Creep Behavior Under Varying Conditions
Posted: Sat Dec 28, 2024 6:52 am
Design Strategies to Minimize Creep
Measures for reducing Creep in the presented plastic materials begin with material upgrading, as exemplified in reinforced plastics. Adding fibers like glass or carbon to the polymer changes its mechanical properties. These elements improve the material's ability to withstand stress. These reinforcements make it difficult for such polymeric chains to move so that they can slide past each other in the long run. For instance, fiberglass-reinforced nylon is used mainly in the automotive industries and some industrial products. These parts have high degrees of mechanical loading.
The other technical management is reducing stress at a certain point in a component through a load-sharing approach. Stress raisers—territories with a high density of an applied force—exacerbate Creep in plastics. Engineers overcome this by avoiding sharp corners and making gradual transitions between geometries. Engineers also incorporate design features like ribs or flanges onto the load paths to increase the loaded surface area. For instance, in plastic piping systems, engineers provide the supports in such a manner that there will be minimal sagging between them. Finally, the choice of polymers with high performance is necessary for the reduction of Creep. High glass transition materials such as PEEK, polycarbonate, and PTFE have excellent resistance to deformation. These new-generation polymers usually apply under severe conditions, such as in aerospace or medical applications. These applications do not need long-term reliability compromised under pressure and heat.
Plastics do not always act the same way. The table below considers different environments in terms of creep rates.
Material Creep in Cold Creep in Heat Creep under UV Exposure Creep under Constant Load Moisture seeps into the air
Polyethylene (PE) Weak High Moderate High Moderate
PVC Weak moderate High Moderate Weak
Polypropylene (PP) Moderate High Weak High Moderate
Polycarbonate (PC) Weak Weak last database Moderate Moderate Weak
Nylon (PA) Moderate High Moderate High High
ABS Weak Moderate Moderate Moderate Weak
PEEK Very weak Very weak Weak Very weak Weak
Polystyrene (PS) Moderate High High Moderate Weak
Comparison of creep behavior of common plastic materials
The graph below shows the creep rate of several plastics under a constant stress of 2 MPa at 25°C. PTFE has the lowest creep rate value, indicating that it can hardly deform over time. PS has the highest creep rate value, indicating its strong tendency to deform over time.
The strength of other plastics such as HDPE, LDPE, PP, PVC, nylon and PC varies depending on their ability to resist creep and depending on the plastic. HDPE and nylon are more resistant to creep than LDPE and PS.
Conclusion
An overview of the causes of creep, methods to minimize its magnitude, and its effects on structures helps engineers select plastic materials. They can understand the use of plastics in industrial applications for the manufacture of polymer-based components. By properly reinforcing plastics, distributing loads well, and correctly applying high-performance polymers, engineers can significantly reduce the effect of creep in their products.
Measures for reducing Creep in the presented plastic materials begin with material upgrading, as exemplified in reinforced plastics. Adding fibers like glass or carbon to the polymer changes its mechanical properties. These elements improve the material's ability to withstand stress. These reinforcements make it difficult for such polymeric chains to move so that they can slide past each other in the long run. For instance, fiberglass-reinforced nylon is used mainly in the automotive industries and some industrial products. These parts have high degrees of mechanical loading.
The other technical management is reducing stress at a certain point in a component through a load-sharing approach. Stress raisers—territories with a high density of an applied force—exacerbate Creep in plastics. Engineers overcome this by avoiding sharp corners and making gradual transitions between geometries. Engineers also incorporate design features like ribs or flanges onto the load paths to increase the loaded surface area. For instance, in plastic piping systems, engineers provide the supports in such a manner that there will be minimal sagging between them. Finally, the choice of polymers with high performance is necessary for the reduction of Creep. High glass transition materials such as PEEK, polycarbonate, and PTFE have excellent resistance to deformation. These new-generation polymers usually apply under severe conditions, such as in aerospace or medical applications. These applications do not need long-term reliability compromised under pressure and heat.
Plastics do not always act the same way. The table below considers different environments in terms of creep rates.
Material Creep in Cold Creep in Heat Creep under UV Exposure Creep under Constant Load Moisture seeps into the air
Polyethylene (PE) Weak High Moderate High Moderate
PVC Weak moderate High Moderate Weak
Polypropylene (PP) Moderate High Weak High Moderate
Polycarbonate (PC) Weak Weak last database Moderate Moderate Weak
Nylon (PA) Moderate High Moderate High High
ABS Weak Moderate Moderate Moderate Weak
PEEK Very weak Very weak Weak Very weak Weak
Polystyrene (PS) Moderate High High Moderate Weak
Comparison of creep behavior of common plastic materials
The graph below shows the creep rate of several plastics under a constant stress of 2 MPa at 25°C. PTFE has the lowest creep rate value, indicating that it can hardly deform over time. PS has the highest creep rate value, indicating its strong tendency to deform over time.
The strength of other plastics such as HDPE, LDPE, PP, PVC, nylon and PC varies depending on their ability to resist creep and depending on the plastic. HDPE and nylon are more resistant to creep than LDPE and PS.
Conclusion
An overview of the causes of creep, methods to minimize its magnitude, and its effects on structures helps engineers select plastic materials. They can understand the use of plastics in industrial applications for the manufacture of polymer-based components. By properly reinforcing plastics, distributing loads well, and correctly applying high-performance polymers, engineers can significantly reduce the effect of creep in their products.