FRACTURE TOUGHNESS OF FILAMENT-WOUND COMPOSITES. PART I. EFFECT OF MATERIAL VARIABLES.
NAVAL RESEARCH LAB WASHINGTON D C
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The application of the theory of linear fracture mehcanics to quasi-brittle, glass- reinforced-plastic composites is an important first step in understanding the basic mechanisms of failure of these materials. In this study, a simple test technique sensitive to small changes in the material based on fracture mechanics concepts. Six different resin-glass combinations were tested. The results of these tests indicate that a there is no difference in the fracture strenght of composites made with either E-glass or S- glass, b composites with 5-mil-diam fibers have a lower resistance to crack propagation than those with conventional 0.4 mil-diam fibers, and c a filament-wound composite has a much lower fracture toughness in the Bstaged state than in the fully cured state. In water immersion was investigated. These tests demonstrate that with the exception of the composite made with the large-diameter 5-mil fibers there is no sysematic decline in fracture strength due to water immersion for periods up to 6 months. Author, modified FOR PERIODS UP TO 6 MONTHS. Author, modified-PL
- Laminates and Composite Materials