Micromechanical analysis for transverse thermal conductivity of composites

2010 ◽  
Vol 45 (11) ◽  
pp. 1245-1255 ◽  
Author(s):  
Sangwook Sihn ◽  
Ajit K. Roy
Keyword(s):  
Thermal Conductivity ◽  
Numerical Solutions ◽  
Volume Fraction ◽  
Numerical Models ◽  
Matrix Material ◽  
Analytic Solutions ◽  
Fiber Distribution ◽  
Fiber Volume ◽  
Volume Fractions ◽  
Transverse Thermal Conductivity

Micromechanical analyses were conducted for the prediction of transverse thermal conductivity of laminated composites. We reproduced and reinvestigated both analytic and numerical models with regular and randomly distributed fibers in matrix material. A parametric study was conducted for wide ranges of fiber volume fractions and fiber-to-matrix thermal conductivity ratios. The numerical solutions using finite element (FE) analysis were compared with various analytic solutions from simple and enhanced rule or mixtures and an effective inclusion method (EIM). It was found that the EIM yields a reasonably agreeable solution with the FE solution using a hexagonal-array of regular fiber distribution for wide ranges of fiber volume fraction and fiber-to-matrix thermal conductivity ratios, which makes the EIM a useful method in predicting various multiphysical transverse properties of composites. Comparison of the results from the regular- and random-fiber models indicates that the transverse thermal conductivity of composites can significantly be affected by the random fiber distributions, especially at high fiber volume fractions. A similar conclusion was made for the foams with random pore distribution. It was shown that the predictions with the random fiber distribution agree well with the experimental data.

Numerical Analysis of the Transverse Thermal Conductivity of Composites With Imperfect Interfaces

2003 ◽  
Vol 125 (3) ◽  
pp. 389-393 ◽  
Author(s):  
Samuel Graham ◽  
David L. McDowell
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Ceramic Composites ◽  
Reinforced Composites ◽  
Continuous Fiber ◽  
Fiber Volume ◽  
Element Analysis ◽  
Imperfect Interfaces ◽  
Transverse Thermal Conductivity ◽  
Johnson Model

Estimation of the transverse thermal conductivity of continuous fiber reinforced composites containing a random fiber distribution with imperfect interfaces was performed using finite element analysis. FEA results were compared with the classical solution of Hasselman and Johnson to determine limits of applicability. The results show that the Hasselman and Johnson model predicts the effective thermal conductivity within 3 percent of the numerical estimates for interfacial conductance values of 1×10−2−1×103W/m2K, fiber-matrix conductivity ratios between 1 and 100, and fiber volume fractions up to 50 percent which are properties typical of ceramic composites. The results show that the applicability of the classical dilute concentration model can not be determined by constituent volume fraction, but by the degree of interaction between the microstructural heterogeneities.

Thermal conductivity of biomimetic leaf composite

2017 ◽  
Vol 52 (13) ◽  
pp. 1737-1746 ◽  
Author(s):  
G Liu ◽  
R Ghosh ◽  
D Mousanezhad ◽  
A Vaziri ◽  
H Nayeb-Hashemi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Composite Structures ◽  
Volume Fraction ◽  
Cell Structure ◽  
Matrix Material ◽  
Mechanical And Thermal Properties ◽  
Ceramic Fibers ◽  
Fiber Morphology ◽  
Fiber Volume

The venous morphology of a typical plant leaf affects its mechanical and thermal properties. Such a material could be considered as a fiber reinforced composite structure where the veins and the rest of the leaf are considered as two materials having highly contrast mechanical and thermal properties. The variegated venations found in nature is idealized into three principal fibers—the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary veins of a typical leaf. This paper addresses the in-plane thermal conductivity of such a composite by considering such a venous fiber morphology embedded in a matrix material. We have considered two cases, fibers having either higher or lower conductivity respect to the matrix. The tertiary fibers do not interconnect the secondary fibers in our present study. We carry out finite element based computational investigation of the thermal conductivity of these composites under uniaxial thermal gradients and study the effect of different fiber architectures. To this end, we use two broad types of architectures both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions are kept constant and a comparative parametric study is carried out by varying the inclination of the secondary fibers. We find the heat conductivity in the direction of the main fiber (Y direction) increases significantly as the fiber angle of the secondary increases. Furthermore, for composite with metal fibers, the conductivity in the Y direction is further enhanced when composite is manufactured by having secondary fibers forming a closed cell structure. However, for composite with ceramic fibers, the conductivity of the composite in the Y direction is little affected by having secondary fibers closed. An opposite behavior is observed when considering conductivity of the composite in the X direction. The conductivity of the composite in the X direction is reduced with increase in the angle of the secondary fibers. Higher conductivity in the X direction is achieved for composite with no closed cells for composites with metal fibers. The results also indicate that for composites with the constant fiber volume fraction, morphology of tertiary fibers may not significantly alter material conductivities. In conclusion, introducing a leaf-mimicking topology in fiber architecture can provide significant additional degrees of tunability in design of these composite structures.

Determination of fiber volume fraction in a cured laminate

2021 ◽  
pp. 002199832110112
Author(s):  
Qing Yang Steve Wu ◽  
Nan Zhang ◽  
Weng Heng Liew ◽  
Vincent Lim ◽  
Xiping Ni ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Fiber Volume Fraction ◽  
Evaluation Method ◽  
Volume Fraction ◽  
Matrix Material ◽  
Volume Ratio ◽  
Gravimetric Analysis ◽  
Fiber Volume ◽  
Laser Ultrasonic ◽  
The Matrix

Propagation of ultrasonic wave in Carbon Fiber Reinforced Polymer (CFRP) is greatly influenced by the material’s matrix, resins and fiber volume ratio. Laser ultrasonic broadband spectral technique has been demonstrated for porosity and fiber volume ratio extraction on unidirection aligned CFRP laminates. Porosity in the matrix materials can be calculated by longitudinal wave attenuation and accurate fiber volume ratio can be derived by combined velocity through the high strength carbon fiber and the matrix material with further consideration of porosity effects. The results have been benchmarked by pulse-echo ultrasonic tests, gas pycnometer and thermal gravimetric analysis (TGA). The potentials and advantages of the laser ultrasonic technique as a non-destructive evaluation method for CFRP carbon fiber volume fraction evaluation were demonstrated.

Performance of Bamboo Fiber Reinforced Composites: Mechanical Properties

2021 ◽  
Vol 879 ◽  
pp. 284-293
Author(s):  
Norliana Bakar ◽  
Siew Choo Chin
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Vinyl Ester ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Bamboo Fiber ◽  
Synthetic Fiber ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
Volume Fractions

Fiber Reinforced Polymer (FRP) made from synthetic fiber had been widely used for strengthening of reinforced concrete (RC) structures in the past decades. Due to its high cost, detrimental to the environment and human health, natural fiber composites becoming the current alternatives towards a green and environmental friendly material. This paper presents an investigation on the mechanical properties of bamboo fiber reinforced composite (BFRC) with different types of resins. The BFRC specimens were prepared by hand lay-up method using epoxy and vinyl-ester resins. Bamboo fiber volume fractions, 30%, 35%, 40%, 45% and 50% was experimentally investigated by conducting tensile and flexural test, respectively. Results showed that the tensile and flexural strength of bamboo fiber reinforced epoxy composite (BFREC) was 63.2% greater than the bamboo fiber reinforced vinyl-ester composite (BFRVC). It was found that 45% of bamboo fiber volume fraction on BFREC exhibited the highest tensile strength compared to other BFRECs. Meanwhile, 40% bamboo fiber volume fraction of BFRVC showed the highest tensile strength between bamboo fiber volume fractions for BFRC using vinyl-ester resin. Studies showed that epoxy-based BFRC exhibited excellent results compared to the vinyl-ester-based composite. Further studies are required on using BFRC epoxy-based composite in various structural applications and strengthening purposes.

Biomimetic composites inspired by venous leaf

2017 ◽  
Vol 52 (3) ◽  
pp. 361-372 ◽  
Author(s):  
Gongdai Liu ◽  
R Ghosh ◽  
A Vaziri ◽  
A Hossieni ◽  
D Mousanezhad ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Stress ◽  
Poisson’S Ratio ◽  
Composite Structures ◽  
Volume Fraction ◽  
Matrix Material ◽  
Poisson's Ratio ◽  
Fiber Volume ◽  
Young’S Moduli

A typical plant leaf can be idealized as a composite having three principal fibers: the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary fibers embedded in a matrix material. This paper introduces a biomimetic composite design inspired by the morphology of venous leafs and investigates the effects of venation morphologies on the in-plane mechanical properties of the biomimetic composites using finite element method. The mechanical properties such as Young’s moduli, Poisson’s ratio, and yield stress under uniaxial loading of the resultant composite structures was studied and the effect of different fiber architectures on these properties was investigated. To this end, two broad types of architectures were used both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions were kept constant and a comparative parametric study was carried out by varying the inclination of the secondary fibers. The results show that the elastic modulus of composite in the direction of main fiber increases linearly with increasing the angle of the secondary fibers. Furthermore, the elastic modulus is enhanced if the secondary fibers are closed, which mimics composites with closed cellular fibers. In contrast, the elastic modulus of composites normal to the main fiber ( x direction) exponentially decreases with the increase of the angle of the secondary fibers and it is little affected by having secondary fibers closed. Similar results were obtained for the yield stress of the composites. The results also indicate that Poisson’s ratio linearly increases with the secondary fiber angle. The results also show that for a constant fiber volume fraction, addition of various tertiary fibers may not significantly enhance the mechanical properties of the composites. The mechanical properties of the composites are mainly dominated by the secondary fibers. Finally, a simple model was proposed to predict these behaviors.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

Study on the In Situ Growth of Carbon Nanotubes for the Reinforcement of Cf/SiC Composite Fabricated by CVI+PIP Process

2013 ◽  
Vol 745-746 ◽  
pp. 582-586 ◽  
Author(s):  
Jian Bao Hu ◽  
Shao Ming Dong ◽  
Xiang Yu Zhang ◽  
Zhen Wang ◽  
Hai Jun Zhou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Bonding Strength ◽  
Volume Fraction ◽  
Interfacial Bonding ◽  
Mechanical And Thermal Properties ◽  
Fiber Volume ◽  
Pull Out ◽  
Interfacial Bonding Strength

Cf/SiC composites were fabricated through in situ growth of carbon nanotubes (CNTs) on three-dimensional needle-punched carbon fabric via chemical vapor deposition and polymer impregnation and pyrolysis process. The mechanical and thermal properties of the composites were investigated. The flexural strength and fracture toughness were decreased due to the fiber volume fraction loss and much shorter pull-out length of fibers which was caused by the higher interfacial bonding strength between fiber and matrix after the growth of CNTs. Brittle fracture character of CNTs was observed due to the strong interfacial bonding strength between CNTs and matrix. The parallel thermal conductivity and perpendicular thermal conductivity were improved to 14.5% and 8.0% respectively.

Determination of the Directional Dependent In-Plane Thermal Conductivity of K63B12 Pitch-Fiber/Epoxy Composite

2004 ◽  
Author(s):  
Jessica N. McClay ◽  
Peter Joyce ◽  
Andrew N. Smith
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
Fiber Composite ◽  
Fiber Volume ◽  
State Technique ◽  
Fiber Composite Materials

Measurements of the in-plane thermal conductivity and the directional dependence of Mitsubishi K63B12 pitch-fiber/Epoxy composite from Newport Composites are reported. This composite is being explored for use in the Avanced Seal Delivery System for effective thermal management. The thermal conductivity was measured using a steady state technique. The experimental results were then compared to a model of the thermal conductivity based on the direction of the fibers. These estimates are based on the properties of the constituent materials and volume of fibers in the sample. Therefore the density and the fiber volume fraction were experimentally measured. The thermal conductivity is clearly greatest in the direction of the fibers and decreases as the fibers are rotated off axis. In the case of pitch fiber composite materials, the contribution of the fibers to the thermal conductivity dominates. The experimental data clearly followed the correct trends; however, the measured values were 25% to 35% lower than predicted.

scholarly journals Effects of Hooked-End Steel Fiber Geometry and Volume Fraction on the Flexural Behavior of Concrete Pedestrian Decks

2019 ◽  
Vol 9 (6) ◽  
pp. 1241 ◽  
Author(s):  
Seung-Jung Lee ◽  
Doo-Yeol Yoo ◽  
Do-Young Moon
Keyword(s):  
Flexural Strength ◽  
Steel Fiber ◽  
Volume Fraction ◽  
Three Dimensional ◽  
High Strength ◽  
Flexural Behavior ◽  
Multiple Cracks ◽  
Fiber Volume ◽  
Volume Fractions ◽  
Steel Rebars

This study investigates the effects of hooked-end fiber geometry and volume fraction on the flexural behavior of concrete pedestrian decks. To achieve this, three different fiber geometries, i.e., three-dimensional (3D), four-dimensional (4D), and five-dimensional (5D), and volume fractions of 0.37%, 0.6%, and 1.0% were considered. Test results indicate that a higher number of hook ends can more effectively enhance the flexural strength and flexural strength margin at all volume fractions than a lower number, so that the order of effectiveness of hooked-end fibers on the flexural strength parameters was as follows: 5D > 4D > 3D. To satisfy the ductility index of 0.39, the amounts of 3D, 4D, and 5D hooked steel fibers should be in the range of 0.98%‒1.10%. Moreover, at a fiber volume fraction of 1.0%, only multiple cracking behaviors were observed, and the numerical results indicated that the volume fraction should be equal to 1.0% to guarantee a deflection-hardening response of pedestrian decks, regardless of the hooked-end fiber geometry. Consequently, a 1.0% by volume of hooked-end steel fiber is recommended to replace the minimum longitudinal steel rebars and guarantee a ductile flexural behavior with multiple cracks for pedestrian decks made of high-strength concrete.

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