The object of this study is to establish experimentally the critical fracture modes of an epoxy m a t r i x in the vicinity of a break in a high modulus, high strength filament. Three distinct failure modes were observed to occur and the nature of these three modes is explained through an analysis of the s t r e s s state in the matrix. A single filament embedded in an epoxy novolac was used to examine the fracture process.this type of resin a r i s e s f r o m its ability to be modified to varying degrees of crack sensitivity.
The advantage of usingThe effects of varying gross strain r a t e were evaluated and the study
An in vivo investigation of a new high molybdenum and nitrogen duplex stainless steel (25Cr--7Ni--4Mo--0.3N) has been performed. Cylindrical pins and specially developed devices, to test in static conditions the in vivo localized corrosion resistance, made of this new duplex steel and of a common austenitic stainless steel were implanted in rabbit's femurs for 6 and 12 months. After sacrifice, SEM observations and EDS microanalyses to detect metallic ion release were carried out on the femur sections surrounding the pins. Morphologic observations with stereoscope and SEM were performed on the metallic surfaces of the special devices in order to detect the presence of localized corrosion. Both ion release and localized corrosion were observed for the specimens made of austenitic stainless steel, but not for those made of 25Cr--7Ni--4Mo--0.3N duplex stainless steel.
A great number of studies have been made to establish the longitudinal strength characteristics of composites, with success being measured in many instances by the degree to which “rule of mixtures” predictions have been attained. Several investigators report good agreement for modulus and tensile strength in metallic filament reinforced composites. Agreement for strength predictions is less frequent in systems using continuous and discontinuous nonmetallic filament arrays. This lack of ability to predict strength of uniaxially reinforced specimens points up the need for further research on the factors contributing to premature and sometimes catastrophic failure of filament reinforced specimens. As a result of using single and multiple filament specimens of boron in epoxy novolac, methods for localizing the damage resulting from individual filament fractures were developed. Optimization of the bonding mechanism is one area of research which has yielded some very interesting results. Contrary to the concept that bond strength should be as high as possible, these studies show that, although a good bond is essential to the reinforcing mechanism, too high a bond strength may render the composite severely matrix limited. Further, it has been demonstrated in this work that varying the nature of the bond surface can be most effective in isolating the sudden energy release at a filament fracture.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.