (MWCNTs) by weight content and pre-stretched fabric at 0, 1.27, and 2.47 kg weight. In comparison with pure GFRPs sample, MWCNT-modified specimens are effective in improving the impact resistance under impact energies at 9, 16, and 22 J in terms of reduced damage factor and enhanced perforation threshold. Microscopic fractographic analysis indicated that the incorporation of MWCNTs in epoxy matrix offered additional mechanisms through breakage, bridging, and pull-out of carbon nanotubes to favor load transfer effect, prevent crack propagation, and thus dissipate more energy. The dynamic thermo-mechanical analysis proved that MWCNTs improved the storage modulus and glass transition temperature of the composites. In addition, the pre-stretched GFRP composites showed more impact resistant than the non-stretched ones through instant load transfer effect.

Evaluation of effective elastic properties of layered composite fiber-reinforced plastic plates by piezoelectrically induced guided waves and laser Doppler vibrometry

An approach to non-destructive evaluation of laminate composite plate elastic properties based on piezoelectrically induced elastic guided waves and laser Doppler vibrometry is presented and discussed. The reconstruction procedure is based on the genetic algorithm minimization of an objective function defined by the set of elastic moduli of the composite prepregs. The objective function defines discrepancy between theoretically calculated and experimentally measured dispersion characteristics of guided waves generated in the laminate anisotropic plate by piezoelectric wafer active sensors. The input data used for the identification are group velocities or wavelengths of the fundamental Lamb waves measured at varying excitation frequencies and propagation directions. The proposed approach has been experimentally tested on unidirectional and cross-ply carbon-fiber reinforced plastic plates and validated by conventional tensile tests.

Recent studies on numerical modelling of damage progression in fibre-reinforced plastic composites

Recent studies on numerical modelling of damage progression in fibre-reinforced plastic composites

Experimental Methods for the GRP Bogie Structure Integrity Assessment

A cost effective bogie is developed at a revolutionary design by the use of advanced fibre reinforced plastics composites operating under extreme load bearing conditions in a hostile environment.This 22.5 tonnes per axle bogie comprises an upper and lower bogie GRP frame. These frames are moulded direct to the final shape and under a load the bogie frames deflect to provide the suspension part of the bogie. The composite GRP bogie is designed allows the wheels to follow more accurately the line of the track by self-steering effects of this bogie, with consequently a corresponding reduction of the track forces and improved the ride quality.The concept of GRP bogie was evaluated at fifth-scale model by making, instrumenting and testing two bogies which have been in service more than 9 years fitted to a passenger wagon at Southampton's Lakeside Railway to study the interactions between the track and the wagon. Every feature of the full scale bogie has been replicated including the axle boxes, central pivot point and the disc brakes. Two different suspension types were monitored during the runs at the Eastleigh railway track: a steel-bogie and a GRP-bogie equipped wagon.A shaker test rig has been developed for testing the whole rail vehicle at various performance conditions as well as with various suspension types to get these interactions using electro-hydraulic testing system Schenck. Several tests were performed like drop test, sweep tests, track profile test and so on to assess the properties and structural integrity of the developed bogie.

Optimization of Laser Cutting Parameters on the Laminated Carbon Fibre Reinforced Plastics (CFRP) Composites Using DOE Technique

Nowadays, carbon fiber reinforced plastics (CFRP) composites is widely used in the aerospace industry due to its excellent mechanical properties. In laser cutting process, high powers are used to cut materials then material melts and burns leaving edges with a high quality finish. To fulfill the high demand of cutting quality, a set of laser cutting parameters of CFRP material are studied. The objective of this experiment is to obtain an optimum laser cutting parameter thus minimizing the cutting defects particularly on kerf width at the top and bottom surfaces. The analysis of process parameter was carried out using DOE, Design Expert 6.0.8. Cutting speed, pulse duration, pulse repetition rate and pulse energy were analyzed at two levels. By the optimizing the parameter setting, significant improvement in cutting quality has been achieved.

3D FEA modelling of laminated composites in bending and their failure mechanisms

This paper developed three-dimensional (3D) Finite Element Analysis (FEA) to investigate the effect of fibre lay-up on the initiation of failure of laminated composites in bending. Tsai-Hill failure criterion was applied to identify the critical areas of failure in composite laminates. In accordance with the 3D FEA, unidirectional ([0]16), cross-ply ([0/90]4s) and angle-ply ([±45]4s) laminates made up of pre-preg Carbon Fibre Reinforced Plastics (CFRP) composites were manufactured and tested under three-point bending. The basic principles of Classical Laminate Theory (CLT) were extended to three-dimension, and the analytical solution was critically compared with the FEA results. The 3D FEA results revealed significant transverse normal stresses in the cross-ply laminate and in-plane shear stress in the angle-ply laminate near free edge regions which are overlooked by conventional laminate model. The microscopic images showed that these free edge effects were the main reason for stiffness reduction observed in the bending tests. The study illustrated the significant effects of fibre lay-up on the flexural failure mechanisms in composite laminates which lead to some suggestions to improve the design of composite laminates.

Study on the impact of fiber length on the correlation of separation and orientation in flow molded glass fiber-reinforced plastic composites.

During the compression molding of fiber-reinforced plastic composites, there are two issues: one is separation of fiber and matrix because of the different flow state and fiber orientation. Due to separation and orientation, moldings become nonhomogeneous, and show anisotropy. Therefore, separation and orientation should be closely corresponded to molding condition and fiber structure. If fiber shows strong agglomeration, it increases the separation, but fiber orientation will be limited. That is, separation and orientation of fiber is closely related, and the relationship should be clearly defined. In this study, fiber content and length is varied for stacked laminates, and primary sheet is fabricated with thermal compression press. Primary sheet is heated and molded with 30-ton hydraulic press. Nonhomogeneity, one of indicators for separation, is measured from one-dimensional rectangular plate after compression. Orientation function is calculated using X-ray image on moldings and image scanner for processing imagery data. From the correlation between the separation and the orientation of fiber and matrix, the correlation coefficient is defined, and the impact of fiber length on the coefficient is evaluated.

Influence of Laser Process on Mechanical Behavior during Cutting of Carbon Fiber Reinforced Plastic Composites

Carbon fiber-reinforced plastics (CFRP) composite is most attractive materials to reduce the weight of transportations. To increase the production volume and the efficiency in the field of CFRP component, fast, highly precise and cost-efficient technologies are required. Although laser cutting meets these requirements, it is not used because of insufficient knowledge about the effect of thermal damage on the material behavior. In this study, the effect of several cutting processes on the static tensile strength and the fatigue strength was evaluated for CFRP consisting of thermoset resin matrix and carbon fibers. The CFRP was cut using two different-type of lasers; a CO2 gas laser and single-mode fiber lasers, and a conventional mechanical tool. The mechanical cutting specimen produced a cut of high quality. While, the laser cutting specimens clearly showed a heat-affected zone (HAZ). The static tensile strength and the fatigue strength by laser cutting specimens clearly decreased in comparison with mechanical cutting specimen. The laser cutting specimen exhibited a linear dependency of the tensile strength on the HAZ, indicating that the main effect resulted from thermal destruction of CFRP within the HAZ.

Investigation into property control of VaRTM composites by resin infusion process

This paper proposes a property control method in vacuum-assisted resin transfer molding (VaRTM) using porous mold process (PMP) to fabricate carbon fiber-reinforced plastics (CFRP) composites. Low-cost VaRTM process generally induces the variation in quality and properties of fabricated composites, depending on infusion and curing process, dimension and configuration of stacked fabrics, etc. and involves difficulty in control of the properties of fabricated composites. As resin content in the composites can be easily controlled in VaRTM process combined with PMP, this paper investigates the effect of infused resin content on the final mechanical properties of CFRP. It is demonstrated that volume fraction of carbon fibers and the resultant mechanical properties of CFRP can be controlled by the infusion process control. Finally, application of the present control method to the manufacturing of a complex CFRP panel with thickness variation is demonstrated. It is concluded that the measured mechanical properties fit well with the designated properties.

Delamination propagation analysis in tufted carbon fibre-reinforced plastic composites subjected to high-velocity impact

Impact-induced delamination propagation on both tufted and untufted carbon fibre-reinforced plastics composite laminates was investigated. High-velocity impacts were performed on a ballistic gas gun. Initial and residual velocities were monitored with optical sensors especially developed for this study. Energy-absorption abilities were compared for different tufting parameters. The perforated specimens were inspected with an original technique allowing the observation of interlaminar delamination area for each interface. The existence of preferential propagation direction is highlighted. It is concluded that tufting helps to contain delamination and provides improved energy absorption depending on the tufting pitch.

Crushing behavior of hybrid hexagonal/octagonal cellular composite system: All made of carbon fiber reinforced epoxy

Cellular carbon fiber-reinforced plastic (CFRP) composites, either unfilled or filled with foam, may be of interest for energy absorption application due to their improved crashworthiness. In the current paper, new combinations of octagonal and hexagonal cellular CFRP composites are introduced as energy absorption devices. Different arrangements of cells are tested. In addition, the effect of filling the structure with foam is studied. The well-known crashworthiness parameters are being used to compare the different configurations. In addition, 2 new parameters (crush load stability and springback coefficient) are introduced to assess both the difference between the peak and the average crushing load and the stability during the post crushing stage as well as the capability of the structure to retain its original height after crushing. The results show that the configurations with closed cells are advantageous in terms of the peak and the average crushing load and the energy absorption, whereas the open cells are of great interest when comparing the stability of the crushing load in the post-crushing stage.

Effects of process parameters on epoxy flow behavior and formability in deep drawing process with CR340/carbon fiber–reinforced plastic composites

In this study, a hybrid composite material was fabricated by stacking carbon fiber–reinforced plastic on CR340 plates to increase the specific strength and specific stiffness, compared to thick boron steel plates or dual-phase steels. A deep drawing test was conducted for this hybrid composite material, using various process parameters, to assess its formability and potential use in vehicle parts. The experimental results showed that the forming depth was reduced in both CR340 and the CR340/carbon fiber–reinforced plastic composite when the blank holding force (Bf) was increased. Although the forming depth of CR340 was decreased abruptly when Bf >= 30 kN, the forming depth of the CR340/carbon fiber–reinforced plastic composite was not reduced, highlighting its superior formability compared to CR340. The forming depth for CR340 did not show significant differences with increasing punch velocity. On the other hand, the forming depth of the CR340/carbon fiber–reinforced plastic composite decreased with increasing punch velocity. As the punch velocity increased, carbon fiber–reinforced plastic flowed abruptly toward the round part of the die. The thinning rate in each position of the drawing product and the problems encountered during the deep drawing process were reviewed by a comparison of the experimental results.

Environmental damage and degradation of FRP composites: A review report

Fiber‐reinforced plastics (FRP) composites are prime choice materials in various civil engineering structures and high performance aerospace components. They exhibit superior mechanical properties than their metallic counterparts. However, they are susceptible to environmental damages and degradations. To utilize the full potential of FRP composite materials their physical, chemical, and mechanical behavior in different environmental conditions should be well established. Present review is an attempt at highlighting different damage/degradations that may be caused to the FRP composite on its exposure to various environmental conditions. POLYM. COMPOS. 36:410–423, 2015. © 2014 Society of Plastics Engineers

Inclusion of Lignocellulosic Fibers in Plastic Composites

Solutions for the production of sustainable plastics have motivated the scientific community to search for new alternatives for the replacement of raw materials from non-renewable sources such as glass fibers. Therefore, plant fibers appear to be a feasible alternative, since they present low cost, suitable mechanical strength, wide availability, as well as are renewable. This work aimed to evaluate the replacement of glass fibers by lignocellulosic fiber in plastic composites used in civil construction sectors. The resin used was ortho unsaturated polyester. Three plant fibers were tested (sugar cane bagasse, eucalypt and pine) with and without chemical modification. The chemical modifications were performed with sodium hydroxide. The composites were evaluated by their physical and mechanical properties. The initial results showed the potential of using plant fiber in the production of fiber-reinforced plastic composites. Keywords: plant fibers, residues, polyester resin

Application of Multilayered Paper Processing to Hybrid Random Natural Fiber Mat

Fiber reinforced plastic composite (FRP) has gained remarkable development because of its excellent properties, such as low density, high stiffness, high strength, corrosion resistance, long fatigue life, and so on. However, as more and more products made of FRP, the rubbish of FRP is also increasing which has become an important problem to the environment. Recycling and reusing is a noticeable method to reduce trash discharge and to save resource. Although it is a more challenging work for FRP, many researchers have report their scores in this area, such as the group from The University of Nottingham who have developed a new technology to recycle the carbon fiber. The objective of this research is to make short fiber mat from recycled carbon fiber by paperboard making method. In this method the fiber can be made into very thin layers and be laid into mat. After that the mats were used to fabricate FRP and the tensile property of the materials was investigated. The property was evaluated between recycled carbon fiber and jute fiber as well as hybrid one. It was found that the hybrid one has better performance.

Influence of Lay-up Configuration and Feed Rate on Surface Integrity when Drilling Carbon Fibre Reinforced Plastic (CFRP) Composites

Experimental data is presented relating to surface roughness (2D and 3D) and workpiece integrity when drilling unidirectional CFRP laminates with varying lay-up configurations (Type 1, 2 and 3) at different feed rates (0.2 and 0.4mm/rev) using diamond coated carbide tools. Drill feed rate was ramped down to 0.01mm/rev for the final 0.5mm in all trials. Surface roughness at hole exit was typically lower (up to 4.04μm Ra) compared with the entry section in all tests due to the lower feed rate applied. High resolution SEM micrographs and 3D topographic maps showed that Type 2 ([45/0/135/0/90/0/135/0/45]2S) lay-up gave the lowest roughness of ∼1.16μm Sa after 384 holes at a cutting speed and feed rate of 90m/min and 0.4mm/rev respectively. Cavities, smearing of matrix material and adhered/deposited fibre dust were observed near the exit location at test cessation.

ANALYSIS EFFECT OF DRILLING PARAMETERS ON HOLE DELAMINATION DURING DRILLING OF GLASS FIBER REINFORCED PLASTIC (GFRP) COMPOSITE MATERIALS

Glass fiber reinforced plastic (GFRP) composite mat erials are widely used industrial, aerospace, and a utomotive sector. Its have excellent properties such as high strength to weigh t ratio, higher fatigue limit high stiffness to weight ratio, corrosion resistance and design flexibility. Drilling is one of the major ma chining operations that are carried out on fiber re inforced metal composite materials to the need for components assembly. There are many problems encountered when drilling Glass fiber rei nforced plastic (GFRP) composites. These problems include delaminating of the composite, poor surface roughness and hole devi ation. In present experimental investigation analyse the effect of va rious machining parameters i.e. cutting speed, the feed rate, and the drill diameter on the quality of the drilled holes. Hole deviation of each hole is measured with help of digital vern ier calliper. Taguhi's and ANOVA Technique have been employed to study the effect of the interactions between different drilling parame ters on deviation of holes. After experiments suggests the optimal conditions for min imum hole deviation.