Carbon Fiber-reinforced Epoxy Matrix Composites Research Articles

Effect of solution-blown nanofibrous web on quasi-static punch shear test results and quasi-static indentation behavior of carbon fiber-reinforced epoxy matrix composites

This study investigated the effects of the nanofiber interlayer in carbon fiber-reinforced epoxy matrix composites on quasi-static loading behaviors such as quasi-static punch shear (QS-PST), quasi-static indentation (QSI), and short-beam shear (SBS) loading. The solution-blowing technique was used to produce polyamide-6 (PA6) nanofiber with 1 g/m2 areal density. A 2×2 twill weave carbon fiber fabric with an areal density of 200 g/m2 was covered with solution-blown nanofibers. The vacuum-assisted resin transfer molding (VARTM) method was used to manufacture nanofiber interlayered composites and non-interlayered composites. QS-PS experiments were conducted at three different span to punch ratios (SPR), namely 1.1, 2, and 4. The PA6 nanofiber had a synergetic effect on the composite structure. In the QS-PST experiments, it increased the amount of work achieved by the specimen at rates of 29.5%, 13.5%, and 5.66% for SPR 1.1, 2, and 4, respectively while it provided increases in the maximum force at rates of 15.3%, 15%, and 5.7%, respectively. Additionally, the PA6 nanofiber contributed to the composite material properties determined based on the QSI test including the maximum force, punch crush strength, crush stiffness, and through-thickness modulus at rates of 7.5%, 7.56%, 2.72%, and 5.76%, respectively. Finally, an increase at a rate of 11.43% was determined in the SBS strength of the nanofiber interlayered composite, while it showed an increase in maximum force observed during the SBS experiment at a rate of 12.28%. The enhancements of mechanical properties of structural composites make them more reliable for high technology applications like aerospace, and automotive.

Seawater Effects on Thermally Aged Ambient Cured Carbon/Epoxy Composites: Moisture Kinetics and Uptake Characteristics.

Carbon fiber-reinforced epoxy matrix composites using ambient- and moderate-temperature curing non-autoclave processes have broad applicability in marine, offshore, and naval applications. This research focuses on the characterization of moisture kinetics of ambient cured carbon/epoxy composites subject to immersion in seawater for up to 72 weeks after prior periods of extended thermal aging. A two-stage model is shown to best describe the overall kinetics and response. The level of maximum moisture uptake shows an increasing trend with the temperature and time of prior thermal aging, reaching asymptotic levels at the highest levels. The transition point is seen to represent a shift between the diffusion and relaxation-/deterioration-based dominant regimes, and the ratio of uptake at the transition point to the maximum uptake can be correlated to the relaxation coefficient. Diffusivity, as expected, generally increases with the temperature of prior aging and shows changes based on the level of post-curing and network changes with time. Moisture uptake kinetics and characteristics developed through the sequence of exposures provide a better understanding of phenomena towards the development of a future comprehensive model capable of long-term prediction based on the sequential prior history of exposure to elevated temperatures and immersion in seawater.

Static and Fatigue Tensile Properties of Cross-Ply Carbon-Fiber-Reinforced Epoxy-Matrix-Composite Laminates with Thin Plies

Carbon-fiber-reinforced epoxy-matrix composite (CFRP) laminates with thin plies have strong damage-resistance properties compared with standard prepregs. The static and fatigue tensile fracture behavior of cross-ply CFRP laminates with thin plies should be further studied to establish the applicability of thin-ply prepregs for industrial structures. In this study, the static and fatigue tensile properties of cross-ply, high-strength polyacrylonitrile (PAN)-based carbon-fiber (T800SC)-reinforced epoxy-matrix composites with thin plies were investigated. The fiber orientations of the CFRP specimens were set to cross-ply with [0/90]10S (subscript S means symmetry), [(0)5/(90)5]2S, and [(0)10/(90)10]S. The static and fatigue tensile characteristics of the cross-ply CFRPs with thick plies with [0/90]2S and [(0)2/(90)2]S were also investigated for comparison. Under static loading, the tensile strength and failure strain of the thinnest 90°-ply-CFRP specimens were more than 5% higher than those of the other 90°-ply-thickness specimens. However, the tensile moduli and Poisson’s ratios were comparable between the cross-ply CFRPs with thin and thick plies. Under fatigue loading, the fatigue responses of the thinnest 90°-ply-CFRP specimens were 3% higher than those of the other 90°-ply-thickness specimens during lower-fatigue-cycle testing (<105 cycles). However, during higher-fatigue-cycle testing (>105 cycles), the fatigue responses decreased, with a decrease in the 90°-ply thickness, and the fatigue characteristics of the thinnest 90°-ply-CFRP specimen were 7% lower than those of the other cross-ply thin- and thick-ply-CFRP specimens.

Femtosecond laser micromachining of carbon fiber-reinforced epoxy matrix composites

Unidirectional carbon fiber-reinforced epoxy matrix composites fabricated by compression die molding technique were exposed to femtosecond laser pulses of 1030 nm wavelength, 560 fs duration and a pulse repetition rate of 100 kHz. Laser tracks were engraved on the composite surface using pulse energy from 1 to 5 μJ both in the direction parallel and perpendicular to the fibers axis. The resulted morphology of the laser treated surface was investigated by field emission scanning electron microscopy (FESEM). The laser induced periodic surface structures (LIPSS) with an average periodicity of 195 ± 45 nm were observed on the carbon fiber surface while the epoxy matrix showed fine granular morphology. The surface topography of the laser tracks was quantitatively analyzed by 3D reconstruction of stereographic pairs of FESEM images recorded at two different inclinations of specimen with respect to the incident electron beam. The difference in ablation depth of fiber and epoxy was measured from stereographic images which showed a remarkable change in ablation depth of fiber and the matrix for pulse energy in the range 1–3 μJ and 4–5 μJ. The observations made in this study are expected to be useful for achieving improved bonding in composite structure repaired by adhesive joining.

Effect of graphite oxide content on shape memory performance of graphite oxide‐carbon fiber hybrid reinforced shape memory polymer composites by VIHPS

AbstractGraphite oxide (GO)‐carbon fiber (CF) hybrid reinforced shape memory polymer composites (SMPC) with different GO content were prepared by vacuum infiltration hot‐press forming experimental system (VIHPS). By studying the wettability and adhesion characteristics between the shape memory matrix and CF, it was found that the addition of GO could improve the ability of the matrix to wet the CF surface and enhance the interface bonding. The shape memory performance of the composite with GO was better than that of CF reinforced epoxy matrix composite. The shape fixed rate increased by nearly 8%, and the shape recovery rate increased by nearly 13%. Combined with the test results and the characterization analysis of microstructure, the strengthening effect of GO was mainly reflected in the following aspects. Firstly, the surface folds of GO and its two‐dimensional grid structure increased the surface roughness and wettability of CF, forming a mechanical interlock among GO, reinforcement and matrix. The mechanical interlock promoted the reinforcement and matrix to have an ideal interfacial bonding strength. Secondly, the addition of GO was conducive to the transfer of deformation force and heat to prevent stress concentration in the composite and significantly improved the shape memory performance of the composite.

The Effect of Interlayer Materials on Ceramic Damage in SiC/Al Composite Structure.

The effect of interlayer materials on the damage of ceramics in the SiC/Al composite structure was analyzed through experiments and simulation. Using 0.25 mm thermoplastic polyurethane (TPU) as a reference, a 0.5 mm aramid fabric (AFRP) or a 0.5 mm carbon fiber reinforced epoxy matrix composite (CFRP) was added to the interlayer, respectively. Through the impact tests, it was discovered that the ceramic damaged area in the TPU composite structure was severe. With the addition of AFRP, the damaged area of the ceramic layer was reduced by 73% under the same impact conditions. The addition of CFRP also reduced the damage of ceramics. The evolution process of the tensile stress on the ceramic rear surface was presented by simulation. The tensile evolution process analysis can explain the experimental phenomenon well and can be used to predict the damage of the ceramics.

Graphene oxide modified carbon fiber reinforced epoxy composites

Abstract The interfacial interaction between the fiber and matrix is the most important factor which influences the performance of the carbon fiber-epoxy composites. In this study, the graphitic surface of the carbon fibers was modified with graphene oxide nanomaterials by using a spray coating technique which is an easy, cheap, and quick method. The carbon fiber-reinforced epoxy matrix composites were prepared by hand layup technique using neat carbon fibers and 0.5, 1 and 2% by weight graphene oxide (GO) modified carbon fibers. As a result of SEM analysis, it was observed that GO particles were homogeneously coated on the surface of the carbon fibers. Furthermore, Young's modulus increased from 35.14 to 43.40 GPa, tensile strength increased from 436 to 672 MPa, and the elongation at break was maintained around 2% even in only 2% GO addition.

Improvement in mechanical performance due to hybridization of carbon fiber/epoxy composite with carbon black

Many researchers are doing effort to investigate the effect of different particulates or fillers incorporated in the composite materials. In this investigation, the effect of the incorporation of different amounts of carbon black particulates on the mechanical performance of carbon fiber-reinforced epoxy composites has been studied. The carbon fiber-reinforced carbon black/epoxy hybrids were prepared with keeping constant weight fraction of carbon fiber and varying weight fraction of carbon black (0, 5, 10, and 15 wt%), using hand lay-up technique. After cure, the fabricated composite materials were cut and dimensioned into specimens as per the ASTM standards of testing and submitted to tensile, flexural, and impact tests. The microstructural characteristics and fracture surfaces of the composite were examined by scanning electron microscope (SEM). Increments of 65.78, 32.07, and 36.11% have been noticed in the tensile strength, flexural strength, and impact strength respectively for the hybrid composite (10 wt% carbon black) with respect to the conventional carbon fiber-reinforced epoxy composite. The experimental result has been validated with the numerical technique. This study represents that carbon black/epoxy composites reinforced with carbon fiber show higher mechanical performance than the conventional carbon fiber-reinforced epoxy matrix composites.

Double cantilever-beam test comparisons of Mode I fracture toughness of adherends bonded using DP8010 and DP8005 acrylic-based adhesives

The aim of this study is to not only measure the fracture toughness (GIC) of adherends bonded with a DP8010 acrylic-based adhesive using double cantilever beam (DCB) specimens under Mode I loading, but also to compare them with those bonded with DP8005. Aluminum alloy (5052-H34), glass fiber-reinforced polypropylene matrix composite (GF/PP), and carbon fiber-reinforced epoxy matrix composite (CF/EP) are used as adherends. Tensile tests of the adhesive bulk specimens are performed to measure the mechanical properties. R−curves measured from DP8010 and DP8005 are evaluated by relating them with failure modes observed from the fracture surfaces. Traction−normal separation relationships are considered to compare the fracture behaviors between DP8010 and DP8005. The experimental results show that the modulus of toughness (ur) for the adhesive bulk specimen of DP8010 exhibits similar values with that of DP8005. To maximize the values of GIC using acrylic-based adhesives, the following conditions need to be considered: ① strong bonding between adhesive and adherend, ② defect-free adherends, and ③ high ductile behavior of the adhesive bulk specimen.

Surface treatment of CFRP composites using femtosecond laser radiation

In the present work, we investigate the surface treatment of carbon fiber-reinforced polymer (CFRP) composites by laser ablation with femtosecond laser radiation. For this purpose, unidirectional carbon fiber-reinforced epoxy matrix composites were treated with femtosecond laser pulses of 1024nm wavelength and 550fs duration. Laser tracks were inscribed on the material surface using pulse energies and scanning speeds in the range 0.1–0.5mJ and 0.1–5mm/s, respectively. The morphology of the laser treated surfaces was investigated by field emission scanning electron microscopy. We show that, by using the appropriate processing parameters, a selective removal of the epoxy resin can be achieved, leaving the carbon fibers exposed. In addition, sub-micron laser induced periodic surface structures (LIPSS) are created on the carbon fibers surface, which may be potentially beneficial for the improvement of the fiber to matrix adhesion in adhesive bonds between CFRP parts.

Fatigue crack growth properties of a two-part acrylic-based adhesive in an adhesive bonded joint: Double cantilever-beam tests under Mode I loading

Fatigue lifetime is one of the most important factors that need to be considered when determining a material’s design. This study deals with fatigue behaviors in adhesive bonded joints. Fatigue tests were conducted using double cantilever beam specimens to measure the fatigue crack growth properties of the DP8005 acrylic-based adhesive under Mode I loading on aluminum alloy, glass fiber-reinforced polypropylene matrix composite (GF/PP), and carbon fiber-reinforced epoxy matrix composite (CF/EP) adherends. The fracture surfaces were examined using a microscope to verify the fracture behaviors. The experimental results show that the slope (2.85) and intercept (2.14×10−10), as defined by the Paris law, expressed a relationship between the energy release rate range (ΔGI) and the crack growth rate (da/dN) for the three specimens were the same, in scenarios where the cohesive failures were dominant. The aluminum alloy specimens were found to have another slope and intercept at 1.36 and 6.00×10−7, respectively, when interfacial failures occurred. The threshold energy release rate range (ΔGI.th) for the GF/PP and CF/EP specimens were 69.3 and 72.5Jm−2, respectively. ΔGI.th for the aluminum alloy specimens were 46.5 (denoted as ΔGI.th1st) and 5.4 (denoted as ΔGI.th2nd)Jm−2. ΔGI.th (fracture morphology) can be ranked as aluminum alloy (ΔGI.th2nd, interfacial failure)<aluminum alloy (ΔGI.th1st, mixture of cohesive and interfacial failures)<GF/PP (mixture of cohesive and adherend failures)<CF/EP (cohesive failure).

Fracture toughness of adherends bonded with two-part acrylic-based adhesive: double cantilever beam tests under static loading

Adhesives are used in various industries to bond materials. The failure criteria of adhesive joints are based on the strength (peel) and fracture mechanisms of the materials. It is important to investigate these criteria in relation to the propagation and separation of Mode I, II, and III cracks. The purpose of this study is to use double cantilever beam (DCB) tests to measure fracture toughness in aluminum alloy (5052-H34), glass fiber-reinforced polypropylene matrix composite, and carbon fiber-reinforced epoxy matrix composite adherends bonded with a two-part acrylic-based adhesive. The fracture behaviors of the specimens are also discussed. DCB tests are carried out to measure fracture toughness under Mode I loading of adhesively bonded joints with different types of adherends. The fracture toughnesses of the aluminum alloy, glass-fiber-reinforced polypropylene matrix composite (GF/PP), and carbon fiber-reinforced epoxy matrix composite (CF/EP) specimens are 1071, 1438, and 1652 Jm−2, respectively. The fracture surfaces of the aluminum alloy, GF/PP, and CF/EP specimens are observed to be of the interfacial, adherend, and cohesive types, respectively.

The scratch behavior of accelerated aged carbon fiber-reinforced epoxy matrix composite

This paper deals with the effect of accelerated aging on the scratch behavior of carbon/epoxy composites. Carbon/epoxy composite is one the most important type used in aircraft structural parts and exposed to drastic service conditions under various temperatures resulted with scratch damage. Four different type of accelerated aging procedure applied and scratch behavior of carbon/epoxy composites were evaluated using coefficient of friction and penetration depth. Scratch damage morphologies of both original and accelerated aged samples were determined by optical and scanning electron microscope. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Effects of Seawater Immersion on Mechanical Properties of CFRP Composites

Water absorption behavior and mechanical properties variation of the carbon fiber reinforced epoxy matrix composites (CFRP) immersed into artificial seawater were investigated by experiments. The rate of water absorption of the composite specimens is gradually reducing as the duality of immersion increasing. Due to the reversible and irreversible changes in the resin matrix and the failure of the fiber/matrix interface, the tensile strength, the flexural strength, and the ILSS of the composite specimens after 70 days immersion decreased 9.3%, 13%, and 17% respectively. And the tensile modulus and the flexural modulus the specimens after desorption were 83% and 70% of the original state, respectively

Experimental study of high electric current effects in carbon/epoxy composites

Electrical and thermal behavior of the carbon fiber-reinforced epoxy composites subjected to relatively high (up to 75 A) steady electric currents is studied. A fully automated experimental setup for real time measurements of the electric current, resistance, voltage, and temperature in carbon fiber-reinforced epoxy matrix composites has been developed. A series of electrical characterization tests on IM7/977-3 unidirectional and symmetric cross-ply composite laminates have been performed and the effects of electric current magnitude and duration, electrical resistance, and associated thermal effects have been investigated. It is determined that electrical resistance exhibits time-dependent behavior. It is also found that application of an electric current leads to a significant temperature rise in the composites that is a result of the intense Joule heat produced in the electrically conductive carbon fibers as well as in the composite-electrode contact.

Mechanical properties of carbon fiber/fullerene-dispersed epoxy composites

This study examined the effect of fullerene dispersion on the mechanical properties of carbon-fiber reinforced epoxy matrix composites (CFRPs). Mechanical properties such as tension, compression, open-hole compression, comparession after impact (CAI), binding, short beam shear, and interlaminar fracture toughness were evaluated for [0] 8, [90] 16, [45/0/−45/90] 2S laminates. Tension and compression strengths increased 2–12% by dispersing 0.5% of fullerene into the matrix resin. Furthermore, interlaminar fracture toughness of the composite was improved by about 60%. It was revealed that a small amount of fullerene (0.1–1 wt.%) increased the failure strain of epoxy resin itself, thereby improving the CFRP strength.

Inverse Analysis to Determine Hygrothermal Properties in Fiber Reinforced Composites

Fiber-reinforced composite laminates are often used in severe environments such as high temperature and humidity conditions. Therefore, it is of practical interest to establish a simple but robust method to determine material properties that define the hygrothermal behavior of composites under various conditions. In this article a novel inverse analysis approach is presented to identify the diffusivity, maximum moisture content, and coefficient of thermal expansion (CTE) and coefficient of moisture expansion (CME) of carbon fiber-reinforced epoxy matrix composites subjected to various conditions of environmental exposure. This procedure involves three distinct steps. First, the transient expansions and weight gains are experimentally measured under different temperatures and humidity conditions. Next, reference solutions are established from detailed computational models, which incorporate the heterogeneous nature of composite's microstructure. Finally, the Kalman filter technique is utilized to extract best estimates of the material parameters of interest. The use of inverse analysis is necessitated by the fact that backward relations from the measured parameters to the unknown properties are not directly apparent. The results show diffusivity to be a strong function of temperature while the maximum moisture content to be a strong function of relative humidity. For the case of material expansion, moisture induced strains as well as thermal strains exhibit slight dependence on temperature. In addition to estimating the material parameters of interest, detailed studies are conducted to investigate the source of scatterings observed in the expansion measurements during heating and moisture absorption, and possible 3D effects in measurements.

Effect of Fiber–Polymer Interactions on Fracture Toughness Behavior of Carbon Fiber-Reinforced Epoxy Matrix Composites

The effect of anodic oxidation on high-strength polyacrylonitrile-based carbon fibers has been studied in terms of fiber surface energetics and fracture toughness of the composites. According to contact angle measurements based on the wicking rate of a test liquid, anodic oxidation leads to an increase in surface free energy, mainly due to the increase of its specific (or polar) component. For the carbon-fiber-reinforced epoxy resin matrix system, a direct linear relationship is shown between the specific component and the critical stress intensity factor measured by the single edge notched beam fracture toughness test. From a surface-energetic point of view, the anodic treatment may be suitable for carbon fibers incorporated in a polar organic matrix, resulting in an increased specific component of the surface free energy. Good wetting plays an important role in improving the degree of adhesion at interfaces between fibers and matrices of the resulting composites.

Effect of fiber strength on tensile fracture of unidirectional long carbon fiber-reinforced epoxy matrix composites

Carbon fiber-reinforced epoxy matrix composites, with a tensile fracture stress of either 3.5 or 5.5GPa (designated as 3.5 and 5.5GPa CF/RE composites, respectively), were studied to determine the effect of fiber strength on the tensile fracture behavior. The smooth and notched tensile specimens were loaded in the direction parallel to the fibers. The 5.5GPa CF/RE composite exhibited a higher smooth tensile fracture stress but a significantly decreased notch strength ratio compared with the 3.5GPa CF/RE composite. For the smooth tensile specimens of the 3.5GPa CF/RE composite, a zigzag fracture approximately perpendicular to the loading direction occurred, and the fracture process involved a brittle fracture, or pull out, of the fibers; whereas, for the 5.5GPa CF/RE composite, the fracture was approximately parallel to the loading direction, and fiber-matrix interfacial fracture was observed. For the notch tensile tests, fracture occurred at the fiber-matrix interfaces independent of the composite type. The results are described and discussed.