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Title: Failure modes and durability of Kevlar/epoxy composites

Abstract

The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process, are discussed in relation to fiber and composite performance.

Authors:
; ; ;
Publication Date:
Research Org.:
California Univ., Livermore (USA). Lawrence Livermore Lab.
OSTI Identifier:
5225030
Report Number(s):
UCRL-83875; CONF-801010-2
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 12. National Society for the Advancement of Materials and Process Engineering technical conference, Seattle, WA, USA, 7 Oct 1980
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARAMIDS; FRACTURE PROPERTIES; EPOXIDES; DEFORMATION; DUCTILITY; FAILURES; PRESSURE VESSELS; RESINS; CONTAINERS; MECHANICAL PROPERTIES; ORGANIC COMPOUNDS; ORGANIC OXYGEN COMPOUNDS; ORGANIC POLYMERS; PETROCHEMICALS; PETROLEUM PRODUCTS; PLASTICS; POLYMERS; TENSILE PROPERTIES; 360303* - Composite Materials- Mechanical Properties- (-1987)

Citation Formats

Morgan, R.J., Mones, E.T., Steele, W.J., and Deutscher, S.B. Failure modes and durability of Kevlar/epoxy composites. United States: N. p., 1980. Web.
Morgan, R.J., Mones, E.T., Steele, W.J., & Deutscher, S.B. Failure modes and durability of Kevlar/epoxy composites. United States.
Morgan, R.J., Mones, E.T., Steele, W.J., and Deutscher, S.B. 1980. "Failure modes and durability of Kevlar/epoxy composites". United States. doi:.
@article{osti_5225030,
title = {Failure modes and durability of Kevlar/epoxy composites},
author = {Morgan, R.J. and Mones, E.T. and Steele, W.J. and Deutscher, S.B.},
abstractNote = {The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process, are discussed in relation to fiber and composite performance.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1980,
month = 6
}

Conference:
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  • The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process are discussed in relation to fiber and composite performance.
  • 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 absencemore » 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.« less
  • This paper presents some new data on the strength and stress-rupture of Kevlar-49 fibers, fiber/epoxy strands and pressure vessels, and consolidated data obtained at LLNL over the past 10 years. This data are interpreted by using recent theoretical results from a micromechanical model of the statistical failure process, thereby gaining understanding of the roles of the epoxy matrix and ultraviolet radiation on long term lifetime.
  • The mechanical behavior of a novel interlocked fabric reinforced Kevlar 49/epoxy composite has been measured and compared to those of a laminated Kevlar 49 fabric composite (which served as a reference material). Both composites were 5.0 mm thick, contained the same 50% in-plane fiber volume fraction and were fabricated in a similar manner using the same Dow DER 332 epoxy, Jeffamine T403-hardened resin system. The reference material (Material 1) was reinforced with seven plies of Dupont style 1033 Kevlar 49 fabric. A photomicrograph of a section polished parallel to one of the fiber directions is shown. The interlocked fabric wasmore » designed and woven for Sandia National Laboratories by Albany International Research Co., Dedham, MA. The main design criterion was to duplicate a sewn through-the-thickness fabric used in preliminary studies. The interlocked fabric composite (Material 2) contains roughly 4% by volume of through-the-thickness fiber reinforcement for the purpose of improving interlaminar strength. A photomicrograph of a section showing the warp-aligned binder yarns interlocking the six fabric plies together is shown. 2 refs., 8 figs.« less