top of page

The Hemp Chair

Hemp Chair_Full.jpg

Coreless filament winding is a composite material forming process involving the use of a discrete, minimal framework around which continuous fibre rovings are laid in a pre-determined sequence. The minimal amount of formwork inherent to coreless filament winding also means that the time, energy, and resources that would have gone in fabricating a more extensive formwork are conserved. The typical fibers selected for coreless filament winding are synthetic materials such as glass and carbon fibers, which has proven successful in several construction endeavors. However, there is potential in the exploration of alternative fibrous materials for use in construction, specifically natural fibers derived from plants. Natural fibers, while featuring mechanical properties less than that of synthetic fibers, offer advantages such as their light weight, cost, biodegradability, and availability from renewable resources. Natural fibers can also be integrated into fiber-reinforced composites just as synthetic fibers are, and, in addition, can be produced with the continuous length necessary for winding. Therefore, the combination of coreless filament winding and natural fibers is tapping into a vastly unexplored area of research with potential for the development of environmentally-friendly manufacturing. In order to explore such a paradigm, the aim of this project was to produce a filament-wound chair made from natural fibers.

In collaboration with André Kauffman

Hemp fibers were selected due to their higher mechanical properties compared to to other natural fibers and availability. they are commercially produced in rope-like form, and when pulled through a resin bath of a biobased epoxy resin, form a fiber-reinforced biocomposite. mechanical load tests were performed on composite samples in order to determine a flexural modulus of ~8 GPa.

graph hemp.png

3-point bend test conducted on a sample of hemp biocomposite

3-point bend test results for various resins

Strain

Stress

graph_labels.jpg

Prior experience with coreless filament winding led to the fabrication concept of winding the chair as planar elements to ensure high tension and fiber-fiber interaction, which is critical for ensuring that increased cross-sectional thickness is achieved. Thus, the chair was discretized into two kinds of different parts: bending sheets that would serve as the chair surface, and curved profiles that would provide shape and structure. The elastica curve of the chair profiles was form-found using bending lines in Kangaroo Physics in accordance to the desired height and length of the chair and the angle of the surfaces. Once the form-finding was completed, the fiber layout of the profile had to be generated. Different fiber layouts were tested for resulting structural performance of the chair profile using the FEM plugin Karamba. The fiber layouts were modeled as lines and then converted to beams. The structural simulation provided crucial feedback for the design and fabrication. Most notably, increasing the thickness of some of the beam members in critical regions was necessary in order to increase the buckling load. The fiber layout of the profile was copied and translated in the transversal direction four times to model the width of the chair with its five profiles. This completed the modeling of the chair. The final step of the simulation was to execute a FEM analysis of the entire chair in SOFiSTiK. The results were considered satisfactory for fabrication to commence.

test9_finalealmost-20_reversed.jpg
Portfolio_old-42.jpg
Portfolio_old-41.jpg
Portfolio_old-40.jpg

Load: 100kg + self-weight

First buckling weight: 99kg

Max displacment: 3.06 -Z

Design concept

Fiber layout and chair profile

FEA results

The hemp fibers were wound around makeshift spools and then later pulled through a resin bath to form a composite. The chair parts were wound by hand on a planar cardboard surface with embedded M8 bolts that served as anchor points. The parts were then left to cure at ambient temperature. The bolts were removed and the parts assembled by applying temporary zip ties to hold the parts in place while fibers were wrapped around the connection points. Resin was then applied so that the parts cured together.
 

hemp1.jpg
hemp2.jpg
hemp3.jpg

Hemp fiber spools

Wet winding of hemp composite

Assembly

Final results:
 

test9_finalealmost-55.png
test9_finalealmost-1.png
test9_finalealmost-50.png
Portfolio_old-11.jpg
test9_finalealmost-31.jpg

The Hemp Chair in its natural habitat

© Sachin Sean Gupta 2025

bottom of page