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Giori, C.

Publications and source records attributed to Giori, C..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Mechanisms of degradation of graphite composites in a simulated space environment

Attention is given to degradation mechanisms for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiation in vacuum up to 960 equivalent sun hours and to 10 to the 9th rads, respectively. The materials showed good electron radiation stability as indicated by the low G values for gas formation and no evidence of mechanical property changes. Quantum yields for gas formation indicate poor stability to ultraviolet radiation. Mechanical property measurements did not show significant changes up to 960 ESH, with the possible exception of P1700/C6000. The main products of irradiation were identified as hydrogen and methane, along with high levels of CO and CO2.

Giori, C.↗
NASA NTRS1982

Investigation of degradation mechanisms in composite matrices

Degradation mechanisms were investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 10 to the ninth power rads respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation were identified. The radiation resistance of different matrices was compared in terms of G values and quantum yields for gas formation. All the composite materials evaluated show high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane were identified as the main by-products of irradiation, along with unexpectedly high levels of CO and CO2.

Giori, C.↗
NASA NTRS1979

Space radiation effects on composite matrix materials - Analytical approaches

In-vacuo ultraviolet and gamma radiation exposure tests are utilized in a study aimed at the identification of radiation damage mechanisms in composite materials, with the objective of predicting the long-term behavior of composite structures in a space environment at geosynchronous orbit. Physical and chemical methods of polymer characterization are utilized for the study of composite matrix degradation, in conjunction with GC/MS techniques for the analysis of volatile by-products.

Giori, C.↗
NASA NTRS1977

Space radiation resistant transparent polymeric materials

A literature search in the field of ultraviolet and charged particle irradiation of polymers was utilized in an experimental program aimed at the development of radiation stable materials for space applications. The rationale utilized for material selection and the synthesis, characterization and testing performed on several selected materials is described. Among the materials tested for ultraviolet stability in vacuum were: polyethyleneoxide, polyvinylnaphthalene, and the amino resin synthesized by the condensation of o-hydroxybenzoguanamine with formaldehyde. Particularly interesting was the radiation behavior of poly(ethyleneoxide), irradiation did not cause degradation of optical properties but rather an improvement in transparency as indicated by a decrease in solar absorptance with increasing exposure time.

Giori, C.↗
NASA NTRS1975

Investigation of space radiation effects in polymeric film-forming materials

The literature search in the field of ultraviolet radiation effects that was conducted during the previous program, Contract No. NAS1-12549, has been expanded to include the effects of charged particle radiation and high energy electromagnetic radiation. The literature from 1958 to 1969 was searched manually, while the literature from 1969 to present was searched by using a computerized keyword system. The information generated from this search was utilized for the design of an experimental program aimed at the development of materials with improved resistance to the vacuum-radiation environment of space. Preliminary irradiation experiments were performed which indicate that the approaches and criteria employed are very promising and may provide a solution to the challenging problem of polymer stability to combined ultraviolet/high energy radiation.

Giori, C.↗
NASA NTRS1974

Fundamental investigation of ultraviolet radiation effects in polymeric film-forming materials

A literature search from 1958 to present was conducted on the effect of ultraviolet radiation on polymeric materials, with particular emphasis on vacuum photolysis, mechanisms of degradation, and energy transfer phenomena. The literature from 1958 to 1968 was searched manually, while the literature from 1968 to present was searched by using a computerized keyword system. The primary objective was to provide the necessary background information for the design of new or modified materials with improved stability to the vacuum-radiation environment of space.

Giori, C.↗