Contact Behaviours of Laminated Composite Thin Shells and a Rigid Ball

Wrapping and Through-Thickness Poisson Effects on Composite Plate and Shell Contact Laws

“…In such tests, through-thickness Poisson expansion/contraction or wrapping could add/subtract to the measurement of indentation. Many others have taken the same approach as Sun's group and/or applied their methodology for their own tests to measure contact laws e.g., 13,[30][31][32] .…”

“…As with the overall force-deflection and damage resistance differences in convex shells vs. plates documented in earlier work 47 , it also seems that shells behave differently with regard to a structural effect (attributed here to wrapping) on measured local indentation data. In the two prior works known on composite shell indentation 30,31 , it is unclear from either whether wrapping or other structural effects are present because deflections (and also boundary conditions) for the tests were not documented. However, given the thick specimens tested in those works (15 ply Graphite/Epoxy, 1.65 mm thick laminates 30 , and 20 ply Graphite/Epoxy, 2.77 mm thick laminates 31 ), comparable to T2 or T3 herein, clear evidence in force-indentation data such as that observed in this work for thin (T1) specimens would not be expected.…”

“…In the two prior works known on composite shell indentation 30,31 , it is unclear from either whether wrapping or other structural effects are present because deflections (and also boundary conditions) for the tests were not documented. However, given the thick specimens tested in those works (15 ply Graphite/Epoxy, 1.65 mm thick laminates 30 , and 20 ply Graphite/Epoxy, 2.77 mm thick laminates 31 ), comparable to T2 or T3 herein, clear evidence in force-indentation data such as that observed in this work for thin (T1) specimens would not be expected. Further work is necessary to more completely understand wrapping in this context, but it is clear that relatively thin shells, which are a much better proxy for most aerospace structures than plates, are known to behave differently than plates.…”