Meaning
Fabrication error results in gas bubbles or air pockets remaining caught within a cured adhesive, coating, film or composite laminate. Observation of void entrapment often happens through ultrasonic inspection or cross sectional imaging of the finished part. These empty spaces create localized weak points that can lead to premature failure under mechanical or electrical stress.
Pore Formation
Gas release during chemical reactions or the physical trapping of air during mixing are the primary causes. Improper application techniques or high viscosity can lead to void entrapment by preventing the material from flowing into small gaps. Thermal expansion of trapped air during the cure cycle can also enlarge these pockets.
Quality Impact
Mechanical strength declines because the voids reduce the effective load bearing area of the joint. In electrical applications, void entrapment can lead to partial discharge or dielectric breakdown between high voltage components. These defects also act as collection points for moisture, which accelerates the chemical degradation of the surrounding polymer matrix.
Large voids can even cause the adhesive to peel away from the substrate as internal pressure builds up during thermal cycling.
Prevention Method
Vacuum degassing of resins before application removes dissolved gases that might form bubbles. Optimizing the dispense pattern and using controlled pressure during assembly minimizes the risk of void entrapment in the bond line. Precise control of the cure temperature prevents the resin from boiling.
