The Ethics of Composite Design in Mechanical Engineering

In the 21st century, mechanical engineers work in an increasingly difficult environment. The requirements for systems are changing every day as employers and consumers desire faster, lighter, and stronger designs. To accommodate more extreme requirements, we have developed new tools and materials to meet our goals. Composite materials, which combine fibers and resin to provide a lightweight yet strong material, are a perfect example of this drive to meet higher performance goals [1]. Although composite research is advancing every year, the truth about composites is that their features are relatively unknown, and they can have a drastic impact on our planet.

Our society has been concerned with recycling for decades now; however, consumer goods are the primary target for recycling campaigns. This means that defense, aerospace, automotive, and many other industries can often neglect sustainability in favor of high performance since there is little public pushback. The ethical challenge for a mechanical engineer is choosing when to favor composites over their “green” metallic competitors. As a mechanical engineer who strives for a better future, I believe that it is unethical to use harmful materials like composites when there is a sustainable alternative that meets the design requirements.

Composites are incapable of being efficiently recycled since the epoxy used is a thermoset and incapable of being separated from the fiber matrix following cure [2]. This means that composite materials will likely end up in a landfill; however, this is not the only problem, as there are additional negative implications to consider when using composites. First, the service life of composites is not well known. This means they may not last as long as their predecessors (metal, wood, etc.) which could cause a mass buildup of waste when an influx of composite cars and planes fails in ten years instead of twenty. Composites also contain harmful components that may seep into the ground as they decay [2]. Additionally, there are systemic implications of composite usage that further illustrate the problems composites pose.

As we as engineers seek to build lightweight solutions, our composite designs will inevitably overwhelm landfills and junkyards when they reach the end of their service life. With growing composite implementation, this issue becomes even more prevalent. For example, composite usage has recently expanded into larger scale systems like the new Boeing 787, which is made almost entirely of composite material in order to increase passenger capacity and increase fuel efficiency. However, the 787 will eventually need to be retired which will require the disposal of nearly 35 tons of carbon fiber reinforced polymers per plane [3]. Since composite components cannot be reused or recycled, the 787 will likely remain in a junkyard for the remainder of its days. This is the case for thousands of other products ranging from cars to boats to planes. As someone who is constantly surrounded by composites, I have experienced their growing popularity and witnessed how much goes to waste after prototyping, testing, and a full service life. On my university design team, we are constantly throwing away bags of cured composites that were simply prototypes. This represents a significant potential danger to our environment as we employ more composites.

Although composites cannot efficiently be recycled, they do have their merits in certain applications. For example, the auto industry is employing composites more and more since they are fifty times stronger than steel and thirty percent lighter than aluminum [4]. Many would argue that since composite designs save weight, they should be employed on a massive scale in the automotive industry to pursue fuel efficiency. After all, every ten percent decrease in weight yields about a six to eight percent increase in fuel efficiency for automobiles [4]. While this is true, the answer is not always so black and white.

The ethical responsibilities of an engineer include properly weighing all of the options in a design by performing trade-off studies and environmental cost-benefit analyses. Many use the aforementioned argument of fuel efficiency to defend composite design as ethical; however, an increase in fuel efficiency does not always render a more “green” design. Especially with the advancements of electric vehicles combined with household solar power, fuel efficiency is merely one means of reducing our carbon footprint. The ethical dilemma is still in play for automotive designers, especially once major components have already switched to composite materials. This means that further weight savings will be fairly minimal. The question then becomes: this is ethical to design a small bracket made of composites to save a miniscule amount of fuel when each composite component makes the car more difficult to recycle? I believe that a balance exists; the solution to this ethical challenge should rely heavily on trade studies that examine the net impact of fuel savings or component cost versus the sustainability of that component.

While companies play a significant role in the determination of materials for certain projects, it is ultimately the design engineer’s choice to use a composite component or some other “green” component. As engineers, we are taught to emphasize cost and safety. The fact that we choose what materials our designs will be built from comes with an ethical implication as well. As Yrjö Sotamaa states in the Ethics and Global Responsibility section of the Cumulus Nantes Convention papers, “Serving humanity, or one’s own country, is not possible by limiting one’s activities within a nation-state and its interests” [5]. This applies even more to engineers working within a company. As engineers, it is our responsibility to look beyond profits and company performance to make sure that the materials we use do not harm the environment in years to come. This is reflected in the ethics code for the American Society of Mechanical Engineers (ASME) which requires us as engineers to use our knowledge and abilities for the “enhancement of human welfare,” not simply the enhancement of one’s own profit or that of a company [6]. Given this requirement, it is unethical to use composite materials when components of a green material can satisfy the design requirements.

Additionally, it is unethical as engineers to use composites in products that do not require their high performance. Whether it is at my work where we design fighter jets for the US military, or on my campus design team where we compete to build remote control planes, I consistently see thick composite materials being used to carry compressive loads, which is an absolute waste. One of the most important things that we teach new members on the USC Aero Design Team is the tensile versus compressive capabilities of composites. Often times there is a much lighter and more environmentally friendly alternative for compressive loading, like balsa wood, which we often use for the compressive members of our remote control airplanes. It is immensely important for engineers to recognize that composites are not always the answer just because they are “light.” Many engineers consider their designs to be advanced if they use composites; however, it tends to be the exact opposite. Often we use composite materials as an easy way out since we will not have to design a metallic or wooden shear web and spend large amounts of time modelling and testing our parts. This is highly unethical since it our duty as engineers to ensure the best design possible throughout the entire life cycle of the part.

As engineers, it is unethical to suggest composites in designs for things that offer no societal or financial benefit. While there may be prize money for winning a sailing race, it has a much different impact than large recurring fuel savings which reduce carbon emissions and have the potential to make travel cheaper for the average consumer. Without performing some sort of tradeoff for cost, emissions, or fuel efficiency in order to demonstrate their benefit, composites should not be suggested as an alternative to current materials, especially if the product works without them.

This ethical issue is incredibly relevant today. As the next generation of engineers, my classmates and I were the first group to go through a university program that covers composites in depth. This, coupled with advancements in technology, places us in a position to use more composite material than any engineers before us. As a society, we have reached a tipping point where composite usage is likely to increase exponentially in the next few years, which will have an extreme impact on our environment. As the use of composites rapidly grows, the importance of the ethical implications increases as well.

In the ASME Code of Ethics, fundamental canon number eight states, “Engineers shall consider environmental impact and sustainable development in the performance of their professional duties” [6]. This clause wrongfully separates sustainability from our professional duties. In fact, sustainability is one of our professional duties as engineers, not just something to consider while we do our work. The code fails to support one of its fundamental principles which charges us to use our skills for the “enhancement of human welfare” [6]. Human welfare cannot be enhanced if we are not stewards of the world we call home. Thus, it is our duty to design with as many “green” materials as we can.

The final reason that I believe this to be a responsibility of engineers is that we are the only group equipped with the knowledge and resources to oversee the complete design picture. As engineers, the final product we deliver is a solution to a question. If we require all of our skills and knowledge and experience to provide these solutions, how is anyone else better equipped to solve the same problem with a sustainable solution? It is unethical to consciously or subconsciously push our sustainability responsibilities onto other professions or groups by saying things like, “I’m sure someone will figure out a better way someday.” This mentality leaves little room for advancement and has the potential to cripple our society if engineers do not perform the full range of their duties.

As engineers face this ethical dilemma, we should drive our employers to teach us the fundamentals of composite design and how it relates to sustainability. From a company perspective, much can be done to address this ethical issue. First off, we can ask our companies for information sessions on composites and their benefit over metallic or other “green” designs. Companies can teach employees how to use the least amount of composite material while still meeting the design goal. This will ensure that we are not unnecessarily wasting non-recyclable resources in design. This is also beneficial to the employer since composites can be very expensive.

At the university level, we as engineering alumni need to push for more courses that instruct students on “green” materials. Schools can teach engineers how to run trade studies determining the net benefits versus impacts and cost of implementing certain materials, including composites, in their designs. As a senior in the mechanical engineering degree field, I have only taken one class which addressed sustainability and recycling; this is unacceptable. Outfitting engineers with the proper resources and knowledge of recyclable materials could drastically change the face of design over the next few years. This education would make the ethical decision much simpler since engineers would be better equipped to use alternative, “green” materials.

Finally, as a society of mechanical engineers, we should regulate the use of composites, or we should update our code of ethics to reflect the fact that negligent composite design is wrong. While the ASME currently has a sustainability statement in its code of ethics, the statement does not fully require the creation of a net societal and global benefit. This clause takes a rather passive stance on the issue by simply requiring engineers to “consider” sustainable development. Our code of ethics should be updated to give a charge to engineers. Something more fitting would be: “Engineers shall always consider sustainable materials in their designs and employ environmentally harmful solutions only when no other avenues exist to meet the design requirements.”

While composites may be the future of mechanical engineering materials, careful consideration must be given to account for the environmental implications of composites. This is important at the designer level, since the whole product life cycle is then considered. Given this, it is unethical to employ a composite material over its “green” counterpart without the careful consideration and weighing of cost, efficiency, and sustainability. As engineers, we are one of very few professions that can make globally impactful decisions via the selection of materials. Thus, we must hold each other accountable with our code of ethics, and we must push our companies and universities to give us the resources to develop designs that are centered on sustainability.

By Jonathan Coon, Viterbi School of Engineering, University of Southern California

Works Cited

[1] “What Are Composites?” – American Composites Manufacturers Association (ACMA),, 2017. [Online]. Available: [Accessed: 19- Sep- 2017].

[2] M. Ribeiro, A. Fiúza, A. Ferreira, M. Dinis, A. Meira Castro, J. Meixedo, and M. Alvim, “Recycling Approach towards Sustainability Advance of Composite Materials’ Industry,” Recycling, vol. 1, no. 1, pp. 178–193, Jun. 2016.

[3] R. Waugh, “Not just a load of hot air: Dream becomes reality as Boeing’s new carbon-fibre 787 Dreamliner heralds a new age of air travel”, Mail Online, 2017. [Online]. Available: [Accessed: 19- Sep- 2017].

[4] “Today’s cars are lighter and more fuel efficient thanks to this material”,, 2017. [Online]. Available: [Accessed: 19- Sep- 2017].

[5] Y. Sotamaa, Nantes. Helsinki, Finland: University of Art and Design Helsinki, 2006, p. 5.

[6] American Society of Mechanical Engineers, “Code of Ethics of Engineers (2012) | Ethics Codes Collection”,, 2017. [Online]. Available: [Accessed: 19- Sep- 2017].