Engineering topics

Crossman, F. W.

Publications and source records attributed to Crossman, F. W..

4 records

NASA NTRS1983

A study of stiffness, residual strength and fatigue life relationships for composite laminates

Qualitative and quantitative exploration of the relationship between stiffness, strength, fatigue life, residual strength, and damage of unnotched, graphite/epoxy laminates subjected to tension loading. Clarification of the mechanics of the tension loading is intended to explain previous contradictory observations and hypotheses; to develop a simple procedure to anticipate strength, fatigue life, and stiffness changes; and to provide reasons for the study of more complex cases of compression, notches, and spectrum fatigue loading. Mathematical models are developed based upon analysis of the damage states. Mathematical models were based on laminate analysis, free body type modeling or a strain energy release rate. Enough understanding of the tension loaded case is developed to allow development of a proposed, simple procedure for calculating strain to failure, stiffness, strength, data scatter, and shape of the stress-life curve for unnotched laminates subjected to tension load.

Ryder, J. T.↗

NASA NTRS1983

Analysis of delamination

This paper reviews our understanding of the influence of delamination on the fracture sequence and final fracture of graphite-epoxy laminates. The emphasis here is on tensile fracture.

Crossman, F. W.↗

NASA NTRS1983

Spacecraft material applications: Long-term stability questions

An examination of the materials concerns for a variety of spacecraft components shows that long-term stability within the space environments is a major issue in the design of large space antenna systems. This survey paper will review some of the more recent work on the effect of space environment on (1) thin films, (2) structural composites, and (3) thermal control materials. Degradation in thermal-mechanical and optical properties associated with atmospheric and trapped particles and ultraviolet light will be highlighted. Finally, the dimensional instability associated with microcracking during thermal cycling will be examined and a methodology for estimating thermal fatigue effects from results of mechanical fatigue tests will be presented.

Crossman, F. W.↗

NASA NTRS1979

Hygrothermal damage mechanisms in graphite-epoxy composites

T300/5209 and T300/5208 graphite epoxy laminates were studied experimentally and analytically in order to: (1) determine the coupling between applied stress, internal residual stress, and moisture sorption kinetics; (2) examine the microscopic damage mechanisms due to hygrothermal cycling; (3) evaluate the effect of absorbed moisture and hygrothermal cycling on inplane shear response; (4) determine the permanent loss of interfacial bond strength after moisture absorption and drying; and (5) evaluate the three dimensional stress state in laminates under a combination of hygroscopic, thermal, and mechanical loads. Specimens were conditioned to equilibrium moisture content under steady exposure to 55% or 95% RH at 70 C or 93 C. Some specimens were tested subsequent to moisture conditioning and 100 cycles between -54 C and either 70 C or 93 C.

Crossman, F. W.↗