Three-point flexural test

As with tensile properties, both compressive strength and modulus depend on the fiber content and hber orientation (see Table 5.8). The interlaminar shear strength reported in Table 5.8 is a measure of the shear strength in the thickness direction of the SMC sheet. It is determined by three-point flexural testing of beams with short span-to-depth ratios and is considered to be a quality-control test for molded composites. 

Static mechanical properties of aerogels have been measured mainly by the three-point flexure test [54] or by direct longitudinal compression [55]. The... 

The elastic modulus, measured using the pulse echo method, was about 180 GPa, and the fracture strength determined by the three-point flexure test was about 800 MPa in the grain-alignment direction. This strength, which is relatively high for the large porosity of 25%, is almost equivalent to that of commercially available... 

Three-point flexural tests provide values for the modulus of elasticity in bending, flexural stress, flexural strain, and the flexural stress-strain response of the tested material [63, 64], i.e., the determination of strain recovery and stress recovery ratio. 

Fig. 12 Scheme of a three-point flexural test, (a) Scheme of the shape-memory effect (SME) in polymers as defined by four critical temperatures. The value of 7 is a material property. Tiow is always less than Tg, whereas Tiugh may be above or below Tg, depending on the desired recovery response. (b) Schematic of the three-point flexure thermomechanical test setup. Taken from lef. [63], Copyright 2005. Reprinted with permission of John Wiley Sons, Inc. 

A similar behavior was observed in three-point flexural tests for epoxy based polymer networks (Tg = 90°C), where Tgw, Tg max, and (Tmax increased when ]8h was raised from 2.5 to 10Kmin [64]. 

In this chapter, results from the tensile, flexural and impact tests on HDPE/PA6 and HDPE/PA12 MFC are presented, studying the effects of the compatibilizer, HDPE and PA concentration, as well as the form and arrangement of the reinforcing entities on the mechanical behavior. The UDP MFC laminae were used for tensile tests. Impact strength and three-point flexural tests were performed on the CPC laminates. MRB and NOM composites were analyzed with the three mechanical tests. The data were compared with those of the neat HDPE matrix material and/or the oriented polyamide component [69]. 

Figure 3-20. A three-point flexural test specimen bending fixture designed per ASTM D 790.

HOT Heat Distortion Temperature, or heat deflection under load (HDUL). A three-point flexural test is performed on a bar by applying a load to create a stress of either 1.80 MPa or 0.45 MPa at the midpoint. The temperature is raised by a predetermined rate and when the specimen deflects by a set amount, the temperature is quoted, in °C. 

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