Design and manufacturing considerations for ply drops in composite structures

Citation
Ds. Cairns et al., Design and manufacturing considerations for ply drops in composite structures, COMPOS P B, 30(5), 1999, pp. 523-534
Citations number
13
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science & Engineering
Journal title
COMPOSITES PART B-ENGINEERING
ISSN journal
1359-8368 → ACNP
Volume
30
Issue
5
Year of publication
1999
Pages
523 - 534
Database
ISI
SICI code
1359-8368(1999)30:5<523:DAMCFP>2.0.ZU;2-K
Abstract
Thickness variations are required to optimize the design of modern laminate d composite structures. These thickness variations are accomplished by drop ping plies along the length to match varying in-plane and bending loads. Th is results in a structure which is matched to stiffness and loading require ments. Unfortunately, these ply drops produce internal and local stress con centrations as a consequence of geometric discontinuities and shear lag. In this study, we explore various factors for design of composite structures with ply drops. These factors include: thicknesses, ply stacking sequences, ply drop geometries and manufacturing considerations. In addition, fatigue loading is considered with respect to delamination initiation and growth. A strong sensitivity to the position and the manufacturing details of ply d rops is shown for fatigue damage initiation and growth. All studies were co nducted on a low-cost E-glass/polyester composite system. The results indic ate that it will be difficult to completely suppress damage and delaminatio n initiation in service. However, it was found that, in many cases, there i s a threshold loading under which there is Little growth after initiation i s noted. Factors affecting this threshold are analyzed via the virtual crac k closure method in Finite Element Analysis and verified experimentally. De sign rules for ply dropping are presented on the basis of these results. (C ) 1999 Published by Elsevier Science Ltd. All rights reserved.