What is the difference between Charpy and Izod impact tests?

Charpy uses a horizontally supported, simply supported notched beam struck from behind — providing absolute energy absorption in joules. Izod uses a vertical, cantilevered notched specimen struck from the front — results reported per unit notch width. Charpy is standard for metals; Izod is dominant for plastics. Both provide toughness information but are not directly comparable.

What is the ductile-to-brittle transition temperature (DBTT)?

DBTT is the temperature below which a material transitions from ductile (high-energy, plastic fracture) to brittle (low-energy, cleavage fracture) failure under impact. For structural steels, this transition typically occurs between -20°C and +20°C depending on chemistry and heat treatment — and must be known for safe design of cold-temperature structures.

Why is the notch important in impact testing?

The notch creates a stress concentration that simulates real surface defects, scratches, and geometric discontinuities that components encounter in service. Notched impact tests reveal notch sensitivity — how much a stress concentration reduces toughness — which is critical information for part design and material selection.

Which impact test is standard for comparing plastic grades?

Notched Izod impact testing per ASTM D256 is the dominant standard test for comparing and specifying plastic material grades. It is performed at standard laboratory temperature (23°C) and often also at -30°C or -40°C to evaluate low-temperature impact performance.

What ASTM standards govern impact testing for metals vs. plastics?

For metals: ASTM E23 (Charpy and Izod methods). For plastics: ASTM D256 (Izod) and ASTM D6110 (Charpy). For composites: ASTM D7136 (drop weight impact). For films and sheets: ASTM D5420 and D5628 (falling weight/dart methods).

Dr. Bhargav Raval

Dr. Bhargav Raval is a Materials Scientist and Client Engagement Engineer with expertise in nanomaterials, polymers, and advanced material characterization. He holds a Ph.D. in Nanosciences from the Central University of Gujarat, where his research focused on graphene-based materials for flexible electronics. Professionally, he has led R&D in sensor technologies and coatings, including polymer-functionalized piezoelectric sensors for breath-based cancer diagnostics.
In his current role, Dr. Raval works closely with clients to understand technical requirements, design testing strategies, and deliver tailored solutions in materials selection, failure analysis, and performance evaluation. He effectively bridges scientific depth with practical outcomes, ensuring client-focused project execution. With peer-reviewed publications in high-impact journals and a proven record of applying materials science to real-world challenges, Dr. Raval continues to drive innovation at the intersection of research, engineering, and client engagement.

Email: bhargav@infinitalab.com

Website: https://scholar.google.com/citations?user=rlPTYWgAAAAJ&hl=en&oi=ao