Notch Sensitivity of Plastics

Some grades of engineering plastics have exceptional impact resistance and very good load carrying capacity. However the performance of materials can be greatly compromised by incorrect design and machining parameters that result in sharp corners on finished parts.

A sharp corner on a machined part can be a “weak” point where cracking will most likely occur. Sharp corners not only reduce the impact resistance of a part, but also allow for stress concentration to occur at that point. This will result in premature failure on load carrying plastic parts.

Following correct design and machining guidelines is imperative, and even though minimizing sharp corners may make the machining operation more difficult, it is crucial to long term application success.

Edges of sheet materials used in glazing applications (e.g. PC — Safeguard Polycarbonate) must also be free of sharp notches or cracks.

Parts machined with sharp corners could eventually stress crack. Rounded corners are correct parameters for machining.

Dotmar offer in-house technical support and thermoplastic applications advice. For correct design and machining guidelines contact our technical experts.