Pendulum impact testing looks simple. A hammer swings. A notched bar breaks. The differences live in the setup and the report. Charpy and Izod share the same physics, yet they answer slightly different lab questions.

Most metals programs lean on Charpy. Many plastics programs lean on Izod. Each route defines how you hold the specimen, where the blow lands, and how the number is reported. Cross-comparing results from different routes rarely helps.

This checklist keeps the choice practical. Match your material and geometry to a clear method. Then pick pendulum impact testing systems and supporting plastic testing equipment that can run that route repeatably, with clean reports and simple verification.

Start With Material and the Standard Route

Begin with the material in front of you. Steels and other structural metals usually follow a Charpy route. The method suits simply supported bars and higher energy ranges. Izod on metals exists, but it is less common and usually tied to a specific specification or legacy program.

Plastics and composites often take the Izod route. The clamp is part of the story. Izod treats the bar as a cantilever, which highlights notch sensitivity in many polymers. Some plastics programs do use Charpy. The choice is often set by a customer document or a long running internal method.

Once the route is fixed, lock the reporting path. Metals work often reports absorbed energy in joules. Plastics work may report energy per thickness or per area at the notch. Mixing units across families leads to bad comparisons. Keep one family per program and write it into the method sheet.

Now map hardware to the choice. Confirm that pendulum impact testing systems you are considering include the correct striker noses, spans, and vises for that family. Check that specimen fixtures match the intended sizes. Look for guided workflows that ask for the same inputs every time. A consistent sequence reduces operator drift and eases reviews months later.

If your lab must test both metals and plastics, plan for changeovers. A single frame can support both, but only if fixtures, anvils, and software presets make the switch simple and repeatable. That planning step costs little and saves reruns.

Specimen Orientation, Notch, and Setup Details

Charpy mounts the bar horizontally on two supports. The striker hits the face opposite the notch. The notch then sits on the tension side. This setup reflects bending across a span and is common for metals. Izod clamps the bar vertically at one end. The striker hits near the free end on the notch side. That clamp changes the stress field and often exposes notch effects in plastics.

Small details move numbers. Striker radius shifts the contact zone. Anvil span changes bending moment in Charpy. Vise pressure and jaw condition affect grip in Izod. Record the actual parts used, not just the model name. Replace worn noses and supports before they round over. A tiny change in geometry can reorder a material ranking.

Thickness and notch quality matter. Hold thickness within the stated tolerance. Machine a clean notch with the correct tool. Verify depth and root radius with a gauge or projector. Rough roots or chatter marks can push energy higher and hide brittle behavior. Good prep removes that noise before the first swing.

Climate control is part of the setup, especially for polymers. Condition specimens to the stated temperature and humidity. Test in the same climate. Moisture and temperature shift polymer toughness more than many teams expect. Keep the chain tight from storage to strike.

Pick equipment that supports these controls. Pendulum impact testing systems should help operators set the right span, striker, and height every time. For polymer programs, pair the frame with plastic testing equipment such as conditioning chambers and simple metrology for notch checks. When the setup is steady, the data trends cleanly across heats, grades, and lots.

Reporting, Units, and Machine Verification

Results travel with their units. Metals programs usually report absorbed energy in joules. Plastics routes often normalize by thickness in some methods, or by area at the notch in others. Pick one route and keep it consistent from lot to lot. Mixing unit bases makes comparisons unreliable.

Machine verification ties the numbers to reality. Charpy and Izod frames used for plastics follow the verification practices defined for that family. Metals machines follow their own verification clauses. In both cases, labs confirm striker radius, anvil or span geometry, energy range, and alignment on a schedule. Good records list the parts installed, the checks performed, and the date.

Modern pendulum impact testing systems help operators run these checks the same way every time. They prompt for specimen details, record drop settings, and store calibration logs. Paired plastic testing equipment such as conditioning chambers and notch gauges supports steady climate and clean geometry. With that setup, data from different heats and suppliers remains comparable.

Picking a Method You Can Defend

Start with the governing document. If it names a method and scale, follow it. Define specimen type, notch, striker, span, and the test climate before any hardware discussion. Map fixtures and software presets to that exact route so operators run the same sequence every time.

Plan changeovers only when both metals and plastics must be tested on the same frame. List which fixtures apply to each route and how the switch is performed. Note the order of checks, the acceptable ranges, and who signs off before production work resumes.

Verification and reporting hold the program together. Confirm the schedule for machine checks, the reference blocks to be used, and the records to be kept. Write a concise method sheet that lists the route, units, required checks, and any conditioning steps. Create one example report and treat it as the template for future lots. With that package in place, results read consistently across shifts and audits are straightforward.