• Title/Summary/Keyword: elastic composites

Search Result 458, Processing Time 0.024 seconds

Natural frequency of laminated composite plate resting on an elastic foundation with uncertain system properties

  • Lal, Achchhe;Singh, B.N.;Kumar, Rakesh
    • Structural Engineering and Mechanics
    • /
    • v.27 no.2
    • /
    • pp.199-222
    • /
    • 2007
  • Composite laminated structures supported on elastic foundations are being increasingly used in a great variety of engineering applications. Composites exhibit larger dispersion in their material properties compared to the conventional materials due to large number of parameters associated with their manufacturing and fabrication processes. And also the dispersion in elastic foundation stiffness parameter is inherent due to inaccurate modeling and determination of elastic foundation properties in practice. For a better modeling of the material properties and foundation, these are treated as random variables. This paper deals with effects of randomness in material properties and foundation stiffness parameters on the free vibration response of laminated composite plate resting on an elastic foundation. A $C^0$ finite element method has been used for arriving at an eigen value problem. Higher order shear deformation theory has been used to model the displacement field. A mean centered first order perturbation technique has been employed to handle randomness in system properties for obtaining the stochastic characteristic of frequency response. It is observed that small amount of variations in random material properties and foundation stiffness parameters significantly affect the free vibration response of the laminated composite plate. The results have been compared with those available in the literature and an independent Monte Carlo simulation.

Analysis of Effective Elastic Modulus and Interfacial Bond Strength of Aluminum Borate Whisker Reinforced Mg Matrix Composite by Using Three Dimensional Unit Cell Model (3차원 Unit Cell 모델을 이용한 알루미늄 보레이트 휘스커 강화 Mg 복합재료의 유효 탄성계수 및 계면강도의 분석)

  • Son, Jae Hyoung;Lee, Wook Jin;Park, Yong Ha;Park, Yong Ho;Park, Ik Min
    • Korean Journal of Metals and Materials
    • /
    • v.48 no.5
    • /
    • pp.469-475
    • /
    • 2010
  • In this study, the interfacial bond strength of a squeeze infiltrated $Al_{18}B_{4}O_{33}$/AS52 Mg composite was investigated by using a finite element method. Three types of Mg composites with volume fractions of 15, 25 and 35% were fabricated. Three-dimensional models of the composite were developed by using a unit cell model in order to determine the effective elastic modulus of the metal matrix composite and the interfacial bond strength between the whisker and magnesium matrix. After modeling, numerical results were compared with the experimental tensile test results of $Al_{18}B_{4}O_{33}$/AS52 Mg composites. The results showed that the effective modulus of the composite strongly depended on the interfacial strength between the matrix and reinforcement. Based on the numerical and experimental findings, it was found that the strong interfacial bond was achieved by the interfacial reaction product of 30 nm thick MgO, which led to an improvement in the mechanical properties of the $Al_{18}B_{4}O_{33}$/AS52 Mg composites.

The Effect of Steel-Fiber Contents on the Compressive Stress-Strain Relation of Ultra High Performance Cementitious Composites (UHPCC) (UHPCC의 압축응력-변형률 관계에 대한 강섬유 혼입률의 영향)

  • Kang, Su-Tae;Ryu, Gum-Sung
    • Journal of the Korea Concrete Institute
    • /
    • v.23 no.1
    • /
    • pp.67-75
    • /
    • 2011
  • The effect of steel-fiber contents on the compressive behavior of ultra high performance cementitious composites (UHPCC) was studied to propose a compressive behavior model for UHPCC. The experiments considered fiber contents of 0~5 vol.% and the results indicated that compressive strength and corresponding strain as well as elastic modulus were improved as the fiber contents increased. Compared to the previous study results obtained from concrete with compressive strength of 100MPa or less, the reinforcement effect on strength showed similar tendency, while the effect on the strain and elastic modulus were much less. Strength, strain, and elastic modulus according to the fiber contents were presented as a linear function of fiber reinforcement index (RI). Fiber reinforcement in UHPCC had no influence on the shape of compressive behavioral curve. Considering its effect on compressive strength, strain, and elastic modulus, a compressive stress-strain relation for UHPCC was proposed.

Mechanical Behavior of Indentation Stress in Carbon Fiber Reinforced Silicon Carbide Composites with Different Densities (서로 다른 밀도를 갖는 탄소섬유강화 탄화규소 복합재료의 압흔응력에 의한 기계적 거동)

  • Lee, Kee-Sung;Kim, Il-Kyum;Kim, Tae-Woo;Kim, Se-Young;Han, In-Sub;Woo, Sang-Kuk
    • Journal of the Korean Ceramic Society
    • /
    • v.48 no.4
    • /
    • pp.288-292
    • /
    • 2011
  • In this study, we investigated the mechanical behavior of carbon fiber reinforced silicon carbide composites by indentation stress. Relatively porous and dense fiber reinforced ceramic composites were fabricated by liquid silicon infiltration (LSI) process. Densification of fiber composite was controlled by hardening temperature of preform and consecutive LSI process. Load-displacement curves were obtained during indentation of WC sphere on the carbon fiber reinforced silicon carbide composites. The indentation damages at various loads were observed, and the elastic modulus were predicted from unloading curve of load-displacement curve.

Study of 2-Dimensional Model for the Thermal Expansion of Composite Materials (열팽창 계수의 2차원 해석 모델에 관한 연구)

  • Jeon, Hyeong-Jin;Yu, Sang-Won
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • 2005.11a
    • /
    • pp.95-98
    • /
    • 2005
  • This paper proposes the solutions predicting the coefficient of the thermal expansion changes of composites which include the fiber-like shaped ($a_1$ > ($a_2$ = ($a_3$) and the disk-like shaped (al = a2> a3) inclusions like two dimensional geometries, which has one aspect ratios, ${\alpha}$ = ($a_1$ /($a_3$). The analysis follows the procedure developed for elastic moduli by using the generalized approach of Eshelby’s equivalent tensor. The influences of the aspect ratios, on the effective coefficient of thermal expansion of composites containing aligned isotropic inclusions are examined. This model should be limited to analyze the composites with unidirectionally aligned inclusions and with complete binding to each other of both matrix and inclusions having homogeneous properties. The coefficient of thermal expansion of composites (${\theta}_{11}$,${\theta}_{22}$and ${\theta}_{33}$) are investigated. From material data of the composites with glass fiber in epoxy resin, the thermal expansions along the aspect ratio were obtained and similar to the Chow model. The longitudinal coefficients of thermal expansion ${\theta}_{11}$decrease, as the aspect ratios increase. However, the transverse coefficients of thermal expansion ${\theta}_{22}$increase or decrease, as the aspect ratios increase. And both of them decrease, as the concentration increases.

  • PDF

Effect of interface bonding strength on the recovery force of SMA reinforced polymer matrix smart composites (형상기억합금 선재가 삽입된 폴리머기지 능동복합재료의 회복력에 미치는 계면 접합강도의 영향)

  • 김희연;김경섭;홍순형
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • 2003.04a
    • /
    • pp.18-21
    • /
    • 2003
  • The effect of interface bonding strength on the recovery force of SMA wire reinforced polymer matrix composites was investigated by pullout test. Firstly, the recovery forces and transformation temperatures of various prestrained SMA wires were measured and 5% prestrained SMA wires were prepared for the reinforcements of composites. EPDM incorporated with 20vol% silicon carbide particles(SiCp) of 6, 12, $60{mutextrm{m}}$ size were used as matrix. Pullout test results showed that the interface bonding strength increased when the SiCp size decreased due to the increase of elastic modulus of matrix. Cyclic test of composites was performed through control of DC current at the constant displacement mode. The abrupt decrease of recovery force during cycle test at high current was occurred by thermal degradation of matrix. This was in good agreement with temperature related in the thermal degradation of matrix. The hysteresis of recovery force with respect to the temperature was compared between wire and composite and the hysterisis of composites was smaller than the wire due to less thermal conduction.

  • PDF

Elasticity and Conduction analysis of multi-Phase, Misoriented Metal matrix Composites (방향분포를 가진 다상 금속복합재료의 탄성 및 전도해석에 관한 연구)

  • 정현조
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.19 no.9
    • /
    • pp.2181-2193
    • /
    • 1995
  • The effective elasticity and conduction of composite materials containing arbitrarily oriented multiple phases has been analyzed using the concept of orientation-dependent average fields and concentration factors. The analysis provided closed form expressions for the effective stiffnesses and conductivities. Under the prescribed boundary conditions, the concentration factors were evaluated by the equivalent inclusion principle, through which the interaction between various phases is approximated by the Mori-Tanaka mean-field approximation. SiC particulate(SiC$_{p}$) reinforce aluminum(Al) matrix composites were fabricated and their elastic constants and electrical conductivities were measured together with a careful study of their microstructure. The measured properties showed a systematic anisotropy and this behavior could be attributed to the preferred orientation of SiC$_{p}$. The theoretical model developed was applied to the computation of the anisotropic properties of these composites. Both two-phase and three-phase composites were considered based on the microstructural information. The SiC$_{p}$ was modeled as an ellipsoid with planar random orientation distribution in the extruded Al/SiC$_{p}$ composites. The effect of extraneous phase such as intermetallic compounds was also investigated.tigated.

Numerical Simulation of Mechanical Behavior of Composite Structures by Supercomputing Technology

  • Kim, Seung-Jo;Ji, Kuk-Hyun;Paik, Seung-Hoon
    • Advanced Composite Materials
    • /
    • v.17 no.4
    • /
    • pp.373-407
    • /
    • 2008
  • This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

Long Wavelength Scattering Approximations for the Effective Elastic Parameters of Spherical Inclusion Problems (장파장 산란 근사를 이용한 구형 개재물 문제의 유효 탄성적 성질)

  • Jeong, Hyun-Jo;Kim, Jin-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.23 no.6 s.165
    • /
    • pp.968-978
    • /
    • 1999
  • The effective elastic properties of materials containing spherical inclusions were calculated by the elastic wave scattering theory. In the formulation additional scattering fields by the presence of random multiple scatterers that affects the effective properties were found by the single scattering approximation. In calculating the scattering fields the ensemble average on the displacements and strains inside the scatterer was found from the static approximation at long wavelength limit. The displacements were assumed to be equal to the incident field, while the strains were calculated by Eshelby's equivalent inclusion principle on the single inclusion problem. Four different models were considered and they reflected different degrees of multiple scattering effects based on the approximation introduced in the process of embedding the inclusion in the matrix. The expressions for the effective elastic constants were given in each model, and their relations to the results obtained from other scattering theory and elasticity theory were discussed. The theoretical predictions were compared with experimental results on the epoxy matrix composites containing tungsten particles of different sizes and volume fractions

Preparation and Characterization of Modified Natural Rubber Applied to Seismic Isolation Damper Rubber

  • Seong-Guk Bae;Woong Kim;Yu mi Yun;Jin Hyok Lee;Jung-Soo Kim
    • Elastomers and Composites
    • /
    • v.58 no.3
    • /
    • pp.128-135
    • /
    • 2023
  • To improve the adhesive strength of natural rubber (NR) for a seismic isolation damper, citraconic acid-g-NR (CCA-g-NR) was synthesized via the melt grafting of citraconic acid (CCA) onto NR using an azobisisnomerobutyronitrile (AIBN) initiator. Subsequently, the influence of CCA and AIBN concentrations on the graft ratio G/R (%) and graft efficiency G/E (%) of the CCA-g-NR was investigated. The optimum CCA and AIBN concentrations required to achieve the desired G/R (3.49%) and G/E (49.8%) were found to be 7 phr and 0.13 phr, respectively. Additionally, we studied the influence of CCA-g-NR concentration on the mechanical properties (tensile strength, elongation at break, and modulus at 300%), adhesive strength, and cure characteristics of the rubber compound in the seismic isolation damper. As the concentration of CCA-g-NR increased, the elongation at break and adhesive strength of the compound increased, whereas its tensile strength and modulus at 300% decreased. Moreover, as the concentration increased, the maximum torque decreased and the scorch time was delayed to obtain an optimal vulcanization time.