Experimental and numerical study of increased core surface area on the performance of additively manufactured honeycomb sandwich structures

Abstract

Sandwich composite structures have an efficient structural design that provides high bending stiffness and strength at low weight. However, these structures are plagued with weak core-to-facesheet bond strength. In this work, the effect of increasing the contact area between the composite facesheet and honeycomb core was studied. Sandwich panels were manufactured using two different honeycomb structures, a regular and a modified honeycomb, and their respective bond strengths were evaluated using the flatwise tension test (ASTM C297). The honeycombs were additively manufactured using selective laser melting (SLM) process. The modified honeycomb was designed to have a larger surface area while retaining the same relative density as the regular honeycomb. The facesheets were made out of carbon-fiber, while the core was additively manufactured using 304L stainless steel powder. Impact specimens were manufactured and tested for impact resistance. A finite element model was created to study the integrity of the sandwich structures subjected to localized impact damage. The finite element model of the damage resistance due to impact showed a good agreement with the experimental results. Samples with increased contact area showed higher impact resistance. The average impact strength of the modified samples was 41.3% higher than the average impact strength of the regular samples. Flatwise tension results showed that by increasing the contact area between the core and the facesheet the core-to-facesheet bond strength increased.