A Study on the Thermoelastic Analysis in Shear Deformable Discontinuous Composites

2004 ◽  
Vol 261-263 ◽  
pp. 645-650
Author(s):  
Hong Gun Kim
Keyword(s):  
Thermal Stresses ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Fiber Composite ◽  
Element Model ◽  
Short Fiber ◽  
Elastic Stresses ◽  
Fiber Aspect Ratio ◽  
The Matrix ◽  
Lag Model

A stress analysis has been performed to evaluate the thermally induced elastic stresses which can develop in a short fiber composite due to coefficient of thermal expansion (CTE) mismatch. An axisymmetric finite element model with the constraint between cells has implemented to find the magnitude of thermoelastic stresses in the fiber and the matrix as a function of volume fraction, CTE ratio, modulus ratio, and fiber aspect ratio. It was found that the matrix end regions fall under significant thermal stresses that have the same sign as that of the fibers themselves. Furthermore, it was found that the stresses vary along the fiber and fiber end gap in the same manner as that obtained in a shear-lag model during non-thermal mechanical loading.

Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

1992 ◽  
Vol 50 (1) ◽  
pp. 158-159
Author(s):  
Warren J. Moberly ◽  
Daniel B. Miracle ◽  
S. Krishnamurthy
Keyword(s):  
Thermal Stresses ◽  
Load Transfer ◽  
Coefficient Of Thermal Expansion ◽  
Hot Isostatic Pressing ◽  
Matrix Composites ◽  
Ongoing Research ◽  
Aerospace Applications ◽  
Sic Fiber ◽  
The Matrix ◽  
Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

scholarly journals Stress Transfer from Axially Loaded Fiber to Matrix in a Microcomposite

1994 ◽  
Vol 365 ◽  
Author(s):  
Chun-Hway Hsueh
Keyword(s):  
Analytical Solutions ◽  
Volume Fraction ◽  
Axial Stress ◽  
Stress Transfer ◽  
Radial Dependence ◽  
Shear Lag ◽  
Shear Lag Model ◽  
The Matrix ◽  
Lag Model ◽  
Loaded Fiber

ABSTRACTThe shear lag model has been used extensively to analyze the stress transfer in a singe fiberreinforced composite (i.e., a microcomposite). To achieve analytical solutions, various simplifications have been adopted in the stress analysis. Questions regarding the adequacy of those simplifications are discussed in the present study for the following two cases: bonded interfaces and frictional interfaces. Specifically, simplifications regarding (1) Poisson's effect, and (2) the radial dependences of axial stresses in the fiber and the matrix are addressed. For bonded interfaces, the former can be ignored, and the latter can generally be ignored. However, when the volume fraction of the fiber is high, the radial dependence of the axial stress in the fiber should be considered. For frictional interfaces, the latter can be ignored, but the former should be considered; however, it can be considered in an average sense to simplify the analysis. Comparisons among results obtained from analyses with various simplifications are made.

scholarly journals Role of titanium carbide and alumina on the friction increment for Cu-based metallic brake pads under different initial braking speeds

Friction ◽  
2020 ◽  
Author(s):  
Tao Peng ◽  
Qingzhi Yan ◽  
Xiaolu Zhang ◽  
Yan Zhuang
Keyword(s):  
Wear Resistance ◽  
Titanium Carbide ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Interface Bonding ◽  
Brake Pads ◽  
Reinforced Composite ◽  
The Poor ◽  
The Matrix

AbstractTo understand the effect of abrasives on increasing friction in Cu-based metallic pads under different braking speeds, pad materials with two typical abrasives, titanium carbide (TiC) and alumina (Al2O3), were produced and tested using a scale dynamometer under various initial braking speeds (IBS). The results showed that at IBS lower than 250 km/h, both TiC and Al2O3 particles acted as hard points and exhibited similar friction-increasing behavior, where the increase in friction was not only enhanced as IBS increased, but also enhanced by increasing the volume fraction of the abrasives. However, at higher IBS, the friction increase was limited by the bonding behavior between the matrix and abrasives. Under these conditions, the composite containing TiC showed a better friction-increasing effect and wear resistance than the composite containing Al2O3 because of its superior particle-matrix bonding and coefficient of thermal expansion (CTE) compatibility. Because of the poor interface bonding between the matrix and Al2O3, a transition phenomenon exists in the Al2O3-reinforced composite, in which the friction-increasing effect diminished when IBS exceeded a certain value.

scholarly journals Finite Element Simulation of the Thermo-mechanical Response of Graphene Reinforced Nanocomposites

2018 ◽  
Vol 188 ◽  
pp. 01016
Author(s):  
Androniki S. Tsiamaki ◽  
Nick K. Anifantis
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Mechanical Response ◽  
Volume Fraction ◽  
Matrix Material ◽  
Continuum Theory ◽  
Element Model ◽  
Multilayer Graphene ◽  
Temperature Changes ◽  
The Matrix

The research for new materials that can withstand extreme temperatures and present good mechanical behavior is of great importance. The interest is highly focused on the utilization of composites reinforced by nanomaterials. To cope with this goal the present work studies the mechanical response of graphene reinforced nanocomposite structures subjected to temperature changes. A computational finite element model has been developed that accounts for both the reinforcement and the matrix material phases. The model developed is based on both the continuum theory and the molecular mechanics theory, for the simulation of the three different material phases of the composite, respectively, i.e. the matrix, the intermediate transition phase and the reinforcement. Considering this model, the mechanical response of an appropriate representative volume element of the nanocomposite is simulated under various temperature changes. The study involves different types of reinforcement composed from either monolayer or multilayer graphene sheets. Apart from the investigation of the behavior of a nanocomposite with each particular type of the reinforcement, comparisons are also presented between them in order to reveal optimized material combinations. The principal parameters taken into consideration, which contribute also to the mechanical behavior of the nanocomposite, are its size, the sheet multiplicity as well as the volume fraction.

Fracture behavior of short-fiber reinforced materials

1992 ◽  
Vol 7 (11) ◽  
pp. 3120-3131 ◽  
Author(s):  
Michael Murat ◽  
Micha Anholt ◽  
H. Daniel Wagner
Keyword(s):  
Fracture Process ◽  
Fracture Behavior ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Finite Size ◽  
Critical Length ◽  
Short Fiber ◽  
Fiber Volume ◽  
Linear Elastic ◽  
Fiber Reinforced Materials

A discrete model of springs with bond-bending forces is proposed to simulate the fracture process in a composite of short stiff fibers in a softer matrix. Both components are assumed to be linear elastic up to failure. We find that the critical fiber length of a single fiber composite increases roughly linearly with the ratio of the fiber elastic modulus to matrix modulus. The finite size of the lattice in the direction perpendicular to the fiber orientation considerably alters the behavior of the critical length for large values of the modulus ratio. The simulations of the fracture process reveal different fracture behavior as a function of the fiber content and length. We calculate the Young's modulus, fracture stress, and the strain at maximum stress as a function of the fiber volume fraction and aspect ratio. The results are compared with the predictions of other theoretical studies and experiments.

An Improved Shear-Lag Model for a Single Fiber Composite with a Ductile Matrix

2007 ◽  
Vol 334-335 ◽  
pp. 333-336
Author(s):  
Souta Kimura ◽  
Jun Koyanagi ◽  
Takayuki Hama ◽  
Hiroyuki Kawada
Keyword(s):  
Fiber Composite ◽  
Matrix Material ◽  
Single Fiber ◽  
Uniaxial Tensile ◽  
Fiber Direction ◽  
Stress Distributions ◽  
Shear Lag ◽  
Shear Lag Model ◽  
The Matrix ◽  
Lag Model

A shear-lag model is developed to predict the stress distributions in and around an isolated fiber in a single-fiber polymer matrix composite (PMC) subjected to uniaxial tensile loading and unloading along the fiber direction. The matrix is assumed to be an elasto-plastic material that deforms according to J2 flow theory. The stress distributions are obtained numerically and compared with a different shear-lag model that employs total strain theory as a constitutive equation of the matrix material. An effect of the difference between the models on the derived stress state is discussed.

Mechanical Properties of Biomimetic Leaf Composite

2016 ◽  
Author(s):  
Hamid Nayeb Hashemi ◽  
Gongdai Liu ◽  
Ashkan Vaziri ◽  
Masoud Olia ◽  
Ranajay Ghosh
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Poisson’S Ratio ◽  
Composite Structures ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Poisson's Ratio ◽  
Closed Cell ◽  
Cell Architecture ◽  
The Matrix

In this paper, we mimic the venous morphology of a typical plant leaf into a fiber composite structure where the veins are replaced by stiff fibers and the rest of the leaf is idealized as an elastic perfectly plastic polymeric matrix. The variegated venations found in nature are 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. The tertiary fibers do not interconnect the secondary fibers in our present study. We carry out finite element (FE) based computational investigation of the mechanical properties such as Young’s moduli, Poisson’s ratio and yield stress under uniaxial loading of the resultant composite structures 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 significant effect of fiber inclination on the overall mechanical properties of the composites with higher fiber angles transitioning the composite increasingly into a matrix-dominated response. We also find that in general, composites with only secondary fibers are stiffer with closed cell architecture of the secondary fibers. The closed cell architecture also arrested the yield stress decrease and Poisson’s ratio increase at higher fiber angles thereby mitigating the transition into the matrix dominated mode. The addition of tertiary fibers also had a pronounced effect in arresting this transition into the matrix dominated mode. However, it was found that indiscriminate addition of tertiary fibers may not provide desired additional stiffness for fixed volume fraction of constituents. In conclusion, introducing a leaf-mimicking topology in fiber architecture can provide significant additional degrees of tunability in design of these composite structures.

Effect of Fiber Volume Fraction on High Temperature Creep of Al2O3-SiO2(sf)/AZ91D Composite

2011 ◽  
Vol 474-476 ◽  
pp. 548-552
Author(s):  
Jun Tian
Keyword(s):  
Creep Resistance ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Matrix Alloy ◽  
Short Fiber ◽  
Tensile Creep ◽  
Short Fibers ◽  
Creep Tests ◽  
Fiber Volume ◽  
The Matrix

Constant stress tensile creep tests were conducted on AZ91D–20 vol.%, 25 vol.%, and 30 vol.% Al2O3-SiO2short fiber composites and on an unreinforced AZ91D matrix alloy. The creep resistance of the reinforced materials is shown to be considerably improved compared with the matrix alloy. With the increasing volume fraction of short fibers, the creep resistance of AZ91D composites is improved, and their creep threshold stresses are also increased accordingly. Because of the increasing volume fraction of short fibers, loads of bearing and transmission of short fibers will increase, and thus the creep resistance of AZ91D composites further improves, but the precipitation of β-Mg17Al12precipitate increases in the number, it is easy to soften coarse, so that threshold stress of AZ91D composite does not increase greatly.

scholarly journals Microstructure-based modeling of the dynamic mechanical properties of SiCp/Al composites

2016 ◽  
Vol 23 (4) ◽  
pp. 363-366
Author(s):  
Mei Ni Yuan ◽  
Yan Qing Yang ◽  
Qiao Juan Gong ◽  
Chao Li ◽  
Xian Zhong Lang
Keyword(s):  
Flow Stress ◽  
Volume Fraction ◽  
Dynamic Properties ◽  
Particle Volume Fraction ◽  
Element Model ◽  
Dynamic Mechanical Properties ◽  
Strengthening Effect ◽  
Particle Volume ◽  
The Matrix ◽  
Angular Particles

AbstractUsing image processing and recognition, a microstructure-based finite element model (FEM) was established to predict the dynamic properties of SiCp/Al composites at different strain rates ranging from 200 to 14,000 s-1. In the microstructure-based FEM, the irregular SiC particles were randomly distributed in the matrix, and its configurations did not change. The results showed that the flow stress of SiCp/Al composites with low particle volume fraction first increases and then decreases with the increasing of strain rate during the adiabatic compression. The reducing flow stress of SiCp/Al composites is caused by the inner damage and the heat softening of composites. The angular particles in SiCp/Al composites provide more strengthening effect than the circle particles when the strain is <0.62, while the circle particles provide more strengthening effect than the angular particles for strain >0.62.

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