The Effect of Impact Damage Next to Holes on the Bearing Strength of Carbon Fiber Laminates

This study was undertaken as a follow-on to a previous study that examined the effect of hole quality in the bearing strength of carbon fiber laminates. After the author of that previous study had established that hole quality had little effect on the ultimate bearing strength for carbon fiber laminates, the question was raised as to the effects of impact damage next to a hole on the bearing strength of that hole. While this is an unlikely scenario, it is still possible that this may occur on a launch vehicle structure and thus warranted study. After a literature review, results of a few studies on the hole-impact interaction with respect to resulting damage for carbon fiber laminates were found, but none that specifically addressed the resulting bearing strength. In reference 2, it was found that the holes and impact could interact to develop matrix splits. However, the lay-ups used in this study consisted of clumped plies [04/904]S, which are much more prone to matrix splitting than a laminate that would actually be used in practice (such as a lay-up of [0/90]4S). This study also focused on the analytical aspects of the problem rather than the experimental results. Reference 3 also used [04/904]S laminates (clumped plies) and examined the damage morphology, determining that, as the impact damage neared the hole, the damage zone became more asymmetrical. The effect this would have on bearing strength was not addressed. The experimental work presented in this study was to develop empirical data relating holeimpact damage effects on the resulting bearing strength of a commonly used (quasi-isotropic) lay-up of carbon fiber laminate. The emphasis was not on the morphology of the resulting damage, as it was in references 2 and 3, but rather on the practical aspects of how this damage affected the bearing strength and how this compared to the companion study1 on the effect of hole quality on the bearing strength of the laminate

A low cost method of testing compression-after-impact strength of composite laminates

A method was devised to test the compression strength of composite laminate specimens that are much thinner and wider than other tests require. The specimen can be up to 7.62 cm (3 in) wide and as thin as 1.02 mm (.04 in). The best features of the Illinois Institute of Technology Research Institute (IITRI) fixture are combined with an antibuckling jig developed and used at the University of Dayton Research Institute to obtain a method of compression testing thin, wide test coupons on any 20 kip (or larger) loading frame. Up to 83 pct. less composite material is needed for the test coupons compared to the most commonly used compression-after-impact (CAI) tests, which calls for 48 ply thick (approx. 6.12 mm) test coupons. Another advantage of the new method is that composite coupons of the exact lay-up and thickness of production parts can be tested for CAI strength, thus yielding more meaningful results. This new method was used to compression test 8 and 16 ply laminates of T300/934 carbon/epoxy. These results were compared to those obtained using ASTM standard D 3410-87 (Celanese compression test). CAI testing was performed on IM6/3501-6, IM7/SP500 and IM7/F3900. The new test method and associated fixture work well and is a valuable asset to MSFC's damage tolerance program

Instrumented impact and residual tensile strength testing of eight-ply carbon eopoxy specimens

Instrumented drop weight impact testing was utilized to examine a puncture-type impact on thin carbon-epoxy coupons. Four different material systems with various eight-ply lay-up configurations were tested. Specimens were placed over a 10.3-mm diameter hole and impacted with a smaller tup (4.2-mm diameter) than those used in previous studies. Force-time plots as well as data on absorbed energy and residual tensile strength were gathered and examined. It was found that a critical impact energy level existed for each material tested, at which point tensile strength began to rapidly decrease with increasing impact energy

PRODUCERS' WILLINGNESS TO ADOPT HACCP PRINCIPLES IN THE GOAT MEAT INDUSTRY

The major food safety issue now confronting federal policymakers is making sure that consumers can purchase foods acceptably free of microbial contaminants and of hazardous chemicals including pesticide residues, natural toxins, environmental contaminants, animal drugs, or harmful additives. While these concerns are not new, new dimensions to the problems continually challenge regulators. This paper estimates goat producers' willingness-to-adopt HACCP systems to reduce microbial pathogen. Data used are drawn from a food safety education project for small ruminant producers funded by the USDA Food Safety Inspection Services (FSIS). The data are collected using contingent valuation survey administered among small ruminant producers in Alabama and Tennessee. The probabilities of willingness to adopt HACCP practices are estimated using a probit model. The results reveal a diversified set of preferences among goat producers where by more than half of the survey sample indicated willingness to adopt HACCP practices.Food Consumption/Nutrition/Food Safety, Livestock Production/Industries,

An examination of the damage tolerance enhancement of carbon/epoxy using an outer lamina of spectra (R)

Low velocity instrumented impact testing was utilized to examine the effects of an outer lamina of ultra-high molecular weight polyethylene (Spectra) on the damage tolerance of carbon epoxy composites. Four types of 16-ply quasi-isotropic panels (0, +45, 90, -45) were tested. Some panels contained no Spectra, while others had a lamina of Spectra bonded to the top (impacted side), bottom, or both sides of the composite plates. The specimens were impacted with energies up to 8.5 J. Force time plots and maximum force versus impact energy graphs were generated for comparison purposes. Specimens were also subjected to cross-sectional analysis and compression after impact tests. The results show that while the Spectra improved the maximum load that the panels could withstand before fiber breakage, the Spectra seemingly reduced the residual strength of the composites

A damage tolerance comparison of IM7/8551 and IM8G/8553 carbon/epoxy composites

A damage tolerance study of two new toughened carbon fiber/epoxy resin systems was undertaken as a continuation of ongoing work into screening new opposites for resistance to foreign object impact. This report is intended to be a supplement to NASA TP 3029 in which four new fiber/resin systems were tested for damage tolerance. Instrumented drop weight impact testing was used to inflict damage to 16-ply quasi-isotropic specimens. Instrumented output data and cross-sectional examinations of the damage zone were utilized to quantify the damage. It was found that the two fiber/resin systems tested in this study were much more impact resistant than an untoughened composite such as T300/934, but were not as impact resistant as other materials previously studied

Cross-sectional examination of the damage zone in impacted specimens of carbon/epoxy and carbon/PEEK composites

Drop weight impact testing was utilized to inflict damage on eight-ply bidirectional and unidirectional samples of carbon/epoxy and carbon/PEEK (polyetheretherketone) test specimens with impact energies ranging from 0.80 J to 1.76 J. The impacting tip was of a smaller diameter (4.2-mm) than those used in most previous studies, and the specimens were placed with a diamond wheel wafering saw through the impacted area perpendicular to the outer fibers. Photographs at 12 x magnification were taken of these cross-sections and examined. The results on the bidirectional samples show little damage until 1.13 J, at which point delaminations were seen in the epoxy specimens. The PEEK specimens showed less delamination than the epoxy specimens for a given impact energy level. The unidirectional specimens displayed more damage than the bidirectional samples for a given impact energy, with the PEEK specimens showing much less damage than the epoxy material

The Knowledge and Attitudes Of Oncology Nurses On Advance Directives

Advances in healthcare technology has changed how healthcare professionals care for patients, increasing the importance of Advance Directives (ADs). ADs are legal documents describing patient end-of-life care wishes. Despite the usefulness of ADs, particularly in oncology settings, most patients do not have one. This qualitative content analysis study examined knowledge and attitudes of ADs among oncology nurses to obtain a better understanding of ADs. Literature on ADs and nurses is dominated by quantitative research. This study addresses knowledge gaps best filled by qualitative methods. Ten experienced oncology nurses answered eleven open-ended questions using online video conference interviews. The eleven questions corresponded to five research questions. Content analysis met rigorous standards for trustworthiness, including data saturation. Question 1 related to nurses’ firm understanding of ADs found the category Legality and themes Written Document, Wishes for EOL Care, and Unable to Speak for Self. Question 2, related to AD barriers found the category Barriers and themes Lack of Education on AD, Convenience, and Families. Question 3, related to nurses’ views of AD found the category Usefulness, with themes Prevention of Suffering and Unintended Consequences. Question 4, related to AD benefits found the category Benefits and themes Quality of Life and Peace. Question 5, related to AD discussions found the category Quality of Interactions with themes of Timing, Compassion, and Family Inclusion. Oncology nurse participants understood the meaning, benefits, and barriers of ADs viewed ADs as useful and held AD discussions with families and patients. Results confirmed several findings from previous studies such as barriers to AD identified by Boddy et al. (2013). Results also confirmed aspects of Ruland and Moore’s (1998) theory for a Peaceful End of Life. Oncology nurse participants valued increased knowledge along with AD-focused discussions. Nurses estimated under 40% of their oncology patients had an AD at admission. Additionally, AD education is needed for patients, healthcare providers, and families to ease AD-related confusion, conflict, stress, and uncertainty. Further, increased AD knowledge and awareness empowers patients, families, and fellow nurses to achieve peaceful end-of-life outcomes

Integrating Emotional Affect into Bear Viewing Management and Bear Safety Education

The popularity of viewing wildlife, specifically brown bears (Ursus arctos), is increasing rapidly throughout North America, from Yellowstone National Park (NP) to Denali National Park. In addition, population distributions of both humans and brown bears are expanding, creating larger areas of overlap and an increased possibility of human-bear interactions. In order to prevent negative encounters and injury to either species, park managers must continue to work to encourage appropriate behavior among local residents as well as park visitors. Human behavior, however, is a result of many complex factors, including emotion and cognition. Despite this, the effects of emotions on human-wildlife conflict remain unstudied and therefore may limit success of any mitigation efforts. This thesis employs a quantitative self-assessment questionnaire within a sequential exploratory design to understand the relationship between emotion and behavior within the context of human encounters with bears. Results demonstrate significant variation in negative affect across bear encounter scenarios and highlight several areas of uncertainty among respondents. These results are used to develop a set of meaningful recommendations to improve the efficacy of current bear management and safety education