Mechanical Testing of Composites

S. Beland, B. Shaver, C. Chapman, and S. Desjardins, Non destructive inspection and mechanical testing of composite arm booms for the space station remote manipulator system. In Proc. 10th International Conference on Composite Materials, A. Poursartip and K. Street, eds., Woodhead Publ. Ltd., Abington-Cambridge, UK, Vol. 111,661-668(1995). 

Alkalization Mwaikambo et al. were one of the earher groups who adopted various techniques to analyze the effect of alkali treatment on different natural fibers. Even though they did not conduct mechanical testing of composites, their investigation is vital in understanding the effect of alkali concentrations on the crystallinity index of the fibers. Their studies showed that lower concentrations of alkali would result in... 

New types of molds for SRIM have been developed for the study of polymer flow mechanisms in nonwoven fibrous structures and for the production of samples for the mechanical testing of composites. The molds proved useful during the development of new methods for the investigation of elastomer flow mechanisms in nonwoven mats. A combination of glass and rubber as construction materials for the molds enables visual observation of the polymer flow and easy installation of thermocouples and pressure transducers in the cavity of the mold. 

Pendleton, R.L. and Tuttle, M.E. (1989) Manual on Experimental Methods for Mechanical Testing of Composites, Elsevier, Barking — describes techniques primarily for NDE. 

A significant amount of waste composites is generated each year and the need for a recycling method is becoming a necessity. Environmental Technical Services has developed, with the support of the University of Missouri-St.Louis, a method for recovering valuable constituents from composite materials. The process converts the polymer matrix to lower chain hydrocarbons and fuel gas leaving behind fibres. Mechanical tests of BMC panels, reinforced concrete and compression moulded panels made with recovered fibres were carried out. 10 refs. USA... 

Cook, J. (1970). Mechanical testing of whiskers. Composites, March, 176—180. 

Figure 5.112 Idealized stress-strain curve for a tough ceramic-matrix composite. Reprinted, by permission, from R. W. Davidge and 1. J. R. Davies, in Mechanical Testing of Engineering Ceramics at High Temperatures, B. F. Dyson, R. D. Lohr, and R. Morrell, eds., p. 251. Copyright 1989 by Elsevier Science Publishers, Ltd.

The interaction of two substrates, the bond strength of adhesives are frequently measured by the peel test [76]. The results can often be related to the reversible work of adhesion. Due to its physical nature such a measurement is impossible to carry out for particulate filled polymers. Even interfacial shear strength widely applied for the characterization of matrix/fiber adhesion cannot be used in particulate filled polymers. Interfacial adhesion of the components is usually deduced indirectly from the mechanical properties of composites with the help of models describing composition dependence. Such models must also take into account interfacial interactions. 

Mechanical testing of the three-step cure specimens indicated that no sacrifice in properties resulted from the modification of the process cycle. The retainment of mechanical properties (transverse strength and modulus) coupled with the reduction in dimensionless curvature for the three-step cure cycles investigated provides another suitable cure cycle modification for reduction of residual stresses in composite materials. Overall processing time has not been increased beyond that specified in the MRC cycle. Thus, with no increase in process time and comparable mechanical properties, the residual stresses have been reduced by more than 20 percent in comparison to the MRC cycle baseline data. 

The compositions of both matrix powders pyrolyzed at different temperatures and composites were characterized by XRD. Mechanical properties of composites were measured by three-point-bending tests with 5mmx2mmx40mm specimens in an lnstron-5566 machine, operated at a crosshead speed of 0.5mm/min and a span of 24mm. The microstructures of composites both with and without boron were observed by electron probe microanalyzer (EPMA, JXA-8IOO, JEOL, Tokyo, Japan). 

The literature published on fracture mechanics testing of FRPs in the last 40 years comprises a large database on delamination resistance or fracture toughness of different types of FRPs. An early review [51] compiled the data available at that time. Selected data from quasi-static mode I and mode II tests on FRPs were compared by O Brien [52], and quasi-static mode I test data from carbon—fibre epoxy and poly-ether-ether-ketone (PEEK) by Brunner [53]. Mechanical properties of FRP composites are compiled in the Composite Materials Handbook version F (2002) [9—11], but this does not comprise fracture mechanics data. Hence, there is no comprehensive and up-to-date database on the available data or literature. 

Extensive discussion of the approaches for structural design in the aerospace field is beyond the scope of this chapter, but Goranson [128], for example, provides ample details from an aircraft manufacturer s perspective, albeit with a focus on metaUic materials. Fracture mechanics testing of FRP composites so far has played a minor role in materials selection, materials qualification and structural design for aerospace... 

F. L. Matthews, G. A. O. Davies, D. Hitchings and C. Soutis Mechanical testing of advanced fibre composites... 

Figure 15.13 Flow chart for the mechanical tests of compression type assisted by magnetic field for rubber ferrite composites (RFC).

Figure 17.45 Tube subjected to axial torsion. Source Reprinted from Course on Mechanical Testing of Advanced Fibre Composites, University of London, Imperial College, Sep 1995.

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