Analysis of LDEF micrometeoroid/debris data and damage to composite materials

This report presented published LDEF micrometeoroid/debris impact data in a nomogram format useful for estimating the total number of hits that could be expected on a space structure as a function of time in orbit, angular location relative to ram, and exposed surface area. Correction factors accounting for different altitudes are given. These are normalized to the average LDEF altitude. Examples on how to use the nomograph are also included. In addition, impact data and damage areas observed on composite laminates (experiment AO 180) are discussed

Experimental evaluation of the tensor polynomial criterion for designing composite structures

A comprehensive experimental and analytical evaluation of the tensor polynomial failure criterion was undertaken to determine its capability for predicting the ultimate strength of a composite limina subject to a plane stress state. Results are presented demonstrating that a quadratic formulation is too conservative and a cubic representation is required. Strength comparisons with test data derived from glass/epoxy and graphite/epoxy tubular specimens are also provided to validate the cubic strength criterion. Environmental effects including ambient temperature, exposure to vacuum, length of post-cure time, and rate of cool down were also investigated. Behavior changes associated with polymer (epoxy) matrix composites were determined in terms of variations in stiffness and tensile strength

Additional results on space environmental effects on polymer matrix composites: Experiment A0180

Additional experimental results on the atomic oxygen erosion of boron, Kevlar, and graphite fiber reinforced epoxy matrix composites are presented. Damage of composite laminates due to micrometeoroid/debris impacts is also examined with particular emphasis on the relationship between damage area and actual hole size due to particle penetration. Special attention is given to one micrometeoroid impact on an aluminum base plate which resulted in ejecta visible on an adjoining vertical flange structure

Thermal-vacuum response of polymer matrix composites in space

This report describes a thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites. Experimental results derived from 'control' samples are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples. Coefficient of thermal expansion (CTE) data are also presented. In addition, an example is given illustrating the dimensional change of a 'zero' CTE laminate due to moisture outgassing

Soft-tissue specimens from pre-European extinct birds of New Zealand

We provide the first complete review of soft tissue remains from New Zealand birds that became extinct prior to European settlement (c. AD 1800). These rare specimens allow insights into the anatomy and appearance of the birds that are not attainable from bones. Our review includes previously unpublished records of ‘lost’ specimens, and descriptions of recently discovered specimens such as the first evidence of soft tissues from the South Island goose (Cnemiornis calcitrans). Overall, the soft tissue remains are dominated by moa (with specimens from each of the six genera), but also include specimens from Finsch's duck (Chenonetta finschi) and the New Zealand owlet-nightjar (Aegotheles novaezealandiae). All desiccated soft tissue specimens that have radiocarbon or stratigraphic dates are late Holocene in age, and most have been found in the semi-arid region of Central Otago

Development of failure criterion for Kevlar-epoxy fabric laminates

The development of the tensor polynomial failure criterion for composite laminate analysis is discussed. In particular, emphasis is given to the fabrication and testing of Kevlar-49 fabric (Style 285)/Narmco 5208 Epoxy. The quadratic-failure criterion with F(12)=0 provides accurate estimates of failure stresses for the Kevlar/Epoxy investigated. The cubic failure criterion was re-cast into an operationally easier form, providing the engineer with design curves that can be applied to laminates fabricated from unidirectional prepregs. In the form presented no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exists at present to generalize this approach for all undirectional prepregs and its use must be restricted to the generic materials investigated to-date

Retrospective Analysis of Emergency Medical Services (EMS) Physician Medical Control Calls

INTRODUCTION: Although emergency medical services (EMS) standing-order protocols provide more efficient and accurate on-scene management by paramedics, online medical direction (OLMD) has not been eliminated from practice. In this modern era of OLMD, no studies exist to describe the prevalence of reasons for contacting OLMD. OBJECTIVES: The primary goal of this study was to describe the quantity of and reasons for calls for medical direction. We also sought to determine time diverted from emergency physicians due to OLMD. Finally, we hoped to identify any areas for potential improvement or additional training opportunities for EMS providers. METHODS: This was a descriptive study with retrospective data analysis of recorded OLMD calls from January 1, 2016, to December 31, 2016. Data were extracted by research personnel listening to audio recordings and were entered into a database for descriptive analysis. We abstracted the date and length of call, patient demographic information (age and gender), category of call (trauma, medical, cardiac, or obstetrics), reason for call, and origin of call (prehospital, interhospital, nursing home, or discharge). RESULTS: The total number of recordings analyzed was 519. Calls were divided into four categories pertaining to their nature: 353 (68.5%) medical; 70 (13.6%) trauma; 83 (16.1%) cardiac; and 9 (8%) were obstetrics related. Repeat calls regarding the same patient encounter comprised 48 (9.4%) of the calls. Patient refusal of transport was the most common reason for a call medical direction (32.3% of calls). The total time for medical direction calls for the year was 26.6 hours. The maximum number of calls in a single day was seven, with a mean of 2.04 calls per day (standard deviation [SD] +/- 1.18). The mean call length was 3.06 minutes (SD +/- 2.51). CONCLUSION: Our analysis shows that the use of OLMD frequently involves complex decision-making such as determination of the medical decision-making capacity of patients to refuse treatment and transport, and evaluation of the appropriate level of care for interfacility transfers. Further investigation into the effect of EMS physician-driven medical direction on both the quality and time required for OLMD could allow for better identification of areas of potential improvement and training