CFRP Materials Research Articles

Tensile and flexural behavior of metal/CFRP hybrid laminated plates

AbstractMetal/CFRP hybrid material system has been recently introduced as an effective alternative for automotive applications. This study aimed to investigate tensile responses and flexural behaviors of aluminum/carbon fiber reinforced plastic (CFRP) hybrid laminated plates by comparing with their counterparts made of net CFRP or aluminum materials. The experimental results showed that for the hybrid specimens the tensile strength increased and the tensile modulus decreased with increasing number of CFRP layers. Further, it was found that the bending indicators of the hybrid specimens were in between those of pure CFRP specimen and pure aluminum specimen. With the increasing number of CFRP layers, a reduction in flexural modulus could be observed in the hybrid specimens, while the flexural strength increased. A parametric study was further conducted numerically and it was found that tensile modulus was less influenced by the fiber stacking sequences when the number of 45° CFRP layers was the same, and both tensile modulus and tensile strength decreased with increasing number of 45° CFRP layers. Type II hybrid specimen, fabricated by upper and lower CFRP plates sandwiched with aluminum core, showed the lowest flexural modulus but the highest flexural strength. When the configurational scheme changed from symmetric distribution (type II) into Type I (fabricated by upper CFRP plate and lower aluminum sheet) or Type III (fabricated by upper aluminum sheet and lower CFRP plate), flexural modulus increased but flexural strength decreased. As for the Type II hybrid specimens, the flexural modulus decreased with increasing number of 45° CFRP layers.

Application of Carbon fiber-reinforced plastic composite material in automotive bumper

The emission problem of these traditional gasoline vehicles has become more and more serious. To reduce emission, an important method is to reduce the weight of the car. In this study, a standard model of a vehicle bumper is used to conduct the experiment on lightweight bumper design. The material simulated in the model of the bumper is CFRP material. The angle of each laminate of CFRP material and the layout of the laminate structure contains six layers are modeled in Hypermesh software. Then CFRO material is used to replace the traditional aluminum and reduce the weight of the front bumper component.

Using laminate hybridisation (CFRP-GFRP) and shaped CFRP plies to increase plate post-buckling strain to failure under shear loading

Previous works have established the response and failure behaviour of hybrid (CFRP-GFRP) laminates when subjected to a wide range of destabilising loads. However, to date no works have quantified the influence of selective laminate shapes and hybridisation on plate post-buckling strain to failure. Thus, this paper investigates the plate collapse behaviour of a novel X-braced hybrid (CFRP-GFRP) twill woven laminate, subjected to in-plane shear loading. An experimental and numerical investigation is undertaken, including the consideration of a baseline pure CFRP laminate design. The experimental results illustrate that despite having less CFRP material, a hybrid laminate design with shaped CFRP plies can exhibit a greater strain to failure and buckling to failure load ratio, with only a marginally lower initial plate buckling load. Additionally, the experimental and numerical analysis reveals that the failure mechanism of the hybrid laminate is dominated by shear damage and fibre compressive breakage, whereas compressive and tensile fibre breakage dominate the conventional baseline laminate behaviour. Due to the prevalence of the shear damage and hence cracking and plastic deformation of the matrix, the novel hybrid laminate demonstrates a more gradual failure than the standard baseline laminate design, with failure strains significantly higher than that of the baseline laminate design.

Progressive failure of CFRP tubes reinforced with composite sandwich panels: Numerical analysis and energy absorption

This study investigates a novel CFRP tube by reinforced with composite sandwich panels (CSPs) for enhanced energy absorption. First, CSP-reinforced CFRP tubes with the ply sequence [03/902/03/(0/90)] were manufactured via bottom confinement using epoxy adhesives and then subjected to a 2 mm/min quasi-static compression. Then, numerical models were developed, based on the continuum damage mechanic for intralaminar failure and the cohesive zone method for interlaminar damage of CFRP materials with an elastic–plastic model for honeycombs, to predict the progressive failure of the composite tubes. Finally, the numerical results were validated with experimental study of tubes’ energy absorption and failure mechanisms. The experiments showed that the total energy absorption and crushing force efficiency of the CSP-reinforced CFRP tubes were 37% and 24% greater, respectively, than those of unreinforced CFRP tubes, although the corresponding specific energy absorption exhibited a slight decrease of 1%, demonstrating an overall improvement in energy absorption of the proposed composite tube. Moreover, the presented numerical models exhibited the primary damage behaviours and were used to evaluate the crushing performance of these composite tubes as validated by the experimental results, providing a new available approach for predicting the progressive failure of composites with different layer types (i.e. unidirectional, woven) and composite structures with complex constituents (laminate, honeycomb). Lastly, an efficient predictive approach was developed for designing CSP-CFRP tubes for engineering energy-absorption applications.

Study on kerf characteristics and surface integrity based on physical energy model during abrasive waterjet cutting of thick CFRP laminates

Abrasive waterjet machining was an effective method for cutting CFRP materials in various industries, while machining defects are inevitably observed especially for thick CFRP laminates due to the inherent characteristics of waterjet. In this work, a full factorial experimental array was employed totally involving 18 trials when using abrasive waterjet to cut CFRP laminate up to 10.0 mm thick. The influence of process parameters including hydraulic pressure, traverse speed, and stand-off distance on jet energy was deeply analyzed and the power-to-speed ratio (Ė/u) parameter was obtained, which was combined with the physical energy model of abrasive waterjet based on the energy method. The influence of process parameters on kerf characteristics/surface integrity and the mechanism of defects were further analyzed. Various surface defects along thickness direction were observed and corresponding mechanisms were investigated. Results showed that higher hydraulic pressure, lower traverse speed, and stand-off distance within in the selected range were preferred to obtain better surface quality. From the perspective of power-to-speed ratio (Ė/u), the surface roughness decreased rapidly up to ~ 68% with Ė/u increased from 20,000 to 40,000 J/m. When it exceeded 40,000 J/m, the downward trend gradually reduced and even became stable in the case of high stand-off distance. The level of kerf width generally increased with the increase of Ė/u irrespective of stand-off distance.

Experimental research on ultrasonic vibration countersinking process of CFRP composite laminates

Hole machining is a common operation during manufacturing of CFRP products. However, delamination, matrix chipping, and fiber pull-out easily take place in the machining of CFRP materials. Compared to straight through holes, tapered countersink holes are more difficult to be machined. In this paper, an ultrasonic vibration device was developed. The vibration performance of it was tested, and hole drilling experiments with the developed device are implemented, and the quality of holes is analyzed. The developed device produces 24.84 KHz vibrations on drill bit, and the vibration amplitudes at the drill edge and step edge are 2.62 um and 1.34 um, respectively. With the ultrasonic vibration drilling method, the average thrust drilling forces are reduced 8–21.5%, and the hole quality is improved significantly. This study provides a potential device and technique for countersinking of CFRP composite laminates.

Influence of different cooling strategies on the process temperatures and chip transport quality in one-shot drilling CFRP/Al-stacks

This study focusses on the influence of different cooling strategies on process temperatures and chip transport quality in one-shot drilling CFRP/Al-stacks. In addition to the maximum temperatures in both individual stack components, temperature changes in the CFRP material due to hot aluminium chip interactions are analysed. The following cooling strategies are compared: compressed air through the drilling tool, cryogenic CO2 cooling at the aluminium bore exit as well as the combination of both. It is shown that process temperatures and chip transport quality significantly differ for the tested cooling strategies. Whereas CO2-cooling of the Al-plate results in overall smaller chips, the use of compressed air mainly improves chip evacuation. The combination of both cooling strategies shows high potential to prevent clogging in the chip flute as well as its negative impacts on workpiece quality.

Fatigue Damage Monitoring of CFRP Elements by Thermographic Procedure under Bending Loads

For structural health of mechanical structures, non-destructive detection and material defect characterization represent the main useful tools for mechanical decay prediction caused by local composite damage phenomena. In this work, internal delamination due to alternate bending were characterized in flat specimens, performing fatigue and static tests, coupled with thermographic, optical, and ultrasonic analysis for damage detection and evolution purposes. Damage to rupture behavior of CFRP material through mechanical tensile tests is performed on several samples and non-destructive inspection procedures are optimized during successive HCF tests to detect in real time local compliance variations and damage initiation. Thermographic continuous monitoring and occasional ultrasonic analysis are implemented to analyze composite anomalies during fatigue life and to elaborate a procedure for identification of delamination induced damage before failure. IRT and UT results are computed with MATLAB analysis for damage evaluation with strain and compliance data acquired during tests.

A meso-mechanical material model describing a crash behavior of 2D plain weave fabric composites

In composite aircraft structures, woven carbon-fiber-reinforced composites are used as elements of the boxes to mitigate damage during crash events and provide a measure of protection for the passengers against abrupt decelerations. Due to their multi-scale damage effects and complex coupling between failure mechanisms, despite years of extensive works of researchers around the world, a complete and validated methodology for predicting crushing behavior of woven composite structures has not yet been achieved. In the present paper, experimental and numerical investigations were conducted. The principal contribution is to model and adapt failure mechanisms; fragmentation and kink-bandings, for plain weave fabric CFRP composites, within an advanced numerical model to predict the quasi-static crush behavior of hat-shape cross-section coupons. A meso-scale model, which accounts for intralaminar damage, implemented as a user subroutine VUMAT in Abaqus/Explicit was developed and used. Eight layers of stacked solid elements model were used with saw teeth type and 45° chamfer-type triggering mechanisms to ensure a continuous stable crushing mode of failure. A comparison with experimental and existing numerical model Abq_Ply_Fabric results confirms the computational tool’s accuracy.

Experimental investigation for the determination of material properties of a composite laminate using resin and DIC techniques

Abstract The industrial applications of composite materials have significantly increased during the past few years. This trend is mainly due to the fact that composite materials have excellent properties, which are very different from conventional isotropic materials. Composite materials have high strength-weight, high stiffness-weight ratio and are corrosion resistant, thermally stable and are well suited for structures in which the weight is a fundamental variable in the design process. It has been found from experiments that there is no immediate effect of spray paint on the resin system of the CFRP material as there is no variation with Material Property between tested coupons without paint and tested coupons with paint. It is concluded that Digital Image Correlation Technique (DIC) a viable and feasible technique of whole field strain measurements on the composite materials.

Effectiveness of Hybrid and Partially Confined Concrete Subjected to Axial Compressive Loading Using CFRP and GFRP Composite Materials

Abstract This paper presents the results of an experimental study that investigates the compression behavior of concrete and evaluates the effect of hybrid reinforcement by multiple geometries, and total and partial confinement, using CFRP and GFRP composite materials. A total of nine (09) variants of concrete cylindrical specimens, including one (01) variant of unconfined concrete and eight (08) variants of confined concrete with different geometries were subjected to axial load compression. The objectives of this study were to verify the applicability and effectiveness of partial and total confinement to improve the behavior of concrete, evaluate the effect of the hybrid confinement used, and obtain a typical reinforced model. The results obtained clearly show the effectiveness of the hybrid confinement and partially confined concrete in improving the compressive strength and deformation of the concrete, so it is possible to replace CFRP total confinement by partially confined concrete with two CFRP layers or by a hybrid confinement with a CFRP layer in the central zone and GFRP layers on the top and bottom of the specimen.

Behaviour of RC beams strengthened with FRP strips under combined action of torsion and bending

Many researchers worldwide have extensively used fibre-reinforced polymer (FRP) strengthening materials to enhance the shear and flexural strengths of reinforced concrete (RC) beams. However, Studies on strengthening of RC beam subjected to combined torsion and bending moment using both spiral and vertical strip configuration of CFRP that explored in this study is rare. This study aims to demonstrate the behaviour of RC beams strengthened with FRP sheets (strips) with different configurations and subjected to combined actions of torsion and bending moment. Eight beams with a dimension of 15 × 25 × 200 cm were cast. One of the beams was not strengthened, but the others were strengthened with carbon FRP. The angle of twist at torque intervals, first cracking torque, ultimate torque and ultimate twist angle of the conventional and strengthened beams during the testing process were compared. Results showed a significant improvement in the torsional performance of RC beams using carbon FRP. The fully wrapped beams performed better than the beams with strip wrapping due to the influence of various wrapping configurations. Amongst the wrapping configurations of FRP fabrics, the 45° spiral strip wrapping configuration was the most effective for RC beam strengthening in terms of torsion resistance. Highlights Reinforced concrete (RC) beams strengthened with fiber reinforced polymer composite were tested under combined bending and torsional moment; The effect of composite orientation, spacing and number of plies on the torsional response; Ultimate torsional moments of RC beams; Twist angle of rotation of control and strengthened beams; Analytical prediction for CFRP material contributions to the ultimate torsional moment of strengthened RC beam.

Practicalities of BVID detection on aerospace-grade CFRP materials with optical fibre sensors

Several reports have recently shown the capability of optical fibre sensors for the detection of barely visible impact damage (BVID) on CFRP laminates, based on changes in the optical signal before and after impact. Although this approach was shown to work well in lab conditions, little attention has been paid so far to its practicality when considering realistic ambient conditions or to the detection range. In this work we attempt to derive BVID detection thresholds for fibre Bragg grating-based sensors, by considering standardized temperature and vibration levels for aerospace applications. To the best of our knowledge this is the first practical threshold assessment for BVID detection on aerospace-grade CFRP for such sensors. We have put our detection thresholds to the test by analysing a total of 24 BVIDs on 12 panels made from 4 different CFRP material systems and derived commendable sizes for the detection range on the different material systems.

Nonlinear Finite Element Analysis of RCMD Beams with Large Circular Opening Strengthened with CFRP Material

This paper presents the non-linear finite element method to study the behavior of four reinforced rectangular concrete MD beams with web circular openings tested under two-point load. The numerical finite elements methods have been used in a much more practical way to achieve approximate solutions for more complex problems. The ABAQUS /CAE is chosen to explore the behavior of MD beams. This paper also studies, the effect of both size and shape of the circular apertures of MD beams. The strengthening technique that used in this paper is externally strengthening using CFRP around the opening in the MD beams. The numerical results were compared to the experimental results in terms of ultimate load failure and displacement. The FE results showed a good agreement with experimental results.

Cyclic Behavior of CFRP as Diagonal Ties and Anchors to Rehabilitate Severe Damaged Masonry Wall

Seismic rehabilitation using Carbon Fiber Reinforcement Polymer CFRP is more often used worldwide. CFRP jacketing is the most common layout for columns and walls, however installing the CFRP sheet as diagonal ties increase shear capacity to walls instead of jacketing procedures, besides less CFRP materials is used reducing the cost to the retrofit work. It is know that CFRP sheets can be debonded from the concrete or masonry surface causing that the sheets will not develop its tensile capacity. Then CFRP anchors are introduced. It is presented the behavior of CFRP sheets as diagonal ties working even though sliding and CFRP anchors which attach the diagonal ties to concrete base and top of the masonry wall. The diagonal ties work at full tensile capacity even though the debonding and buckling presented under compression forces. CFRP anchors also provided a resistance capacity against sliding.

Experimental investigation and finite-element modeling of the crushing response of hat shape open section composite

In crash event, aerospace structures are designed to collapse progressively, dissipating high kinetic energy and protecting the passengers against abrupt decelerations. To achieve this goal, a better comprehension of crash failure mechanisms is necessary to improve traditional crash structures by designing and optimizing new energy absorbers. In this paper, the elementary failure mechanisms involved in crushing of open section coupons are investigated; damage initiation and evolution, and absorbed energy of plain weave fabric CFRP Hat-Shape cross section specimens have been studied under quasi-static crushing load. Numerical simulations have been performed by using twelve layers of stacked-shell models with two heights (100-150mm) and two triggers (steeple, chamfer45°), Abq_Ply_Fabric material model embedded in Abaqus/Explicit results was used and compared against experimental data. and good agreement has been found. As results, Coupons with 100mm height and chamfer45° trigger dissipates more energy than coupons with 150mm height and steeple trigger.

Failure behavior of scarf-bonded woven fabric CFRP laminates

We report on the mechanical analysis of scarf-bonded woven fabric CFRP laminates. The study focuses on the effect of the scarf angle on the failure behavior of the repaired composite structures. Composite panel manufacturing was based on twill carbon/epoxy prepregs and followed standardized lay-up and curing procedures. We tensile tested scarf-bonded specimens with scarf angles of 1.9°, 2.8°, and 5.7°. The results show that the tensile strength decreases with increasing scarf angle. There are mainly three types of failure, depending on the scarf angle. The failure type is predominantly cohesive for 5.7°, fiber failure for 1.9°, and a mixture of these for 2.8°. Finite element analysis through cohesive zone modeling accurately predicts the experimentally observed response and provides further insight into the failure behavior. Stress concentration distribution over the bonding area plays an important role in the failure type of the repaired specimens. An additional investigation on the effects of adhesive defects showed that a defect fraction of 10% over the bond area can reduce the strength by almost 20%.

Acoustic Emission Testing of Early Generation of Defects in CFRP Samples under Static and Thermal Loading

Static tests of the samples of Torayca T700, T800 carbon fiber reinforced plastics consisting of nine monolayers with $$\left[ { \pm 45{\text{/}}90{\text{/}}{{0}_{3}}{\text{/}}90{\text{/}} \pm 45} \right]$$ stacking and geometric dimensions $$600 \times 100 \times 0.9$$ mm and $$500 \times 100 \times 1.4$$ mm were carried out. In the process of static and thermal loading, defects were monitored by the acoustic emission (AE) method. Two samples were statically loaded and simultaneously exposed to temperature $$T = 100$$ °C. Six samples were statically loaded at temperature $$T = 20$$ °C. The sources of AE signals corresponding to sample material destruction were localized in real time. For these signals, thin polished sections were prepared from location zones in the sample, and the fractography of the CFRP material was carried out. The analysis of the recorded AE information has been carried out. The main informative parameters of the AE signals localized in the working area of the samples are considered. Using cluster analysis by digital waveform, three types of clusters are identified for the AE signals. For the first type of clusters, the frequency of AE signals exceeded 175 kHz, and a relatively high level of the MARSE energy parameter was noted. In clusters of the second type, AE signals recorded under static loading and sample heating had lower MARSE values and a median frequency not exceeding 170 kHz. When testing samples with no heating, the median frequency did not exceed 140 kHz. The third type of clusters was formed by AE signals with the frequency not exceeding 400 kHz. Such clusters were typical only for samples tested at temperature $$T = 20$$ °C.

Study on the Electrochemical Properties in 5wt% NaCl Automotive Salt Test Conditions on the CFRP Materials with Different Surface Roughness

Study on the Electrochemical Properties in 5wt% NaCl Automotive Salt Test Conditions on the CFRP Materials with Different Surface Roughness

Effect of Delamination in Carbon Fibre Reinforced Polymer during Abrasive Water Jet Machining

Delamination is a type of defect produced while machining composites or layered materials. Due to matrix crack, shear crack and bending crack delamination is caused. Delamination is usually a separation along a plane parallel to the surface as in the separation of a coating from a substrate or layers of coating from each other. The aim of this project is to explore the study of delamination in carbon Fibre/epoxy composites under abrasive water jet machining. An experimental investigation was held to study the effect of delamination due to abrasive water jet machining on carbon fibre reinforced polymer. Effect of various parameters such as transverse speed, standoff distance, abrasive mass flow rate and water pressure was analysed. Taguchi method was used for overall analysis of parameters. Effect of Kerf width in CFRP material and on fibre cut was analysed step by step. Further observation was done on scanning electron microscopes. It can affect the compression strength of composite laminate and it will slowly cause the composite to experience failure through the buckling. Here the composite of Carbon Fibre Reinforced Polymer is made using carbon fibers and epoxy resin. Further cutting of CFRP is done using Abrasive water jet machining and analysis of delamination at various phases of the material is done. Analysis is done at which parameters delamination is reduced to minimum.