Composite fuselage technology

The overall objective is to identify and understand, via directed experimentation and analysis, the mechanisms which control the structural behavior of fuselages in their response to damage (resistance, tolerance, and arrest). A further objective is to develop straightforward design methodologies which can be employed by structural designers in preliminary design stages to make intelligent choices concerning the material, layup, and structural configuration so that a more efficient structure with structural integrity can be designed and built

Composite fuselage technology (summary of year 2)

The overall objective of this work is to identify and understand, via directed experimentation and analysis, the mechanisms which control the structural behavior of fuselages in their response to damage (resistance, tolerance, and arrest). A further objective is to develop straightforward design methodologies which can be employed by structural designers in preliminary design stages to make intelligent choices concerning the material, layup, and structural configuration so that a more efficient structure with structural integrity can be designed and built

Finding Guide to the Paula Hirsch Foster Collection DRAFT

DRAFT of the Guide to the Paula Hirsch Foster Collection, as of February 2016

Damage tolerance and arrest characteristics of pressurized graphite/epoxy tape cylinders

An investigation of the damage tolerance and damage arrest characteristics of internally-pressurized graphite/epoxy tape cylinders with axial notches was conducted. An existing failure prediction methodology, developed and verified for quasi-isotropic graphite/epoxy fabric cylinders, was investigated for applicability to general tape layups. In addition, the effect of external circumferential stiffening bands on the direction of fracture path propagation and possible damage arrest was examined. Quasi-isotropic (90/0/plus or minus 45)s and structurally anisotropic (plus or minus 45/0)s and (plus or minus 45/90)s coupons and cylinders were constructed from AS4/3501-6 graphite/epoxy tape. Notched and unnotched coupons were tested in tension and the data correlated using the equation of Mar and Lin. Cylinders with through-thickness axial slits were pressurized to failure achieving a far-field two-to-one biaxial stress state. Experimental failure pressures of the (90/0/plus or minus 45)s cylinders agreed with predicted values for all cases but the specimen with the smallest slit. However, the failure pressures of the structurally anisotropic cylinders, (plus or minus 45/0)s and (plus or minus 45/90)s, were above the values predicted utilizing the predictive methodology in all cases. Possible factors neglected by the predictive methodology include structural coupling in the laminates and axial loading of the cylindrical specimens. Furthermore, applicability of the predictive methodology depends on the similarity of initial fracture modes in the coupon specimens and the cylinder specimens of the same laminate type. The existence of splitting which may be exacerbated by the axial loading in the cylinders, shows that this condition is not always met. The circumferential stiffeners were generally able to redirect fracture propagation from longitudinal to circumferential. A quantitative assessment for stiffener effectiveness in containing the fracture, based on cylinder radius, slit size, and bending stiffnesses of the laminates, is proposed

Large Steklov eigenvalues via homogenisation on manifolds

Using methods in the spirit of deterministic homogenisation theory we obtain convergence of the Steklov eigenvalues of a sequence of domains in a Riemannian manifold to weighted Laplace eigenvalues of that manifold. The domains are obtained by removing small geodesic balls that are asymptotically densely uniformly distributed as their radius tends to zero. We use this relationship to construct manifolds that have large Steklov eigenvalues. In dimension two, and with constant weight equal to 1, we prove that Kokarev’s upper bound of 8\pi for the first nonzero normalised Steklov eigenvalue on orientable surfaces of genus 0 is saturated. For other topological types and eigenvalue indices, we also obtain lower bounds on the best upper bound for the eigenvalue in terms of Laplace maximisers. For the first two eigenvalues, these lower bounds become equalities. A surprising consequence is the existence of free boundary minimal surfaces immersed in the unit ball by first Steklov eigenfunctions and with area strictly larger than 2\pi. This was previously thought to be impossible. We provide numerical evidence that some of the already known examples of free boundary minimal surfaces have these properties and also exhibit simulations of new free boundary minimal surfaces of genus zero in the unit ball with even larger area. We prove that the first nonzero Steklov eigenvalue of all these examples is equal to 1, as a consequence of their symmetries and topology, so that they are consistent with a general conjecture by Fraser and Li. In dimension three and larger, we prove that the isoperimetric inequality of Colbois–El Soufi–Girouard is sharp and implies an upper bound for weighted Laplace eigenvalues. We also show that in any manifold with a fixed metric, one can construct by varying the weight a domain with connected boundary whose first nonzero normalised Steklov eigenvalue is arbitrarily large

Ardhanārīśvara in Tiruchengode, Tamil Nadu : a case study

There has been a persistent tendency in the study of religion to emphasize its textual and historical elements, at the expense of ritual, practice, and custom. This trend is evident in the available academic works concerning the androgynous Hindu deity, Ardhanārīśvara. Scholarship largely overlooks Ardhanārīśvara in living context, including information about dedicated sites of worship. To attend to this gap, this project explores Ardhanārīśvara in Tiruchengode, Tamil Nadu, as it is home to a hilltop temple wherein Ardhanārīśvara is the presiding deity. An analysis of my fieldwork observations and impressions yields two types of contributions. The first relates to areas of previous scholastic focus; new information is provided on Ardhanārīśvara iconography, mythological narratives, and regarding interpretations of the figure. The second type of contribution involves unexplored content, including information on the aforementioned site of worship and the place of Ardhanārīśvara in ritual within this context. Additionally, the theoretical and methodological underpinnings of this thesis stress understanding observable phenomena as dynamic. This led to astute observations regarding Ardhanārīśvara that also go delineated. These provisions reaffirm the significance of those areas identified as overlooked in the study of religion and provide a more robust treatment of the figure

Aircraft System Design Graduate Curriculum: A Lifecycle Focus

Aircraft system design encompasses technical, social and lifecycle topics, and is suitable for graduate studies at the masters level and beyond. Several degree programs in MIT’s School of Engineering offer opportunities for students seeking subjects and degrees in this area. These programs are summarized, and one subject on Aircraft Systems Engineering is introduced as an illustration of content and pedagogy addressing lifecycle topics. Based upon several years of experience of participation in these programs and in offering curriculum, the authors put forward seven observations to stimulate further dialog and progress on this topic