Failure Problems In Composites

1991 ◽  
Vol 255 ◽  
Author(s):  
Frederick J. Mcgarry
Keyword(s):  
Polymer Matrix Composites ◽  
Matrix Composites ◽  
Stress Concentrations ◽  
Rubber Layer ◽  
The Matrix ◽  
Equipment Failures ◽  
Fiber Matrix ◽  
Compliant Layer ◽  
Almost All ◽  
Transportation Applications

AbstractFiber reinforced polymer matrix composites have become very useful in chemical processing systems, in transportation applications such as automobiles, aircraft and boats, in electrical hardware and in sports equipment. Failures in these rarely involve gross cohesive fracture; usually leaks develop, the stiffness decreases, local delamination occurs, the dielectric properties degrade or the strength declines. Almost all of these failures can be traced to local cracking, either at the fiber matrix interface or within the matrix itself. The cracks are generated by mechanical loads, by thermal excursions or by fluid absorption, because the relevant properties of the fiber and the matrix often differ by orders of magnitude. Current technology attempts to avoid the cracks by maximizing the fiber-matrix adhesion and great progress has been made in this area. An alternative interposes a thin compliant layer, rubber, between the two constituents thereby reducing the stress concentrations which exist because of their greatly different properties. Cracking is inhibited, composite strength is increased and its energy absorption also rises; if the rubber layer is thin (a few thousand Angstroms) no loss of stiffness or heat resistance is evident.

scholarly journals Interfacial Engineering for Optimized Adhesion in Polymeric Composite Materials

1999 ◽  
Vol 586 ◽  
Author(s):  
Lawrence T. Drzal
Keyword(s):  
Failure Modes ◽  
Polymer Matrix Composites ◽  
Polymeric Composite ◽  
Matrix Composites ◽  
Interfacial Engineering ◽  
The Matrix ◽  
Matrix Toughness ◽  
Physical Interactions ◽  
Fiber Matrix ◽  
And Performance

ABSTRACTFiber-matrix adhesion is a variable to be optimized so that optimum composite mechanical properties can be achieved in polymer matrix composites. The contemporary view of adhesion rests on an “interphase” model in which not only the actual chemical and physical interactions between fiber and matrix are considered but also the structure and properties of both the fiber and the matrix in the region near the interface. The optimum design methodology starts with the specification of the fiber and matrix from a structural consideration. Once the constituents are selected, the focus is on the creation of a beneficial fiber-matrix “interphase”. This region where the fiber and matrix interact has to be designed for both “processing” and “performance”. Although no quantitative algorithm is available for interphase optimization, various thermodynamic principles coupled with experimental data can be used to qualitatively design the optimum interphase. Examples will be presented to illustrate how this interface can be engineered with surface treatments and sizings or coatings to insure thorough wetting, protection of the fiber, chemical bonding between fiber and matrix, toughness and desirable failure modes.

Mechanical Analysis of Unidirectional Fiber-Reinforced Polymers under Transverse Compression and Tension

2010 ◽  
Vol 139-141 ◽  
pp. 84-89 ◽  
Author(s):  
Hong Chang Qu ◽  
Xiao Zhou Xia ◽  
Hong Yuan Li ◽  
Zhi Qiang Xiong
Keyword(s):  
Polymer Matrix Composites ◽  
Glass Fibers ◽  
Constitutive Models ◽  
Mechanical Analysis ◽  
Interface Strength ◽  
Fiber Reinforced Polymers ◽  
Matrix Composites ◽  
Transverse Compression ◽  
Cohesive Elements ◽  
The Matrix

The mechanical behavior of polymer–matrix composites uniaxially reinforced with carbon or glass fibers subjected to compression/tension perpendicular to the fibers was studied using computational micromechanics. This is carried out using the finite element simulation of a representative volume element of the microstructure idealized as a random dispersion of parallel fibers embedded in the polymeric matrix. Two different interface strength values were chosen to explore the limiting cases of composites with strong or weak interfaces, and the actual failure mechanisms (plastic deformation of the matrix and interface decohesion) are included in the simulations through the corresponding constitutive models. Composites with either perfect or weak fiber/matrix interfaces (the latter introduced through cohesive elements) were studied to assess the influence of interface strength on the composite behavior. It was found that the composite properties under transverse compression/tension were mainly controlled by interface strength and the matrix yield strength in uniaxial compression/tension.

Determination of Vibrational Characteristics of Coir, Banana and Aloe Vera Fibres Reinforced Hybrid Polymer Matrix Composites

2019 ◽  
Vol 24 (No 1) ◽  
pp. 12-19
Author(s):  
S. Vimal Anand ◽  
G. Venkatachalam ◽  
Tushar D. Nikam ◽  
Omkar V. Jog ◽  
Ravi T. Suryawanshi
Keyword(s):  
Polymer Matrix Composites ◽  
Low Cost ◽  
Aloe Vera ◽  
Natural Fibre ◽  
Fibre Volume ◽  
Matrix Composites ◽  
Green Composites ◽  
Hybrid Polymer ◽  
The Matrix ◽  
Vibrational Characteristics

In the last few years, green composites are becoming more suitable for applications over synthetic composite. There has been a growing interest in recent years in the utilisation of natural fibres in making low-cost building material. However, these natural fibre-based composites are not fully environmentally friendly because the matrix resins are non-biodegradable. In this paper, an attempt is made to fabricate green composites with coir, banana, and aloe vera fibres as reinforcement and hybrid polymer as matrix. The hybrid polymer is prepared from natural and synthetic resins. This work intends to find the vibrational characteristics of these composites. The influence of three parameters, i.e. CNSL in hybrid polymer, fibre volume, and fibre discontinuities on vibrational characteristics are considered. This work is carried out using FEA and the FEA results are validated by experimental results.

Mechanical Behavior of Microwave Processed Polymer Matrix Composites: the Effect Of The Temperature Increase Rate

1996 ◽  
Vol 430 ◽  
Author(s):  
M. Delmotte ◽  
J. Fitoussi ◽  
J. Toftegaard-Hansen ◽  
C. More ◽  
H. Jullien ◽  
...  
Keyword(s):  
Polymer Matrix Composites ◽  
Tensile Tests ◽  
Crosslinking Reaction ◽  
Matrix Composites ◽  
Mechanical Behaviors ◽  
Homogenous Distribution ◽  
Increase Rate ◽  
The Matrix ◽  
Matrix Flow ◽  
Experimental Pressure

AbstractMicrowave processed glass reinforced epoxies or glass reinforced polyesters exhibit mechanical behaviors different from conventionally cured materials, relatively to tensile tests. The faster increases of temperature due to microwaves cause a competition between the matrix flow and the crosslinking reaction which can be estimated by porosity variations. Higher mechanical moduih are also obtained, because of both an effect on chemical kinetics and a more homogenous distribution of temperature in materials. Nevertheless, to provide such specific mechanical behaviors in microwave processed composite materials, a best control of the experimental pressure parameters is requested.

Mechanical Properties of Densified Untwisted Carbon Nanotube Yarn / Epoxy Composites

2015 ◽  
Author(s):  
Risa Yoshizaki ◽  
Kim Tae Sung ◽  
Atsushi Hosoi ◽  
Hiroyuki Kawada
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Polymer Matrix Composites ◽  
High Strength ◽  
Matrix Composites ◽  
Specific Strength ◽  
The Matrix ◽  
Cnt Arrays ◽  
Strength And Stiffness ◽  
Long Fibers

Carbon nanotubes (CNTs) have very high specific strength and stiffness. The excellent properties make it possible to enhance the mechanical properties of polymer matrix composites. However, it is difficult to use CNTs as the reinforcement of long fibers because of the limitation of CNT growth. In recent years, a method to spin yarns from CNT forests has developed. We have succeeded in manufacturing the unidirectional composites reinforced with the densified untwisted CNT yarns. The untwisted CNT yarns have been manufactured by drawing CNTs through a die from vertically aligned CNT arrays. In this study, the densified untwisted CNT yarns with a polymer treatment were fabricated. The tensile strength and the elastic modulus of the yarns were improved significantly by the treatment, and they were 1.9 GPa and 140 GPa, respectively. Moreover, the polymer treatment prevented the CNT yarns from swelling due to impregnation of the matrix resin. Finally, the high strength CNT yarn composites which have higher volume fraction than a conventional method were successfully fabricated.

A Study on Characteristic of Polymer Matrix Composites Using Experimental and Statistical Approach

2013 ◽  
Vol 368-370 ◽  
pp. 683-686
Author(s):  
Ahmad Mubarak Tajul Arifin ◽  
Shahrum Abdullah ◽  
Rozli Zulkifli ◽  
Dzuraidah Abd Wahab
Keyword(s):  
Polymer Matrix ◽  
Statistical Approach ◽  
Polymer Matrix Composites ◽  
Stacking Sequence ◽  
Matrix Composites ◽  
The Matrix ◽  
Thermoset Epoxy ◽  
Chopped Strand Mat ◽  
Materials Used ◽  
And Behavior

This paper focuses on the characteristic study of polymer matrix composites using a statistical approach, in terms of difference experimental and reflected to difference stacking sequence and orientation of composite lamination. Composite material, have an excellent characteristic and behavior, but with a difference application and materials used, it have a difference phenomenon occurred before the composite structure are collapsed. Therefore, in order to understand the characteristic of polymer matrix composites, it needs to investigate the phenomenon that influences the structure of composite lamination before failures. In this research, polymer matrix composites are produced using difference material and stacking sequence of lamination. The matrix used is thermoset epoxy and polyester resin with chopped strand mat (CSM) and woven roving (WR) as reinforcement materials. It has been produced using hand lay-up technique. The experimental work is carried out using the tension and flexural test accordance to ASTM-D3039 and D-D790 standard. By using a statistical approach, it can clearly show the differential between materials used with a characteristic of composite materials. It is noted, based on this investigation it also showed difference phenomenon failures and damage structure of polymer matrix composites with difference type of experimental.

Fiber-Matrix Bonding in Boron-Reinforced Aluminum Composites

1969 ◽  
Vol 27 ◽  
pp. 32-33
Author(s):  
I. Corvin ◽  
H. Morrow ◽  
O. Johari ◽  
N. Parikh
Keyword(s):  
Aluminum Matrix ◽  
Surface Characteristics ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Boron Fiber ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

A significant amount of research has been done in the past few years in the development of suitable composite materials in general and on boron fiber-aluminum matrix composites in particular. The mechanical properties of the composite depend on the structures and strengths of the matrix and fibers; on the amount, distribution, and surface characteristics of the fibers; and on the quality of the bond at the fiber-matrix interface. The results presented here illustrate the application of the SEM in studying the structure of the fiber-matrix interface and the fracture features of boron and aluminum.

Measuring Interface Strength in Single Fiber Composites: The Effect of Stress Concentrations

2000 ◽  
Vol 629 ◽  
Author(s):  
G. A. Holmes ◽  
R. C. Peterson
Keyword(s):  
Fragment Length ◽  
Interface Strength ◽  
Matrix Interface ◽  
Stress Concentrations ◽  
New Model ◽  
Testing Rate ◽  
Mechanics Model ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

ABSTRACTFiber-matrix interface strength is known to be a critical factor in controlling the long-term performance of structural composites. This parameter is often obtained by using the average fragment length data generated from the single-fiber fragmentation test (SFFT). The interfacial shear strength is then determined by using this data in a micro-mechanics model that describes the shear-stress transfer process between the matrix and the fiber. Recently, a non-linear viscoelastic micro-mechanics model was developed to more accurately account for the matrix material properties. This new model indicates that the interface strength is dependent on the testing rate. Experimentally, it has been shown that the final fragment length distribution in some systems is dependent on the testing rate. However, data analysis using the new model indicates that the distribution change with testing rate is promoted by the presence of high stress concentrations at the end of the fiber fragments. From the model, these stress concentrations were found to exist at very low strain values. Experimentally, the fragment distributions obtained from specimens tested by different testing rates were found to be significantly different at strain values well below the strain values required to complete the test. These results are consistent with the research of Jahankhani and Galiotis and finite element calculations performed by Carrara and McGarry. These authors concluded that stress concentrations can promote failure of the fiber-matrix interface on the molecular level. Our results support this conclusion. In addition, our research results suggest that altering the SFFT testing rate can lower the magnitude of these stress concentrations and minimize failure of the fiber-matrix interface.

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