EFFECTS OF LOW-VELOCITY IMPACT ON STRENGTH OF DIFFERENT COMPOSITE STRUCTURES

摘要

Experimental and analytical results are needed to fully understand the effects of impact damagernon the flexural strength of a composite sandwich structure under bending loads. In this study, therneffects that varying facesheet and core materials have on the flexural behavior, before and after arnlow-velocity impact, of sandwich structures are investigated. The tested sandwiches arerncomprised of Nomex honeycomb and foam cores combined with carbon fiber pre-preg and hemprnfacesheets of three ply thicknesses and were studied under low-velocity impact and 4-point bendrntesting using ASTM D7250, D7249, D7136 and C0393. The goal of this study is to improverndesign considerations of composite sandwich facesheet and core material selection for structuresrnthat experience low-velocity impacts and bending loads. After experimental and theoreticalrnanalysis, it was found that carbon fiber/honeycomb sandwich designs perform significantly betterrnunder 4-point bending loads than the three other sandwich designs but are affected by impactrndamage significantly more than the other three designs. Hemp facesheet sandwiches could notrncarry as much load as carbon fiber facesheet sandwiches but they were much more ductile.rnLastly, foam core sandwiches were affected by impact damage much less than honeycomb corernsandwiches, in general. An error of ~20% was found between theoretical and averagernexperimental deflection results due to degraded material characteristics for facesheet materials.