In order to evaluate the changes in the flexural properties of three types polymer-matrix composites (phenolic resin reinforced with woven basalt and carbon fibers at a total volume fraction of approximately 35%) affected by transient thermal conditions, mechanical tests were performed to specimens, which have previously been subjected to a certain number of thermal shock cycles.
During the thermal shock cycling test performed in the air, there is a coupling effect between matrix oxidation occurring at high temperatures of the cycle, and the matrix cracking due to thermo-mechanical ply stresses induced by the prevented differential expansions of the plies.
It is at the interfacial area where the stress concentration develops, due to the differences in the thermal expansion coefficients between the reinforcement and the matrix phase.
The reduction of ultimate flexural strength after thermal shock cycling was less than 6% of that initial thermal cycling for composites reinforced with woven basalt fibers. The flexural strength of the composite reinforced carbon fibers was reduced to more than 10% of the initial values
In addition, the reduction of flexural modulus after thermal shock cycling was about 6–9% of that initial thermal shock cycling for basalt/phenolic and basalt/carbon/phenolic composites.
Moslem Najafia, Seyed Mohammad Reza Khalilib, RezaEslami Farsaniba
Islamic Azad University, Tehran, Iran