Direct measurements of non-linear stress-strain curves and elastic properties of metal matrix composite sandwich beams with any core material

• Published in: Journal of materials science 1985-12, Vol.20 (12), p.4421-4430
• Main Author: SCHOUTENS, J.E
• Format: Article
• Language: English
• Subjects: Analysing. Testing. Standards; Applied sciences; beams; composite materials; elasticity; Exact sciences and technology; Industrial metrology. Testing; Measurement of properties and materials state; Mechanical engineering. Machine design; Metals. Metallurgy; Nondestructive testing; stress strain relations
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF00559331

A theory for measuring non-linear stress--strain curves and elastic properties of metal matrix composite (MMC) sandwich beams subjected to pure bending loads is discussed. The beam is made from any core material sandwiched between an upper facing of unreinforced metal and a lower facing of MMC with unidirectional fibre reinforcement or vice versa. The model developed shows that the determination of the position of the neutral axis is critical to the measurements discussed. The analysis removes the restriction of the effects of the core. With the aid of this model, it is shown that the position of the neutral axis can be determined directly from the surface strain measurements. Measurements of neutral axis position lead directly to the determination of the beam elastic properties and, thus, directly obtained from surface strain measurements. It is shown that the model predicts longitudinal stresses and strains within any layer of the beam. The analysis includes the limiting case of a very weak core material. A consequence of this model is the determination of the MMC facing fibre volume fraction. A detailed error analysis predicts that the longitudinal elastic modulus of an MMC material facing can be obtained with an uncertainty between 4-6% if the surface strain measurements and beam dimensions can be obtained with an uncertainty of 1%. The volume fraction can be obtained within 10% uncertainty, although better methods are available for that measurement. 5 ref.--AA