DETERMINATION OF THE INTERFACIAL PROPERTIES OF COMPOSITE LAMINATES FROM PHASE VELOCITY DATA

Ajit K. Mal and Shyh-Shiuh Lih Mechanical, Aerospace and Nuclear Engineering Department University of California Los Angeles, California
Yoseph Bar-Cohen Jet Propulsion Laboratory Pasadena, California

ABSTRACT

The feasibility of using ultrasonic techniques to determine the properties of the interface zones of composite laminates is studied. The influence of thickness, density, and elastic properties of the inter-laminar interface layers on the phase velocity of elastic waves in the medium are investigated through a parameter study. The results show that only the thickness of the inter-laminar interface has a strong influence on the phase velocity of guided waves in the laminate and thus it can be determined accurately from careful analysis of phase velocity data. The elastic moduli and density of the interface were found to have little effect on the phase velocity and thus they can not be determined accurately from phase velocity data.

INTRODUCTION

Composite laminates are widely used in aerospace and other engineering structures. Fiber reinforced composites with organic matrices, e.g. graphite/epoxy are the most widely used materials at the present time. Structural laminates are composed of layers of laminar of relatively small thickness containing a larger number of long, parallel fibers embedded in a matrix. The laminate provides a very desirable combination of toughness, specific strength, specific modulus and damage tolerant. However, the fracture and failure properties of these materials are highly complex and are not well understood at present. It is well known that the interface zones between the successive laminar (FIGURE 1) play a significant role in the failure of these materials. Thus a good knowledge of the mechanical properties of these zones is a prerequisite to the design and reliable prediction of the performance of composite structures. No reliable techniques exist at present for the determination of the properties of interfaces

Ultrasonic Characterization and Mechanics of Interfaces ASME 1993 (AMD-Vol. 177) (Book Contents)
ISBN No. 0-7918-1043-7
Library of Congress Catalog Number 93-73596
Copyright 1993 by
THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A.

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