Microstructure and tensile properties of carbon-epoxy laminates produced by automated fibre placement: Influence of a caul plate on the effects of gap and overlap embedded defects

Automated fibre placement (AFP) enables the trajectory of unidirectional composite tape to be optimized, but laying down complex shapes with this technology can result in the introduction of defects. The aim of this experimental study is to investigate the influence of gaps and overlaps on the microstructure and tensile properties of carbon-epoxy laminates. First, a comparison between a hand-layup and AFP layup, draped and cured under the same conditions, shows equivalent microstructures and tensile properties. This provides the reference values for the study. Then, gap and overlap embedded defects (more or less severe) are introduced during manufacturing, on two cross-ply layups [(0°/(90°)5/0°] and [(90°/0°)2/90°]. Autoclave cure without a caul plate results in local thickness variation and microstructural changes which depend on the defect type. This has a strong influence on mechanical performance. Use of a caul plate avoids these variations and in this case embedded defects hardly affect tensile properties.

Straddling The Gap: A MIddle School Teacher's Journey Towards Good Geography

Research points to a gap between academic or disciplinary based geography and what is taught in secondary classes across the nation. This study documents a teacher’s journey and efforts to bring a more disciplinary approach to two suburban heterogeneous sixth grade geography classrooms. The researcher traces student perspectives on geography and facility with geographic reasoning as well as his own perspectives and pedagogy with respect to student data. The study attempts to map the space where school geography meets and interacts with disciplinary oriented geography based upon the Geography for Life National Geography Standards. Participants completed two sets of baseline assessments and two sets of end of year assessments as well as an initial intake survey. The seven primary participants were interviewed five times each throughout the academic school year and data were openly coded. The data suggest that students can learn geography and geographic reasoning from a disciplinary perspective. Students sharpened their geographic skills through deeper subject matter knowledge and developing spatial and ecological perspectives. The data also indicate that the teacher researcher faced considerable challenges in implementing a disciplinary approach to teaching geography. The coverage demands of a crowded history-centric curriculum together with ill-fitting resources required a labor-intensive effort to put together and execute this study. Study findings indicate that the path to good geography pedagogy can be impeded by a host of external and internal challenges. However, to forward thinking practitioners, the effort to straddle the gap between school geography and disciplinary-based geography may be well worth it.

Education & health: the gap between opportunities

The aim of this study is to associate cardiovascular health, health spending and socio-economical differences in a Portuguese sample.

Delaware Water Gap National Recreation Area. Aug. 1968.

Scale ca. 1:220,000.

Delaware Water Gap National Recreation Area, New Jersey and Pennsylvania.

Scale ca. 1:130,000.

Delaware Water Gap National Recreation Area, New Jersey and Pennsylvania /

Scale ca. 1:130,000.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

Relief shown by shading.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

Relief shown by shading.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

Relief shown by shading.

Delaware Water Gap National Recreational Area, New Jersey and Pennsylvania /

Panel title.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

"*GPO: 1986--491-417/40047."

Delaware Water Gap National Recreation Area, New Jersey and Pennsylvania /

Relief shown by shading and spot heights.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

Relief shown by shading.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

Relief shown by shading.

Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey, official map and guide /

Relief shown by shading.