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01/23/2015

carbonWound – Lightweight Composites

Megha Chandrasekhar, Christopher Mascari, Brandon Vieth (website)
University of Michigan, Taubman School of Architecture and Urban Planning
Thesis Project – Novel Constructions
Faculty: Glenn Wilcox (website), Wesley McGee (website)
2013  

 

Lightness is a multi-disciplinary term that implies different narratives. Historically, lightness in architecture has often been associated with aesthetic quality and spatial presence; whereas physical characteristics of mass, maneuverability, and performance typically parallel other material sensitive disciplines.

As part of the _novelconstructions thesis studio, carbonWound explores lightness as an element within the realm of architecture that utilizes the methodologies deployed in the design and manufacture of marine and aeronautic bodies. Within these disciplines, performance relies on material capacity and the flexibility of fiber composite construction­­, such as carbon fiber through its ability to accommodate dynamic lightweight, yet structurally stable forms.

In architecture, the role of the composite remains attuned to the “mud-and-straw” mentality as a standard method of achieving the ultimate material performance. Concrete while strong and heavy is visually opaque; steel while strong is also heavy. However, fiber composites are both strong and light and deliver both physically and visually. Advances in fiber strength, resin chemistry and fabrication processes have dramatically changed the ways in which composites are designed to perform under extreme conditions. While these qualities are prevalent in other fields their potential in architecture has yet to be fully realized.

The new paradigm surrounding fiber composites in architecture, particularly through the influence of Greg Lynn, focuses on the process of creating continuous free form objects entailing complex CNC manufactured formwork. This approach significantly increases cost, material waste, production time, and often yields a single customized part. A primary ambition behind this project was to limit the amount of custom formwork while maintaining a high level of geometric variability.

The research began with a series of material investigations to develop an understanding of the phase change process, fabrication limitations, and formal potential of four composite materials. Resin pre-impregnated carbon fiber, basalt, and fiber glass were tested along with fiber reinforced thermoplastics. Each material required a unique time and temperature sensitive curing process to solidify into the resultant geometry. After a series of tests, carbon fiber was chosen for its availability, strength and aesthetic qualities.

Material composition also played a pivotal role. Rather than utilizing woven cloth as a base – which involves a laborious layup process – spooled carbon fiber filament provided increased flexibility by allowing for automated production and designed fiber orientation. The use of filament as a base material eliminated the dependency on standardized dimensional stock while creating opportunities for customization without wasting material.

In many ways, this project questions the role of the architect. Rather than resorting to standardized manufacturing processes, digital and physical tooling was designed and created from scratch in response to material and production demands. The leap from conceptual design to material form required the manifestation of three key elements.

A custom filament winding tool was developed first – which functioned as an extension to a standard industrial 7-axis robot. Robotic fabrication provides a high level of accuracy and timely production over the process of hand winding. The tool was responsible for accurately orienting and delivering carbon fiber onto a customizable jig while having the ability to be adjusted on the fly to accommodate changing geometric and material conditions. These included directional changes, rewind force and drag – a byproduct of resin moisture loss. To ensure a tight form and proper fusion during the curing cycle, constant tension was applied to the winding process through a local rewind mechanism.

In order to translate between design intent and physical form, a set of generative computational tools were developed as primary communication between the digital model and the physical output. The project utilizes code as a generative production tool contrary to formal exploration. A custom python script translated a generic digital model into detailed vector data that was programmed to account for connection tolerances, expected material behavior, and discrepancies between the robot, winding tool and jig. This ensured that each component was constructed to a level of accuracy required to maintain integrity in the entire assembly. Additional variables were added to the system that allowed for programmed material placement and density.

The typical process for manufacturing a composite artifact requires a pre-manufactured mold, over which the composite is formed. Working with filament as the base material provided an opportunity to experiment with much simpler forming alternatives. Point coordinates were gathered from each module during the scripting process and fed into a secondary line of code that automatically generated a set of curve profiles that were manufactured and assembled on a base. This “comb shaped” profile acted as a material spacer that later became the point of connection between modules. Once the robot finished winding each component, the entire jig assembly was placed in the oven, baked, cooled and then reused.

The project culminated with the installation of a full scale prototype at the annual graduate thesis exhibition. A diligently designed global form significantly decreased production time by limiting the amount of custom formwork. Variability was achieved by locally tailoring each components density to meet its structural demand and location in space; thus allowing for certain components to geometrically repeat and formwork to be reused.

The finished prototype was composed of ninety nine unique components formed around eleven custom molds. Components were later aggregated and epoxy welded onsite to create a composite form. Strategic material placement allowed for the twenty five pound structure to withstand the forces of gravity – spanning twenty feet on two pinned connections. Pertinent to the ongoing discourse surrounding digital fabrication and material ecology in architecture, carbonWound demonstrates a potential future for lightweight composites within a larger conversation of architectural building systems.

 

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