Mechanisms of degradation of polymer composites by galvanic reactions between metals and carbon fiber

摘要

AbstractToughened and untoughened epoxy and BMI carbon fiber reinforced composites were evaluated in terms of their matrix chemical stability in galvanic reactions between metals and composites. It has been known that the presence of moisture and salts and contact between unprotected metals and BMI carbon fiber composition constitute prerequisite conditions for composite degradation. This study has further demonstarated that these conditions were necessary, but not sufficient. It was found that the OH species generated by galvanic reactions had to be concentrated in localized spots to induce composite degradation at a significant rate. A mechanism was proposed to elucidate how degradation took place under those necessary conditions with the aid of localized aggregation of the OH−species. Additionally, thoughening of BMI composite matrix resins resulted in poorer resistance to degradation by galvanic reactions. On the other hand, none of the eposy composites (toughened or untoughened) exhibited any degradation due to galvanic reactions at room temperature, nor did they degrade in a concentrated caustic NaOH solution (pH = 14,82°C) that simulated a highly accelerated galvanie reacti