02 Mar The Challenge of ‘Lightweighting’ High-Performance Parts with Engineered Plastics
Traditionally manufactured in heavy steel or other high-strength metal alloys, high-performance parts are expected to functionally do more for longer, often in more extreme environments than standard component counterparts. However, metal parts are heavy, cumbersome, and costly to transport. In certain applications, such as automotive components, heavy parts impact fuel efficiency goals, and can put excess stress on other structures. To address these problems and more, engineers and designers are turning to engineered plastics and the growing ‘lightweighting’ trend.
Lightweighting: the process of redesigning products or components to reduce overall product weight, often converting designs from metal to engineered plastics.
Unfortunately, the demands on high-performance parts often don’t align with those of commodity plastics, and metal-to-plastic part conversion will often have special requirements to be done successfully. Even seemingly simple parts may appear easy to convert to plastics in theory, but in practice, however, that’s an entirely different story.
Why You Shouldn’t Rely on Just Engineered Plastics for Lightweight Components
Engineered plastics are highly versatile materials that can be customized to meet specific requirements, making them ideal when durability, performance, and weight reduction are critical. However, for optimal results, ‘lightweighting’ should begin well before resin selection with a thorough review of the part’s geometry, real-world operating environment, and manufacturing limitations.
The Geometry Does the Heavy Lifting
Too often, ‘lightweighting’ projects rely on two key data points: The material’s strength-to-weight ratio and tensile strength. While these two numbers are critical considerations, they can be misleading. Engineered plastics in general may have a better strength-to-weight ratio than structural steels, but their lower material density requires greater mass to achieve the same performance specifications as their predecessor metal materials. Alternatively, high-performance resins can provide the necessary strength without excessive wall thickness, but these exotic engineered plastics come with a higher price tag.
Instead of leaning on the material for strength, engineering leverages the component’s geometry. Applying specific design features where applicable can reduce material requirements and improve component performance. Redesigning areas of excessive wall thickness with integrated ribbing or hexagonal grid supports, for example, can provide the required durability and strength with a fraction of the material requirements.
The key to lightweight, high-performance design is having the material work with the geometry, not against it.
Reinforcements Matter
The greatest benefit to engineered plastics is the ability to customize blends and fillers for specific applications and price points. Including fillers drastically boosts the material’s strength and durability, enabling targeted improvements in specific material properties. Enforcing resins with glass or carbon fiber fillers drastically improves the material’s performance, enabling significant weight reductions for high-performance parts. Leveraging resin additives and fillers is a cost-effective approach to ‘lightweighting’, allowing manufacturers to use more economical materials without compromising product quality.
PPS (Polyphenylene Sulfide): A Case-in-Point
PPS (Polyphenylene Sulfide) is well known for its superior dimensional stability and chemical resistance. However, as a PAEK-type thermoplastic, PPS can stress budgets. Glass-filled polyester resin, which is more economical in most cases, can also provide excellent stability and chemical resistance.
Reinforced engineered plastics allow designs to leverage geometry to carry load efficiently, rather than brute-forcing thickness.
Engineered Plastics Reality Check
While material science has expanded the versatility of engineered plastics, they are not without their limitations. When exposed to high levels of sustained stress or tension, the bonds weaken, leading to deformation known as creep. High-performance component designs should take creep-inducing stresses into consideration and adjust accordingly.
Lightweighting often fails when designers chase tensile strength but ignore creep, fatigue, or thermal distortion.
Thermal, chemical, and moisture exposure can also contribute to part failure and must be accounted for by selecting the appropriate engineered plastics and filler materials. A common error here is assuming that the plastic’s heat deflection temperature (HDT) equates to its continuous service temperature. Prolonged exposure to the material’s max HDT will result in premature thermal distortion.
Tooling quality is another important aspect of high-performance parts that often goes unappreciated. Thin walls and fine details can disrupt resin flow, altering fiber orientation in unpredictable ways and affecting directional stiffness.
Selecting Engineered Plastics for High-Performance Lightweight Parts
Matching the resin to the operating conditions is vital for long-term performance. Everything from mechanical loads and operating environments to regulatory requirements and manufacturing methods will dictate which engineered plastic is best suited for each part. Medical devices, for example, are manufactured from medical-grade PEEK, while fasteners for a warehouse cart may leverage PC or nylons instead.
Engineered Plastics That Enable ‘Lightweighting’
- PEEK/PEKK
- Exceptional strength-to-weight, chemical resistance, high temp
- Expensive, but unmatched for demanding applications
- PPS
- Excellent dimensional stability and chemical resistance
- Ideal for thin-wall, tight-tolerance parts
- Nylons (PA)
- Great balance of cost, toughness, and strength
- Moisture sensitivity must be designed around
- PC
- Impact resistance, clarity, and moderate weight
- PBT/PET
- Stiffness, chemical resistance, and electrical performance
- ABS/PC-ABS Blends
- Toughness with easier processing
The Engineered Plastics Experts
At Quantum Plastics, we leverage extensive experience in plastic injection molding, using a wide range of commodity and high-performance engineered plastics to benefit our customers. From improving manufacturability to expert resin selection advice, our collaboration model ensures cost-effective solutions to ‘lightweighting’ high-performance parts.
Contact us today to learn more.