Effect of the microstructure on compressive strength of infiltrated ceramic-elastomer composites
Kamil Babski, Anna Boczkowska, Mikołaj Szafran, Krzysztof J. Kurzydłowski 1, 2, 4 Politechnika Warszawska, Wydział Inżynierii Materiałowej ul. Wołoska 141, 02-507 Warszawa, Poland 3 Politechnika Warszawska,Wydział Chemiczny, ul. Noakowskiego 3, 00-664 Warszawa, Poland
Quarterly No. 3, 2008 pages 285-290
DOI:
keywords: composites, porous ceramic, polyurethane, infiltration, energy absorption
abstract The present work concerns mechanical properties of ceramic-elastomer composites under compressive loads. The ceramic-elastomer composite investigated here have a microstructure of percolated phases. Such composites exhibit high initial strength and stiffness with the ability to sustain large deformations due to combining the ceramic stiffness and rubbery elasticity of elastomer. The microscopic observations reveal that the pores of matrix are fully filled with the elastomer. The porous ceramic matrix was sintered from SiO2 powders with controlled particles diameter. Since the stress-strain curve in compression for composites has a nonlinear characteristic, specific loading stages can be identified during straining. These stages are related to the type of the microstructure damage. The recognized stages are: I - elastic region, II - stable non localized microcracking, III - localized microcracking, IV - microcracking, fragmentation and straining of the elastomer. The observed plateau stress at large deformations implies that such composites can be used as a strain energy absorber. The mechanical properties in compression test were estimated in terms of: maximum compressive strength (initial maximum peak force), apparent modulus of elasticity (linear part of the stress-strain curve), the flow stress at 25% of strain. The absorbed energy was calculated as the area beneath the loading-unloading stress-strain curve. The compression tests reveal a significant difference in mechanical properties depending on composite microstructure and straining rate. It was found that the maximum compressive strength, relative modulus of elasticity and stresses at plateau region depends mainly on composite microstructure. The straining rate has a significant effect on relative modulus of elasticity and partly affects the maximum compressive strength and stresses at plateau region. It was found that ceramic-elastomer composites effectively absorb the energy at comparable value and have stress-strain characteristic similar to some aluminium foams or energy absorbing structures. In order to evaluate the complex usability of the composites as a potential shock absorbing material, the composites are currently investigated at higher straining rates.