Carbon Fiber Reinforced Plastic Materials Research Articles

Theoretical Analysis of Grinding Temperature Field for Carbon Fiber Reinforced Plastics

A three-dimensional finite difference method (FDM) model of grinding temperature field for carbon fiber reinforced plastics (CFRP) was established, based on the homogenization of the thermal properties of the CFRP material. The effect of the fiber direction on grinding temperature distribution at different workpiece velocity was numerically simulated and analyzed. It is found that the effect of the fiber direction on grinding temperature field is remarkable in lower workpiece velocity but unapparent in higher workpiece velocity due to the anisotropy of CFRP material and the velocity of moving heat source. More than 230 °C surface grinding temperature, which will badly damage CFRP performance, may be produced in dry grinding according to the simulated analysis. During grinding the heat affected zone of CFRP is about 0.22 mm in depth direction. Furthermore, experimental results are well in agreement with those of the theoretical analysis.

A Comparison of the Vibration Characteristics of Carbon Fiber Reinforced Plastic Plates with those of Magnesium Plates

An experimental and numerical investigation is conducted to evaluate vibration characteristics of an advanced composite material system, namely carbon fiber reinforced plastic (CFRP), relative to a magnesium alloy currently used in the vibration testing industry. Experimental test specimens for both materials, with varying thicknesses, are tested with two boundary conditions — the free condition, to evaluate the natural frequencies and damping of the two materials and, secondly, a general constrained condition, typical of vibration testing. Experimental modal analysis techniques are used to measure the vibration characteristics including natural frequencies, damping and mode shapes. The results from these tests show that the natural frequency and mode shape for relatively thin CFRP plates were comparable with those of magnesium plate. Although the mode shapes also compare well for thick CFRP and magnesium specimens, the natural frequencies were found to have significant differences between the two material systems. The largest difference between the two material systems, present for all thicknesses, is found to be the damping values for the respective vibration modes. This unique characteristic of the CFRP material presents an opportunity for a performance increase in the vibration testing system’s community.

Fiber optic acoustic emission sensor and its applications in the structural health monitoring of CFRP materials

A fiber optic acoustic emission sensor based on fused-tapered coupler and its applications in structural health monitoring are proposed in this paper. The fiber optic acoustic emission sensor (FOAES) was tested using pencil lead break tests compared with the commercial acoustic emission sensor (R15 PZT). Besides, the sensor was embedded into the carbon fiber reinforced plastics (CFRP) materials and tested in the same way. It successfully detected the AE signals. FOAES was applied in the structural health monitoring (SHM) of CFRP materials. Damages of carbon fiber/epoxy composite laminates during three-point-bending test were monitored by surface-mounted and embedded FOAES, respectively. Results identified that the sensor embedded into composite structures could monitor damage of composite laminates on-line as the surface-mounted sensor did.

The extrinsic influence of carbon fibre reinforced plastic laminates to strengthen steel structures

The intrinsic advantages of strengthening the steel-based structures by the use of fibre reinforced plastic (FRP) material have not yet been fully exploited. In this paper, a succinct overview of recent studies made to enhance the strength of steel beams using FRP laminates is presented. The results presented and discussed in this paper were obtained by closely studying the behaviour of steel beams strengthened with carbon FRP material. An attempt is made to succinctly summarise the findings for two different types of strengthening of the steel beams using carbon FRP laminates. The first type of beams focuses on enhancing the strength of steel in flexure while the second focuses on increasing the shear strength of the beams. Three beams were designed so as to cause them to fail in flexure. Of the beams studied, two were strengthened using carbon FRP strips attached to the tension flange. One of the beams was tested to facilitate comparison of their behaviour to the two beams which are strengthened in flexure. Three other beams were designed such that they failed predominantly in shear. Of these three, two were strengthened with carbon FRP strips attached to the webs while the third beam was used as a control beam for the purpose of drawing comparisons. Preliminary results revealed a noticeable increase in the strength for both the flexure strengthened beams and the beams strengthened in shear. The observed increase in shear strength of the beams was 26% while the increase in strength for the beams tested in flexure was 15%. This study convincingly shows that it is possible to strengthen steel beams using carbon FRP laminates in both flexure and in shear.

A new vibration damping CFRP material with interlayers of dispersed piezoelectric ceramic particles

In this paper, the author summarizes the previous works on the passive damping of carbon-fiber reinforced plastic (CFRP) cantilever beams using: (1) interleaving of viscoelastic thermoplastic films, (2) surface-bonded piezoelectric ceramics, and (3) dispersed PZT particles interlayers. Introducing polyethylene-based film interlayers between composite plies resulted in a significant increase in the vibration loss factor. It is also shown that the vibration damping of CFRP laminates can be improved passively by means of resistively shunted, surface-bonded piezoelectric ceramic, PbZrO 3–PbTiO 3 (PZT) sheets. In particular, the author developed an original method to enhance vibration damping of CFRP laminates via dispersed PZT particles interlayers. All these damping methods can be jointly used to improve the damping of CFRP laminates/structures. The usefulness of the damping concepts dealt in this work is verified through an application of the method to the actual design of robotic arm. The robotic arm designed and manufactured using damping CFRP materials showed an excellent vibration damping in comparison with those made with conventional CFRP and aluminum materials.

Intralaminar fatigue behaviour of carbon fibre reinforced plastics

A new approach is discussed for characterizing the damage state of FRP with the appearance of micro cracking and its influence on the residual strength. For the quantitative analysis of micro cracking, X-ray refraction topography was used. Fatigue treatment of carbon fibre reinforced plastics (CFRP) laminates were performed to create defined damage states. With regard to real loading conditions of CFRP, studies on tube samples were performed to investigate two dimensional (tension–torsion) loads. A rheological material model was presented which described the increase of micro cracking in ±45° CFRP laminates with a continuum mechanical approach. The correlation between the results of the X-ray refraction topography, the damage parameter of the rheological model and the decrease of residual strength were shown. The inter fibre fracture surface of the investigated CFRP materials was determined with tension–torsion loaded tube specimens of 90°-laminate and a layer-wise strength analysis was done. Micro cracking occurs even at 50% inter-fibre fracture loading and can lead to a distinct strength reduction. The intralaminar fatigue effect itself seems to be an indication for the damage accumulation and the load history.

Drilling carbon fiber reinforced plastics manufactured by autoclave—experimental and statistical study

Abstract Drilling laminates composites materials are significantly affected by delamination tendency of these materials under action of cutting forces (thrust force and torque). On the other hand, drilling is an operation frequently used in industry due to the need for component assembly in mechanical pieces and structures. So the aim of this paper is the study of the cutting parameters (cutting velocity and feed rate) on power (Pc), specific cutting pressure (Ks), and delamination in carbon fiber reinforced plastics (CFRPs). A plan of experiments, based on the techniques of Taguchi, was established considering drilling with prefixed cutting parameters in an autoclave CFRP composite laminate. The analysis of variance was preformed to investigate the cutting characteristics of CFRPs using cemented carbide (K10) drills with appropriate geometries. The objective was to establish a correlation between cutting velocity and feed rate with the power (Pc) specific cutting pressure (Ks) and delamination factor (Fd) in a CFRP material. Finally, this correlation was obtained by multiple linear regression.

A constitutive model for concrete confined with carbon fiber reinforced plastics

Uni-axial compression tests on three different strengths of concrete cylinders confined with different number of layers of carbon fiber reinforced plastics (CFRP) were used to develop a constitutive model for confined concrete in the use of retrofitting and strengthening reinforced concrete structures. The peak strength of this constitutive model (named L–L model) is derived from the Mohr–Columb failure envelope theory and can be explicitly expressed as a function of the unconfined concrete strength, the lateral confining stress and the angle of internal friction of concrete. The strain at the peak strength in this model is obtained from the regression analysis of the experimental results. A second-order polynomial equation is used to present the stress–strain curve of the L–L model. In the L–L model, the lateral confinement of the concrete came from the CFRP composite material. Test results of 108 concrete cylinders confined by CFRP material were recorded to show the accuracy and effectiveness of the L–L model. For concrete confined by steel reinforcement and CFRP material, a modified L–L model was also proposed. And 18 concrete cylinders with a dimension of ø30×60 cm were tested to verify the accuracy of the modified L–L model.

Detection of internal cracks and delamination in carbon-fiber-reinforced plastics using SQUID-NDI system

Recently, thick boards of carbon-fiber-reinforced plastic (CFRP) are often used in space crafts and space structures. Nondestructive inspection (NDI) using superconducting quantum interference device (SQUID) is a prospective NDI method for the thick CFRP materials. To estimate the potential of SQUID-NDI for detection of deep-lying defects in CFRP, the skin effect must be clarified. So we applied a SQUID-NDI method to hidden slots and delaminations at various depths in thick CFRP boards to obtain the dependence of the peak amplitude of the magnetic response to the defects on the defect depth. Magnetic field response due to slots of up to 15 mm depth was detected. The response peak amplitude exponentially reduced as the depth increased. We estimated the depth dependence by a simple calculation assuming the same skin effect in CFRP as in metals. The estimated dependence differs a little from the experimental one. The difference suggests that a more accurate calculation is necessary.

Applicability of CFRP materials to the cryogenic propellant tank for reusable launch vehicle (RLV)

It is essential to utilize carbon fiber reinforced plastics (CFRP) for main structural materials of cryogenic propellant tanks in order to realize the drastic weight reduction needed for efficient reusable space transportation systems. Recently developed toughened CFRP materials, which are expected to show good cryogenic properties, are considered promising candidates for these kinds of applications. The present study investigates cryogenic properties of candidate materials and structural elements, including Y-joint structural models. 300 mm diameter filament wound tank and 600 mm diameter lay up tanks were fabricated and tested. Based on these experimental data, the feasibility of a CFRP cryogenic tank is discussed and future research tasks are proposed. This research is being conducted under the cooperation contract between NASDA and NAL.

Acoustic emission in carbon fibre-reinforced plastic materials

The mechanical behaviour of unidirectional (UD) and 2D-laminate Carbon Fibre-Reinforced Plastic composites was investigated under 4-point bending and tensile loads at room temperature. The mechanical behaviour of UD composites was first studied. The mechanical behaviour of a quasi-isotropic laminate was subsequently investigated under the same loading conditions and correlated to that of the UD plies. The damage and the failure mechanisms were identified by microscope observations on both UD and laminate composites. Two families of damage mode were identified, involving interfibre cracks and inter-layer delamination cracks homogeneously distributed within the composite. The fracture process is assigned to the propagation of the macrocrack in the failure envelope through a large intra and inter-layer delamination process interrupted by fibres/bundles fracture. Acoustic emission measurement was performed during the tests. An approach using a combination of acoustic waveform parameters as indicators of the physical damage is discussed.

Reactor irradiation effects on the ultimate tensile and the interlaminar shear strength of carbon fibre reinforced epoxies at 77 K

A carbon fibre reinforced plastics material (CFRP) `TORAYCA T300 3K', which was developed for various applications, including cryogenics, was irradiated at 5 K and 340 K with different reactor spectra up to a fast neutron fluence of 5×10 22 m −2 ( E>0.1 MeV). All investigations in the interlaminar shear mode as well as the tensile tests were made at 77 K, the samples subjected to 5 K irradiation were measured before and after an annealing cycle (of about one day) to room temperature. Fractographic examinations of the tensile samples were used to examine the complicated fracture process. Both the interlaminar shear strength and the ultimate tensile strength show good radiation resistance at the lowest total absorbed dose (∼5×10 6 Gy), but fail at higher dose levels (∼10 8 Gy).

Behavior of Precracked RC Beams Strengthened with Carbon FRP Sheets

Experimental data obtained from strengthened, precracked, reinforced concrete (RC) specimens are presented together with the results of material characterization. Strengthening was attained with the adhesion of carbon fiber-reinforced plastic (CFRP) sheets to the concrete surface. The CFRP was applied as in situ (i.e., working under the beam). Several variables were investigated, including: two CFRP material systems, two concrete surface preparations, two RC cross sections, and the number and location of CFRP plies. For two specimens, the presence of applied load (simulating the total service load) as well as external prestressing during the adhesion of the CFRP reinforcement, were investigated. It is shown that the effect of CFRP strengthening was considerable, but the effect of some of the tested variables was modest. An existing analytical model has been extended to simulate the load-deflection behavior as well as the failure mode of the precracked RC specimens. Different failure mechanisms from ductile to brittle were simulated and verified, adopting the mechanical properties of the constituent materials obtained via standard tests or using a simple test for the concrete-adhesive interface.

Stresses around fasteners in composite structures in flexure and effects on fatigue damage initiation part 1: cheese-head bolts

This study concerns a programme of research on stresses around cheesehead bolts in multilayered Carbon Fibre Reinforced Plastic (CFRP) material; both theoretical and experimental studies have been carried out. Commercially available finite element (FE) software was used to carry out three dimensional (3D) stress analyses of CFRP material specimens with holes, loaded in flexure in a cantilever-type of arrangement, the specimen being attached to a rigid support via bolts through the holes. The types of specimens studied were those used in experiments in a robust fatigue rig which was built for the project. The theoretical models showed regions of high direct and shear stresses in the specimens when bent over and away from the clamping support. The practical fatigue tests showed, via ultrasonic scanning and electron microscopy, where damage initiated in the test specimens after a large number of flexural loading cycles and the type of damage induced. Comparisons between theoretically predicted regions of high stresses and induced damage were made in order to establish damage inducing mechanisms and the levels, types and combinations of internal stresses which cause damage to occur.

Photo- and exoelectron analysis of the surface layer of carbon fibre-reinforced plastic

Abstract In this paper, the possibility of using photo- and exoelectron analyses to determine changes to the surface layer of carbon fibre-reinforced plastic material after exposure to mechanical, thermal and light treatments is demonstrated. A periodic variation of the structure of the surface layer during its irradiation by white light was detected. The model explaining this effect has been worked out.

Effects of Water Absorption upon Fatigue Characteristics of Carbon-Fiber-Reinforced Epoxy Resin Composites.

This paper discusses the environmental degradation behavior of carbon-fiber-reinforced plastic (CFRP) laminated material, due to water absorption. In order that the CFRP materials can be used more effectively as structural members with higher safety and reliability for factories, it is considered indispensable to understand in detail the influence of environment factors that accelerate dynamic degradation, such as fatigue. A summary of the results is as follows. Fick's diffusion law is applicable to analysis of water desorption and absorption characteristics of the uni-directional fiber reinforced (UD) and plain woven reinforced (CL) materials. The desorption and absorption processes are diffusion-controlled processes within matrix resins, including the skin layer. The properties of the skin layer significantly influence the fatigue life of the CFRP laminates. Furthermore, the decrease of fatigue strength is caused by the lowering of molecular weight in the regions of resin close to the reinforced fibers in the skin layer, when a small amount of absorbed water and repeated stress coexist.

Mechanical investigation of fibre reinforced materials for superconducting poloidal field coil design

This Paper reports the results of flexural and shear measurements of fibre reinforced plastic materials. The materials tested were carbon fibre reinforced plastics (CFRP) and glass fibre reinforced plastics (GFRP). The objectives of the tests were to determine the mechanical properties of the industrially manufactured thick walled structures. The rectangular hollow section made of CFRP material produced has a wall thickness of ≈30 mm. The anisotropic characteristics of the flexural properties were determined at ambient temperature and at 77 K. In addition, pultruded GFRP complex shaped sections were measured with respect to their mechanical behaviour. Results on the thermal shrinkage measurements of CFRP- and GFRP-structures are also reported. An evaluation of the data and their impact on design were discussed under the consideration of superconducting poloidal field coil aspects.

Vibration and Damping Analysis of Fibre Reinforced Composite Material Cylindrical Shell

The vibration and damping analysis of a multilayered cylindrical shell consisting of an arbitrary number of orthotropic material layers developed by authors [1,2] has been ap plied to study the damping for axisymmetric vibrations of fibre reinforce composite material laminated shells. The analysis considers bending, extension and shear deforma tions in each of the layers and also includes rotary, longitudinal translatory and transverse inertias. The variations of the resonance frequency and the associated system loss factor for the axisymmetric vibrations of a six layered angle-ply carbon fibre reinforced plastic (CFRP) cylindrical shell with fibre orientation has been studied at various values of the shell length parameter. The system loss factors for axisymmetric vibrations of cross-ply laminated shells of GFRP, BFRP and CFRP materials are also reported.