EFFECT OF ADHESIVE LAYERS ON IMPACT DAMAGE AND DYNAMIC RESPONSE IN COMPOSITE LAMINATES
Abstract
Adhesive layers were included along the interfaces of a base line graphite/epoxy 0(,5)/90(,5)/0(,5) laminate for impact study. Impacted specimens were sectioned longitudinally and transversely for observation of the damage modes. The presence of adhesive layers resulted in the following effects: (1) Delamination was effectively suppressed up to very high impact velocities. (2) Matrix cracking in the upper lamina was greatly reduced. (3) The contact area was appreciably increased, thus the stress concentration effect significantly reduced. One major disadvantage in using adhesive layers was found: the bending crack in the bottom lamina which could branch out into delamination when adhesive layers were absent tended to penetrate in the middle lamina and breaks fibers. It is suggested that the use of adhesive strips along the bottom interface would prevent the bending crack from penetrating into adjacent lamina. A simple experimental technique has been proposed for crack propagation studies. Calculated crack propagation speed was about 45% the wave speed of graphite/epoxy, in the case of cross ply adhesive, and about 30% the wave speed velocity of graphite/epoxy, for the case of 0(,5)/90(,5)0(,5) composite laminate.
Degree
Ph.D.
Subject Area
Aerospace materials
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