Investigation on interlaminar shear stresses in laminated composite beam under thermal and mechanical loading

Nagaraj Murugesan,Vasudevan Rajamohan 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.3

In the present study, the combined effects of thermal and mechanical loadings on the interlaminar shear stresses of both moderately thin and thick composite laminated beams are numerically analyzed. The finite element modelling of laminated composite beams and analysis of interlaminar stresses are performed using the commercially available software package MSC NASTRAN/PATRAN. The validity of the finite element analysis (FEA) is demonstrated by comparing the experimental test results obtained due to mechanical loadings under the influence of thermal environment with those derived using the present FEA. Various parametric studies are also performed to investigate the effect of thermal loading on interlaminar stresses generated in symmetric, anti-symmetric, asymmetric, unidirectional, cross-ply, and balanced composite laminated beams of different stacking sequences with identical mechanical loadings and various boundary conditions. It is shown that the elevated thermal environment lead to higher interlaminar shear stresses varying with the stacking sequence, length to thickness ratio, ply orientations under identical mechanical loading and boundary conditions of the composite laminated beams. It is realized that the magnitude of the interlaminar stresses along xz plane is always much higher than those of along yz plane irrespective of the ply-orientation, length to thickness ratios and boundary conditions of the composite laminated beams. It is also observed that the effect of thermal environment on the interlaminar shear stresses in carbon-epoxy fiber reinforced composite laminated beams are increasing in the order of symmetric cross-ply laminate, unidirectional laminate, asymmetric cross-ply laminate and anti-symmetric laminate. The interlaminar shear stresses are higher in thinner composite laminated beams compared to that in thicker composite laminated beams under all environmental temperatures irrespective of the laminate stacking sequence, ply-orientation and boundary conditions.

적층복합재료 T-빔 기반의 3차원 직조 프리폼 π-빔 개발

박건태 ( Geon-tae Park ),이동우 ( Dong-woo Lee ),변준형 ( Joon-hyung Byun ),송정일 ( Jung-il Song ) 한국복합재료학회 2020 Composites research Vol.33 No.3

적층복합재료, 특히 탄소섬유 복합재료는 금속에 비해 가벼우며 상대적으로 비강도 및 비강성이 뛰어나기 때문에 항공 우주 산업 및 자동차 산업 등과같이 광범위한 분야에서 사용되고 있다. 그러나, 적층 복합재료는 섬유의 배열이 모두 면내방향으로 배열되어있기 때문에 박리가 발생한다는 큰 단점이 있으며, 이는 적층복합재료의 응용분야를 제한한다. 본 연구에서는 먼저 π-빔과 평판이 결합된 형태의 적층복합재료 T-빔을 개발하고, 구조해석 및 기계적 물성평가를 통하여 설계변수를 최적화하였다. 이후 적층복합재료 T-빔의 설계변수를 3D 직조 프리폼에 동일하게 적용하여 T-빔을 개발하였으며, 적층구조에 비하여 향상된 기계적 강도를 달성할 수 있었다. 이러한 연구결과는 강도향상을 필요로 하는 기존의 적층복합재료 구조물에 적용 가능할 것으로 기대된다. Laminate composites, especially Carbon fiber-reinforced composites are wide used in various industry such as aerospace and automotive industry due to their high specific strength and specific stiffness. However, the laminate composites has a big disadvantage that delamination occurs because the arrangement of the fibers is all arranged in the in-plane direction, which limits the field of application of the laminate composites. In this study, we first developed a laminate composites T-beam in which π-beam and flat plate were combined and optimized the design parameters through structural analysis and mechanical tests. Afterwards, 3D weave preform T-beam was developed by applying the same design parameters of laminate composites T-beams, and improved mechanical strength was achieved compared to laminated structures. These findings are expected to be applicable to existing laminated composite structures that require increased strength.

Effect of agglomerated zirconia-toughened mullite on the mechanical properties of giant cane fiber mat epoxy laminated composites

Pruthwiraj Sahu,Sambit Kumar Parida,Sisir Mantry 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.2

This paper depicts the development and characterizations of laminated composites made with cellulosic giant cane (Arundinaria gigantea) fiber mats and epoxy resin. Zirconia-toughened mullite (ZTM) is used as a filler material in the laminated composite which was prepared from sillimanite through plasma processing technique. The mechanical characterizations of this composite have been carried out as per ASTM standards to evaluate its usability as a structural material. The effects of varying weight percentages of the filler and two different fiber orientations namely, angle-ply [+45°/-45°/+45°] and balanced cross-ply [0°/90°/0°] on the physical and mechanical properties such as density, microhardness, impact strength, tensile strength and interlaminar shear strength of the layered composite specimens have been investigated. The study indicates that the inclusion of zirconia-toughened mullite in the composite laminate as filler improves its mechanical properties. Moreover, the use of giant cane fiber mat in the laminate is more eco-friendly than the synthetic fibers. This research also helps in generating additional data to enrich the repository of natural fiber reinforced laminated composites.

Optimization Mechanisms of Microstructure and Mechanical Properties of SiC Fiber Reinforced Ti/Al3Ti Laminated Composite Synthesized Using Titanium Barrier

Chunfa Lin,Siyu Wang,Haoran Yan,Yuqiang Han,Junyi Zhu,Hao Shi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.2

A novel structure-optimized SiC fiber reinforced metal-intermetallic-laminated composite (SiCf-Ti/Al3Ti) without intermetalliccenterline defect has been fabricated by vacuum hot pressing using stacked fibers and foils as well as Ti barrierlayer. Through microstructure characterization by SEM and EBSD, the mechanisms of centerline formation and structuraloptimization were investigated detailedly. The mechanical properties and fracture behaviors of the optimized and nonoptimizedSiCf-Ti/Al3Ti composites were studied via quasi-static compression tests. The experimental results indicatedthat the intermetallic centerline region existing at the mid-plane of Al3Tilayer in non-optimized composite mainly containsnewly-formed Kirkendall voids and gathered metallic oxides. Additionally, owing to the similar moving trails of fibers,oxides and voids in molten Al during hot pressing, SiC fiber is always accompanied with centerline, which causes the poorbonding of SiCf/Al3Ti interface. Unlike that, due to the adding of Ti barrier layer, SiC fibers are separated from centerlineand metallurgically bonded with Al3Tiintermetallic in the optimized composite. The compression testing results proved thatthe optimized SiCf-Ti/Al3Ti composite possesses superior strength and toughness compared with those of the non-optimizedcomposite. Besides, the extending of cracks along centerline often leads to large-scale centerline splitting and untimelySiCf/Al3Ti interface debonding in non-optimized composite. Nevertheless, cracks formed in optimized composite tend topropagate at the interfacial zone between layers instead of cutting off Al3Tilayer along its mid-plane. Moreover, ascribedto the well-bonded SiCf/Al3Ti interface, SiC fibers play an important role in strengthening and toughening the optimizedSiCf-Ti/Al3Ti composite by fiber bridging mechanism.

Fuzzy reliability analysis of laminated composites

Chen, Jianqiao,Wei, Junhong,Xu, Yurong Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.6

The strength behaviors of Fiber Reinforced Plastics (FRP) Composites can be greatly influenced by the properties of constitutive materials, the laminate structures, and load conditions etc, accompanied by many uncertainty factors. So the reliability study on FRP is an important subject of research. Many achievements have been made in reliability studies based on the probability theory, but little has been done on the roles played by fuzzy variables. In this paper, a fuzzy reliability model for FRP laminates is established first, in which the loads are considered as random variables and the strengths as fuzzy variables. Then a numerical model is developed to assess the fuzzy reliability. The Monte Carlo simulation method is utilized to compute the reliability of laminas under the maximum stress criterion. In the second part of this paper, a generalized fuzzy reliability model (GFRM) is proposed. By virtue of the fact that there may exist a series of states between the failure state and the function state, a fuzzy assumption for the structure state together with the probabilistic assumption for strength parameters is adopted to construct the GFRM of composite materials. By defining a generalized limit state function, the problem is converted to the conventional reliability formula that enables the first-order reliability method (FORM) applicable in calculating the reliability index. Several examples are worked out to show the validity of the models and the efficiency of the methods proposed in this paper. The parameter sensitivity analysis shows that some of the mean values of the strength parameters have great influence on the laminated composites' reliability. The differences resulting from the application of different failure criteria and different fuzzy assumptions are also discussed. It is concluded that the GFRM is feasible to use, and can provide an effective and synthetic method to evaluate the reliability of a system with different types of uncertainty factors.

굴곡된 탄소나노튜브로 보강된 적층 복합재 판구조의 고유진동 특성

출템수렌천트 ( Chunt Chultemsuren ),최형배 ( Hyung Bae Choi ),이상열 ( Sang-youl Lee ) 한국복합재료학회 2021 Composites research Vol.34 No.2

본 논문은 Mori-Tanaka법, 혼합법칙 및 Halpin-Tsai 이론식을 적용하여 굴곡진 탄소나노튜브(CNT)로 보강된 복합재의 멀티스케일 고유진동 특성을 규명하였다. Eshelby 텐서를 이용하여 곡률을 갖는 CNT가 함유된 폴리머의 하중 전달 특성값이론을 유도하였다. 도출된 수치해석 결과는 기존의 연구결과와 잘 일치하였다. 본 연구에서 제시한 새로운 결과는 적층 복합재의 CNT 함유량, 굴곡성 및 적층배열의 상호작용 특성을 규명하였다. 주요 결과에 대하여 분석하였으며, CNT 보강 복합재의 실용적 설계를 위한 중요 고려사항을 제시하였다. This paper dealt with multi-scale natural frequency characteristics of wavy CNT (carbon nanotube) reinforced composites by applying the Mori-Tanaka method, rule of mixture, and Halpin-Tsai equation. By compelling benefit of an ad-hoc Eshelby tensor, the load-transfer characteristics of CNT with a waviness implanted in the polymer matrix was determined. The numerical results obtained are in good agreement with those reported by other investigators. Furthermore, the new results reported in this paper show the interactions between CNT weight, waviness ratios and layup sequences of laminated composites. Key observation points are discussed and significant considerations are given in practical designing of CNT reinforced composites.

Residual Stress on Concentric Laminated Fibrous Al₂O₃-ZrO₂ Composites on Prolonged High Temperature Exposure

Sarkar, Swapan Kumar,Lee, Byong Taek Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.9

This paper investigates the effect of prolonged high temperature exposure on concentric laminated $Al_2O_3-ZrO_2$ composites. An ultrafine scale microstructure with a cellular 7 layer concentric lamination with unidirectional alignment was fabricated by a multi-pass extrusion method. Each laminate in the microstructure was $2-3{\mu}m$ thick. An alternate lamina was composed of 75%$Al_2O_3$-(25%m-$ZrO_2$) and t-$ZrO_2$ ceramics. The composite was sintered at $1500^{\circ}C$ and subjected to $1450^{\circ}C$ temperature for 24 hours to 72 hours. We investigated the effect of long time high temperature exposure on the generation of residual stress and grain growth and their effect on the overall stability of the composites. The residual stress development and its subsequent effect on the microstructure with the edge cracking behavior mechanism were investigated. The residual stress in the concentric laminated microstructure causes extensive micro cracks in the t-$ZrO_2$ layer, despite the very thin laminate thickness. The material properties like Vickers hardness and fracture toughness were measured and evaluated along with the microstructure of the composites with prolonged high temperature exposure.

A modified particle swarm approach for multi-objective optimization of laminated composite structures

A. Sepehri,F. Daneshmand,K. Jafarpur 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.3

Particle Swarm Optimization (PSO) is a stochastic population based optimization algorithm which has attracted attentions of many researchers. This method has great potentials to be applied to many optimization problems. Despite its robustness the standard version of PSO has some drawbacks that may reduce its performance in optimization of complex structures such as laminated composites. In this paper by suggesting a new variation scheme for acceleration parameters and inertial weight factors of PSO a novel optimization algorithm is developed to enhance the basic version’s performance in optimization of laminated composite structures. To verify the performance of the new proposed method, it is applied in two multi-objective design optimization problems of laminated cylindrical. The numerical results from the proposed method are compared with those from two other conventional versions of PSObased algorithms. The convergancy of the new algorithms is also compared with the other two versions. The results reveal that the new modifications inthe basic forms of particle swarm optimization method can increase its convergence speed and evade it from local optima traps. It is shown that the parameter variation scheme as presented in this paper is successful and can evenfind more preferable optimum results in design of laminated composite structures.

등분포 축하중을 받고 첨가질량이 재하된 적층복합판의 고유진동수에 관한 연구

홍창우,김경진,Hong, Chang-Woo,Kim, Kyeong-Jin 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 논문집 Vol.4 No.4

Vibration analysis for some of simple supported antisymmetric composite laminated plate loaded uniform axial-loading and attached mass was carried out. Because it is complicated to analyze this type of plate by theory of antisymmetric laminate possibility for application of theory of special orthotropic laminate was studied, and natural frequency of laminated plate attached mass was calculated. Stiffness $B_{16}$, $B_{26}$, $D_{16}$, $D_{26}$ for this type of antisymmetric laminated plate converge on zero as the number of ply increases and it is possible to use classical theory by reason that considered plate has quasi-homogeneity without relevance to variation of angle. Difference between results by theory of antisymmetric and special orthotropic laminate is 0.36~1.96%, therefore it is convenient to analyze this by use of theory of special orthotropic laminate. When composite laminated plate with attached mass is analyzed range that Was able to neglect self-weight of plate was proposed.

Application of silk composite to decorative laminate

Kimura, Teruo,Aoki, Shinpei The Korean Society for Composite Materials 2007 Advanced composite materials Vol.16 No.4

Recently, natural fiber reinforced composite is attracting attention and considered as an environmentally friendly material. Usually cellulosic fibers are used to reinforce the composites, but some protein fibers such as silk and wool serve the same purpose. In this paper, we proposed a method of producing artistic composite from artistic fabric by using silk fiber reinforced biodegradable plastic, which is designated as 'silk composite', for reinforcement. In order to expand applications of the silk composite, we performed the compression molding of decorative laminates with woody material, which was selected as a core material, and examined the properties of molded decorative laminates with various content of the silk composite. Since plywood and medium-density fiberboard (MDF) are widely used for decorative laminates, we selected them as core materials. As a result, flexible decorative laminates with high flexural strength were obtained by compounding the silk composite with wood materials.