Modes of deformation and failure of Kevlar 49 fibers and composites

Conference · Mon Dec 05 04:00:00 EST 1983

OSTI ID:5277375

Pruneda, C O; Morgan, R J; Kong, F M; Hodson, J A; Kershaw, R P; Casey, A W

Fracture-topography and stress-optical-microscopy are utilized to study the deformation and failure modes of Kevlar 49 fibers and their epoxy composites. Fracture topographies of bare yarns, composite strands, and pressure vessels reveal Kevlar 49 fibers fail in tension by axially splitting 20 to 50 times their diameter D (20 to 50D) along their lengths. This type of fiber failure involves shear-induced microvoid growth throughout the fiber which occurs principally along the fiber axis, followed by macroscopic crack propagation through such microscopic crack propagation through such microvoids. Fiber splitting in the fracture of single filaments is < 5D because of the absence of external shear stresses. The topographies observed in fractured single filaments are described in terms of longitudinal and transverse fiber crack propagation paths in the fiber skin and core. Hydrolytically-degraded Kevlar 49 fibers exhibit lower fiber split lengths in composites. There is a correlation between the percentage of fibers that exhibit transverse failure without splitting and the composite strength. Stress-optical-microscopy studies of the deformation and failure processes of simple composite laminates are reported as a function of laminate geometry, temperature, and fiber surface treatment.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5277375
• Report Number(s): UCRL-89626; CONF-840459-3; ON: DE84004162
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360303* -- Composite Materials-- Mechanical Properties-- (-1987)
360403 -- Materials-- Polymers &amp; Plastics-- Mechanical Properties-- (-1987)
ARAMIDS
COMPOSITE MATERIALS
DEFORMATION
ELECTRON MICROSCOPY
EPOXIDES
FAILURES
FIBERS
FILAMENTS
FRACTURES
MATERIALS
MICROSCOPY
OPTICAL MICROSCOPY
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
SCANNING ELECTRON MICROSCOPY
SYNTHETIC MATERIALS
TOPOGRAPHY