Effects of Using Composite Materials in the Simulation of a Prothesis
Author: Carlos M. Domenech Pineiro
Advisor: Bernardo Restrepo P.H.D
Mechanical Engineering Department
Abstract Methodology On a similar matter the figure 4 presents the results for the stress test and a 
typical curve of the stress vs strain curve for the model of carbon fiber. On Conclusions
this case the part didn’t reach the elastic limit of 2.26GPa, therefore the part 
The work was performed trough simulations with the SolidWorks 
This design project investigated the effects of weight and durability of a didn’t suffer significant damage. The test was also performed on the 
software. The first phase involved the design of the parts of the transtibial Taking in consideration the results obtained, it can be said that the 
transtibial prothesis modeled on composite materials subjected to loads. titanium and fiberglass. The optimal option resulted on the carbon fiber.  
prothesis, which included the foot, the pylon, and the socket. The parts objectives of the project were met. It was proved that the composite 
The work focused on solid mechanics and modules of failure such as For the other components the test was performed and similarly the 
were assigned materials according to its purpose and usage, involving material alternatives are lighter, as seen that the optimal option was the 
stress, strain, and fatigue. The work was achieved through simulation and composite alternatives were the best alternative.
the simulation of models on common material alloys and composite assembly simulated on carbon fiber and HDPE, giving a mass of 0.95 kg 
tests on the SolidWorks software. Three models were designed and 
material alternatives. The common materials were Aluminum 6061T6, or 2.1 lb. In terms of stresses, the carbon fiber alternatives withstanded 
tested, involving some common and composite alternatives that were Figure 4. Stress results and typical curve for the carbon fiber
Titanium Ti-13V-11Cr, meanwhile the composite alternatives included the loads without reaching elastic limits, as well as for the HDPE. Also, 
designated based on the geometry and usage of the part. Some of the 
Carbon Fiber AS4C 3k, Fiberglass and HDPE. The next phase involved the strain deformation for the composites was very low giving results on 
materials considered were aluminum, titanium, and carbon fiber, among −5
the tests in which the stress, strain and displacement were analyzed due the order of 10 , therefore considered small strains due to it being 
others. The results obtained were as expected because the composite 
to applied forces to each individual part. The last phase involved the smaller than 1. The displacements for the composites were way lower 
alternatives exceeded on the tests, translating into lighter and more 
fatigue test that was performed  on the assembly subjecting it to cyclic than the ones for the common materials, this is associated to the strain 
durable parts that complied with the purpose.  The outcome of the project 
loads. After that the results were analyzed. deformations. In regard of the fatigue the composite alternatives reached 
is relevant to understand better the applications and improvements that high cycle fatigue and, on the pylon,  infinite life was achieved opposed to 
the composite materials can contribute to daily life activities. common alternatives that failed at low cycles. In conclusion the 
On the case of the strain, for demonstration purpose the socket was composite materials alternatives excelled the tests and behaved better 
Results and Discussion considered, comparing the results present on the figure 5 the average 
Introduction than the common materials options. deformation strains were significantly low on the order 10−5, which means 
Based on the results obtained from the analysis and tests the following it is considered small strain due to it being lower than 1. On the other 
was found. In terms of mass as shown on the figure 1 the optimal 
The main issue that prothesis wielders experience is that the equipment components the test was performed resulting on the same values lower 
alternative was a foot and pylon made of carbon fiber and a socket made 
become heavy after prolonged time of usage. This project is focused on than 1.  Future Work
of HDPE. 
studying mechanical properties of common materials and composite 
materials, and how it can improve the weight of the parts and its Figure 5. strain results comparing perlon fiber with HDPE Since the field of composite materials and its properties is an extensive 
Figure 1. Mass of each component based on the material
durability. The prothesis that was studied was a transtibial prothesis, study area some tasks for future work are, to expand the variety of 
composed of a foot, a pylon, and a socket. composite alternatives that are studied, explore other geometries for the 
parts, and study the economic impact due to the materials. 
Background
The project mainly focusses on the principles of solid mechanics, The displacement  is represented on figure 6 which demonstrate how the 
specifically the stress and strains [1]. The stress focusses on the elastic This combination is optimal because the total mass as shown on figure 2 part was moved when the load was applied. For this section, the pylon was 
and plastic behavior of the materials. The strain is the degree of was of 2.1lb, from which 54% of mass is on the foot, this helps in terms of considered showing that the displacement for the aluminum alternative was 
deformation present on the part due to the loads applied. To achieve stability. The 14% on the connecting rod and the remaining 32% on the of 0.0081mm meanwhile the displacement for the carbon fiber was of 
better results without having heavier parts, composites are the best socket. This complies with the objective to stablish lightweight alternative 0.0023mm, therefore demonstrating that the composite alternative behaved 
option [2]. Composite materials are the binding of two or more types of for the prothesis. better than the common alternatives 
materials (metals, ceramics, and polymers) to improve the properties. To Acknowledgements
understand better the prothesis equipment that was studied, previous Figure 2. Mass distribution of the optimal assembly Figure 6. Displacement results comparing aluminum with carbon fiber
works were reviewed for the individual parts. For the foot, the stress test Among the acknowledgements are the advisor Dr. Bernardo Restrepo, for 
was performed in which the composite alternatives prevailed on the tests his help and advice during this project and my family for always giving me 
[3]. For the socket, the work showed a lighter and more durable the energy to keep fighting for my goals. 
alternative when using the composites [4]. For the pylon, the alternatives 
gave better results when analyzed for the composites [5]. 
In terms of the fatigue test, it was performed on the assembly, for display 
For the stress the test was performed on all the elements, for purpose the Al-Al-HDPE and Cf-Cf-HDPE alternatives are shown. The 
demonstration purpose, the foot analysis is presented for the aluminum aluminum assembly presented low cycle fatigue, which means the element References
and the carbon fiber. On figure 3 is presented the aluminum alternative has finite life. The carbon fiber alternative on the other hand reached infinite 
for the foot and a typical stress vs strain curve. The model presented life as presented on the figure 7. Therefore, in terms of durability, the 1) R.C. Hibbeler, “Mechanical Properties of Materials,” in Mechanics of Materials, 9th ed. Boston, USA, Prentice 
Problem localized areas in which the stress overcame the yielding limit of composite alternative excelled on the test. Hall,2014, Ch. 3, pp. 82–117
275MPa, therefore the part failed. 2) K. Kaw, “Introduction to composite Materials” in Mechanics of Composite Materials, 2nd ed. New Wark, FL, 
Taylor & Francis Group, 2006, Ch. 1, pp. 1–46
Figure 7. Fatigue test results performed on Al-Al-HDPE and CF-CF-
3) L. Yousif, K. Resan, R. Fenjan, Temperature Effect on Mechanical Characteristics of a New Design Prosthetic 
This project will focus on analyzing a 3D model of a prosthetic leg Figure 3. Stress results and typical curve of aluminum HDPE Foot, Journal of Mechanical Engineering and Technology, 9(13), 2018, pp.1431–1447 
simulated on several material alternatives such as common and http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=13
composite materials, subjected to static and cyclic loadings to establish 4) Jweeg, Muhsin J., et al. “Optimized Analysis, Design, and Fabrication of Trans-Tibial Prosthetic Sockets.” IOP 
an optimal alternative when designing and manufacturing equipment. Conference Series: Materials Science and Engineering, vol. 433, 30 Nov. 2018, p. 012058, 
This project will contribute to the knowledge of materials behavior in https://doi.org/10.1088/1757-899x/433/1/012058.
5) M. S. A.-D. Tahir and F. M. Kadhim, “Design and Manufacturing of New Low (Weight and Cost) 3D Printed 
relation to its applications and mechanical properties on the medical Pylon Prosthesis for Amputee,” IOP Conference Series: Materials Science and Engineering, vol. 1094, no. 1, 
equipments.   p. 012144, Feb. 2021, doi: https://doi.org/10.1088/1757-899x/1094/1/012144.