When it comes to preventing product failures, selecting the right materials is key. However, all the material knowledge in the world will not help if the product being developed is not fully understood.
No one intentionally designs a product to fail. When developers become aware of any product failure, our instinct is to investigate “What went wrong?” The answer can be a whole lot of things, including the materials the product is made of.
Material selection has become increasingly complicated and critical as consumers have become more demanding. Consider the long list of product requirements and design considerations as well as the extensive collection of available materials. Despite all that complexity, it’s essential to get material selection right. Faulty material selection can have grave repercussions, including property damage, injury and even death.
In the race to innovate and get new products to market quickly, material selection can often be given inadequate consideration — or worse, treated as an afterthought. There is no greater nightmare to a material expert than to have their first interaction with a new product to be the “signoff” stage in its fully designed state.
Engaging materials experts early in the development process is critical. It’s the only way they’ll be able to assist the team in making sound material choices for the product. That said, engagement alone is not enough.
As a Materials Science Engineer with over 20 years of product development and testing experience, I have seen three critical areas in which a lack of knowledge or understanding can lead to failure: product requirements, system influences and material behavior. Here’s how each of these areas can make or break material selection.
The formation of detailed requirements is critical for successful product design and material selection. A product may fail if these requirements are incomplete or not representative of how a consumer will use it in the real world.
With that in mind, product requirements must take into consideration intended use, potential abuse and atypical use situations. These requirements may address environmental exposure, operating temperatures, mechanical loads, electrical requirements and regulatory compliance, to name just a few.
Consumer research and field testing should function to mitigate the risk of product failure. For example, when designing a water pump for residential pools, a robust chemical resistance requirement list should be included. These requirements will strongly impact the compatible material candidates for the pump and increase the probability of product success.
In order to make this requirement consumer-relevant, it should be based on the typical chlorine, chloramine and salt content of the pools – both nominally and after shock treatment (if applicable). The most accurate way to obtain this information would be to test pool water samples of a representative population.
A thorough understanding of system influences in material selection is crucial to product success. Often, material selection is performed on a component-by-component basis without a holistic understanding of how the complete product is assembled and operates. Ignoring the impact of these complex system influences on the component can lead to product failures.
Consider a designer that selects material for a plastic housing used in an assembly on a heavy-duty truck located in the engine compartment. The designer knows that the chemical compatibility of the plastic housing material is an important part of the selection process. The housing will be exposed not only to under-hood chemicals such as oil, gas and antifreeze, but also to road salts. As such, the appropriate material must be selected accordingly.
During product testing, the assembly begins to fail prematurely as fasteners fall out of the housing. Upon investigation, the designer discovers that failure was the result of chemical attack on the housing material, even though the designer diligently reviewed the chemical exposures in the application and selected a resistant material. What happened?
The designer failed to consider system influences such as secondary chemical reactions — in this case, the formation of corrosion byproducts on the fasteners. If the chemical resistance of plastic would have been considered in conjunction with the corrosion byproducts, the designer would have understood that chemical attack would have been likely.
As mentioned previously, a clear picture of requirements is critical for successful product design and material selection. However, those requirements are hollow if one fails to understand the true functional behavior of materials. Proper material selection takes into account time and temperature dependencies, especially for time- and temperature-sensitive materials such as plastics.
Consider a plastic material that was selected based on its mechanical behavior at room temperature. In the product application, the material is subjected to a continuous operating temperature nearly four times higher than room temperature. The plastic’s stiffness is reduced by over half in that environment, resulting in performance failure due to permanent deformation of the part.
Diligent material selection must go beyond reviewing the room temperature and short-term mechanical property data, which is typically provided by material suppliers via technical datasheets. The material selection process needs to include investigation of both short- and long-term effects of moisture, as well as chemical and elevated-temperature exposures that may be experienced in the application or use.
MATERIAL SELECTION IS A SCIENCE
Attentively pursuing successful products goes beyond consumer satisfaction. Proper material selection isn’t just essential for consumer safety, it can also make or break your brand’s reputation.
Engaging material experts early in the development process is essential to their impact on the selection process and product success. It is just as important to provide them with a complete list of accurate product requirements, as well as knowledge of the entire product system.
Not every product development team is fortunate enough to include a material expert. In those cases, the team will need to take the time to understand the behavior of material candidates as it relates to the product requirements.