EFFECT OF HUMIDITY AND TEMPERATURE ON THE STRENGTH OF REPAIRED WOVEN FABRIC COMPOSITES

The durability of repaired CFRP components under environmental conditions such as high humidity and temperature is critical for reliable long-term operation. This study investigates the effects of temperature and moisture on the repair strength of prepreg and wet lay-up repairs performed on M21/AS4C carbon/epoxy fabric panels. A series of wet lay-up and prepreg step-repaired specimens produced according to standardized aerospace procedures were tested under uniaxial tension. For each case, dry specimens and hot-wet specimens immersed in water at 70°C for 14 days were considered. The experimental measurements on 3.8° scarf angle repairs showed that the strength recovery could be as high as 68% for the prepreg repairs and 59% for the wet lay-up repairs for unconditioned specimens. The moisture and humidity exposure did not have a significant impact on the strength of the prepreg-based repairs. Wet lay-up repaired specimens, on the other hand, showed a 30% reduction in strength upon exposure to humidity and temperature. The results show that prepreg repairs should be preferred over wet lay-up repairs for the long-term reliable operation of repaired components.