Compressive strength of aluminum honeycomb core sandwich panels with thick carbon–epoxy facesheets subjected to barely visible indentation damage

Abstract

An experimental study of damage tolerance under quasi-static indentation (QSI) was performed for sandwich composite panels consisting of 16-ply carbon-epoxy facesheets bonded to an aluminum honeycomb core. To determine how indentation damage and compression strength after indentation depend on the facesheet layup, three facesheet stacking sequences were used, varying the maximum ply angle change and placement of the outermost 0 ply. Similarly, to determine the effect of core parameters on damage and strength following indentation, three cores with varying density and thickness were studied. Specimens were indented in QSI to the barely visible indentation damage threshold by spherical indenters of 25.4 or 76.2 mm diameters. Damaged specimens were tested to failure in compression to determine the post-indentation compressive strength and resulting failure mode. Compression-after-indentation (CAI) strength is compared to the undamaged strength obtained from edgewise-compression tests of specimens with the same geometry type. Three distinct failure modes were observed in the CAI experiments: compressive fiber failure, delamination buckling and global instability. Post-indentation compressive strength was independent of indenter size and there was no clear propensity for a particular failure mode dependent on a given specimen geometry. Specimens with a high core density and facesheets with a primary ply angle change of 90 were found to be the most damage resistant. Specimens with facesheets having the outer 0 plies closest to the center of the laminate were found to be the most damage tolerant.

Effects of honeycomb core damage on the performance of composite sandwich structures

“…Singh et al. 7–10 studied the effects of core density and thickness on compression strength and failure modes by compression after indentation testing. They determined that a higher core density resulted in an increased damage resistance.…”

“…As such, strength and damage characteristics of aluminum honeycomb sandwich structures have been widely studied. These studies include experimental measurements, [1][2][3][4][5][6][7][8][9][10][11][12] finite element methods, 1,5,13,14 and theoretical calculations. [15][16][17] In particular, Sun et al 1 studied the influence of honeycomb structural parameters on the crushing behavior of honeycomb sandwich structures, where three-point bend tests showed that increasing the core height resulted in an increased stiffness and peak load.…”

“…Similarly, Ivanez et al 13 studied the effects of cell size on the crush behavior and energy absorption capacity of aluminum honeycomb core by creating and experimentally validating a three dimensional finite element model. Singh et al [7][8][9][10] studied the effects of core density and thickness on compression strength and failure modes by compression after indentation testing. They determined that a higher core density resulted in an increased damage resistance.…”

Experimental investigation of low velocity impact on textile cellular composite with different energy construction

“…It is reported that cellular cores are produced either by expanding the pre-impregnated sheets or by applying a corrosive resistant coating to the foil sheets firstly, then printing the adhesive lines with curing process, followed by yielding the corrugated sheets plastically at the node-free wall joints to retain their expanded geometric shape [14,15]. Cellular core made by the above two methods requires expensive, labor intensive manufacturing and is prone to delaminate due to the lack of through thickness reinforcement [16]. However, textile cellular composite can address the issue due to the binder yarns, which stitch the adjacent layers together to ensure the integration of the cellular structure [17] and the interlaminar properties of the cellular are improved greatly.…”

Development of Aluminum Honeycomb Cored Carbon Fiber Reinforced Polymer Composite Based Sandwich Structure

“…Composite sandwich structures have been used in many applications ranging from satellites, aircraft, ships, automobiles, rail cars, wind energy systems to bridge constructions due to their light weight, high flexural and transverse shear stiffness, and corrosion resistance [1,2].…”