Stacking Sequence Of Composite Laminates Research Articles

Efficient design of Kevlar/basalt hybrid composite laminates under ballistic impact

Advanced composite materials such as Kevlar and basalt are most commonly used for the efficient design of body armor to predict the safety and reliability of the armor systems. The aim of this study is to develop the lightweight and efficient design of armor plate using the 3D Kevlar/basalt hybridization and different stacking sequences of composite laminates impacting with two impactors under high-velocity impact. Damage initiation and damage propagation based on the Yen criteria are developed to investigate the different failure modes of composites. The hybrid composite panels are modeled using 3D solid element considering the four different types of panels such as H3B3, H3K3, B3K3 and K3-16 impacting with fragment simulating projectile (FSP) and 9 mm full metal jacket(FMJ) projectiles. The efficient design of hybrid panel B3K3 showed excellent ballistic performance parameters in comparison to the other hybrid panels designed under the FSP and FMJ projectiles.

Failure mechanisms of kenaf/glass sandwich laminates subjected to low velocity impact loading

Stacking sequences of composite laminates have significant effects not only on the properties of composites but also on the types of damage occurred on the composites structure. The current study investigated the low velocity impact properties and the damage progression of kenaf core sandwich laminates in different layering sequence of fibre laminates. There were three different sequences of kenaf (K) and glass (G) fibre reinforced unsaturated polyester composites, that is, G/K/G hybrid, G/K/K hybrid and K/K/K composites, which were fabricated using hand lay-up method. The layer of gelcoat provided a protective layer and finishing to the composite. The composites experienced the low velocity impact at three different energy levels which were 5 J, 10 J and 15 J. Through the research, a diamond shape matrix cracking was exhibited on the gelcoat surface. The main failure mode that occurred on the specimen during the low velocity impact was matrix cracking, fibre breakage, delamination and fibre pulled-out. From the results, G/K/G hybrid resisted the highest impact energy which is up to 10 J and G/K/K hybrid resisted up to 5 J. Meanwhile K/K/K composite failed to resist any of designated energy. Therefore, it can be suggested that G/K/G hybrid composites had shown good performance in low velocity impact properties to be used as the bus bumper material.

Fundamental frequency maximization of composite rectangular plates by sequential permutation search algorithm

Due to the classical thin plate theory based governing equations of composite rectangular plates for dynamic problems are linear homogeneous equations on bending stiffness coefficients, a general sequential permutation search (SPS) algorithm is presented to optimize stacking sequences of composite laminates by exploiting convexity of lamination parameters, sensitivity of bending stiffness, and bending-twisting coupling stiffness feature. Numerical examples are conducted for 8-layer composite rectangular plates with different boundaries to maximize the fundamental frequency evaluated by the Rayleigh–Ritz method, and the results are compared with those of layerwise optimization approach and genetic algorithm, demonstrating robustness and efficiency of SPS.

Realistic Stacking Sequence Optimisation of an Aero-Engine Fan Blade-Like Structure Subjected to Frequency, Deformation and Manufacturing Constraints

Aims:A procedure to optimise the stacking sequence of a composite fan blade-like structure is proposed in this article. The aim of the optimisation is to minimise weight when respecting deformation, frequency and strain constraints. The literature often deals with stacking sequence optimisation of airplane wings or wind turbine blades whilst less attention has been dedicated to aero-engines fan blades, the objective of the present paper. The manufacturing constraints are also implemented in the optimisation process in order to obtain a manufacturable structure.Background:Stacking sequence of composite laminates can be tailored to drive the deformation towards the desired shape (potentially exploiting unbalanced laminates and their anisotropy). When optimising the stacking sequence (including blending/tapering) of an aero-engine fan blade-like structure, manufacturing constraints must be included in order to apply the results of the optimisation procedure into a “Real World” design.Objectives:To define an engineering procedure able to provide a good design point to minimise the weight of a fan blade-like structure subjected to deformation (tip extension and untwist), frequency and strain constraints.Methods:A two-level optimisation procedure is proposed. At the first level, the stacking sequence is optimised in such a way to maximise stiffness (and therefore to minimise deformation). Less stringent limits are applied to the constraints of such a level 1 optimisation. In the second step of the optimisation, the blending/tapering of each ply of the stacking sequence is searched.Results:The fan blade-like structure is loaded only with a centrifugal load (the main load acting on this kind of components). The stacking sequence obtained to minimise the weight contains 42.3% of 0 degrees fibres, 19.25% of 45 degrees fibres, 19.25% of -45 degrees fibres and 19.2% of 90 degrees fibres. Blending in terms of width and length of each layer is given in the numerical results section.Conclusions:When the fan blade-like structure is loaded with a centrifugal force only, in order to minimise weight by respecting untwist, tip extension, frequency and integrity constraints, no unbalance in the laminate has been found necessary. An “Optimum” point has been found after a two steps optimisation. This design point is claimed as a good industrial design point rather than as “optimum” in the mathematical sense. Such a “Best Solution” design point has been verified by exploring the design space near it. All the performance of the neighbour points has been found worse. A comparison between a quasi-isotropic laminate and a zero degreed dominated laminate has been also performed.

A block-queue based optimization method for composite structures blended with multiple templates

Maintaining the continuity (blending) of stacking sequences is very vital when the stacking sequences of a multi-region panel is being optimized. The traditional attempt simplifies the difficulty of the blending problem by designing the whole panel based on one stacking template. However, this simplification adds an unnecessary constraint that regions with the same thickness should have the same stacking sequence. In order to overcome the drawback, this paper introduces a region block queue based method to obtain the optimal manufacturable stacking sequences of composite laminates blended from multiple stacking templates. The method discussed here groups regions into blocks, forming a block queue, and designs the entire laminate panel with multiple stacking templates, which are respectively applied to different blocks. The continuity between two adjacent blocks is guaranteed by sequentially rebuilding the template of a block from the sequences of adjacent regions within its previous block in the queue. An 18-region benchmark problem is chosen to prove the effectiveness of the proposed method, and the solution obtained is 0.27kg lighter than the traditional template-based method. The reduction of mass reveals that the use of multiple templates does contribute to searching for lighter solution.

Improved one-dimensional beam model for unbalanced composite single-lap joint

An analytical nonlinear solution was provided for unbalanced composite single-lap joint (CSLJ) using an improved one-dimensional beam model, which incorporated the effect of bending–tension coupling. The bending–tension coupling stiffness was introduced to characterize the coupling bending and tension behavior induced by the un-symmetric stacking sequence of composite laminates. The governing differential equations captured the bending–tension coupling behavior and the geometrically nonlinear features were constructed based on the displacement compatibility conditions of flexible interface. The transverse deformation in overlap region, edge moment factors and adhesive stress distributions for the unbalanced CSLJ with inflexible, intermediate flexibility and flexible adhesive can be determined by the present one-dimensional beam model. The accuracy of the present model was validated by the comparison with nonlinear finite element model. The effect of bending–tension coupling on edge moment factors and peak values of adhesive stresses was shed light on with the present model.

Effect of Quasi-Static Loading on the Composite Laminates

The low velocity impact is a common phenomenon which occurs in fiber reinforced polymer composite products like LPG cylinders, fighter aircraft fuel drop tanks, aircraft wing surfaces, sports goods etc. The consequences of low velocity impact will create a considerable damage and ultimately lead to a premature failure of the structure. Hence the polymer composites for engineering applications must be provided with a better design solution. From the literature survey it is observed that, the response of composite laminates subjected to quasi-static loading, exhibits similar results as that of low velocity impact. Polymer reinforced composites are poor in damage tolerance with better strength to weight ratio than conventional materials. However composite materials can be tailored to meet the design requirements by manipulating fiber orientations and laminae stacking sequence. In the present paper, principles of classical laminate theory are considered for analysis. FEM is implemented for thorough understanding of the failure mechanism of each laminate by layer wise. Simulated quasi-static loading tests and observed the layer wise distribution of transverse strain intensity. The experimental setup is designed and fabricated as per ASTM D 6264 standards. The E-glass/epoxy composite laminate is quasi-statically loaded at its center by a steel ball indenter of diameter 8.7mm and its response is measured by the degree of opacity or translucency in terms of interlaminar and intra-laminar damage area. The stacking sequence of composite laminates are chosen as [00/600]12, [00/750]12 and [00/900]12. The damage areas obtained from numerical analysis are in good agreement with experimental results.

Finite element study into the effects of fiber orientations and stacking sequence on drilling induced delamination in CFRP/Al stack

Abstract This research work has been aimed at understanding the effects of different fiber orientations and different stacking sequences of composite laminates on their damage during drilling of CFRP/Al stack. Finite element code Abaqus/CAE has been used for the implementation and analysis of the numerical model. Surface-based cohesive behavior available in Abaqus/CAE contact pairs has been used to simulate delamination behavior in the adhesive interfaces. In order to use the Hashin damage criterion (for intra-laminar damage) available in the finite element code, continuum shell elements have been used for laminates. Three stacking sequences each with 24 layers including [0°]24, [0°/90°]12s, and [−45°/90°4/45°2/−45°]3s have been considered for this study. The display group manager available in Abaqus/CAE visualization module enabled the individual access of the damage in each layer. Two layers both at drill entry and at CFRP/Al interface were used to study peel-up and push-down delamination, respectively. Sequence [0°]24 was found to have the largest damaged in both entry and interfaces, while sequence [−45°/90°4/45°2/−45°]3s was found to show better resistance to delamination damage.

Residual stress and electromagnetic characteristics in loop type frequency selective surface embedded hybrid structures

Residual stresses occur in frequency-selective surface (FSS)-embedded composite structures after co-curing due to differences between the coefficients of thermal expansion between composite skins and FSSs. Furthermore, the electromagnetic characteristics may be affected by the deformation of the FSS pattern by residual stresses. Therefore, we studied the changes in electromagnetic characteristics due to the deformation of FSS, using residual stresses to deform loop-type FSS-embedded hybrid composites. We considered the effects of loop-type FSS patterns of equal dimension as well as the stacking sequences of composite laminates on the electromagnetic characteristics of FSSs: Square loop, triangular loop and circular loop. The stacking sequences of composite laminates considered in this study were [0]8, [0/90]4, [±45]4 and [0/±45/90]2. The FSS was located between composite laminates in the middle plane. To determine the residual stresses and deformations in the FSS embedded laminate structures, the thermal loading condition in the finite element analysis was induced by cooling the hybrid structures from 125°C to 20°C based on the cure cycle of the composite. Also, the electromagnetic reflection characteristics of the hybrid structures were predicted using deformed models by residual stresses, considering the effects of stacking sequence of composite laminates. The results showed that the maximum residual stresses and deformations were produced in the [0]8 composites with all three loop-types of FSS pattern. However, the maximum resonance frequency shifts occurred in the square and triangle loop-types with stacking sequence of [0]8, while the maximum resonance frequency shift occurred in the circular loop-type with stacking sequence of [0/±45/90]2.

Free-edge stress analysis of functionally graded material layered biocomposite laminates.

A stress function based theory is proposed to obtain free-edge stress distributions for three-dimensional, orthotropic, linearly elastic rectangular biocomposite laminates with surface-bonded functionally graded materials (FGM). The assumed stress fields automatically satisfy the pointwise equilibrium equation, as well as traction-free and free edge boundary conditions. The complementary virtual work principle, followed by the general eigenvalue solution procedure, is used to obtain 3-D free edge stress states. A typical stacking sequence of composite laminate is used as numerical investigation with surface bonded FGMs. It is shown that with proper exponential factor of FGMs, the interlaminar stresses at the FGM layer interface can be reduced significantly, in return to prevent debonding of FGM layers. This approach can be useful in the design of functionally graded material layered biocomposite structures.

루프 종류의 FSS가 결합된 복합재료 구조의 잔류응력과 전파 투과 특성

Abstract In this paper, the delamination and failures in frequency selected surface(FSS) caused by residual stresses in the FSS embedded hybrid composites due to the difference between the coefficients of thermal expansion of components and the transmission characteristic changes due to deformation of FSS patterns by residual stresses were studied. FSS may have different electromagnetic characteristics depending on the type of element, design variables, and arrangement. Design variables of dipole FSS were determined using PSO(Particle Swarm Optimization) to obtain the transmission characteristic for the target resonant frequency. Subsequently, the design variables of other types of N-pole(tripole, cross dipole, and Jerusalem cross) were determined based on the dimensions of the dipole for the comparisons of residual stresses of FSS embedded composite structures and transmission characteristics. In addition, effects of FSS pattern, and stacking sequence of composite laminates were considered.

Glass composite vibration isolating structure for the LNG cargo containment system

The primary barrier of the cargo containment system (CCS) for the liquefied natural gas (LNG) carriers is subjected to large impact loads due to the cavitation of LNG. Therefore, the impact loads should be reduced to protect the insulation foam from cracking because the foam has very low fracture toughness at the operating temperature of −163°C.In this study, a corrugated-plate type vibration isolating structure (VIS) has been developed using glass fiber reinforced composites to reduce the load transmissibility from the primary barrier to the insulation foam of the CCS at cryogenic temperature. The uniform spring constant characteristic was achieved by optimizing the stacking sequence of the composite laminate and the wavelength of the corrugation. The crack resistance of the VIS against the impact load was measured by the drop weight impact test with respect to the stacking sequence of the glass composite laminate. The specifications of the VIS were obtained by the finite element analysis and experiments. Also, the durability against repetitive impacts on the VIS was investigated.

Thermal deformation constraint using response surfaces for optimization of stacking sequences of composite laminates

Carbon fiber reinforced plastic (CFRP) laminates are used extensively in aerospace structures. The laminated CFRP composite structures require optimal design of the stacking sequences. Modifications to the stacking sequences change the thermal deformation that results from the CFRP laminate curing process. Even if a stacking sequence provides maximum buckling load, the laminate is unacceptable if it displays large deformations after the curing process. Therefore, this study deals with the constraint of thermal deformation after the curing process. Maximization of the buckling load was targeted as the objective function here. Three types of response surfaces were proposed to estimate the thermal deformation and their fit was investigated. The mode classification method was found to be excellent. Using the mode classification response surface, a stacking sequence optimization to maximize the buckling stress was performed. The new mode classification method was shown to be appropriate for optimization of the curing process constraints.

N-pole 종류의 FSS가 결합된 복합재료 구조의 잔류응력과 전파투과특성

In this paper, the delamination and failures in frequency selected surface(FSS) caused by residual stresses in the FSS embedded hybrid composites due to the difference between the coefficients of thermal expansion of components and the transmission characteristic changes due to deformation of FSS patterns by residual stresses were studied. FSS may have different electromagnetic characteristics depending on the type of element, design variables, and arrangement. Design variables of dipole FSS were determined using PSO(Particle Swarm Optimization) to obtain the transmission characteristic for the target resonant frequency. Subsequently, the design variables of other types of N-pole(tripole, cross dipole, and Jerusalem cross) were determined based on the dimensions of the dipole for the comparisons of residual stresses of FSS embedded composite structures and transmission characteristics. In addition, effects of FSS pattern, and stacking sequence of composite laminates were considered.

Stacking sequence optimization of laminated composite structures using genetic algorithm with local improvement

Interest in the application of genetic algorithms (GA) to the stacking sequence of composite laminates has grown in recent years. However, the huge calculation time of GA is a major problem for designers. In this study, a local improvement is inserted into a standard GA, and the real calculation, by finite element analysis (FEA) for example, required in the local search is replaced by a regression model. Accordingly, the improved GA converges much sooner than a standard GA and the calculation time is greatly reduced. The regression analysis applies chosen trigonometric functions as base functions, and estimates objective function values accurately using only few sample points. The GA with local improvement is then applied to a sandwich plate and composite propeller, the amount of calculation is reduced by over half.

A comparison between two optimization methods on the stacking sequence of fiber-reinforced composite laminate

This article is dealing with the study of optimization for the stacking sequence of composite laminates by two optimization methods of simplex and interior penalty. In the simplex method, both the applicable domain of magnifying factors (MFs) and the differences of stacking sequence optimization between symmetrical and unsymmetrical laminate composites are studied. When the values of MFs are 50, 70, 85, the converging of optimization process is faster and its result is more accurate. The strength of the unsymmetrical laminate with fewer layers is larger than that of the symmetric one by 8% only. But when the layers are increased, the strength of symmetric laminate is higher. In the interior penalty method, the error value can be kept within 5–6%, while in the simplex method the more layers the larger the error value. To sum up, proved by progressive failure simulation of finite element analysis, the best strength of composite laminate with optimal stacking sequence can be obtained.

低速／高速衝撃試験によるＣＦ／ＰＥＥＫの耐衝撃損傷性の評価

The subperforation flatwise impact damage resistance of carbon fiber/PEEK (CF/PEEK) laminated composites (APC-2/AS4) was evaluated under low and high velocity impact tests. The stacking sequences of the specimens were [0°/30°/0°/-30°]s, [0°/60°/0°/-60°]s and [0°/45°/90°/-45°]s. The drop weight test system as the low velocity impact test and the air gun test system as the high impact test were used to consider the effect of impact velocity on damage area. The damage areas after impact were measured with the ultrasonic C-Scan. The impact damage resistance was assessed as the ratio of the damage area (DA) and the impact energy (IE). To estimate the effect of the stacking sequence related to the impact resistance (DA/IE), the stacking parameter β, which indicates the difference in in-plane stiffness between the adjacent laminae, is proposed. From the experimental results, it is obtained that the stacking parameter β is valid to select better stacking sequence of composite laminate for impact resistance.

Optimum stacking sequence of composite laminates for maximum strength

A method is presented for maximum strength optimum design of symmetric composite laminates subjected to in-plane and transverse loadings. The finite element method based on shear deformation theory is used for the analysis of composite laminates. Ply orientation angles are chosen as design variables. The quadratic failure criterion which is meant to predict fracture, is used as an object function for optimum stacking sequence design of a laminated plate. The Broydon-Fletcher-Goldfarb-Shanno optimization technique is employed to solve the optimization problem effectively. Numerical results are given for various loading conditions, boundary conditions, and aspect ratios. The results show that the quadratic failure criterion such as Tsai-Hill theory is effective for the optimum structural design of composite laminates.