scholarly journals An extension of the strain transfer principle for fiber reinforced materials

2021 ◽  
Vol 67 (5) ◽  
pp. 1453-1463
Author(s):  
Felix Ospald ◽  
Kai Bergermann ◽  
Roland Herzog
Keyword(s):  
Matrix Material ◽  
Fiber Direction ◽  
Transfer Principle ◽  
Underlying Assumption ◽  
Strain Transfer ◽  
Soft Matrix ◽  
Surrounding Matrix ◽  
Sensor Position ◽  
Fiber Reinforced Materials ◽  
The Matrix

AbstractFiber optical strain sensors are used to measure the strain at a particular sensor position inside the fiber. In order to deduce the strain in the surrounding matrix material, one can employ the strain transfer principle. Its application is based on the assumption that the presence of the fiber does not impede the deformation of the matrix material in fiber direction. In fact, the strain transfer principle implies that the strain in fiber direction inside the fiber carries over verbatim to the strain inside the matrix material. For a comparatively soft matrix material, however, this underlying assumption may not be valid. To overcome this drawback, we propose to superimpose the matrix material with a one-dimensional model of the fiber, which takes into account its elastic properties. The finite element solution of this model yields a more accurate prediction of the strain inside the fiber in fiber direction at low computational costs.

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.

scholarly journals Micromechanical evaluation of failure models for unidirectional fiber-reinforced composites

2019 ◽  
Vol 54 (6) ◽  
pp. 791-800
Author(s):  
Azam Arefi ◽  
Frans P van der Meer ◽  
Mohammad Reza Forouzan ◽  
Mohammad Silani ◽  
Mahmoud Salimi
Keyword(s):  
Matrix Material ◽  
Element Model ◽  
Failure Criteria ◽  
Fiber Reinforced Composites ◽  
Fiber Direction ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Wide Range ◽  
The Matrix ◽  
Stress States

In this paper, micromechanical simulations are employed to evaluate the performance of the Tsai–Wu and Hashin failure criteria for fiber-reinforced composites, especially in stress states whose experimental reproduction is complicated. Micromechanical responses are generated using a finite element model of a representative volume element, in which only the matrix material experiences damage and the fibers are assumed to be elastic. Micromechanical simulations of basic load cases are used to calibrate macrolevel criteria. Finally, the response of the micromodel and macromodels is compared for various load combinations. Despite a good agreement between Tsai–Wu criterion predictions and micromodel results in a wide range of stress states, some stress combinations are highlighted for which the strength is not predicted accurately. Additionally, accuracy of the Hashin criterion suffers from ignoring the influence of stress in fiber direction on matrix failure.

The electron spin resonance spectrum of trapped phenyl radicals prepared by chemical reaction at low temperature

1966 ◽  
Vol 293 (1433) ◽  
pp. 246-258 ◽  
Keyword(s):  
Unpaired Electron ◽  
Matrix Material ◽  
Electron System ◽  
High Reactivity ◽  
Phenyl Radical ◽  
Phenyl Radicals ◽  
Alkyl Radicals ◽  
Surrounding Matrix ◽  
Aromatic Radicals ◽  
The Matrix

Phenyl radicals have been prepared and trapped in a variety of solid matrices by the reaction of either sodium or potassium atoms with iodobenzene on the surface of the matrix material which was frozen at 77°K. A rotating cryostat was used to accumulate many layers of the products. The same e. s. r. spectrum was obtained in every case when water, benzene, deuterobenzene and perfluorocyclohexane were used as matrices. This spectrum has been attributed to the phenyl radical. When camphane, hexamethylethane and cyclohexane were used as matrices, different spectra were obtained in each case, and these have been attributed to the radicals formed by the abstraction of a hydrogen atom from a molecule of the matrix. This demonstrates the exceptional reactivity of the phenyl radical. When iodobenzene and xenon were used as matrices the spectra obtained may have been those of the phenyl radical, but modified by the surrounding matrix. The spectrum of the phenyl radical consists of nine hyperfine lines which can be attributed to a major hyperfine coupling of 18·1 Oe to the two ortho protons and a smaller coupling of 6·4 Oe to the two meta protons. It indicates that the unpaired electron remains in an sp 2 orbital on the carbon atom at which bond scission has occurred, to give a σ type radical. Such a structure contrasts with those of many aromatic radicals, such as benzyl, where the unpaired electron is delocalized over the π electron system, and is in accord with the high reactivity of the phenyl radical. This reactivity, however, is even higher than that of alkyl radicals, where the unpaired electrons are localized in π orbitals, and is attributed to the projection of the sp 2 orbital radially outwards from the ring of carbon atoms.

A Metal Matrix Composite Damage and Life Prediction Model

1998 ◽  
Vol 120 (4) ◽  
pp. 825-832 ◽  
Author(s):  
J. Ahmad ◽  
U. Santhosh ◽  
S. Hoff
Keyword(s):  
Metal Matrix ◽  
Fiber Strength ◽  
Matrix Material ◽  
Constitutive Models ◽  
Material Behavior ◽  
Fiber Direction ◽  
Matrix Composites ◽  
Composite Damage ◽  
Mechanistic Approach ◽  
The Matrix

A simple analytical model is derived for the prediction of time-dependent deformation and damage response of metal matrix composites under fiber direction loading. The model can be used in conjunction with a number of viscoplastic constitutive models to describe the matrix material behavior. Damage in the form of progressive fiber fractures is incorporated using a mechanistic approach. The criterion for fiber fractures can be based on statistical information on fiber strength. When used in conjunction with a prescribed failure condition for a composite, the model provides a means for predicting composite life under general thermomechanical load conditions. Based on comparison of results with detailed finite element analyses and with laboratory test data, it appears that the simple model provides reasonably accurate predictions.

scholarly journals MODELS FOR INTRALAMINAR DAMAGE AND FAILURE OF FIBER COMPOSITES - A REVIEW

2016 ◽  
Vol 14 (1) ◽  
pp. 1 ◽  
Author(s):  
Klaus Rohwer
Keyword(s):  
Failure Modes ◽  
Mutual Influence ◽  
Failure Process ◽  
Matrix Material ◽  
Fiber Composites ◽  
Fiber Direction ◽  
Shear Stresses ◽  
Fiber Failure ◽  
Damage And Failure ◽  
The Matrix

In order to fully exploit the potential of structures made from fiber composites, designers need to know how damage occurs and develops and under what conditions the structure finally fails. Anisotropy and inhomogeneity cause a rather complex process of damage development which may be one reason for an exceptionally large number of existing models. This paper intends to provide an overview over those models and give some hints about current developments. As such it is an updated version of a recent publication [1]. The survey is limited to laminates from unidirectional layers out of straight continuous fiber polymer composites under quasi-static loading. Furthermore, focus is laid on intralaminar damage.Many failure models smear out the inhomogeneity between fibers and the matrix. Simply limiting each stress component separately can lead to surprisingly good results as documented in the first World-Wide Failure Exercise. Interpolation criteria consider mutual influence of normal and shear stresses, predominantly through a quadratic failure condition. Traditionally one distinguishes between interpolation criteria and physically based ones. As an important physical effect the difference between fiber failure and inter-fiber failure is considered. Furthermore, stress invariants are taken as a basis, increased shear strength under compression is accounted for, and characteristic failure modes are captured. Fibers and the matrix material are characterized by a large disparity in stiffness and strength. Micromechanical models consider this inhomogeneity but suffer from the difficulty to determine relevant material properties. Compressive strength in fiber direction has attracted special attention. However, the role of kink band formation, which is observed in the failure process, seems to be not yet fully understood.In summary it must be concluded that despite the tremendous effort which has been put into the model development the damage and failure simulation of fiber composites are not in a fully satisfying state. That is partly due to lack of accurate and reliable test results. 

A Metal Matrix Composite Damage and Life Prediction Model

1997 ◽  
Author(s):  
Jalees Ahmad ◽  
Unnikrishnan Santhosh ◽  
Sandra Hoff
Keyword(s):  
Metal Matrix ◽  
Fiber Strength ◽  
Matrix Material ◽  
Constitutive Models ◽  
Material Behavior ◽  
Fiber Direction ◽  
Matrix Composites ◽  
Composite Damage ◽  
Mechanistic Approach ◽  
The Matrix

A simple analytical model is derived for the prediction of time dependent deformation and damage response of metal matrix composites under fiber direction loading. The model can be used in conjunction with a number of viscoplastic constitutive models to describe the matrix material behavior. Damage in the form of progressive fiber fractures is incorporated using a mechanistic approach. The criterion for fiber fractures can be based on statistical information on fiber strength. When used in conjunction with a prescribed failure condition for a composite, the model provides a means for predicting composite life under general thermomechanical load conditions. Based on comparison of results with detailed finite element analyses and with laboratory test data, it appears that the simple model provides reasonably accurate predictions.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

Application of cross correlation to HREM images of surfaces

1987 ◽  
Vol 45 ◽  
pp. 754-755
Author(s):  
D. E. Luzzi ◽  
L. D. Marks ◽  
M. I. Buckett
Keyword(s):  
Cross Correlation ◽  
A Priori ◽  
Matrix Material ◽  
Correlation Method ◽  
Accurate Knowledge ◽  
Complex Image ◽  
Fourier Filtering ◽  
The Matrix ◽  
Low Pass ◽  
Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

Impact Strength, Flexural Modulus and Wear Rate of PMMA Composites Reinforced by Eggshell Powders

2020 ◽  
Vol 38 (7A) ◽  
pp. 960-966
Author(s):  
Aseel M. Abdullah ◽  
Hussein Jaber ◽  
Hanaa A. Al-Kaisy
Keyword(s):  
Impact Strength ◽  
Wear Rate ◽  
Flexural Modulus ◽  
Matrix Material ◽  
Weight Fraction ◽  
Pure Pmma ◽  
Calcination Process ◽  
The Matrix ◽  
The Impact ◽  
Interface Bond

In the present study, the impact strength, flexural modulus, and wear rate of poly methyl methacrylate (PMMA) with eggshell powder (ESP) composites have been investigated. The PMMA used as a matrix material reinforced with ESP at two different states (including untreated eggshell powder (UTESP) and treated eggshell powder (TESP)). Both UTESP and TESP were mixed with PMMA at different weight fractions ranged from (1-5) wt.%. The results revealed that the mechanical properties of the PMMA/ESP composites were enhanced steadily with increasing eggshell contents. The samples with 5 wt.% of UTESP and TESP additions give the maximum values of impact strength, about twice the value of the pure PMMA sample. The calcination process of eggshells powders gives better properties of the PMMA samples compared with the UTESP at the same weight fraction due to improvements in the interface bond between the matrix and particles. The wear characteristics of the PMMA composites decrease by about 57% with increases the weight fraction of TESP up to 5 wt.%. The flexural modulus values are slightly enhanced by increasing of the ESP contents in the PMMA composites.

scholarly journals Self-Reinforced Nylon 6 Composite for Smart Vibration Damping

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1235
Author(s):  
Bidita Salahuddin ◽  
Rahim Mutlu ◽  
Tajwar A. Baigh ◽  
Mohammed N. Alghamdi ◽  
Shazed Aziz
Keyword(s):  
Matrix Material ◽  
Nylon 6 ◽  
Vibration Damping ◽  
Vibration Energy ◽  
Damping Factor ◽  
Passive Vibration Control ◽  
Reinforced Composite ◽  
Coiled Structure ◽  
The Matrix ◽  
3D Printed

Passive vibration control using polymer composites has been extensively investigated by the engineering community. In this paper, a new kind of vibration dampening polymer composite was developed where oriented nylon 6 fibres were used as the reinforcement, and 3D printed unoriented nylon 6 was used as the matrix material. The shape of the reinforcing fibres was modified to a coiled structure which transformed the fibres into a smart thermoresponsive actuator. This novel self-reinforced composite was of high mechanical robustness and its efficacy was demonstrated as an active dampening system for oscillatory vibration of a heated vibrating system. The blocking force generated within the reinforcing coiled actuator was responsible for dissipating vibration energy and increase the magnitude of the damping factor compared to samples made of non-reinforced nylon 6. Further study shows that the appropriate annealing of coiled actuators provides an enhanced dampening capability to the composite structure. The extent of crystallinity of the reinforcing actuators is found to directly influence the vibration dampening capacity.

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