Tensile Impact Test for Plastics: ASTM D1822 Method & Applications
Conventional tensile testing measures how a plastic responds to slowly applied loads. But many real-world loading events — impacts during handling, drop events, sudden mechanical shocks — apply loads at very high strain rates where material behavior differs fundamentally from quasi-static response. The tensile impact test for plastics measures the energy absorbed by a plastic specimen during a high-speed tensile fracture event, providing impact resistance data that complements conventional Charpy, Izod, and drop weight impact tests.
What Is the Tensile Impact Test for Plastics?
The tensile impact test applies a high-speed tensile load to a plastic specimen using a pendulum or drop weight impact mechanism — pulling the specimen apart in tension rather than bending it as in Charpy or Izod tests. The energy absorbed during fracture is measured from the pendulum swing angle or equivalent, and the tensile impact strength is calculated as energy absorbed per unit cross-sectional area.
The tensile impact test is standardized by ASTM D1822 — Standard Test Method for Tensile-Impact Energy to Break Plastics and Electrical Insulating Materials.
Why Tensile Impact Testing?
Different impact test geometries load specimens in fundamentally different ways and measure different aspects of impact resistance:
- Charpy and Izod (ASTM E23, ASTM D256): Apply bending loads — primarily measuring notch toughness and sensitivity to stress concentration
- Drop weight / puncture (ASTM D3763): Apply biaxial loading — simulating puncture impact on films and panels
- Tensile impact (ASTM D1822): Applies pure tensile loading — measuring resistance to high-rate pulling apart with no notch stress concentration effect
The tensile impact test is particularly useful for evaluating plastics that perform differently in tension versus bending during impact — for example, materials that are notch-sensitive under bending impact (low Charpy energy) but tougher under unnotched tensile impact. It is also valuable for films, thin sheets, and molded parts where tensile separation is the failure mode in service.
Test Procedure and Specimen Types
Per ASTM D1822, two specimen types are defined:
Type S (Short specimen): A shorter dumbbell specimen for materials with high tensile impact strength. Type L (Long specimen): A longer dumbbell specimen for materials with lower tensile impact strength, which provides more resolution in the measurement.
The specimen is clamped between two fixtures — one fixed to the base and one to the pendulum striking head. The pendulum is released from a defined height and accelerates to a defined velocity at the point of impact. The energy required to fracture the specimen is calculated from the pendulum’s residual swing after fracture.
Results are reported as tensile impact strength in kJ/m² or ft-lbf/in². The failure mode (complete break vs. non-break, fracture location) is also documented.
Materials and Applications
The tensile impact test is applicable to a wide range of plastic materials:
- Films and thin sheets: For packaging films, agricultural films, and protective wraps where tensile impact determines real-world resistance to sharp edge impacts
- Injection-molded plastics: For automotive interior components, electrical enclosures, and consumer product housings subject to dropping or impact
- Thermoset composites: For electrical insulating materials and structural composites where tensile impact data supports material qualification
- Elastomers and rubber: For flexible polymers where tensile impact characterizes dynamic tearing behavior
Industrial Significance
Automotive: Interior plastic components — door panels, instrument panels, pillar trims — must pass tensile impact qualification to demonstrate resistance to occupant impact forces in crash events.
Electronics: Enclosures, connector housings, and mounting hardware must withstand handling drops and shipping impacts without catastrophic fracture.
Packaging: Protective packaging films and trays must maintain containment integrity under tensile impact loads during distribution.
Infinita Lab’s Tensile Impact Testing Services
Infinita Lab provides ASTM D1822 tensile impact testing for plastics and electrical insulating materials through its nationwide accredited laboratory network. Testing covers both Type S and Type L specimen geometries across a range of plastic materials and temperatures. Results are reported with complete fracture energy data, failure mode documentation, and statistical analysis.
Contact Infinita Lab: (888) 878-3090 | www.infinitalab.com
Frequently Asked Questions (FAQs)
How is the Tensile Impact Test conducted? A notched plastic specimen is clamped between two grips, and a pendulum strikes it at a predetermined velocity. The energy required to break the specimen is calculated by measuring the height of the pendulum before and after impact.
What are the main differences between the Charpy and Izod impact tests? The Charpy test strikes the specimen at the center. The notch faces away from the pendulum, and the specimen is placed horizontally. The Izod test, on the other hand, strikes the specimen above the notch. The notch faces the pendulum, and the specimen is placed vertically.
What is the significance of the notch in impact testing? The notch in the sample concentrates the stress at one point and induces fracture. The notch shape and orientation affect the material's behavior under test and can be used to determine the material's toughness in impact tests.
How does the Tensile Impact Test help in product development? The test provides critical information about a material's behavior under sudden impacts, which helps engineers and designers optimize plastic parts for impact resistance and ensure they meet performance standards before being used in real-world applications.
Why is the Tensile Impact Test important? This test determines the suitability of a particular plastic material for specific applications by determining its impact resistance and strength. It also ensures that the material withstands sudden forces without breaking or failing, ensuring product safety and durability.
