Low frequency acoustic characteristics of periodic honeycomb cellular cores: The effect of relative density and strain fields. (1st December 2015)

• Record Type: Journal Article
• Authors: Alkhader, Maen; Iyer, Sumantu; Shi, Weixiao; Venkatesh, T.A.
• Is Part Of: Composite structures. Volume 133(2016)
• Page Start: 77
• Page End: 84
• Publication Date: 2015-12-01
• Subjects: Aluminum honeycomb cores -- Nondestructive testing -- Bloch theory -- Acoustic characteristics -- Sandwich structures; Composite construction -- Periodicals; Composites -- Périodiques; 624.18
• DOI: 10.1016/j.compstruct.2015.07.102
• Languages: English
• ISSNs: 0263-8223

Abstract

Abstract: Aluminum honeycomb cores, widely used in lightweight composite sandwich structures, are inherently weak and highly susceptible to buckling, permanent deformation and damage. This damage can detrimentally affect the structural integrity of sandwich structures and should be detected and repaired. Detecting damage to honeycomb cores is difficult as cores are sandwiched between composite sheets and not accessible. Typically, for such scenario a non-destructive testing method such as ultrasound is appealing. However, with the periodic and porous structure of honeycomb cores, at ultrasound frequencies they are dispersive and exhibit high transmission loss; thus they are incompatible with standard ultrasound techniques. Conversely, at sub-ultrasound frequencies honeycomb cores are less dispersive. Therefore low frequency elastic waves can potentially be used to non-destructively inspect honeycomb cores. To enable low frequency non-destructive testing of honeycombs, it is instrumental first to characterize their sub-ultrasound wave propagation and dispersion characteristics. Accordingly, this work, using finite element analysis, provides insights into the propagation characteristics of low frequency acoustic elastic waves in aluminum honeycomb cores in terms of phase velocity; dispersion and directionality characteristics; and frequency band gaps. Also, the effect of relative density and defects in the form of deformation on sub-ultrasound wave characteristics are explored.