A void or a pore is three-dimensional region that remains unfilled with polymer and fibers in a composite material. Voids are typically the result of poor manufacturing of the material and are generally deemed undesirable. Voids can affect the mechanical properties and lifespan of the composite.[1] They degrade mainly the matrix-dominated properties such as interlaminar shear strength, longitudinal compressive strength, and transverse tensile strength.[2] Voids can act as crack initiation sites as well as allow moisture to penetrate the composite and contribute to the anisotropy of the composite.[3][4] For aerospace applications, a void content of approximately 1% is still acceptable, while for less sensitive applications, the allowance limit is 3-5%. Although a small increase in void content may not seem to cause significant issues, a 1-3% increase in void content of carbon fiber reinforced composite can reduce the mechanical properties by up to 20% [5]
- ^ ASTM D2734-09, Standard Test Methods for Void Content of Reinforced Plastics, ASTM International, West Conshohocken, PA, 2009, www.astm.org
- ^ Mehdikhani, M; Gorbatikh, L; Verpoest, I; Lomov, S (2018). "Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance". Journal of Composite Materials. 53 (12): 1579–1669. doi:10.1177/0021998318772152.
- ^ Mehdikhani, M; Steensels, E; Standaert, A; Vallons, K; Gorbatikh, L; Lomov, S (2018). "Multi-scale digital image correlation for detection and quantification of matrix cracks in carbon fiber composite laminates in the absence and presence of voids controlled by the cure cycle". Composites Part B: Engineering. 154: 138–147. doi:10.1016/j.compositesb.2018.07.006. S2CID 139188965.
- ^ Hull, D., & Clyne, T. (1996). Fiber Architecture - Voids. In An introduction to composite materials (2nd ed., pp. 55-56). Cambridge: Cambridge University Press.
- ^ Lacovara, Bob (2013). "Why out of Autoclave Processing Is Good for the Composites Industry". High-Performance Composites. 23 (4): 261–265. doi:10.1016/0010-4361(92)90186-X.