Flexural strength, composites subjected

Shih, G.C. and Ebert, L.J. (1986). Interface strength effects on the compressive-flexure/shear failure mode transition of composites subjected to four-point bending. J. Mater. Sci. 21, 3957-3%5. 

Figure 27. Flexural strength and bulk density of unidirectional composites subjected to graphitizing heat treatments either for each densification cycle or after the densification cycles were completed (20,52) The matrix was a coal-tar binder pitch with 10 wt.-% sulfur the high-modulus PAN-based fiber was Sigrafil HM.

Figure 34. Comparison of the flexural strengths of unidirectional carbon/carbon composites (left-hand side) with those of hybrid composites in which the final impregnation is made with an epoxy resin (34) The composites were fabricated with high-modulus fibers rigidized with phenolic resin, and subjected to four densification cycles with coal-tar pitch plus sulfur.

Hence, direct comparisons of flexural strength data published on different composite deck boards should be viewed with the respective reservations. Data on flexural modulus, as it is shown below, are subjected to these factors even much greater. 

The specimens of suitable dimensions were cut from the composite sheets by using a Diamond cutter and were subjected for analysis of tensile, compressive and flexural strength in accordance with ASTM standards on a computerized universal testing machine (Housfield H25KS). Three specimens of each sample were used for the measurement of each mechanical property at ambient laboratory conditions and average results have been reported. 

Another comparative study analyzed the effect of different curing strategies on the composite properties, when samples made of same amounts of woven glass fabric and an epoxy-vinyl ester (Derakane 510A— brominated bisphenol A-based vinyl ester) were single-sided UV-cured in the presence of 2 % bisacylphosphine oxide (BAPO) as photoinitiator, or thermally cured in the presence of 1.2 % benzoyl peroxide (BPO) [191]. Data obtained for flexural strength indicated the laminates had comparable characteristics and the procedure may be subjected to further optimization [192]. 

An ASTM draft standard test method has been developed mid readied for full-consensus ballot to determine the flexural strength of composite tubes subjected to pure bending. Numerical modeling mid empirical tests of composite tubes provided validation of the parameters specified in the test metiiod. The draft standard addresses the following experimental issues - test specimen geometries/preparation, test fixtures, test equipment, interferences, testing modes/procedures, data collection, calculations, reporting requirements, precision/bias. 

If concrete removal is not required or supplementary reinforcing bars cannot be used, external reinforcement can be applied. For instance, steel bars may be encased in a shotcrete layer or steel plates may be bonded onto the concrete surface. Recently, the use of steel plates has been substituted by fibre-reinforced plastics (F. R.P.), that are composite materials with glass, aramide or carbon fibres embedded in a polymeric matrix (usually an epoxy system). F. R.P. are available in the form of laminates or sheets that are bonded to the concrete surface using an epoxy adhesive [11]. They are typically used to improve the flexural and shear strength or to provide confinement to concrete subjected to compression. The... 

Performance and durability of wood products bonded with isocyanate and urethane adhesives have been the subject of several investigations. The strength of composition board is generally determined by its modulus of rupture (MOR), which is a flexure to break test its modulus of elasticity (MOE), or stiffness and its internal bond strength (IB), or tensile strength. These tests are run on dry and on water-soaked or wet samples, and are described in ASTM test method D 1037. As compared to phenol-formaldehyde adhesives, composition boards prepared with isocyanate or urethane adhesives are reported to display similar or superior initial strengths. Moisture resistance of isocyanate-bound par-... 

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