Ply Sequence Research Articles

Metrological assessment of the carbon tubes behavior under thermal variation for the compensation of 3D devices

Abstract Composite materials are increasingly used in 3D metrology, especially for portable measuring devices such as articulated arm coordinate measuring machines (AACMM), 3D scanners, and ball bars. Their use is justified by their interesting mechanical properties including their low density, good rigidity, and especially their light weight, which makes them ideal for portable devices, that are meant to be often transported by the user. However, due to their complex composition, the characterization of the thermal behavior of composite materials remains complicated compared to standard materials and is nowadays an active research subject. In fact, the coefficient of thermal expansion of composite materials is dependent of the very specific composition of the composite material considered. Hence, it is function of several parameters such as the orientation of the fibers, the fiber volume fraction, the ply sequence, the cooling rate, etc. In the other hand, in 3D metrology, and especially in portable 3D metrology, determining the expansion coefficient of the different part of the measurement devices used is necessary. In fact, the portable measurement machines are often integrated and used directly on the shop floor, where the thermal variations can be important and then heavily impact the measurements results. In some cases, the lack of knowledge of the coefficient of thermal expansion of the composite materials that compose the portable measuring machine can significantly increase the measurement uncertainty.

INFLUENCE OF PLY ORIENTATION ON INTERLAMINAR FRACTURE TOUGHNESS OF CARBON/EPOXY COMPOSITES

Delamination is a concern for the structural integrity of fiber-reinforced polymer composite structures. The decisive material parameter for delamination is fracture toughness (G<sub>Ic</sub>). The main objective of this study was to investigate the in-plane, quasi-static fracture toughness (both initiation and propagation) of two laminate composites. Both composites contain carbon fibers in an epoxy matrix. The tests were performed using double cantilever beam specimens with different ply orientations according to ASTM standards. The effect of ply orientation was evaluated using data reduction methods to obtain fracture toughness. The experiments revealed that the ply sequence changed the crack propagation mechanism, increasing the initiation and propagation fracture toughness values for 90/90 layup during mode I interlaminar tests, by 80% and 69%, respectively. In addition, the mode I fracture toughness increased by 40% after 50 mm crack extension.

Fractographic Investigation of Cryogenic Temperature Mode-II Delamination Behavior of Filament Wound CFRP Laminates with Varied Resin Systems

This study investigates the mode-II delamination performance of filament-wound unidirectional composites with different types of epoxies as their matrix phase under room and cryogenic temperatures. A typical vacuum infusion resin, an aerospace-grade cold-curing resin and crack-resistant toughened resin systems were wet-wound with 12K carbon fiber tows to manufacture the composite samples. Test samples with a (0)16 ply sequence were tested according to ASTM D7905-19. The tested samples were investigated via microscopic analysis to assess the failure mechanisms associated with varying the matrix material and temperature. ENF tests at room temperature were found to be susceptible to the inherent variance in the fiber architectures along with resin-viscosity-driven fiber wetting. Cryogenic conditions induce a shift in the mode-II delamination behavior from a rather complex failure mechanism to a consistent fiber/matrix debonding mode with diminishing GIIc values except for the toughened resin system. The provided comprehensive fractographic analysis enables an understanding of the various causes of fracture, which determines the laminate performance. The combined evaluation of the distinctive damage modes reported in this study provides guidance on the conventional wet-winding process, which still remains a volumetrically dominant and viable option for cryogenic applications, particularly for vessels with limited operational durations like sounding rockets.

Research on the axial energy-absorbing characteristics of CFRP thin-walled tubes based on material modification

The specific energy absorption of thin-walled hybrid carbon fibre tubes is significantly enhanced by matrix materials. To further improve the energy absorption characteristics of CFRP, in this study, three types of CFRP thin-walled tubes were produced using various resin-modified carbon fibre prepregs, and quasi-static compression tests were carried out on the three types of tubes. By contrasting the energy absorption characteristics of three groups of tubes through experimental data, it was feasible to determine the impact of matrix modification on the energy absorption properties of CFRP tubes. The best absorption effect tube material was chosen for the relevant mechanical properties tests to obtain the material mechanical parameters, and the quasi-static compression process was simulated numerically using the explicit nonlinear finite element software LS-DYNA. The good correlation between the simulation data and the experimental results verified the reliability of the test method and the numerical model. On this basis, the effects of different ply parameters such as ply ratio, ply angle, and ply sequence on the energy absorption characteristics of the hybrid tubes were investigated by adding other modified fibre materials to the common carbon fibre material and performing finite element simulation.

Mechanical characterization of high-strength carbon-epoxy composite laminates

High-strength carbon/epoxy composites (HSCEC) are known to exhibit comparably high specific strength and stiffness than high-strength steel alloys. Consequently, they have a range of applications in the automotive, aerospace, and ship-building industries But extensive studies on the mechanical properties of HSCECs, especially at the laminate level, are lacking in the literature. This study characterizes the tensile and compressive properties of HSCEC laminates with various uni-directional (UD) and bi-directional (BD) ply sequences. The ply sequence that best combines specific strength and modulus is identified. The effects of fiber volume fraction on load–displacement behavior are analyzed. An increase in the fiber volume fraction increases the stiffness and strength of the laminate but decreases its failure strain. Overall, this study highlights the sensitivity of the specific modulus, specific strength, and percentage elongation of the composite laminates to the stacking sequence and fiber volume fraction.

In search of the quasi-isotropic laminate with optimal delamination resistance under off-axis loads

Delamination is one of the most feared failure modes in laminated composites and yet there is a lack of well established procedures to find the ply configuration with the highest delamination resistance for a given geometry of the component and a set of elastic and strength constraints. This paper presents a methodology for determining the quasi-isotropic ply sequence more resistant to delamination under off-axis uniaxial tension. Delamination is considered to be triggered by interlaminar stresses at free-edges or by matrix cracks. Two different ply thicknesses (standard and thin) and two sets of ply orientations (multiples of π/4 or π/8) are considered. The results show that the use of thin plies enlarges the design domain by up to 70% and generates a practically isotropic safe space. The methodology presented is also suitable for optimizing the delamination resistance of other load cases with stress singularities.

A collaborative grading optimization method of rib-reinforced ultra-thick composite pressure hull

With the service environment of underwater vehicles gradually moving to the deep sea, the high load-bearing requirements lead to an increase in the thickness of the composite pressure hull, which not only reduces the molding quality but also increases the difficulty of design. Thus, in order to improve the design efficiency, a collaborative grading optimization method for geometry and layup of rib-reinforced ultra-thick composite pressure hull is proposed. Firstly, the sensitivity analysis of geometric parameters on weight, stability and strength of the pressure hull are conducted based on approximate model technology, and the reinforcement efficiency of different configurations under different length to diameter (L/D) ratios of hull is compared. Secondly, based on geometric factors and approximate model techniques, the complex ultra-thick layup optimization is gradually decomposed into bearing characteristics analysis, optimization of ply ratio, ply thickness and ply sequence. Finally, the results show that when the L/D ratio of the hull is less than 3, the hat-shaped rib has the best reinforcement efficiency, while the total thickness of the hull is large. Otherwise, the I-shaped rib is better. Compared with the mono-shell, the buoyancy factor of the optimized rib-reinforced configuration is reduced by 41%.

Low-velocity impact behavior of interlayer hybrid foldcore sandwich structures with carbon/glass fibers

Interlayer hybrid foldcore sandwich structures have been introduced in this study. Both facesheets and foldcores were hybridized in the same ply sequence with two layers of plain woven carbon (C) and two layers of satin woven glass (G) fiber prepregs (Carbon-to-Glass ratio 1:1). Foldcore sandwich structures with six-ply combinations were designed including two symmetric layups (GCCG and CGGC) and four asymmetric layups (CGCG, GCGC, CCGG, and GGCC). The static compression and low-velocity impact performance of foldcore sandwich structures of different ply sequences were investigated. A user-defined material subroutine (VUMAT) was employed to characterize the damage evolution of composite materials based on selected failure criteria. The findings revealed that hybridization was effective in enhancing its energy absorption value of pure carbon fiber foldcore sandwich structures in terms of static compression performance. The damage degree of the interlayer hybrid foldcore sandwich structures increased gradually with the increasing impact energy. Moreover, the damage of facesheet was mainly caused by fiber tensile, matrix tensile damage and delamination, and damage of foldcore was mainly delamination. GCGC sandwich panel with asymmetrical cross-ply sequence has the optimal load bearing capacity, and CGGC sandwich panel with symmetrical layup has a strong energy absorption capacity under high-energy impact load. The foldcore sandwich structure showed smaller peak load, longer crushing distance, and more energy absorption value under larger oblique impact angle. The simulation and experimental results show good agreement in peak force, maximum energy absorption, and damage mode.

Crashworthiness and Failure Analyses of FRP Composite Tubes under Low Velocity Transverse Impact

Currently, FRP composite tubes are drawing increasing attention in many industrial applications, due to their excellent mechanical and lightweight properties, with reduced energy consumption and enhanced sustainability. This study investigates the failure mechanisms and crashworthiness performance of glass and carbon fibre reinforced polymer (GFRP and CFRP) composite tubes under low velocity transverse impact. Finite element methods were developed to establish numerical models to predict the failure responses of FRP composite tubes with a complex ply sequence of both woven and unidirectional layers. In the modelling, continuum damage mechanics and cohesive zone method were used to calculate the intralaminar and interlaminar failure behaviours, respectively, in FRP composite tubes. The numerical models were validated by corresponding experiments, and the effects of the impact energy and material type were investigated. The experimental results show that the initial impact energy does not significantly affect the specific energy absorption (SEA) and peak force (PF) of GFRP composite tubes, and the SEA and PF are generally around 0.5 kJ/kg and 600 N, respectively, when the impact energy varies from 10 J to 50 J. Failure mechanism analyses show that GFRP tubes and CFRP tubes with totally unidirectional plies present global bending deformation with significant matrix damage, and CFRP tubes with “hybrid layer type” exhibit local penetration with severe fibre and matrix damage. The crashworthiness analyses indicate that CFRP tubes perform better in SEA while GFRP tubes possess smaller PF when subjected to low velocity transverse impact.

Study on impact behavior of glass fiber/PVC curved sandwich structure composites

AbstractComposite materials have the characteristics of light weight, high strength, high modulus, and corrosion resistance. In this article, glass fiber/PVC curved sandwich structure composites with three curvature radiuses (80, 150, and 260 mm) and different sandwich structures were prepared by vacuum assisted resin transfer molding. The specimens were subjected to quasi‐static indentation test and drop hammer impact test. The influence of curvature radius and ply sequence on the impact behavior of composites were analyzed by comparing the load displacement curve, pit depth, and energy loss. The compression after impact of specimens with different curvature radius and structure was carried out to explore the damage limit and toughness of composites. It is found that the maximum tensile properties of sandwich specimens are determined by the degree of resin infiltration into PVC foam panels. The impact performance is mainly attributed to the laying sequences of reinforcement. The instantaneous impact performance of free falling body is greatly affected by the curvature radius, and the post impact compression performance of sandwich composites is increased with increase of the curvature. The research could provide a theoretical basis for the application of combining curved surface and sandwich structure composites.

The effects of loading direction on the compression after impact strength of quasi-isotropic face sheet honeycomb core sandwich structure

This study presents experimental results of compression after impact (CAI) testing of aluminum honeycomb core sandwich structure with face sheets made of quasi-isotropic carbon/epoxy with two orthogonal directions of testing. In a previous study examining the CAI strength of honeycomb sandwich structure,1 it was found that that specimens had different CAI strengths depending on whether the core was oriented in the “L” or “W” direction. Since the face sheets were quasi-isotropic and the core should not (theoretically) affect the CAI strength for a given amount of damage (if the specimens fail by face sheet failure), this result was puzzling. In the study presented in this paper, further CAI tests, along with open hole compression testing were used in an attempt to ferret out the cause of the differing CAI strengths in the aforementioned study. The results showed that the lower CAI strength values were not due to the core orientation, but to the change in the quasi-isotropic face sheet ply sequence due to the 90° rotation.

Assessment of ply sequencing on the mechanical performance of hybrid composite materials

The importance of natural fiber composites (NFC) has been growing day by day owing to their lower cost and biodegradable nature. The hybridization of Natural fiber with another natural or synthetic fiber helps obtain combined advantages. In the present paper, an investigation of ply sequencing with combination of natural and synthetic fiber layer studied under tensile and flexural loading. The natural fibers used in the study are Jute (J) and Flax (F) and synthetic fiber is Glass (G). The matrix used is Epoxy with hardener. The six layer of ply sequences studied are JJJJJJ, JJFFJJ, JJGGJJ and GJJJJG. Fabrication of Composite specimen is conducted using Hand lay- up Method. The composite specimen is subjected to tensile and flexural loading at room temperature. Elastic modulus and Flexural modulus are assessed using the theoretical model Classical Lamination Theory (CLT). The results showed that hybridization has improved mechanical properties significantly. The sequence GJJJJG exhibited extremely higher flexural strength compared to sequence JJGGJJ, this shows the ply sequence optimally helps to achieve properties as desired in a particular application with the same cost. Theoretical model predicts the properties with reasonable error limit of 10-12%.

Development of Numerical Modelling Techniques for Composite Cylindrical Structures under External Pressure

Submarine hulls are pressure vessels for which excellent structural integrity under underwater pressure loads is essential. The use of light-weight materials contributes to reduced fuel consumption, improved speed, and increased payload while strength properties are retained. The focus of this paper is on the collapse behavior of a filament-wound cylindrical structure that serves as the main hull of a submarine subject to hydrostatic pressure loads. This paper presents a computational modelling approach for the prediction of the collapse behavior mechanism using a commercial finite element (FE) solver. The collapse strength obtained from the numerical model corresponded closely to available experimental data. The composite and aluminum material models were compared and the effects of stacking angle and thickness portion in the ply sequence on collapse strength were investigated. The advantages and disadvantages of available design codes (i.e., American Society of Mechanical Engineers (ASME) BPVC-X and National Aeronautics and Space Administration (NASA) SP-8007) were reviewed by direct comparison with numerical results. It is concluded that the application of effective engineering constants for the prediction of the collapse pressure of submarine hulls may be feasible.

Influence of imperfection sensitivities on postbuckling of laminated cylindrical panel under axial load: Numerical and experimental investigation

Influence of geometric imperfections on postbuckling of layered (laminated) composite cylindrical panels has been performed under axial compression load using finite element code, ANSYS and validated experimentally. Finite element code was initially validated with available literature for performing the further analyses on the panel. Eigen imperfection irregularities were considered for predicting postbuckling loads of layered composite cylindrical panels with SSSS and SFSF boundary conditions with different r/t ratio and ply sequence and compared the results. Glass-polyester laminated cylindrical panels were fabricated and tested using fixture which accommodates different boundary conditions for investigating the postbuckling phenomenon. Experimental postbuckling analysis was carried out to validate the finite element analysis results and found satisfactory. The influence of imperfections with different r/t, stacking sequences with SSSS and SFSF boundary conditions were carried out and compared. As the r/t ratio of the cylindrical panel increases the postbuckling load decreases for a given boundary conditions and with magnitude of imperfection sensitivities. It has been observed that SFSF boundary conditions with angle play layup sequences taking more axial loads than SSSS boundary conditions with same layup sequence and imperfection sensitivity.

Experimental study of the influence of thickness and ply sequence on woven composite plates subjected to out of plane impact

In this work the different failure mechanisms have been studied on 5HS woven composite laminates subjected to low velocity impacts. A large range of energies (5-75J) has been used to induce different failures: delamination, fiber failure, out-plane shear and perforation. In addition, different configurations of AGP 280-5HS woven coupons have been manufactured to analyze the influence of thickness ((0/90)4S, (0/90)6S and (0/90)8S) and ply sequence ((0/90)8S, (±45)8S, [(±45)/(0/90)]4S, [(±45)2/(0/90)2]2S, and [(±45)4/(0/90)4]S)). Laminates have been subjected to low velocity impact using an INSTRON-CEAST Fractovis 6875 drop weight tower according to ASTM standards (D7136). Each test has been recorded with two high speed video-cameras (Photron SA-Z 2100K) in order to analyze the plate behavior during the impact. In addition, a three dimensional high velocity digital image correlation (HV-DIC) analysis has been performed to measure the out of plane displacement. Once impacted, the damaged area of the composite laminates was evaluated by ultrasonic inspections. The analysis of the influence of the plate thickness and ply sequence have been made according to the Composite Structure Impact Performance Assessment Program (CSIPAP) proposed by Feraboli and Kedward using the peak force and the absorbed energy.

Effects of laminate thickness and ply-stacking sequence on the low velocity impact resistance of carbon fiber-reinforced laminates

Carbon/epoxy pre-impregnated has become one of the most demanded materials for some aeronautics structures. Boeing 787 and Airbus A350 are pioneers in incorporating carbon fiber-reinforced composite materials in primary structures as wings and airframe. Tailoring the laminate ply sequence involves a difficult challenge owing to the rigorous design and operational criteria. Given that composite materials present a high sensitivity to impact loads, it has been indispensable to examine the influence of different factors in the failure mechanisms after an impact event. In this work, the effect of impact energy, stacking sequence and thickness on the impact damage resistance of CFRP composites was investigated. Damage response parameters as peak force, absorbed energy and delamination threshold were obtained from the impact curves. Then, a C-Scan imagen showed the damage extension using the non-destructive inspection Phased Array.

Characterization of mechanical and dynamic properties of natural fiber reinforced laminated composite multiple-core sandwich plates

The present article deals with the study of material, mechanical and dynamic characteristics of natural fiber reinforced composite sandwich plates with multiple-core layers. The multiple-core sandwich structure contains the jute fibers reinforced polymer composites as face layers and the natural rubber and cork as core layer. The material characterization such as X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscope (SEM) was carried out to investigate the crystallinity, thermal stability, and morphology of untreated and treated jute fiber materials. The tensile and flexural properties of natural composite material was examined using ASTM D3039 and ASTM D7264 standards. The governing equations for the natural fibers reinforced composite sandwich plates are developed using a finite element method. The performance of the developed model is validated by comparing the results available in the published literature. The numerical results indicate that the multiple-core natural composite sandwich plate greatly influences the structural stiffness compared with a single-core natural composite sandwich plate. Furthermore, the influence of core layer configuration, end condition, aspect ratio and ply sequence on the dynamic properties of the multiple-core natural composite sandwich plate are presented.

Burst strength analysis of composite overwrapped pressure vessel using finite element method

The purpose of this numerical study was to investigate the burst performance of a type III composite overwrapped pressure vessel (COPV) using finite element methods. An Aluminum overwrapped composites pressure vessel was modeled from four layers of carbon fiber/epoxy ply with 0.762 mm and arranged in two different sequences and orientations. The overwrap composite pressure vessel burst performance was examined by applying an internal pressure of 55 MPa on a ply arrangement of [-15°/0°/+15°/90°] and other research findings on [+55°/-55°] as an optimum filament winding angle were used for comparison purpose. Moreover a ply level orientation effect analysis, which is a superior feature of ABAQUS, was used for the composite modelling. The designed ply sequence and orientation exhibit a higher burst pressure at [0°] ply and minimum at [90°] ply orientation. The vertical COPV design displays a maximum stress along the axial direction that leads to the consideration of maximum vessel thickness to be along axial direction for burst resistant design of COPV.

Effect of patch dimension and fiber orientation on non-linear buckling of hybrid composites

AbstractIn this study, first circular hole layered hybrid composite plates were repaired by wet patch method, and then buckling behavior was investigated experimentally and numerically. In the experimental study, composite plates were produced by vacuum infusion method using hybrid fabrics made of carbon and aramid. Circular holes were drilled in the produced plates and then these holes were repaired with the same material. In the wet patch repair method, wet hybrid fabrics impregnated with epoxy resin were placed around the hole and then this area was subjected to pressure and temperature by vacuum infusion method. In experimental tests, pressure force was applied to the fixed sides and force-displacement graphs were obtained. In a numerical study, non-linear buckling analysis was performed by creating numerical models of plates and patches using the finite element method. As a result, experimental and numerical load-displacement graphs were obtained in accordance with pre- and post-buckling. Thanks to the repair in accordance with practical applications, no interface debonding damage occurred in ideal samples. Increasing the patch length from 30 mm to 40 mm increased the maximum damage load by 6 %, while increasing the patch length to 50 mm increased damage load by 12 %. Increasing the patch thickness from 0.65 mm to 1.1 mm increased the load by 67 %, while increasing it to 2.16 mm increased the load to 247 %. Fiber orientation was found to be a more influencing factor in critical buckling and damage load than the ply sequence.

Lightweight cylindrical composite shell structures to support optical instruments in extremely large telescopes: A case study.

Aiming at the issues of heavy weight and insufficient structural performance of optical instrument supporting structures in extremely large telescopes, the Wide-Field Optical Spectrograph (WFOS) of the Thirty Meter Telescope (TMT) was taken as a case to study. In order to develop lightweight structures which satisfies the design requirements for mass and stiffness, a design scheme of cylindrical composite shells supporting structure was proposed and their finite element models were developed. A size optimisation and a ply sequence optimisation of the composite structure were carried out. The structures before and after optimisation were evaluated from the aspects of mass, displacement, failure index and fundamental frequency. After the optimised design, the mass of the optimised WFOS cylindrical composite shell structure is reduced to approximately 50%, but its maximum displacement (0.513 mm) and fundamental frequency (8.275 Hz) are nearly unchanged. The study indicates that a cylindrical composite shell structure is an efficient structural form for large optical instruments.