DELAMINATION INITIATION OF LAMINATES WITH PIN-LOADED HOLES

A finite element analysis is conducted to determine the three-dimensio nal stress held in a composite laminate with a pin-loaded hole. The ac curacy of computation is established by comparison with the strain gau ge measurements near and away from the hole boundary. An acoustic emis sion technique was used to determine the initial failure load as the s pecimen was subjected to a quasi-static loading rate. Specimens were e xamined between the load steps using radiography and micrography in or der to detect delamination initiation. The delamination initiation sit e and the corresponding load level are predicted by applying the strai n energy density criterion. The critical parameters were extracted fro m the experimental measurements and finite element analysis of a doubl e cantilever beam specimen. The analysis predictions indicate that del aminations could initiate close to the free surface at the interface b etween layers with a fiber orientation of +/-45 degrees relative to th e load direction. These predictions confirm the experimental observati ons. (C) 1998 Elsevier Science Ltd. All rights reserved.