Earticle

The object of this study is to investigate the penetration characteristics according to the change of stacking sequences and curvature radius in the composite laminated shell. They are staked to [02/902]S and [0/902/0]s, their interlaminar number are two and four. We manufactured the composite laminated shells with various curvature radiuses. Curvature radiuses of composite shell are 100, 150, 200mm and ∞ (it's meaning flat-plate). In general, the kinetic energy before and after impact increased linearly in all specimens, and the absorbed energy of the specimen [02/902]S with a small number of the interlaminars was higher than specimen [0/902/0]s.

An efficient procedure to obtain the optimal stacking sequence and the minimum weight of stiffened laminated composite curved panels under several loading conditions and stiffener layouts has been developed based on the finite element method and the genetic algorithm that is powerful for the problem with integer variables. Often, designing composite laminates ends up with a stacking sequence optimization that may be formulated as an integer programming problem. This procedure is applied for a problem to find the stacking sequence having a maximum critical buckling load factor and the minimum weight. The object function in this case is the weight of a stiffened laminated composite shell. Three different types of stiffener layouts with different loading conditions are investigated to see how these parameters influence on the stacking sequence optimization of the panel and the stiffeners. It is noticed from the results that the optimal stacking sequence and lay-up angles vary depending on the types. of loading and stiffener spacing.

This study is to investigate the energy absorption characteristics of CFRP(Carbon-Fiber Reinforced Plastics) tubes on static and dynamic tests. Axial static compression tests have been carried out using the static testing machine(Shin-gang buckling testing machine) and dynamic compression tests have been utilized using an vertical crushing testing machine. When such tubes are subjected to crushing loads, the response is complex and depends on the interaction between the different mechanisms that could control the crushing process. The collapse characteristics and energy absorption have been examined for various tubes. Energy absorption of the tubes are increased as changes in the lay-up which may increase the modulus of tubes. The results have been varied significantly as a function of ply orientation and interlaminar number.

The CFRP composite has a lot of merits such as mechanical characteristic, light and thermal resistance. For these merits, CFRP is applied to so many industrial area. In order to use the composite materials in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise ,machining. In this study, the specimens differentiating the stacking sequence of 5kinds were used. When drilling the carbon fiber reinforced plastics, it was checked on whether the stacking sequence reached any effect on the cutting force. Also relationship between the drill diameter is examined from the drilling experiment, which is the drilling of Fabric, Unidirectional specimen with ∅6mm, ∅10mm, ∅12mm cemented carbide drill. Considering cutting force and drilling diameter, the results are analyzed.

This study aims to examine an effect of stacking sequence and curvature on the penetration characteristic of a composite laminated shell. For the purpose, we manufactured specimens with different stacking sequences and curvatures, and conducted a penetration test using an air-gun. To examine an influence according to stacking sequence, as flat plate and curvature specimen had more plies, their critical penetration energy was higher, Critical penetration energies of specimen A and C with less interfaces somewhat higher than those of B and D with more interfaces. The reason that with less interfaces, critical penetration energy was higher is pre-impact bending stiffness of composite laminated shell with less interfaces was lower than that of laminated shell with more interfaces, but bending stiffness after impact was higher. And it is because interface, the weakest part of the composite laminated shell, was influenced by transverse impact. As curvature increases, critical penetration energy increases linearly. It is because as curvature increases, resistance to in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. Patterns of cracks caused by penetration of composite laminated shells include interlaminar crack, intralaminar crack, and laminar fracture. A 0$^{\circ}$ply laminar had a matrix crack, a 90$^{\circ}$ply laminar had intralaminar crack and laminar fracture, and interface between 0$^{\circ}$and 90$^{\circ}$laminar had a interlaminar crack. We examined crack length and delamination area through a penetration test. For the specimen A and C with 2 interface, the longest circumferential direction crack length and largest delamination area were observed on the first interface from the impact point. For the specimen B and D with 4 interface, the longest crack length and largest delamination area were observed on the third interface from the impact point.

In this study, the three-dimensional finite element method is used to determine the stress intensity factor in Mode I and Mixed mode of a centered crack in an aluminum specimen repaired by a composite patch using contour integral. Various mesh densities were used to achieve convergence of the results. The effect of adhesive joint thickness, patch thickness, patch-specimen interface and layer sequence on the SIF was highlighted. The results obtained show that the patch-specimen contact surface is the best indicator of the deceleration of crack propagation, and hence of SIF reduction. Thus, the reduction in rigidity of the patch especially at adhesive layer-patch interface, allows the lowering of shear and normal stresses in the adhesive joint. The choice of the orientation of the adhesive layer-patch contact is important in the evolution of the shear and peel stresses. The patch will be more beneficial and effective while using the cross-layer on the contact surface.

In this study, the effect of stacking sequence on the flexural and fracture properties of carbon/basalt/epoxy hybrid composites was investigated. Two types of carbon/basalt/epoxy hybrid composites with a sandwich form were fabricated: basalt skin-carbon core (BSCC) composites and carbon skin-basalt core (CSBC) composites. Fracture tests were conducted and the fracture surfaces of the carbon/basalt/epoxy hybrid composites were then examined using scanning electron microscopy (SEM). The results showed that the flexural strength and flexural modulus of the CSBC specimen respectively were ~32% and ~245% greater than those of the BSCC specimen. However, the interlaminar fracture toughness of the CSBC specimen was ~10% smaller than that of the BSCC specimen. SEM results on the fracture surface showed that matrix cracking is a dominant fracture mechanism for the CSBC specimen while interfacial debonding between fibers and epoxy resin is a dominant fracture process for the BSCC specimen.

Impact damages induced by a low-velocity impact load on carbon fiber reinforced polymer (CFRP) composite plates fabricated with various stacking sequences were studied experimentally. The impact responses of the CFRP composite plates were significantly affected by the laminate stacking sequences. Three types of specimens, specifically quasi-isotropic, unidirectional, and cross-ply, were tested by a constant impact carrying the same impact energy level. An impact load of 3.44 kg, corresponding to 23.62 J, was applied to the center of each plate supported at the boundaries. The unidirectional composite plate showed the worst impact resistance and broke completely into two parts; this was followed by the quasi-isotropic lay-up plate that was perforated by the impact. The cross-ply composite plate exhibited the best resistance to the low-velocity impact load; in this case, the impactor bounced back. Impact parameters such as the peak impact force and absorbed energy were evaluated and compared for the impact resistant characterization of the composites made by different stacking sequences.

In this research, the effects of fiber stacking sequence on damage behaviors of FML(Fiber Metal Laminates) subject to indentation loading. SOP (Singly Oriented Ply) FML and angle ply FML were fabricated to study fiber orientation effects and angle ply effects. FML were fabricated by using 1050 aluminum laminate and carbon/epoxy prepreg. To increase adhesive bonding strength, Al laminate was etched using FPL methods. The static indentation test were conducted by using UTM(5ton, Shimadzu) under the 2side clamped conditions. During the tests, load and displacement curve and crack initiation and propagation behaviors were investigated. As fiber orientation angle increases, the crack initiation load of SOP FML increases because the stiffness induced by fiber orientation is increased. The penetration load of SOP FML is influenced by the deformation tendency and boundary conditions. However, the macro-crack of angle ply FML was initiated by fiber breakage of lower ply because angle plies in Angle ply FML prevents the crack growth and consolidation. The Angle ply FML has a critical cross-angle which prevent crack growth and consolidation. Damage behavior of Angle ply FML is changed around the critical cross-angle.

An optimization procedure is proposed to determine the optimal stacking sequence on the buckling of laminated composite plates with midplane symmetry under various loading conditions. Classical lamination theory is used for the determination of the critical buckling load of simply supported angle-ply laminates. Analysis is performed by the Galerkin method and Rayleigh-Ritz method. The approximate solution of buckling is replaced by the algorithms that produce generalized eigenvalue problem. Direct search technique is employed to solve the optimization problem effectively. A series of computations is carried out for plates having different aspect ratios, different load ratios and different number of lay-ups.

탄소섬유 복합재료는 우수한 물성을 바탕으로 산업 전반에 활용되고 있으나 취성이 강하다는 단점이 있다. 연신율이 높은 소재와의 하이브리드화를 통해 강도는 다소 감소되더라도 파괴인성을 향상시킬 수 있다. 이 연구에서는 탄소섬유와 아라미드섬유를 하이브리드한 적층 판재의 물성을 평가하되, 적층 순서를 다르게 하여 이종 재료와의 계면 형성 정도를 조절하였다. 그 결과 25%의 아라미드 섬유 포함 시 순수 탄소섬유 대비 최대 63%의 Izod 충격강도의 향상을 확인할 수 있었으며, 중간 정도의 복잡도를 가진 적층순서 [CF/CAF₂/CF]_s 에서 가장 우수하였다. 그러나 전체적인 복합화 효과는 부정적인 것으로 분석되었다.

Carbon fiber-reinforced composites have excellent mechanical properties. However, the fracture toughness is a disadvantage due to brittle failure mode. The fracture toughness can be enhanced using hybridization with large-elongation fibers. In this study, polyamide (aramid) fibers are hybridized with carbon fiber with various stacking sequences. As a result, the Izod impact strength was enhanced by 63% with 25% aramid fiber hybridization. It is also shown that there is an optimal point in laminated composite hybridization, [CF/CAF₂/CF]_s stacking sequence.

천연 하이브리드 복합재는 친환경성, 경량성, 저비용 등의 장점으로 인해 기존 합성 복합재를 대체할 수 있는 유망한 소재로 간주되고 있다. 본 연구에서는 이러한 복합재의 충격 흡수 성능을 극대화하기 위한 방안으로 양자 어닐링(Quantum Annealing, QA)이 적용되었다. 적층 순서의 최적화는 6종의 천연섬유(Bamboo, Flax, Hemp, Ramie, Jute, Kenaf)와 19가지 섬유 각도의 조합으로 구성된 총 114개의 변수에 대해 수행되었으며, 각 조합의 굽힘 특성은 고전 적층판 이론에 기반한 곡률 반경 분석을 통해 산정되었다. 이 곡률 반경은 충격 하중 하에서의 변형 저항성을 반영하는 지표로 활용되었으며, 목적함수는 QUBO(Quadratic Unconstrained Binary Optimization) 형태로 변환되어 양자 어닐러에 임베딩되었다. 비중 및 비용에 대한 제약 조건이 반영된 QA 기반의 조합 최적화가 수행되었고, 도출된 적층 조합은 샤르피 충격 해석을 통해 평가되었다. 분석 결과, Ramie와 Jute 섬유가 상호보완적으로 적층된 조합 D에서 가장 높은 충격 흡수 에너지가 기록되었다.

Natural hybrid composites are considered promising alternatives to conventional synthetic composites due to their eco-friendliness, light weight, and low cost. In this study, quantum annealing (QA) was applied as a strategy to maximize the impact energy absorption performance of such composites. The stacking sequence optimization was performed on 114 variables derived from the combinations of six natural fibers (Bamboo, Flax, Hemp, Ramie, Jute, and Kenaf) and 19 fiber orientation angles. The bending characteristics of each combination were evaluated through radius of curvature analysis based on classical laminate theory, and the resulting values were used as indicators of deformation resistance under impact loading. The objective function was reformulated into a Quadratic Unconstrained Binary Optimization (QUBO) model and embedded into a quantum annealer. QA-based combinatorial optimization was conducted under specific gravity and cost constraints, and the resulting stacking configurations were evaluated through Charpy impact simulation. The analysis revealed that combination D, in which Ramie and Jute fibers were complementarily stacked, achieved the highest impact energy absorption.

현대의 방탄 장갑은 우수한 관통 저항성을 갖추어야할 뿐만 아니라 군인과 군용차량의 기동성이 확보되어야 하기 때문에 경량화가 중요한 개발 요소가 되었다. 이종 적층 평판 구조의 방탄 장갑의 방탄 성능은 동일 중량 대비 구성 재료의 배열에 따라 달라진다. 본 논문에서는 케블라, 초고분자량 폴리에틸렌 그리고 에바 폼으로 구성된 방탄 장갑의 적층 배열에 따른 방탄 성능을 분석한다. 구성 재료의 두께가 5mm와 6.5mm인 두 가지 경우에서 6가지 적층 배열에 대하여 7.62 × 51mm NATO 탄환의 M80 탄을 856m/s의 속도로 충돌시키는 피탄 해석을 수행하였다. 방탄 성능을 평가하기 위해 이종 적층 평판을 관통한 발사체의 잔류 속도와 잔류 에너지를 측정하였다. 시뮬레이션 결과를 통해 케블라, 초고분자량 폴리에틸렌, 에바 폼의 배열 순서를 갖는 적층 구조가 동일 중량에 대해 가장 우수한 방탄 성능을 가짐을 확인하였다.

Modern bulletproof armor must be light and have excellent penetration resistance to ensure the mobility and safety of soldiers and military vehicles. The ballistic performance of heterogeneous structures of laminated flat plates as bulletproof armor depends on the arrangement of constituent materials for the same weight. In this study, we analyze bulletproof performance according to the stacking sequence of laminated bulletproof armor composed of Kevlar, ultra-high molecular weight polyethylene, and ethylene-vinyl-acetate foam. A ballistic analysis was performed by colliding a 7.62 × 51 mm NATO cartridge's M80 bullet at a speed of 856 m/s with six lamination arrangements with constituent materials thicknesses of 5 mm and 6.5 mm. To evaluate the bulletproof performance, the residual speed and residual energy of the projectile that penetrated the heterogeneous laminated flat plates were measured. Simulation results confirmed that the laminated structure with a stacking sequence of Kevlar, ultra-high molecular weight polyethylene, and ethylene-vinyl-acetate foam had the best bulletproof performance for the same weight.

Stacking sequence optimization needs discrete programming techniques because ply angles are limited to a fixed set of angles such as $0^{\circ},\;{\pm}45^{\circ},\;90^{\circ}$. Two typical methods are genetic algorithm and branch and bound method. The goal of this paper is to compare the methods in the light of their efficiency and performance in handling the constraints and finding the global optimum. For numerical examples, maximization of buckling load is used as objective and optimization results from each method are compared.

In this study, hybrid composites for a door impact beam were manufactured through a stacking sequence and design conditions. Non-crimped fabrics, epoxy resin for prepreg compression molding (PCM), hardener, and reinforcement such as p-Aramid and high strength polypropylene (PP) were used in manufacturing the hybrid composites. Curing behaviors of the PCM epoxy resin were confirmed by analytical methods such as dynamic DSC and FT-IR spectroscopy. The storage modulus, loss modulus, and damping behaviors of these hybrid composites were analyzed by dynamic mechanical analyses. Mechanical properties of the hybrid composites, such as tensile strength, flexure strength, compressive strength, and interlaminar shear strength (ILSS), were measured with a universal testing machine. Dynamic drop impact tests were conducted to measure the impact resistances of the hybrid composites on the stacking sequence. After the drop impact test, fracture shapes of the specimens were observed using a stereoscopic microscope. Based on the fracture shapes developed during the drop impact test, it was concluded that the specimens reinforced either by p-Aramid or PP effectively resisted impact transformations.

본 연구에서는 탄소섬유 강화 복합재료(Carbon Fiber Reinforced Polymer, CFRP) 압력용기 실린더의 적층 순서가 충격 손상 및 잔류 파열압력에 미치는 영향을 분석하였다. 이를 위해 연속체 손상역학(Continuum Damage Mechanics, CDM) 기반의 손상 모델을 적용한 유한요소해석(Finite Element Analysis, FEA)을 수행하여, 충격 에너지에 따른 실린더의 충격 거동, 손상 양상 및 파열압력을 평가하였다. 분석 결과, 적층 순서 변화만으로도 충격 거동과 손상 양상이 크게 달라졌다. 30 J 충격 시 BM의 경우 잔류 파열압력이 34.6 MPa에서 24.2 MPa로 30.1% 감소한 반면, 교차 적층(M1, M4) 모델의 경우 각각 30.2 MPa(-12.5%)와 33.2 MPa(-3.5%)로 저하폭이 현저히 줄었다. 이는 후프층과 헬리컬층을 교차 배치할 경우 층간 분리가 다소 늘어나더라도 후프층 섬유 손상이 억제되어 파열압력의 급격한 저하는 방지되는 것을 확인하였다.

This study analyzes the effect of the stacking sequence of a carbon fiber reinforced polymer (CFRP) pressure vessel cylinder on impact damage and residual burst pressure. To achieve this, finite element analysis (FEA) incorporating a continuum damage mechanics (CDM)-based damage model was conducted to evaluate the impact behavior, damage patterns, and burst pressure of the cylinder under different impact energy levels. The results indicate that the impact behavior and damage characteristics vary significantly depending on the stacking sequence of the composite material. Under a 30 J impact, the BM’s residual burst pressure dropped from 34.6 MPa to 24.2 MPa (-30.1%), whereas the cross-ply models M1 and M4 fell only to 30.2 MPa (-12.5%) and 33.2 MPa (-3.5%), respectively. When hoop and helical layers are alternately stacked, delamination damage increases internally. However, the dispersion of impact energy effectively suppresses fiber damage in the hoop layers, preventing a significant reduction in burst pressure.