Application Of Carbon Fiber Reinforced Polymer Research Articles

Research on chloride ion permeability resistance of concretes bonded with CFRP sheets under dry-wet cycles

Considering the widespread application of carbon fibre-reinforced polymer (CFRP) as a protective material for reinforced concrete (RC) structures, this study focuses on the ability of CFRP laminates with different numbers of layers bonded to the concrete surface to reduce the ingress of chloride ions. Variations in the free chloride concentration distribution in concrete before and after CFRP bonding were explored systematically. Nonlinear fitting was applied to the experimental data to establish a calculation model for the diffusion of free chloride ions in concrete with CFRP bonded to the surface, which was subsequently validated. Based on the proposed model, the reduction in the surface chloride concentration of concrete after bonding different numbers of CFRP layers was quantified as the reduction value. Moreover, recommendations for the durable design of RC structures bonded with CFRP in wet-dry cyclic environments are provided. The results indicate that the surface chloride concentration in concrete increases continuously with increasing wet-dry cycles, eventually reaching a steady state. Compared with the concrete specimens without CFRP bonding, the bonding of one, two, or three layers of CFRP led to reductions in the stable surface chloride concentration of concrete by 70.8%, 82.6%, and 84.9%, respectively. And no obvious convection zone was observed in the concrete after CFRP bonding. The validation results of the proposed calculation model demonstrated its high accuracy, making it suitable for durable design and service life prediction.

Experimental Investigation on the Rehabilitation of RC Flat Slabs Using CFRP Sheets to Enhance Punching Shear Capacity

In this paper, the feasibility of strengthening a flat column–slab connection within the carbon fiber reinforced polymer (CFRP) has been investigated through experimental study. The experimental program includes a set of nine reinforced concrete flat slab specimens. Three unaltered specimens served as control slabs, while an additional six samples were strengthened with various CFRP configurations to enhance their shear capacity. The strain distribution, ductility, punching shear resistance, stiffness, and crack formation were studied. The result of experimental studies showed that in the direct method of strengthening in which two layers of unidirectional CFRP sheets were employed in two opposite directions, the ultimate punching shear resistance improved by 64%, 44.7%, and 15.3%, with respect to the location of the column connection, as compared with the control specimens. In the case of using one layer of unidirectional CFRP strips, the punching shear resistance was enhanced by approximately 16% and 39%, considering the configuration of CFRP sheets and the amount of strengthened and adhesive layers used. Following the outcomes of this research, the application of CFRPs in improving the resistance capacity of flat slabs against the punching shear is considerable. The reported outcomes were compared with the latest provisions of ACI to show the efficiency of the presented strengthening. Finally, a parametric study was performed assuming different loading locations to assess the effect of the loading region on the response of RC slabs. Results indicate that approaching the loading location toward the RC slab supports results of an increase in the load-bearing capacity and a reduction in the ductility of the RC slab.

Induction Heating Characteristics of Electroless Ni-Coated CFRP for Deicing and Anti-Icing

Ice accumulation on the surface of aircraft is a serious threat to flight safety and a fatal factor causing air accidents. However, traditional aircraft deicing methods no longer meet the requirements of safe flight due to changes in aircraft structural materials. In recent years, the application of carbon fiber-reinforced polymer (CFRP) materials in the aviation structure industry has increased. In this study, we demonstrate an economical, easy-to-prepare, and pollution-free approach to deice an aircraft through induction heating. The nickel-coated carbon fiber-reinforced polymer used as the induction heater for aircraft deicing is obtained by electroless nickel plating on the surface of the CFRP. The result shows that it takes just 110 s to achieve a temperature of 205 °C on the nickel-plated CFRP when the input voltage is 30 V, as well as melting the ice layer with a thickness of 30 mm, while the temperature of this material can reach up to 81 °C by electric heating when the input voltage is 1.5 V. Meanwhile, the nickel-plated CFRP exhibits good repeatability during the induction heating. Based on the excellent electrothermal properties, the nickel-plated CFRP polymer shows a prominent deicing ability, which provides a promising strategy for the deicing of aircraft.

A study on effective rehabilitation method of shear buckling strength by CFRP in steel girder

To increase the shear strength of steel girders, several conventional methods and materials exist, such as bolting or welding of steel plates to the girder end area. However, recently Carbon Fiber Reinforced Polymer (CFRP) has been widely studied and used as an effective material for increasing the shear strength of the web plate in steel girder ends. However, the conventional approach of covering the entire web area with CFRP can be costly and excessively conservative. To efficiently increase shear buckling strength, this research aimed to determine the suitable area for CFRP coverage on the web plate along with the impact of CFRP application direction and the effect of attaching CFRP only to the web center. Through adopting an experimental approach, the study tested eight specimens, and the CFRP was applied in two distinct patterns to tension and compression directions. Furthermore, as for the CFRP coverage area, initially, the whole web area was covered with CFRP, and subsequently, the CFRP coverage area was parametrically reduced. The findings indicate that covering around 40% of the web area by CFRP can produce similar results as CFRP covering the whole web area. Additionally, it was found that the web and CFRP act as a unified composite section until the initiation of shear buckling, making the direction of CFRP application insignificant.

Fatigue performance improvement of U-rib butt-welded connections of steel bridge decks using externally bonded CFRP strips

U-rib butt-welded connections in steel bridge decks are known to be highly susceptible to fatigue cracking, which can pose a direct threat to the safety and durability of bridge structures. Carbon fiber-reinforced polymer (CFRP) materials have shown promising potential for fatigue strengthening. This study investigated the effectiveness of CFRP application on the fatigue performance of U-rib butt-welded connections by employing full-scale fatigue tests and finite element analysis. Two single U-rib specimens with welded splice joints were initially tested to initiate real fatigue cracks under cyclic loading. Different techniques of CFRP installation were then proposed to promote the fatigue performance of cracked butt-welded connections. The failure modes and fatigue strength of the tested specimens were evaluated before and after strengthening. Research results showed that fatigue cracks were observed at the arc transition of butt welds, where remarkable incomplete penetration was also discovered. The fatigue strength grade of the tested U-rib butt-welded details was less than 71 MPa stipulated by Eurocode 3. However, after being repaired by CFRP sheet bonding, the equivalent fatigue life of U-rib butt welds with different damage degrees can be extended by 0.5–16.6 times that of the original ones. These findings suggest that CFRP strengthening should be applied instantly on U-rib butt-welded connections once fatigue cracks are found.

Employing Carbon Fiber Reinforced Polymer Composites toward the Flexural Strengthening of Reinforced Concrete T-Beams.

Reinforced concrete structures are exposed to various loads under critical environmental conditions, which might lead to the deterioration of the structures prior to their designed service life. Hence, to improve the serviceability of the reinforced concrete (RC) structures and meet the design requirements, the structures are strengthened using carbon fiber reinforced polymer (CFRP) composites. The application of CFRP is done using two major techniques, namely externally bonded (EB) reinforcement and near surface mounted (NSM) techniques. The purpose of this study was to examine and compare the behavior of RC T-beams that had been flexurally reinforced utilizing EB and NSM techniques. Six full-size RC T-beams were evaluated, including a reference beam and four beams that had been flexurally reinforced using laminates made of EB and NSM CFRP. The findings of the experimental tests reveal that, when using the same quantity of CFRP, the beams strengthened with NSM laminates outperformed those strengthened with EB laminates in terms of ultimate load.

Understanding friction and wear properties of carbon fiber/epoxy stitched composites

Due to its low friction coefficient and wear rate, and good self-lubrication, carbon fiber reinforced polymer (CFRP) composite is used as friction material. The easy interlaminar delamination and low impact damage tolerance of conventional CFRP laminates lead the friction materials to wear seriously, which causes the early-stage failure. Here, carbon fiber/epoxy stitched composites were prepared by the resin transfer molding technology. Effects of load and stitch parameters on the friction and wear properties of stitched composites under dry conditions were investigated through experiment and simulation. The coefficients of friction (COFs) of composites increase linearly at the initial stage, and then decrease from a maximum peak to a relatively stable state value. Samples with a high stitch density and a small stitch spacing along the sliding direction has low COF values and wear rates. With the increase of the normal load, COFs and the wear rate both decrease first and then increase. The wear tracks on the surface of CF/EP stitched composites are generated by comprehensive effects of cutting, adhesive and fatigue wears. This study provides comprehensive characterization and deep understanding of friction and wear properties of carbon fiber/epoxy stitched composites, which will broaden the CFRP application as frication material.

Torsional strengthening using carbon fiber reinforced polymer of reinforced concrete beams subject to combined bending, shear and torsion

The results of an experimental investigation of six large scale rectangular reinforced concrete (RC) beams subject to different ratios of combined bending, shear, and torsion strengthened with externally-bonded carbon fiber reinforced polymer (CFRP) U-wraps are presented. All beams exhibited torsion-dominated behaviour. The presence of discrete CFRP U-wrap strips controlled the cracks well and the resulting torsional cracks were observed to be oriented at about 50°. Regardless of loading ratio, strengthened beams exhibited a 70% increase in torsional capacity. Before cracking, torsion to flexure ratio had a small effect on the flexural and torsional stiffness indicating that twist and deflection have a small counteracting effect on each other. Existing beam capacities were assessed using ACI 318-19 and GB 50010-2010 while CFRP strengthening was assessed based on fib Bulletin 14. Main findings are as follows: the ACI 318-19-predicted torsional capacity was conservative while GB 50010-2010 appeared to result in better capacity-prediction of unstrengthened RC beams. Even though load capacities derived from GB 50010-2010 are consistent with torsion-dominated behaviour, neither standard-based approach addresses the complete interaction of internal forces which is necessary to determine existing in situ strength for FRP strengthening applications. The fib Bulletin 14 approach to FRP strengthening for torsion was extrapolated to U-wraps and shown to overestimate the strengthening effect of the CFRP system applied. Critically, the assumed angle of inclination of torsional cracking was increased by the presence of the U-wraps, reducing the efficacy of the CFRP application.

Multi-impact performance of prestressed CFRP-strengthened RC beams using H-typed end anchors

To address the problem of insufficient ductility of traditional Carbon Fibre-reinforced polymer (CFRP) strengthened marine structures and to enhance the application of CFRP in marine engineering, the present study develops novel prestressed CFRP-strengthened RC beams using H-type end anchors with ductility controllable devices. In this device, part of the reinforcement bars are replaced by CFRP, which is prestressed as the structural enhancement material. The CFRP sheet is connected with a tensioned screw, which is used to realize the function of early warning based on a large plastic deformation when the structure is overloaded. Thus, the ductility of the composite structure could be improved based on yielding of the screw rod rather than the fracture failure of the CFRP sheet compared to that with CFRP bonded. This study investigates the flexural static and impact performance of the representative large-scale RC beams strengthened by prestressed CFRP through four-point bending and drop-weight impact. The results show that the H-typed end anchor and raising the prestress level of CFRP not only improve the ultimate resistance and ductility, but also realize the overload warning function under static load. Accordingly, the design still shows advantages in energy consumption and impact resistance through drop-weight impact. An advanced 3D nonlinear finite element model is built to simulate well the multiple impact performance in terms of the failure modes, impact force and displacement history. This study provides a new approach to address design deficiencies with insufficient ductility behaviour while using CFRP as a strengthening material. This prestressing technology is able to utilize the material efficiency of high-strength CFRP and open a new path for CFRP applications in marine civil engineering.

Non-ordinary state-based peridynamic fatigue modelling of composite laminates with arbitrary fibre orientation

For the safe application of carbon fibre-reinforced polymer (CFRP) materials in engineering structures, fatigue life prediction and failure modelling are essential. In this paper, an application of a nonordinary state-based peridynamics (NOSB-PD) approach for the fatigue failure prediction of multilayer CFRP was presented. To characterize the structure of composite laminates, matrix and fibre bonds were introduced within the plies, and normal and shear bonds were introduced between the plies. The fatigue simulation model of composite materials was established by combining the fatigue theory of peridynamics and Paris-Erdogan law, and a method to obtain model parameters was proposed. To demonstrate the accuracy of the model, tension and fatigue experiments were conducted. By comparing the results of tensile and fatigue experiments, it was shown that the model developed in this paper can accurately predict the failure process of multidirectional CFRP laminate under the action of tensile or fatigue loading. The crack initiation and propagation for different laminae during the tensile and fatigue processes can be obtained from the proposed model.

Life-Cycle Cost Analysis of Long-Span CFRP Cable-Stayed Bridges

With the advantages of high strength, light weight, high corrosion and fatigue resistance, and low relaxation, carbon-fiber-reinforced polymer (CFRP) is an excellent cable material for cable-stayed bridges. However, the relatively high unit price of CFRP compared to that of steel may hinder the large-scale application of CFRP stay cables. This paper presents the economic comparison between long-span cable-stayed bridges using CFRP cables and the corresponding steel cable-stayed bridges through life-cycle cost analysis (LCCA). Three CFRP cable-stayed bridges with a main span of 600 m, 1200 m, and 1800 m, respectively, along with their steel counterparts, were designed, and their life-cycle costs (LCCs) were calculated. The comparison of LCCs was not only between the CFRP and steel cable-stayed bridges with the same span, but also between the cable-stayed bridges with different spans. Furthermore, the different unit prices of CFRP cables and different replacement frequencies of steel cables were also investigated. The results show that the initial design and construction cost of the long-span CFRP cable-stayed bridge is higher than that of the corresponding steel cable-stayed bridge, although using CFRP cables can reduce the materials used, primarily due to the higher unit price of the CFRP cable. Despite the higher initial cost, the long-span CFRP cable-stayed bridge can still achieve lower LCC than the steel cable-stayed bridge, because it has significantly lower rehabilitation cost and user cost, as well as slightly lower vulnerability cost. Furthermore, with the increase in the main span and the decrease in the unit price of CFRP cables, the LCC advantage of the long-span CFRP cable-stayed bridge becomes more obvious.

Evaluation of Mechanical Properties and Pyrolysis Products of Carbon Fibers Recycled by Microwave Pyrolysis

Disposal of the waste from carbon fiber reinforced polymers (CFRPs) has become an urgent problem due to the increasing application of CFRPs in many industries. A novel method for the rapid recovery of carbon fibers by a microwave pyrolysis and oxidation process was proposed in this study. The resin matrix was rapidly pyrolyzed by heating CFRPs directly with microwave radiation, and then the residual carbon and organic matter on the surface of carbon fibers were removed by oxidation to obtain recycled carbon fibers (RCFs). The recovery rate of recycled carbon fibers was measured, and their mechanical properties were evaluated by tensile strength and tensile modulus tests. The results showed that, after microwave pyrolysis at 500 °C for 15 min and oxidation at 550 °C for 30 min, the maximum tensile strength of RCFs was 3042.90 MPa (about 99.42% of that of virgin carbon fibers), the tensile modulus was 239.39 GPa, and the recovery rate was about 96.5%. The microstructure and chemical composition of RCFs were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, and the components of the pyrolysis byproducts were detected by gas chromatography–mass spectrometry. These results indicate that this method is suitable for the effective recovery of high-quality carbon fibers from CFRPs.

Fatigue Performance of CFRP-Strengthened Rib-to-Diaphragm Welded Details of Orthotropic Steel Decks: Experimental and Numerical Evaluation

Rib-to-diaphragm welded details of orthotropic steel decks (OSDs) are susceptible to fatigue cracking. To deal with such cracking problem, a strengthening method using externally bonded carbon fiber-reinforced polymer (CFRP) plates was investigated by fatigue experiment and numerical evaluation. A full-scale OSD specimen with two ribs and two diaphragms was tested to evaluate fatigue cracking behavior, as well as the stress before and after strengthening. An experimentally validated numerical model was established to confirm the optimal opportunity for CFRP strengthening. The influence of different CFRP strengthening measures were then discussed on the stress intensity factors at crack tips. It was shown that bonding of CFRP plates can significantly reduce stress of rib-to-diaphragm welded details. The best opportunity for CFRP strengthening is selected as the length of crack reaches at 25.00 mm where the amplitude of stress intensity factor is the smallest. The attachment of CFRP plates by bonding on the surface of cracked plates can reduce stress response at cracked region by more than 30%. The length of crack is of no flat growth until the total number of loading cycle after strengthening arrived at 0.8 million. Results of SIFs calculated by numerical model dropes after strengthening with reduction rate more than 35% and 18% at two crack tips and crack midpoint, respectively. Compared to the geometric dimensions of CFRP, the elastic modulus of CFRP and glue layer shows more significant influence on the fatigue performance of Rib-to-diaphragm welded details due to their stronger restraint to the propagation of crack peaks. This study provided a technical reference to the design and actual application of CFRP in the strengthening of welded details in OSDs.

Structural Behavior of Large-Scale Hollow Section RC Beams and Strength Enhancement Using Carbon Fiber Reinforced Polymer (CFRP) Composites.

An experimental program was conducted to ascertain the efficiency of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the flexural response of hollow section reinforced concrete (RC) beams. Nine beams were tested under four-point bending in three groups. Beams were categorized to reflect the presence or configuration of the CFRP sheet. Each group consisted of three beams: one with a solid section, one with a square mm × mm opening and 1 with mm × mm opening. Beams in 1st group were tested in as-built conditions. Beams in the 2nd group were strengthened with a single CFRP sheet bonded to their bottom sides. Configuration of CFRP sheet was altered to U-shape applied to the tension side of 3rd group beams. The inclusion of openings, regardless of their size, did not result in degradation of ultimate load and corresponding deflections. However, cracking loads were found to decline as the opening size increased. Regardless of the opening size and CFRP configuration, ultimate loads of beams increased with the application of CFRP. However, this improvement was limited to the debonding and rupture of CFRP in group 2 and 3 beams, respectively. A comparison in the behavior of group 2 and 3 beams revealed that the application of the U-shape CFRP sheet yielded better flexural performance in comparison with the flat-CFRP sheet bonded to the bottom of beams. In the end, In order to further evaluate the economic and performance benefits of these beams, the cost-benefit analysis was also performed. The analysis showed that the feasibility of the hollow section RC beams is more than the solid section RC beams.

The effect of different levels of pre-damage loading on the strength and structural behavior of CFRP strengthened R.C. beams: Experimental and analytical investigation.

In order to investigate the effect of pre-loading damage on the structural performance of Carbon Fiber Reinforced Polymer (CFRP) strengthened Reinforced Concrete (R.C.) beams, experimental and Finite Element Modelling (FEM) investigation was carried out on six R.C. beams. Five of the R.C. beams were damaged up to different levels of strain in the main steel bars before Flexure CFRP strengthening. One of the R.C. beams loaded up to failure and was kept as a control beam for comparison. The experimental results showed that the failure mode of the CFRP strengthened specimen was controlled by CFRP debonding followed by concrete crushing; however, the control beam failed in concrete crushing after yielding the steel bars, which is a ductile failure. The CFRP sheet increases the strength and initial stiffness of the R.C. beams and reduces ductility and toughness. Also, CFRP application increases the first crack and yielding steel bars load by 87.4% and 34.4%, respectively. Furthermore, the pre-damage level does not influence the strength and ductility of the strengthened R.C. beams except for the highest damage levels, which experienced a slight decrease in load capacity and ductility. However, the initial stiffness decreases with increasing pre-damage levels by 40%.Design guideline ACI 440.2R (2004) predicts the ultimate load capacity marvelously for externally bonded Fiber-Reinforced Polymer (FRP) beams compared to the experimental maximum load capacity. The excellent agreement between experimental and FEM results indicates that the constitutive models used for concrete and reinforcement and the cohesive interface model can well capture fracture behavior. However, The FEM analysis predicts the beam to be slightly stiffer and more robust, probably because of the assumed perfect bond between concrete and reinforcement. The developed FEM can be used for further parametric study.

An experimental study of impulse-current-induced mechanical effects on laminated carbon fibre-reinforced polymer composites

Lightning strike damage has become a primary issue limiting the extensive application of carbon fibre-reinforced polymer (CFRP) composites in the aerospace field. A detailed understanding of the physical interactions involved in the lightning strike process is still lacking, especially regarding the lightning-induced mechanical effects that potentially contribute to fracture and ply delamination in CFRP structures. This paper presents research on shock wave pressure induced by impulse currents on CFRP laminates. A novel method that exploits a polyvinylidene fluoride (PVDF) piezoelectric sensor was developed to directly measure the pressure induced by arc channel expansion. The influences of discharge polarity, strike distance and surface condition on the shock wave pressure were investigated. The results showed that the shock wave pressure produced by negative discharge was greater than that produced by positive discharge, the difference between which was reasonably explained based on the polarity effect concept. Increases in current amplitude and strike distance both contributed to larger measured pressures. A woven copper mesh protection could diminish the shock wave pressure to some extent, while an additional insulating epoxy resin layer enhanced it. Analysis results demonstrated that the pressure imposed on the laminated samples was related to the energy injected into the arc channel. In addition, the energy consumed by vaporized materials at the interface between the arc root and sample was defined as another source of shock wave pressure. The presence of an insulating layer confined the diffusion of the plasma channel at the arc root, as confirmed by high-speed imaging observations.

CFRP for strengthening and repairing reinforced concrete: a review

Carbon fibre-reinforced polymer (CFRP) is an emerging reinforcement in concrete materials and possesses many attractive mechanical and physical characteristics. Amongst other mechanical properties, CFRP has good compressive, flexural and shear strengths, and its usage improved ductility and suitability for preventing cracks. Thus, the application of CFRP is increasing in the construction industry. This review work highlights the effect of CFRP reinforcement on mechanical properties of reinforced concrete (RC) and self-compacting concrete (SCC) members. The scope of this review work is to highlight the effect on strengthening and repairing of RC members and SCC reinforced with CFRP material. A variety of research work has been reviewed on the use of CFRP in RC members, but the data remain limited yet. Thus, the critical review has been conducted from last 2-decades research on CFRP reinforcement in RC and SCC, and almost 60 researches and review articles have been involved in this discussion. The reviewed articles indicated that CFRP reinforcement can be suitable for the strength enhancement of RC members considering the strength-to-weight ratio despite its failure to produce more strength than steel reinforcement. Furthermore, CFRP is a good choice for repairing RC members due to its easy installation and other characteristic values. Therefore, CFRP reinforcement, which offers resistance to cracking, corrosion and temperature, is the best choice for concrete production.

Strengthening of elevated home slabs on grade with external fiber-reinforced polymer (FRP) laminate

Concrete slab on grade homes are being increasingly elevated above the base flood elevation for mitigation of coastal and inland flooding. This is typically accomplished through placing additional beam and pier supports under a raised slab home. In this process, the slab support conditions are changed from uniform soil support to beam supports. This may lead to unanticipated stress/strain changes, concrete cracks and slab failure. This paper presents a numerical parametric study of such elevated slabs with non-linear finite element approach. The models were calibrated with data obtained from full-scale testing of two concrete slabs under uniform floor load, one of which was retrofitted with external carbon fiber reinforced polymer (CFRP) laminates at critical locations. The slabs were supported by typical wide-flange steel beams over hollow square concrete block masonry piers. The results showed that typical elevated slabs can behave in a brittle manner with low ductility and sudden explosive collapse. A single layer of a uniaxial CFRP application at the negative moment locations increased the floor load capacity by about 30% and more than three times the minimum building code specified live load. Increased beam spacing and lower slab thickness decreased the slab load capacity, as expected.

Buckling Behavior of Sulfate-Corroded Thin-Walled Cylindrical Steel Shells Reinforced with CFRP

In this study, the buckling behavior of thin-walled cylindrical tanks exposed to sulfuric acid corrosion was investigated, and the buckling performance losses were recovered by reinforcing with Carbon fiber reinforced polymer (CFRP). Experiments were planned for three groups: Control samples without corrosion, full CFRP models and variable CFRP application group. The experiments were performed with 12 models of 800 × 400 × 0.45-mm dimensions. The prepared solutions were applied to the sealed test models as full and ½-filled and then exposed to sulfuric acid solution for 24 h, after which the experiments were performed. The mass losses were determined from the weights of the cylindrical samples, which were discharged after 24 h. After the corrosion, CFRP was applied to the cylinder, at ½ height of the cylinder and at 10 cm from its midpoint. The prepared model samples were placed in the test apparatus and sealed. In the experiments, vacuum was made using the vacuum pump, and data were recorded using the load cell. Deformations were measured by strain gauges and LVDT and transferred to the computer using a data collection device (datalogger). After data collection, vacuum-displacement plots were made. We aimed to recover a material that has undergone acid corrosion. The main goal of this work is to use the theoretical model, which is evaluated for limited geometrical ratios and for the perfect models, for the prediction of buckling behavior of sulfuric acid corroded thin-walled steel shells. We observed that the samples exposed to corrosion recovered 20–60% of their lost strength by CFRP application.

Optimized selection of process parameters based on reasonable control of axial force and hole-exit temperature in drilling of CFRP

Drilling is a key link of manufacturing carbon fiber-reinforced polymer (CFRP) components. However, due to CFRP’s anisotropy and heterogeneity, effects of drilling induced axial force and hole-exit temperature are much more complicated than conventional metals, which always results in undesirable surface damages at hole exit hindering the engineering application of CFRP. Since the axial force and the hole-exit temperature are highly correlated to process parameters in drilling of CFRP, for effectively overcoming such difficulties, this study focuses on optimized selection of process parameters. The suitable ranges of the axial force and the hole-exit temperature are figured out, upon the specific analysis on the combined effects of the axial force and the hole-exit temperature on the formation of hole-exit surface damages. With that, through establishing the relations between the axial force, the hole-exit temperature, and the drilling parameters, the optimized drilling parameters are finally given. By experimental verifications, it is found that the optimized drilling parameters can control the axial force and the hole-exit temperature within the suitable ranges, and thereby effectively suppress the hole-exit surface damages in drilling of CFRP. The findings of this study will be helpful to further improve the drilling qualities of CFRP.