What factor can cause issues during the resin curing process?

High humidity can significantly impact the resin curing process. When the environment is too humid, moisture can interfere with the chemical reactions that take place during curing, potentially leading to incomplete curing or defects in the final product.

Proper ventilation is essential because it ensures that the fumes and byproducts of the curing process are effectively dissipated. While proper ventilation is crucial for safety and effectiveness, it's not typically a factor that would directly cause issues with the curing itself unless it's lacking.

The use of old resin can also pose problems because resin has a shelf life, and as it ages, its chemical properties may change. This can lead to improper mixing or a failure to cure adequately, which may compromise the integrity of the finished composite material.

Considering that a combination of factors can negatively affect the curing process, the answer reflects that all of these factors—high humidity, inadequate ventilation, and the use of old resin—can contribute to issues during the resin curing process. Thus, recognizing that multiple elements need to be managed properly is critical for achieving the desired results in aerospace assembly applications.