Composite Stacking Sequence Research Articles

Damage mechanics and energy absorption capabilities of natural fiber reinforced elastomeric based bio composite for sacrificial structural applications

The present study deals with the experimental, finite element (FE) and analytical assessment of low ballistic impact response of proposed flexible ‘green’ composite make use of naturally available jute and rubber as the constituents of the composite with stacking sequences namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ) and jute/rubber/jute/rubber/jute (JRJRJ). Ballistic impact tests were carried out by firing a conical projectile using a gas gun apparatus at lower range of ballistic impact regime. The ballistic impact response of the proposed flexible composites are assesses based on energy absorption and damage mechanism. Results revealed that inclusion of natural rubber aids in better energy absorption and mitigating the failure of the proposed composite. Among the three different stacking sequences of flexible composites considered, JRJRJ provides better ballistic performance compared to its counterparts. The damage study reveals that the main mechanism of failure involved in flexible composites is matrix tearing as opposed to matrix cracking in stiff composites indicating that the proposed flexible composites are free from catastrophic failure. Results obtained from experimental, FE and analytical approach pertaining to energy absorption and damage mechanism agree well with each other. The proposed flexible composites due to their exhibited energy absorption capabilities and damage mechanism are best suited as claddings for structural application subjected to impact with an aim of protecting the main structural component from being failed catastrophically.

Prediction of failure behavior of adhesively bonded CFRP scarf joints using a cohesive zone model

In this article, the tensile behavior of adhesively bonded scarf joints (SAJs) of CFRP laminates with ductile adhesive is investigated by experiments and finite element (FE) simulations. Experimental tests considering joints with six different scarf angles are performed, and three-dimensional (3D) FE models are established in ABAQUS to study the failure mechanism. A user-defined cohesive zone model (UCZM) is proposed to predict the failure of ductile adhesive. The load-displacement response and failure modes of SAJs obtained by FE simulations are compared with the experimental results to validate the accuracy and applicability of UCZM. Moreover, the widely used triangular cohesive zone model (TCZM) is also employed to predict the failure. The comparison between experimental and numerical results exhibits that UCZM is able to predict the joint strength and failure displacement more precisely although TCZM also achieves certain accuracy. Furthermore, the influence of adhesive properties and composite stacking sequence on the tensile performance of joints is discussed using UCZM. Finally, the stress distribution within the adhesive layer and its variation along with different scarf angles are analyzed.

A continuation-based method for finding laminated composite stacking sequences

A method of recovering laminate ply stacking sequences from a set of up to twelve lamination parameters using polynomial homotopy continuation techniques is presented. The ply angles are treated as continuous variables, and are allowed to take any value between -90° and +90°. The individual plies are assumed to be orthotropic and have constant stiffness. The method is fully deterministic, and does not rely on an optimisation process to establish the stacking sequence. Polyhedral continuation methods are used to limit the solution space in which the stacking sequences are sought. The method can reliably find every stacking sequence solution that exists to achieve a precisely specified set of lamination parameter “targets”, with the number of real solutions to a feasible combination of target properties found to vary from 1 to over 100. The same method is also demonstrated to be able to find stacking sequences to satisfy a set of specified ABD stiffness matrix terms, as might be required following a direct-stiffness modelling design process.

Influence of Simulation Parameters in the Combined Loading Compression Testing of CFRP Specimens

In this paper a sensitivity study of a FEM model representing a carbon/epoxy composite material tested in Combined Loading Compression (CLC) is presented and the results are compared to experimental results. The present study aims to simulate the failure of composite materials when subjected to compression and crush loading conditions. This is required as a first step of a Building-Block Approach towards full-scale modelling of complex structures.In the experimental part of the work, a laminate panel was manufactured with carbon unidirectional prepreg (Deltapreg UTS-300-DT120-37EF) in a cross-ply, balanced and symmetric stacking sequence, cured in autoclave at 120°C and 5 bar for 90 min. A number of six samples, extracted from the panel, were tested in compression following ASTM D6641/D6641M-16.Numerical simulations have been implemented by means of the commercial software, ESI-VPS PAM CRASH. Boundary conditions, specimens’ dimensions and material properties emulated real test conditions. A sensitivity study was performed on critical simulation parameters: the effect of mesh size and number of shell surfaces representing the composite stacking sequence was initially investigated. Furthermore, the specimen failure mode was inspected by the application of TIED links between the composite plies. Numerical results have been compared with experimental data and the comparison provided references for testing scale-up in the Building-Block Approach.

An automatic multi-objective optimization tool for the optimum design of a cracked pressure vessel with composite coating

This paper proposes an automatic multi-objective optimization tool for the optimum design of a cracked pressure vessel with composite coating based on the non-dominated sorting genetic algorithm (NSGA-II) and maximum tangential strain energy density (MTSED) criterion. The proposed tool takes into consideration all the important parameters of the optimization of composite materials such as the angle, thickness, number, and material of each layer, as well as the effective parameters of fracture mechanics such as the orientation, length, and aspect ratio of cracks in the metallic liner of vessels. The optimization processes have been conducted for 3D longitudinal, circumferential and inclined semi-elliptical cracks in the sample composite pressure vessel and optimal stacking sequences and Pareto’s front for each kind of crack are presented. The in-plane and out of plane fracture envelop predicted by the MTSED criterion before and after optimization under mixed mode I/II/III have been investigated. The proposed tool is validated against collected results from existing literature and these results have largely agreed with each other.

Bearing failure and influence factors analysis of metal-to-composite bolted joints at high temperature

In this paper, experiments were conducted to study the tensile performance of metal-to-composite bolted joints at room temperature and 250 °C. Furthermore, numerical models were developed to simulate tensile behavior of the joint. After achieving a decent validation between numerical models and experimental results, more detailed studies were conducted through finite element models to find out the influence of temperature, bolt material, the thickness of composite laminate and stacking sequence on tensile properties of the joint at room temperature and 250 °C. The research showed that temperature significantly affects the bearing strength of the joint. Around 42–50% decrease in bearing strength was observed at 250 °C as compared to room temperature. Stacking sequence variations have a little more effect on bearing strength at higher temperature than at room temperature. With the change of stacking sequences, around 11–24% variation in bearing strength was observed at 250 °C as compared to 8–20% at room temperature.

Effect of delamination on the fatigue life of GFRP: A thermographic and numerical study

Delamination is the major failure mechanism in composite laminates and eventually leads to material failure. An early-detection and a better understanding of this phenomenon, through non-destructive assessment, can provide a proper in situ repair and allow a better evaluation of its effects on residual strength of lightweight structural components. Here we adopt a joint numerical-experimental approach to study the effect of delamination on the fatigue life of glass/epoxy composites. To identify and monitor the evolution of the delamination during loading, we carried out stepwise cyclic tests coupled with IR-thermography on both undamaged and artificially-damaged samples. The outcome of the tests shows that IR-thermography is able to identify a threshold stress, named damage stress σD, which is correlated to the damage initiation and the fatigue performance of the composite. Additionally, we performed FE-simulations, implementing the delamination by cohesive elements. Such models, calibrated on the basis of the experimental fatigue results, can provide a tool to assess the effect of parameters, such as the delamination size and location and composite stacking sequence, on the residual strength and fatigue life of the composite material.

Composite layup effect on the failure mechanism of single lap bonded joints

Single lap bonded joints with four different composite adherend stacking sequences were tested and numerically simulated. The aim was to evaluate the effect of the layups on the quasi-static tensile failure of the bonded joints. The study shows that increasing the adherends bending stiffness postpones the damage initiation in the joint. However, this is no longer valid for final failure. The ultimate load is influenced by how the damage progresses. For similar bending stiffness, a layup that leads to the crack propagating from the adhesive towards the inside layers of the composite increases the ultimate load. The failure mode is highly influenced by the orientation of the interface lamina in contact with the adhesive, such that, a 0° interface ply causes failure within the bond line, while a 90° interface ply causes failure inside the composite adherend.Finally, it is concluded that a quasi-isotropic layup may not be the best choice in terms of tensile joint strength. In order to improve tensile strength up to damage initiation, the layup should be optimized for bending stiffness, while up to final failure, a stacking sequence that yields to a complex crack path inside the composite can lead to higher ultimate loads.

Simple Progression Law in Predicting the Damage Onset and Propagation in Composite Notched Laminates

The aim of this article is to simulate the damage initiation and progression in unidirectional (UD) laminates. A three-dimensional (3D) failure criteria of Puck incorporated with degradation scheme is developed. Two types of degradation law known as sudden degradation are used to predict the damage progression in UD laminates. The establishment of constitutive law in progressive damage model (PDM) is achieved through implementation of user subroutines in Abaqus. The failure analysis is applied to various composite stacking sequences and geometries, as well as different fiber reinforced polymer (FRP) composite materials. The comparative studies revealed that the predicted ultimate failure load agree well with those available in the literature.

Simple Progression Law in Predicting the Damage Onset and Propagation in Composite Notched Laminates

The aim of this article is to simulate the damage initiation and progression in unidirectional (UD) laminates. A three-dimensional (3D) failure criteria of Puck incorporated with degradation scheme is developed. Two types of degradation law known as sudden degradation are used to predict the damage progression in UD laminates. The establishment of constitutive law in progressive damage model (PDM) is achieved through implementation of user subroutines in Abaqus. The failure analysis is applied to various composite stacking sequences and geometries, as well as different fiber reinforced polymer (FRP) composite materials. The comparative studies revealed that the predicted ultimate failure load agree well with those available in the literature.

Investigation of tensile behavior and influence factors of composite-to-metal 2D-scarf bonded joint

Composite-to-metal 2D (two dimensional) scarf bonded joint (SBJ) specimens with 4scarf angles were tested to study their tensile behaviors. Based on the experimental results, progressive damage finite element models (FEM) were established in ABAQUS/Standard, and the effects of three variables: the metal material, composite stacking sequence and adhesive properties, with respect to the joint tensile properties were investigated. The results show that the metal plasticity and scarf angle can affect the tensile plastic behavior of the joint. Compared with Q235 (steel), 7075-T6 (aluminium) and 30CrMnSiNi2A (steel) plates, TC4 (titanium) plate makes the joint possess higher tensile strength. Changing the composite plate (laminate) stacking sequences can result in the variation of plastic behavior and failure location of the joints. The adhesive properties have significant effects on the joint plastic behavior and ultimate loads.

Mechanical Characterization of Glass-Basalt-Carbon/Polyester Hybrid Composites

Influence of the stacking sequences of hybrid composites on the tensile strength, flexural strength, inter-laminar shear strength (ILSS) and impact energy was investigated. The hybrid glass-basalt-carbon/polyester composite laminates were processed by hand lay-up procedure at room temperature. The fracture surface of the composite laminates after the tension and flexural test was examined by scanning electron micrograph (SEM). The results show that the best mechanical properties were obtained for the composite laminates S5 at stacking sequences [C/B/C/B/C]; where the tensile strength, flexural strength, and ILSS were 148 MPa, 448 MPa, and 25 MPa, respectively. This decline in mechanical properties attributed to the good interfacial bonding between the fibres and the matrix in this configuration. On the other hand, the largest impact strength (43.70 kJ/mm2) was clearly observed for laminates S2 at the stacking sequences [C/G/C/G/C] compared to other laminates simply due to the high stiffness and strength of the carbon fabrics.

Experimental analysis of the linear and nonlinear vibration behavior of flax fibre reinforced composites with an interleaved natural viscoelastic layer

In this paper, linear and nonlinear vibration analyses are carried out on flax fibre reinforced composites with and without an interleaved natural viscoelastic layer. Experimental analysis was done in a clamped-free configuration on two stacking sequences of composites, [0]8 and [02/902]s. The procedure consists on exciting the specimens with different amplitude levels for the first six bending modes. The dynamic properties as frequencies and damping factors were studied, and the results obtained were analyzed and compared. Then, the amplitudes of deformations were determined and discussed for the different excitation levels. The presence of the non-linearity generated by the viscoelastic layer was clearly identified by the shift observed in the values of natural frequencies and loss factors with increasing excitation levels. The linear and nonlinear, elastic and dissipative parameters were calculated and compared.

Effects of the composite stacking sequence on the failure load of the single lap bonded joint

Composite materials are widely used in aircraft structures, their relative rigidity/weight confers their advantage over metal structures, and the stacking sequence plays an important role for their use. The objective of this work is to analyze by the finite element method the mechanical behavior of a single lap joint of composite/composite type under a tensile load. In order to see the effects on the failure load, two basic parameters are taken into consideration; the stacking sequence of composite and thickness of each layer constituting the composite. Calculation of the failure load is made numerically with the ABAQUS code using the developed technique of VCCT (Virtual Crack Closure Technique) based on fracture mechanics. Finally, the influence of the bonding defect on the failure load is analyzed. The results clearly show the importance of optimizing fiber orientation and hence the stacking sequence for proper use of composite in bonded assemblies.

The effect of fiber undulation on the strain field for pinned composite/titanium joints under tension

The way fiber undulation around pins affects pinned composite/titanium joints’ stiffness and strength properties is illustrated for double-lap-shear joints under quasi-static tensile loading. 3D digital-image-correlation techniques were employed to measure in-plane strain distribution on the surface of the composite joint member. Pinned joints with formed holes and three different composite stacking sequences were manufactured and compared to joints with drilled holes. Whereas in the case of joints with formed holes, the process of inserting the pin into uncured prepreg material created undulations, joints with drilled holes are characterized by a uniform fiber direction but partly broken fibers. Due to homogenization of the strain field within the load-carrying 0° layers, pinned composite/metal joints with formed holes proved to significantly outperform joints with drilled holes in terms of tensile stiffness and strength.

Composite stacking sequence optimization for aeroelastically tailored forward-swept wings

A method for stacking sequence optimization and aeroelastic tailoring of forward-swept composite wings is presented. It exploits bend-twist coupling to mitigate aeroelastic divergence. The method proposed here is intended for estimating potential weight savings during the preliminary aircraft design stages. A structural beam model of the composite wingbox is derived from anisotropic shell theory and the governing aeroelastic equations are presented for a spanwise discretized forward swept wing. Optimization of the system to reduce wing mass is undertaken for sweep angles of −35° to 0° and Mach numbers from 0.7 to 0.9. A subset of lamination parameters (LPs) and the number of laminate plies in each pre-defined direction (restricted to {0°,±45°, 90°}) serve as design variables. A bi-level hybrid optimization approach is employed, making use of a genetic algorithm (GA) and a subsequent gradient-based optimizer. Constraints are implemented to match lift requirements and prevent aeroelastic divergence, excessive deformations, airfoil stalling and structural failure. A permutation GA is then used to match specific composite ply stacking sequences to the optimum design variables with a limited number of manufacturing constraints considered for demonstration purposes. The optimization results in positive bend-twist coupling and a reduced structural mass. Results are compared to an uncoupled reference wing with quasi-isotropic layups and with panel thickness alone the design variables. For a typical geometry and a forward sweep of −25° at Mach 0.7, a wingbox mass reduction of 13 % was achieved.

Surface profile texture characterization of trimmed laminated composite in the stacking sequence direction

The surface texture characterization of laminate composites is complex due to its heterogeneous structure and to the different stratified surface properties. Profile roughness parameters are highly impacted by those different layer properties, and their distributions are relatively spread out. A new filtering technique is proposed to improve the surface roughness parameter efficiency. To present issues from current filtering methods and to highlight this new approach, profile surface roughness taken from trimmed carbon fibre reinforced plastics samples are inspected in the composite stacking sequence using a contact profilometer. For each measurement, several roughness parameters are calculated. The efficiency of different filtering techniques is investigated through the roughness parameters distribution, calculated for up- and down-milling and for different tool wear. The new proposed technique, based on the separate characterization of plateaus and large deep valleys of the composite surface profiles, is found to be particularly efficient on the down-milling face.

Failure Analysis of Composite Thin Walled Multi-Cell Closed Cross Section Beams with Multi-Tapered Configuration

This paper explicitly highlights the failure analysis and study of thin walled composite beams (multi-cell and multi-tapered) in cantilever configurations when subjected to constrained torsional load, using MSC Patran / Nastran finite element package. Initially, the verification of the model was done with the analytical results in order to ensure the model accuracy. All the multi-tapered beams under examination are composed of closed section and three cell configuration with twisting moment applied at the free end. There is a vivid description of all the effects of different composite material and various stacking sequences on the margin of safety and failure loads. This paper also verifies the influence of various geometrical configurations (Beam lengths, tapered angles and point of variation of tapered angles) of beams on the failure loads. This paper would help in the wing design phase of modern agile and high speed aircraft in which multi-cell closed cross section beams are integral part.

Optimisation of 700 bar type IV hydrogen pressure vessel considering composite damage and dome multi-sequencing

This study investigated with the optimisation of the composite stacking sequence of hydrogen pressure vessels manufactured by filament winding. It is a response to the need to develop cost-effective hydrogen energy carriers to permit greater use of hydrogen technology for transport and thus satisfy current environmental requirements. Within the framework of the OSIRHYS IV project, a comparison of the optimal solutions is presented. This comparison focuses on different optimisation strategies and methods including multi-sequence dome lay-up characteristics and composite damage. Optimisation results are compared and discussed with the aim of identifying optimal design rules to meet industrial needs. Finally, prospective work is presented.

Behavior of Circular Glass Fiber Reinforced Polymer Tubes Under Axial Compression

This project involves an evaluation of behaviour of circular GFRP tubes under axial compression. Circular tube columns having different length and cross sections resulting in the range of combinations of global and sectional slenderness, were tested under axial load. From this study, the compressive strength, ultimate load and failure modes were determined. After experimental investigation on evaluation of behavior of GFRP tubes, numerical investigation process is started, using ANSYS. Finite element models of the circular tubes will be generated and analyzed using SHELL elements. In this process orthotropic properties has been defined to align the material direction of the composite lay-up and stacking sequence. The experimental results were compared with the analytical results. It includes the parametric study of L/D and D/t ratio of various dimensions and orientation in finite element model. It gives the best orientation angle for the compressive behavior of GFRP tubes