Test MethodDetermination of tensile and compressive moduli by flexural tests

One of the basic hypotheses of the Classical Beam Theory (CBT) is that the tensile and compressive moduli are the same. In fiber-reinforced composites, tensile and compressive moduli are different. Based on the equations that relate flexural, tensile and compressive moduli, an experimental procedure for determining the three moduli by flexural tests is proposed. Two specimens of two different unidirectional carbon/epoxy composite materials with longitudinally oriented fibers have been tested. Three-point bending, four-point bending and tensile tests were carried out on the same specimens in order to compare moduli obtained in different ways. The strain range for measurements was between 0.1% and 0.3% in all cases. The agreement between moduli obtained in different experimental ways is good.