Carbon Fiber Reinforced Aluminum Laminates Research Articles

An experimental investigation into the high velocity penetration resistance of CFRP and CFRP/aluminium laminates

Carbon fibre-reinforced composite materials are of high potential as protective casing in the aerospace area, acting as an effective solution to lighten components against the collision. The high velocity penetration resistance abilities of unidirectional CFRP laminates and two carbon fibre reinforced aluminium laminates CRALL2/1 and CRALL3/2 (fabricated from T700S CFRP layers combined with aluminium alloy 2024-T3 layers) were evaluated by the ballistic tests with a flat, hemispherical or conical nosed projectile. Revealed from ballistic tests that fracture modes, ballistic limits and specific energy absorptions of CRALLs and CFRP were sensitive to nose shapes. Higher ballistic limits and specific energy absorption ability were performed by CRALLs than monolithic CFRP impacted by all shapes due to the strain rate hardening effect and failure conversion effect. In particular situation of flat nose projectiles penetrating, the specific energy absorption of the CRALL3/2 was 8% higher than that of monolithic aluminium alloy 2024-T3 at same thickness. The CRALLs may then be designed as effective lightweight structures to protect frames against collision in the aerospace area and outperform the traditional single CFRP laminates.

Impact Response and Damage Characteristics of Carbon Fibre Reinforced Aluminium Laminates (CARAL) under Low Velocity Impact Tests

This paper investigates impact response of a novel fibre metal laminate (FML) system based on a carbon fibre reinforced Aluminium Laminates (CARAL). These composites are fabricated using hand lay-up technique and the detailed preparation methodology was presented. Epoxy resin along with TETA hardener was used as the excellent adhesion agent throughout the layer. Three types of layers were prepared from CARAL and machined as per ASTM Standard. Low velocity impact response and damage characteristics of CARAL specimens were studied. Damage characteristics were evaluated using drop weight impact tester. Impact properties of CARAL were increased with the increase in number of layers of CARAL laminates. Finally cross- sectional morphology analysis was done using scanning electron microscope (SEM) and the internal structure of the broken specimen was discussed.

Effect of various surface preparation techniques on the delamination properties of vacuum infused Carbon fiber reinforced aluminum laminates (CARALL): Experimentation and numerical simulation

Carbon fiber reinforced aluminum laminates (CARALL) are one of the aluminum based Fiber metal laminates (FMLs) which, due to their high strength to weight ratio and good impact resistance are greatly replacing aluminum alloys in aircraft structures. In this research work, interlaminate shear strength of Vacuum assisted resin transfer molding (VARTM) manufactured CARALL has been investigated. Numerical simulation model incorporated with real time material data has been developed to predict the delamination behavior of CARALL laminates. Standard CARALL specimens with different surface morphologies were prepared by electric discharge machining, mechanical, chemical and electrochemical surface treatments. T-peel tests were carried out according to standard ASTM D1876-08 to find out inter laminate shear strength. FMLs made out of mechanically, chemically and electrochemically cleaned metal sheets depicted high interlaminate shear strength. SEM micrographs of failed surfaces verify the high adhesive strength of epoxy. Developed numerical simulation model accurately predicts the delamination behavior of CARALL as observed during experimentation.

Optimization of Corrosive Properties of Carbon Fiber Reinforced Aluminum Laminates due to Integration of an Elastomer Interlayer

Fiber-Metal-Laminates (FML) show superior dynamic mechanical properties combined with low densities. The mechanical performance of for example commercially available fiber-metal-laminate, glass laminate aluminum reinforced epoxy, can be improved by the substitution of glass fibers with carbon fibers. However, carbon fiber reinforced aluminum laminate introduces a mismatch of coefficients of thermal expansion and the possibility of galvanic corrosion. The fiber-metal-laminate is altered by the integration of an elastomer interlayer which is desired to solve both problems. The high electrical resistance is supposed to inhibit the corrosion. This study focuses on the effect of galvanic corrosion caused by neutral salt spray tests on fiber-metal-laminates, the influence of an elastomer interlayer and the quantification of the residual mechanical properties. The galvanic corrosion affects the interfaces of the laminates, therefore in this study edge shear tests and flexural tests were carried out to quantify the residual properties and thereby the corrosive damage. The elastomer interlayer was found to inhibit galvanic corrosion in the salt spray chamber, whereas the fiber-metal-laminate without interlayer showed corrosive damage. Furthermore, the mechanical properties of the fiber-metal-laminate with elastomer interlayer remained constant after the corrosion tests, whilst the fiber-metal-laminate’s properties decreased with corrosive loads.

Open‐hole tensile behaviour and failure prediction of carbon fibre reinforced aluminium laminates

In this article, the open‐hole tensile behaviour of carbon fibre reinforced aluminium laminates (CARALL) were investigated experimentally and numerically. Two specimens with different fibre orientations ([0°/90°/0°] and [45°/0°/−45°]), consisting of T700 carbon fibre/epoxy prepreg and 2024‐T3 aluminium with a 3/2 configuration, were manufactured by the autoclave process. Damage initiation and progression were considered in modelling the CFRP layers and interface bonding layers. Isotropic hardening behaviour was defined for aluminium layers. A major contribution of this study was to reveal the failure mechanisms and failure sequences of notched CARALL with different fibre orientations by numerical method. Damage evolution processes of the two specimens were compared. Effects of hole sizes and laminate configurations (stacking sequences & stacking structures) on both the specimens were further evaluated based on simulation. Point stress failure criterion and Wu's modified point stress failure criterion were applied in comparison with the numerical method as well. POLYM. COMPOS., 39:4123–4138, 2018. © 2017 Society of Plastics Engineers

In-plane flexural behaviour and failure prediction of carbon fibre-reinforced aluminium laminates

This paper investigated the in-plane bending behaviour of carbon fibre-reinforced aluminium laminates (CARALL). The flexural progressive damage and failure mechanisms were analysed numerically and experimentally. Four types of CARALL specimens with a 3/2 configuration were prepared via hot-pressing using different aluminium alloy materials (2024-T3, 7075-T6 aluminium alloy) and fibre orientations ([0°/90°/0°]3, [45°/0°/−45°]3). The three-point bending tests were conducted under static loading. It was found that the primary damage modes were aluminium layer yielding in the mid-span and delamination between the aluminium and carbon fibre-reinforced polymer (CFRP) layers. A user-defined FORTRAN subroutine VUMAT based on ABAQUS was used to simulate the failure of the CFRP, a cohesive zone model was used to predict the inter-laminar failure, and a von Mises plastic model was used to define the isotropic hardening behaviour of the aluminium layers. The predicted results agreed well with the experimental ones. Two convenient calculation methods based on the elasticity mechanics and material mechanics were derived. And the non-linear behaviour of aluminium was considered in the elasticity mechanics method. The theoretical results matched closely with the experimental findings during the linear elastic deformation process.

Compression after impact characteristics of carbon fiber reinforced aluminum laminates

The influence of layer structure and resin rich (polyester veil cloth) layers which were used for enhancement of interfacial bond adhesion on the compression after impact response of carbon fiber reinforced aluminum laminates (CARALL) was investigated in this research study. The addition of resin rich layers at interfaces of CFRP and aluminum layers shows significant reduction in delaminated area (40–50%) due to crack bridging effect. The residual compressive strength of CARALL laminates was increased by 30–35% as a result of reduction in delamination area. Excessive damage was found in CARALL-B FMLs during impact events as compared to CARALL-A FMLs. Thus, the Compressive residual strength of these laminates was lower as compared to standard CARALL-A laminates having aluminum layers placed exterior to CFRP layers. Numerical simulations were performed by utilizing commercially available finite element (FE) code, LS-DYNA to predict the CAI response of these laminates. Compressive residual strength vs. delamination area results showed good correlation between experimental and FEA results for CARALL-A and CARALL-B FMLs at lower energy levels (14–21J) but diverged at high impact energy level (31J). Numerical simulation was found to successfully capture the location and initiation of compressive buckling in specimens.

Effect of Layer Structure on Dynamic Response and Failure Characteristics of Carbon Fiber Reinforced Aluminum Laminates (CARALL)

The effect of placing carbon fiber reinforced composite layers exterior or interior to the aluminum layers on the low-velocity impact performance of CARALL FMLs was investigated in this research study. In this study, CARALL laminates having 3/2 configuration, with aluminum in the outer layer for the first case (CARALL A) and one with carbon fiber composite (CFC) layer in the outer layer (CARALL B) were prepared using a vacuum press without using any adhesive film. In addition, CARALL-A FML was modified with a thin veil cloth layer between CFC and aluminum layers (CARALL-C). Force–displacement histories, damage morphologies and energy absorption capabilities of these laminates in relation to different energy levels are presented and discussed. The influence of resin rich layers (veil cloth) at the interfaces of aluminum and carbon fiber/epoxy layers on the impact behavior and damage size is also investigated. CARALL-A FMLs absorb the energy mainly through plastic deformation and delamination initiation and propagation whereas CARALL-B absorbs the impact energy through penetration and perforation of the laminate. The introduction of resin rich layers (veil cloth) affects the overall dynamic response with higher contact forces, smaller ultimate central deflections, reduced delamination damage area, and provides hindrance to the growth of cracks in the non-impacted aluminum layer and thereby increasing the impact resistance of CARALL-C FMLs.

Experimental and numerical investigation of flexural behavior of carbon fiber reinforced aluminum laminates

Fiber metal laminates (FML) combine the strength of carbon fiber composite layer with ductility of the aluminum layer for desirable mechanical characteristics. For these composites, progressive failure behavior can be complex and require attention. In this study, two carbon fiber reinforced aluminum laminates (CARRAL) with a 3/2 configuration, with aluminum in the outer layer for the first case and one with carbon fiber composite layer in the outer layer were prepared using a vacuum press without any adhesive layer between the layers—a significant departure from similar aerospace materials. Epoxy from the prepreg provides adequate adhesion during consolidation in these lower cost FMLs with a pressure level of 0.35 MPa. Three-point flexural behaviors of these two material systems were evaluated under static loading and failure modes were recorded. Primary failure modes observed were crack in lower aluminum layer, carbon fiber (CFRP) layer fracture and delamination between upper aluminum and CFRP layer. A major contribution of this study was to predict the flexural response of these FMLs using LS-DYNA finite element code. Modeling the progressive damage behavior of FML by considering stress based material failure and shear stress based delamination failure between adjacent layers were key aspects of finite element modeling. Predicted mechanical behavior matches well with experimental results and the progressive nature of damage are recovered in the model.

Modeling Low Velocity Impact Response of Carbon Fiber Reinforced Aluminum Laminates (CARALL)

Fiber metal laminates (FMLs) have shown great potential in lightweight aerospace applications. Carbon fiber reinforced aluminum laminates (CARALL) is a lightweight system that has received less attention than aramid reinforced aluminum laminates. These FMLs have adhesively bonded layered plies. We have developed CARALL without the use of adhesives. The epoxy resin from the carbon fiber epoxy is used to adhesively bond the aluminum layers. In this study, CARALL laminates having a 3/2 configuration, with Aluminum 5052-H32 as the outer layer were prepared using a vacuum press without using any adhesive film. Primary failure modes observed were cracks in non-impacted aluminum layer, carbon fiber (CFRP) layer fracture and delamination between aluminum and CFRP layers. Finite element modeling was used to predict low velocity impact response of these FMLs by considering Chang–Chang damage criteria for CFRP layers and nonlinear elasto-plasticity along with progressive damage mechanics for aluminum layers. Delamination was modeled by using traction separation law and damage criterion proposed by Benzeggagh–Kenane was used for interface damage evolution. The damage size of CARALL FMLs was characterized using C-scan equipment and compared with the finite element predictions. Numerical simulation was used to predict load–displacement histories, delamination area, absorbed energy, damage morphologies on impacted and non-impacted sides and tensile failures of CFRP layers for impact event at three different energy levels. Predicted impact behavior results match well with experimental results. The threshold impact energy, energy at which perforation failure was induced in all metallic and fiber reinforced layers for these CARRAL laminates was found to be around 31 J.

Effect of strain rate on tensile behavior of carbon fiber reinforced aluminum laminates

In this paper, the tensile behavior of carbon fiber reinforced aluminum laminates (CRALL) has been determined at a strain rate range from 0.001 s − 1 to 1200 s − 1 . Experimental results show that CRALL composite is a strain rate sensitive material, and the tensile strength and failure strain both increased with increasing strain rate. A linear strain hardening model has been combined with Weibull distribution function to establish a constitutive equation for CRALL at different strain rates. The analysis of the model shows that the Weibull scale parameter, σ 0, increased with increasing strain rate, but Weibull shape parameter, β, can be regarded as a constant.

Delamination growth and its effect on crack propagation in carbon fiber reinforced aluminum laminates under fatigue loading

The fatigue crack growth in Fiber Reinforced Aluminum Laminates (FRALL) involves two inter-related damage processes, i.e. crack growth within the aluminum layer and delamination growth between the aluminum layer and the composite core. In this study, the fatigue crack growth behavior in Carbon fiber Reinforced Aluminum Laminates (CARALL) was analyzed using a simplified model which takes both fiber bridging effects and the delamination propagation into account, supplemented by an iterative calculation scheme. Results indicated that the delamination growth during the fatigue process exhibits an effective “self-adjusting” property such that the size of the delamination zone would converge rapidly, irrespective of the initial size. This is explained in terms of the decrease in the fiber bridging force, the driving force for delamination, as the delamination size increases. In general, however, the effect of delamination growth on the fatigue crack growth in CARALL was shown to be of secondary significance as compared to that of the stiffness of the composite core. It was argued that qualitative conclusions should be applicable to FRALL in general.

Fatigue delamination growth in carbon fibre-reinforced aluminium laminates

An experimental study was conducted to examine the fatigue delamination growth in carbon fibre-reinforced aluminium laminates (CARALL) under cyclic loading. The growth rate of cyclic delamination between the aluminium sheets and the fibre/epoxy composite core could be related to the effective strain energy release rate (Gmax - Gth) by a Paris type equation, dDdN = c(Gmax - Gth)m, where c and m are fitting constants. The threshold energy release rate Gth could be separated into two terms, Gth0 and Gr. It was shown that Gr could be related to the strain energy release rate solely due to thermal residual stresses in the laminate, while Gth0 might represent a parameter related to the intrinsic interfacial characteristics. Interestingly, the three constants c, m and Gth0 were found to be independent of the volume fraction of carbon/epoxy and the magnitude of thermal residual stress. Therefore, once the constants c, m and Gth0 were determined, the fatigue delamination growth in the hybrid laminate with various carbon/epoxy contents and/or thermal residual stresses could be predicted readily by this empirical equation.

Effect of fiber bridging on the fatigue crack propagation in carbon fiber-reinforced aluminum laminates

A superior crack propagation resistance was observed on various carbon fiber-reinforced aluminum laminates (CARALL) under tension-tension fatigue. It might be attributed to the restraint on the crack opening imposed by intact fibers in the crack wake. These fibers bridging the crack could reduce the effective stress intensity factor actually experienced by the crack tip. Based on the measurement of crack length and delamination size, the effective stress intensity range, ΔK eff, of fatigue-damaged CARALL laminate was calculated by using a simplified analytical model. It was shown that the fatigue crack propagation rate in CARALL could be expressed as a unique function of the calculated ΔK eff, which agree well with the Paris equation for the unreinforced aluminum alloy. This result confirmed the applicability of this simplified analytical model in CARALL laminates.

Thermal residual strains in carbon fibre-reinforced aluminium laminates

Abstract The thermal residual strains in various carbon fibre-reinforced aluminium laminates ( carall ), which were generated during cooling from the curing temperature, have been evaluated by both experimental methods and theoretical analysis. The experimental methods used include the deflection of an asymmetric laminate and the yield point shift of the aluminium alloy in the carall laminate. The theoretical calculation performed was based on the classical lamination theory. Residual strains determined by each experimental method and by theoretical calculation show good agreement. In addition, the possible errors associated with each method were carefully assessed and shown to be acceptable. For carall laminates reinforced with unidirectional carbon fibres, the thermal residual stress in the aluminium layer was found to be roughly proportional to the volume fraction of the carbon/epoxy layer.

Fatigue behaviour of carbon fibre-reinforced aluminium laminates: Lin, C.T., Kao, P.W. and Yang, F.S. Composites Mar. 1991 22, (2), 135–141

Fatigue behaviour of carbon fibre-reinforced aluminium laminates: Lin, C.T., Kao, P.W. and Yang, F.S. Composites Mar. 1991 22, (2), 135–141

Fatigue behaviour of carbon fibre-reinforced aluminium laminates

A new hybrid composite (CARALL), consisting of thin layers of carbon fibre/ epoxy prepreg sandwiched between aluminium sheets, has been developed. It is shown that this class of materials offers higher modulus, higher tensile strength and lower density than 2024-T3 alloy in the longitudinal direction. Under tension-tension fatigue loading, the hybrid laminates showed superior fatigue crack propagation resistance in the longitudinal direction, which may be attributed to the bridging effect imposed by the intact fibres in the crack wake. It has also been shown that the effectiveness of fatigue crack growth reduction increases with the thickness of the carbon fibre/epoxy layer. The resistance to fatigue crack propagation can be further improved by introducing compressive residual stresses in the aluminium layer by postcure stretching the laminate in the plastic region of the aluminium alloy.