Accession Number : ADA329787

Title :   Fracture Characteristics of Fiber Composites,

Descriptive Note : Final technical rept. Jun 93-Nov 96,

Corporate Author : ILLINOIS UNIV AT CHICAGO CIRCLE DEPT OF CIVIL ENGINEERING MECHANICS AND METALL URGY

Personal Author(s) : Botsis, John

PDF Url : ADA329787

Report Date : JAN 1997

Pagination or Media Count : 81

Abstract : Investigations of the effects of fiber spacing on the mechanical properties and strength of a model composite system with well aligned and uniformly spaced fibers are reported. Monolayer and multilayer fiber architectures were investigated. For the monolayer fiber architecture specimens, strength sigmac depended on the fiber spacing, lambda, according to sigmac = K/square root of lambda where K is a constant related to the matrix properties. The linear portion of the stress-strain curves collapsed' when multiplied by the term square root of lambda/square root of W, where W is the specimen width. Acoustic emission indicated that the non-linear stress-strain behavior was coincided with activity at the fiber-matrix interface. For the multilayer fiber architecture, strength was found to depend on fiber spacing in the form, sigmac = K/square root of lambda + sigmao where sigmao was an intercept of undetermined origin. No scaling of any portion of the load-displacement curves was observed. For this fiber architecture the stiffness of the specimens decreased with a decrease in fiber spacing while the toughness increased with a decrease in fiber spacing. This behavior was directly related to the increase in fiber-matrix interface area that accompanied the decrease in fiber spacing. A boundary element algorithm was used to investigate the stress intensity factor of a 2-dimensional representation of the reinforced specimens. Good correlation was found between the numerical and experimental results.

Descriptors :   *FIBER REINFORCED COMPOSITES, *FRACTURE(MECHANICS), STRESS STRAIN RELATIONS, ALGORITHMS, FIBERS, MECHANICAL PROPERTIES, INTERFACES, STIFFNESS, NUMERICAL ANALYSIS, BOUNDARY LAYER, TOUGHNESS, MATRIX MATERIALS, NONLINEAR SYSTEMS, ARCHITECTURE, ACOUSTIC EMISSIONS, REINFORCING MATERIALS, SQUARE ROOTS, STRESS CONCENTRATION.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE