Accession Number : ADA326166

Title :   Load Transfer, Interface Characterization and Toughening Mechanism of Composites.

Descriptive Note : Final rept. 11 Mar 93-31 Dec 96,

Corporate Author : STATE UNIV OF NEW YORK AT STONY BROOK DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Chiang, Fu-Pen

PDF Url : ADA326166

Report Date : MAR 1997

Pagination or Media Count : 68

Abstract : A Micromechanics Measurement Technique called SIEM (Speckle Interferometry with Electron Microscopy) has been developed which has a spatial resolution of 10(exp -6) m and a displacement resolution of 10(exp-9) m. It utilizes a random pattern of submicron particles as markers on a specimen. Their movements under load are used for displacement/strain calculations through a correlation scheme. It has been successfully applied to the determination of the mechanical property of composite interphases. It is also applied to the determination of crack tip deformation along a bimaterial interface. It is found that even in a region as small as 100 (micrometers) squared there is no evidence pointing to the existence of an oscillatory stress field. It is shown that the William's asymptotic solution can be expressed in a form that indicates that the stress field at an interfacial crack tip is intrinsically asymmetric with respect to the phase angle. An interfacial toughness function is proposed that possesses this feature. This function agrees very well with the then existing five sets of experimental data in the open literature. Three dimensional photoelasticity is used to study the load transfer characteristics of strongly and weakly bonded interfaces due to the presence of dilatational strain of a sphere. The result compares favorably with theoretical predictions of H.Y.Yu of the Naval Research Laboratory.

Descriptors :   *MECHANICAL PROPERTIES, *INTERFACES, *COMPOSITE MATERIALS, *LOADS(FORCES), *TOUGHNESS, *TRANSFER, STRESSES, SPATIAL DISTRIBUTION, EXPERIMENTAL DATA, DEFORMATION, CRACKS, DISPLACEMENT, RESOLUTION, STRAIN(MECHANICS), SPHERES, PHASE, ELECTRON MICROSCOPY, THREE DIMENSIONAL, ASYMMETRY, BONDED JOINTS, PATTERNS, NAVAL RESEARCH LABORATORIES, MARKERS, MICROMECHANICS, OSCILLATION, PHOTOELASTICITY, SPECKLE INTERFEROMETRY.

Subject Categories : Optics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE