Failure mode maps for four-point-bending of hybrid sandwich structures with carbon fiber reinforced plastic face sheets and aluminum foam cores manufactured by a polyurethane spraying process

Abstract

This work focuses on failure mode maps of sandwich panels exposed to bending load, which were produced using a polyurethane spraying process. This process allows for an automated production of sandwich panels omitting a separate bonding step of the face sheets to the core. The investigated sandwich panels consisted of carbon fiber reinforced face sheets in various configurations, and four different core structures of aluminum foam or Nomex honeycomb. After production, measurements of the pores inside the core foam structures, the fiber package thickness inside the face sheets, and the density homogeneity of the core structure were made using X-ray computed tomography. The failure mode maps were based on the individual mechanical properties of the face sheets and the core, determined by mechanical testing. The critical forces determining the failure modes were partially modified to fit the application on foam core structures and face sheets with a porous matrix. The verification of the failure modes was performed with four-point bending tests. Since all tested configurations of sandwich specimens were produced using the same process route, the applied models for the creation of the failure mode maps could be verified for numerous parameter combinations. Except for two parameters with inconstant properties, the failure modes determined by the failure mode maps matched the observed failure modes determined by the bending tests.

Low-Velocity Impact Properties of Sandwich Structures with Aluminum Foam Cores and CFRP Face Sheets

“…The sandwich structures were produced using a modified PUR spraying process. Both the material combinations and the production process are also described in earlier publications by the authors [21][22][23]; however, all necessary information for the low-velocity impact properties are given here.…”

Evaluation of the influence of design in the mechanical properties of honeycomb cores used in composite panels

“…9 The materials of the core may be metallic such as, aluminum, 1,10 other alloys, 11 or polymers. 12 The core may consist on a cellular material that can be a two-dimensional (2D) or a 3D cellular material. The 2D materials involve honeycombs, while the 3D materials comprise foams and truss/lattices.…”

“…Among the cellular materials, foams exhibit a random porous structure, in contrast with honeycombs or truss/lattices that possess periodic ordered arrangements. 2,[12][13][14][15][16] Truss or lattice cores have received considerable attention because, in comparison with the honeycomb, they may exhibit superior buckling resistance, at low relative density. 13,16,17 Intensive research was carried out by several researchers to study the mechanical behavior of cellular materials or of honeycomb sandwich panels under different loading conditions.…”

Experimental and theoretical research on four-point bending performance of Nomex honeycomb sandwich panels

“…where γ indicates the degree of shear failure of the core layer after the indentation failure occurs, which is obtained based on the experimental data of failure Type-A 46 γ ¼ 1 n…”