Microstructure and Fracture of Engineering Polymers and Composites

1986 ◽  
Vol 79 ◽  
Author(s):  
K. Friedrich
Keyword(s):  
Composite Laminates ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Short Fiber ◽  
Related Factors ◽  
Fracture Characteristics ◽  
Microstructural Parameters ◽  
Reinforcing Fibers ◽  
Injection Molded ◽  
Engineering Polymers

AbstractThe fracture properties of engineering polymers and composites are strongly affected by two major areas of influence. The first one covers the microstructural parameters of the material, whereas the second one includes the external testing conditions. In this contribution, it is mainly outlined how area one can determine the fracture characteristics. An introductory section illustrates the variety of microstructural details, for example molecular structure and semicrystalline polymer morphology, and filler related factors, such as volume fraction of reinforcing fibers, their orientation etc. In the following part, effects of these parameters on fracture mechanical properties are discussed. It is distinguished between the fracture behavior of unfilled engineering polymers, of short fiber reinforced, injection molded thermoplastics, and of continuous fiber composite laminates. In the latter group, special emphasis is given to the effect of new, high temperature resistant thermoplastic matrices, for instance PEEK, on the interlaminar fracture energy of the composites.

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.

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.

Thermal Residual Stress in a Two-Dimensional In-Plane Misoriented Short Fiber Composite

1990 ◽  
Vol 43 (5S) ◽  
pp. S294-S303 ◽  
Author(s):  
M. Taya ◽  
M. Dunn ◽  
B. Derby ◽  
J. Walker
Keyword(s):  
Residual Stress ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Short Fiber ◽  
Two Dimensional ◽  
Fiber Distribution ◽  
Fiber Volume ◽  
Distribution Type ◽  
Short Fiber Composite

Residual stress induced in a misoriented short fiber composite due to thermal expansion mismatch between the matrix and fiber is investigated. The case of two-dimensional in-plane fiber misorientation is considered. The elastic model that is developed is based on Eshelby’s equivalent inclusion method and is unique in that it accounts for interactions among fibers at different orientations. A parametric study is performed to demonstrate the effects of fiber volume fraction, fiber aspect ratio, fiber distribution cut-off angle, and fiber distribution type on thermal residual stress. Fiber volume fraction and aspect ratio are shown to have more significant effects on the magnitude of the thermal residual stresses than the fiber distribution type and cut-off angle.

Effect of Euphorbia Coagulum on Flexural Property of Polyester Banana Fiber Composite

2013 ◽  
Vol 664 ◽  
pp. 764-767 ◽  
Author(s):  
Bhuvneshwar Rai ◽  
Rajinder K. Diwan ◽  
Gulshan Kumar
Keyword(s):  
Polyester Resin ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Flexural Modulus ◽  
Weight Fraction ◽  
Flexural Property ◽  
Strength Increase ◽  
Banana Fiber ◽  
Partition Walls ◽  
Reinforcing Fibers

Presently composites made up of either both the binder and the reinforcing fibers are synthetic or either one of the material is natural or synthetic. In the present study coagulum (dried latex) of Euphorbia royleana has been used for replacing polyester resin as a natural binder in polyester banana fiber composite. The influence of different volume fraction of the coagulum in the composite is studied. It is observed that with the increase in the coagulum fraction, the flexural property of the polyester banana fiber composite increases. The flexural strength increase by 25% and flexural modulus by 15% at 40% of coagulum weight fraction. This study presents the possibility of preparation of composites using coagulum of Euphorbia latex. The developed composite may be used in partition walls, roof tiles, interior linings of automobiles, etc as wood substitute.

Prediction of the In-Plane Electrical Conductivity of a Misoriented Short Fiber Composite: Fiber Percolation Model Versus Effective Medium Theory

1987 ◽  
Vol 109 (3) ◽  
pp. 252-256 ◽  
Author(s):  
Minoru Taya ◽  
Naoki Ueda
Keyword(s):  
Electrical Conductivity ◽  
Volume Fraction ◽  
Effective Medium Theory ◽  
Fiber Composite ◽  
Short Fiber ◽  
Effective Medium ◽  
Percolation Model ◽  
Threshold Behavior ◽  
Medium Theory ◽  
Short Fiber Composite

The in-plane electrical conductivity of a misoriented short fiber composite was studied both by fiber percolation model (FPM) and effective medium theory (EMT). A misoriented short fiber composite consists of insulating matrix and conductive short fibers, thus it exhibits a threshold behavior in the conductivity at a certain volume fraction of fibers. A comparison between FPM and EMT indicates that FPM can predict the threshold behavior well, while EPT fails, but it becomes valid at high volume fraction of fibers.

Size Effect and Fracture Characteristics of Composite Laminates

1996 ◽  
Vol 118 (3) ◽  
pp. 317-324 ◽  
Author(s):  
Zdeneˇk P. Bazˇant ◽  
Isaac M. Daniel ◽  
Zhengzhi Li
Keyword(s):  
Size Effect ◽  
Composite Laminates ◽  
Process Zone ◽  
Fiber Composite ◽  
Maximum Load ◽  
Two Dimensions ◽  
Effective Length ◽  
Smooth Transition ◽  
Fracture Characteristics ◽  
Nominal Strength

Measurements of the size effect on the nominal strength of notched specimens of fiber composite laminates are reported. Tests were conducted on graphite/epoxy crossply and quasi-isotropic laminates. The specimens were rectangular strips of widths 6.4, 12.7, 25.4 and 50.8 mm (0.25, 0.50, 1.00 and 2.00 in.) geometrically similar in two dimensions. The gage lengths were 25, 51, 102 and 203 mm (1.0, 2.0, 4.0 and 8.0 in.). One set of specimens had double-edge notches and a [0/922]s crossply layup, and another set had a single-sided edge notch and a [0/±45/90]s, quasi-isotropic layup. It has been found that there is a significant size effect on the nominal strength. It approximately agrees with the size effect law proposed by Bazˇant, according to which the curve of the logarithm of the nominal strength versus the logarithm of size represents a smooth transition from a horizontal asymptote, corresponding to the strength criterion (plastic limit analysis), to an inclined asymptote of −0.5 slope, corresponding to linear elastic fracture mechanics. Optimum fits of the test results by the size effect law are obtained, and the size effect law parameters are then used to identify the material fracture characteristics, particularly the fracture energy and the effective length of the fracture process zone. Finally, the R-curves are also identified on the basis of the maximum load data. The results show that in design situations with notches or large initial traction-free cracks the size effect on the nominal strength of fiber composite laminates must be taken into account.

Effect of fibre content on the mechanical properties of hemp fibre woven fabrics/polypropylene composite laminates

2021 ◽  
pp. 096739112110239
Author(s):  
Sheedev Antony ◽  
Abel Cherouat ◽  
Guillaume Montay
Keyword(s):  
Mechanical Properties ◽  
Polymer Matrix ◽  
Composite Laminates ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Woven Fabrics ◽  
Fibre Content ◽  
Viscoelastic Behaviour ◽  
Hemp Fibre

Nowadays natural fibre composites have gained great significance as reinforcements in polymer matrix composites. Composite material based on a polymer matrix reinforced with natural fibres is extensively used in industry due to their biodegradability, recyclability, low density and high specific properties. A study has been carried out here to investigate the fibre volume fraction effect of hemp fibre woven fabrics/PolyPropylene (PP) composite laminates on the tensile properties and impact hammer impact test. Initially, composite sheets were fabricated by the thermal-compression process with desired number of fabric layers to obtain composite laminates with different fibre volume fraction. Uniaxial, shear and biaxial tensile tests were performed and mechanical properties were calculated. Impact hammer test was also carried out to estimate the frequency and damping parameters of stratified composite plates. Scanning Electron Microscope (SEM) analysis was performed to observe the matrix and fibre constituent defects. Hemp fabrics/PP composite laminates exhibits viscoelastic behaviour and as the fibre volume fraction increases, the viscoelastic behaviour decreases to elastic behaviour. Due to this, the tensile strength increases as the fibre content increases. On the other hand, the natural frequency increases and damping ratio decrease as the fibre volume fraction increases.

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