Impact strength: Izod vs Charpy, notched vs unnotched

Impact strength shows how well a material survives a sudden blow. Learn the difference between Izod and Charpy, and notched and unnotched.

阅读约 3 分钟 · 更新于 October 11, 2026 · 数据实时来自我们的材料数据库。

What it means in practice

Impact strength is the energy a material absorbs when it is struck hard and fast. It separates materials that shrug off a knock from those that shatter. Strength and stiffness alone cannot tell you this.

Key takeaways

Impact strength is the energy a material absorbs when struck hard and fast.
Charpy and Izod load the bar differently; their numbers cannot be converted.
Only compare matching tests: notched with notched, same units.
Use the numbers to rank materials, then test your own part.

Filaments (notched Charpy)8 kJ/m²典型值 · 范围 1.6–115 · 98 种材料

Resins (notched Charpy)1.54 kJ/m²典型值 · 范围 0.6–44 · 20 种材料

Pellets (notched Charpy)6.75 kJ/m²典型值 · 范围 4–44 · 20 种材料

It matters for:

Handheld devices and housings that may be dropped.
Protective covers, guards and bumpers.
Tool holders, clips and latches that get knocked about.
Any part used in the cold, where plastics turn more brittle.

How it’s measured

A heavy pendulum swings down and breaks a small bar. The energy it loses in doing so is the energy the bar absorbed.

Izod vs Charpy

Charpy

(ISO 179): the bar lies flat across two supports and is hit in the middle, from the side opposite the notch.

Izod

(ISO 180, ASTM D256): the bar is clamped upright at one end, like a post, and hit near the top on the notched face.

The two set-ups load the bar differently, so their numbers cannot be converted into each other.

Notched vs unnotched

Notched: a small V-notch is cut into the bar first. It acts like a crack or sharp internal corner. It tells you how the material copes once a flaw exists.
Unnotched: a plain bar. Values are much higher, and many tough plastics simply do not break (often shown as “NB”).

Units

ISO results are in kJ/m²: energy divided by the cross-section behind the notch.
ASTM Izod results are in J/m: energy divided by the bar’s width.

Watch out

Different units mean different maths. Never compare a kJ/m² value with a J/m value directly.

How to read and compare it

Match the test exactly: Charpy with Charpy, notched with notched, same units. Our hub stores Charpy values separately for notched and unnotched bars for this reason.
Notch quality. A machined notch and a notch printed into the bar give different results. Good sheets say which.
Orientation. Printed bars hit across their layers can split along a layer line. See print orientation: XY vs Z.
Temperature. Most values are at room temperature. Many plastics lose much of their toughness below freezing.
Moisture. Nylons are noticeably tougher when conditioned than when bone dry.
Not a drop test. Real parts have corners, holes and thin walls. Use the number to rank materials, then test your own part.

Range in our catalog

Notched Charpy

All materials: 0.6–115 kJ/m² (中位数 6.7 kJ/m²，共 144 种材料)
Filaments: 1.6–115 kJ/m² (中位数 8 kJ/m²，共 98 种材料)
Resins: 0.6–44 kJ/m² (中位数 1.54 kJ/m²，共 20 种材料)
Engineering materials: 0.9–53 kJ/m² (中位数 7.4 kJ/m²，共 81 种材料)

Notched Charpy impact strength of common filaments (kJ/m²)

PLA 172.4–38.9
PETG 92.6–11.6
PC 53–21.28
ABS 106.1–38.6
PA12 410.2–16
PEEK 77–30
PEI 44–11

色条 = 最低至最高，圆点 = 中位数。共 56 种材料，数据实时来自我们的数据库。

Unnotched Charpy

All materials: 11–224.8 kJ/m² (中位数 38 kJ/m²，共 69 种材料)
Filaments: 11–224.8 kJ/m² (中位数 35 kJ/m²，共 57 种材料)

Highest and lowest in our catalog

Toughest, notched Charpy

材料	聚合物	简支梁冲击强度（缺口）
Ultrafuse TPU 64D	TPU	115 kJ/m²
Kexcelled THE K8 TPU 64D	TPU	62–66 kJ/m²
Fiberlogy PC ABS	PC/ABS	53 kJ/m²
Formfutura ReForm rPP GF30 UV Pellets	PP	44 kJ/m²
Formlabs PU Rigid 650 Resin	Polyurethane	44 kJ/m²

Most brittle, notched Charpy

材料	聚合物	简支梁冲击强度（缺口）
Ultracur3D RG 1100	Photopolymer	0.6 kJ/m²
Ultracur3D RG 35	Photopolymer	0.6 kJ/m²
Ultracur3D EPD 2006	Photopolymer	0.7 kJ/m²
Ultracur3D RG 9400 B FR	Photopolymer	0.9 kJ/m²
Ultracur3D RG 3280	Photopolymer	0.98 kJ/m²

Toughest, unnotched Charpy

材料	聚合物	简支梁冲击强度（无缺口）
Ultrafuse PPSU	PPSU	224.8 kJ/m²
Ultrasint PA11 Black	PA11	193 kJ/m²
LEHVOSS LUVOCOM 3F PEEK 9581	PEEK	185 kJ/m²
Ultrasint PA11	PA11	184 kJ/m²
Formlabs Tough 1000 Resin	Photopolymer	180 kJ/m²

Elongation at break — a rough guide to ductility.
Tensile strength — toughness needs strength as well as stretch.
Young’s modulus — very stiff materials are often less tough.
Glass transition temperature — explains why some plastics turn brittle in the cold.

Find tough, impact-resistant materials