What Is Impact Resistance?

Introduction

Many products are designed to survive sudden force. A phone case may protect a device when it falls. A car bumper must absorb energy during impact. A toolbox should resist cracking when dropped. Industrial equipment, protective housings, packaging, wheels, and structural parts may all face sudden shocks during use.

One material property behind this performance is impact resistance.

Impact resistance describes how well a material, component, or finished product tolerates rapid loading without unacceptable cracking, fracture, chipping, deformation, or loss of function. The acceptable outcome depends on the application: a bumper may deform to absorb energy, while a wheel must still rotate and support its load. It is different from hardness, abrasion resistance, or simple load capacity because the force is applied quickly rather than gradually.

This article explains what is impact resistance, how it is tested, what impact strength means, how Izod and Charpy tests work, which materials generally perform well under impact, and why impact resistance matters in industrial products, wheels, and caster systems.

What Is Impact Resistance?

Impact resistance is the ability of a material or product to absorb energy during rapid loading and avoid an unacceptable failure mode under stated conditions.

The word “sudden” is important.

A material supporting a steady load experiences a different type of stress from a material hit by a fast-moving object or dropped onto a hard floor. Impact energy and peak force are related but not identical. The force history depends on mass, speed, contact time, stiffness, damping, geometry, and how the bodies deform. A short, stiff collision can create a high peak reaction even when the moving mass is modest.

Impact may come from:

• dropping
• collision
• sudden contact
• a moving object hitting an obstacle
• equipment crossing a floor joint
• tools striking a surface
• material being loaded or unloaded roughly

A material with good impact resistance can absorb some of this energy through elastic deformation, plastic deformation, or internal material behavior instead of immediately cracking.

Impact resistance does not mean a material is impossible to damage. Every material has limits. The goal is to understand how it behaves when force is applied quickly.

Impact Resistance Meaning and Impact Strength

The impact resistance meaning becomes easier to understand with simple examples.

Imagine dropping three objects onto a hard floor.

A glass cup may shatter because it is hard but brittle. A flexible plastic container may deform and survive. A rubber part may compress, absorb part of the energy, and return close to its original shape.

The difference is not simply hardness. It is how each material handles sudden energy.

The term impact strength is closely related to impact resistance, but they are not always used in exactly the same way.

The practical distinction is:

• Impact resistance:the broader ability of a material, part, or product to survive a defined impact event.
• Impact strength:a numerical result from a specified test method, specimen, notch, conditioning, temperature, and reporting unit.
• Product impact performance:the response of the finished geometry, joints, fasteners, interfaces, and surrounding structure under a representative event.

A test value is meaningful only with its test basis. A material data-sheet number is not automatically a safe design load or a prediction of finished-product life.

Impact resistance is often used as a broader description. Impact strength usually refers to a numerical result obtained under controlled testing conditions.

For example, a manufacturer may describe a polymer as having good impact resistance, while the technical data sheet provides an Izod or Charpy impact strength value.

For buyers, both are useful. The first describes intended performance. The second gives a way to compare materials under specific test conditions.

Why Is Impact Resistance Important?

Impact resistance matters because sudden failure can be more serious than gradual wear.

A surface wearing slowly may provide visible warning. A brittle part may fail immediately after one hard impact.

Good impact resistance can help:

• reduce sudden cracking
• protect users and equipment
• extend component life
• reduce repair frequency
• lower replacement costs
• improve reliability during transport
• reduce damage from handling
• support safer operation

This is especially important for components used in transportation, construction, packaging, material handling, automotive systems, tools, protective equipment, and industrial machinery.

The property becomes even more important when a part operates in an environment where impact cannot be completely controlled.

A warehouse cart may hit floor joints. A machine cover may be struck by tools. Outdoor equipment may face stones, uneven surfaces, or rough handling. A wheel may collide with a threshold while carrying load.

The material does not only need to survive normal operation. It needs enough resistance to unexpected events.

How Is Impact Resistance Tested? Izod vs Charpy

An impact resistance test applies a defined impact to a specimen or product and records an outcome such as absorbed energy, force-time response, damage, crack growth, rebound, or pass/fail performance. Pendulum tests are common, but drop-weight, falling-dart, component and full-product tests may be more representative for other failure modes.

Two common test methods are the Izod impact test and the Charpy impact test.

In conventional non-instrumented pendulum methods, absorbed energy is inferred from the pendulum energy before and after the strike. Instrumented systems can also record force and displacement. Machine losses, specimen motion and failure type are controlled or reported by the applicable method, which is why results should not be compared without the full test designation.

A notch is often machined into the sample. The notch creates a controlled stress concentration so different materials can be compared more consistently.

Izod Impact Test

In an Izod test, the specimen is normally held vertically and clamped at one end. The pendulum strikes the sample above the clamped area, usually near the notch.

Izod results depend on the specified specimen, notch, conditioning, pendulum and reporting basis.

This method is widely used for plastics and some other materials. ASTM D256-26 covers standardized Izod pendulum impact resistance testing of plastics and requires attention to specimen preparation, notch quality, dimensions, conditioning, pendulum setup, and failure category.

Charpy Impact Test

In a Charpy test, the specimen is usually positioned horizontally and supported at both ends. The pendulum strikes the sample near the center.

Charpy geometry differs from Izod geometry, so results from the two methods are not interchangeable.

Charpy testing is widely used for metals and can also be applied to plastics under the appropriate method. The striker normally contacts the face opposite the notch. ISO 179-1:2026 specifies non-instrumented Charpy impact testing for plastics, while ASTM E23-25 covers notched-bar impact testing of metallic materials.

The practical setup differs:

• Izod:the specimen is normally vertical and clamped as a cantilever; the specified notch and strike orientation must match the method.
• Charpy:the specimen is supported horizontally as a simple beam and struck at midspan on the face opposite the notch.
• Reporting:absorbed energy may be normalized by specimen width or cross-sectional area, depending on the method and material.

Izod and Charpy values should never be treated as interchangeable. Compare data only when the standard, specimen dimensions, notch, conditioning, temperature, impact velocity, units, and failure category are compatible.

The important point is that Izod and Charpy values should not be compared casually. Test geometry, sample dimensions, notch type, temperature, and standard all affect the result.

A high value in one method does not automatically equal the same performance under another method.

What Factors Affect Impact Resistance?

Impact resistance is influenced by both the material and the testing or operating environment.

Temperature and specimen conditioning can change the fracture behavior of polymers and other materials.

Important factors include:

• material composition
• temperature
• thickness
• notches
• surface defects
• impact speed
• manufacturing process
• material aging
• moisture
• chemical exposure
• internal stress
• fiber reinforcement

Temperature can make a major difference. Some polymers and metals show a transition toward more brittle behavior as temperature falls. A material that performs well indoors may crack more readily in a cold room or outdoor application, so test temperature and conditioning should match the intended service range.

Thickness also matters. A thicker part may absorb more energy, but poor geometry can still create weak points.

Notches and sharp corners are especially important because they concentrate stress. A small crack, molding defect, or damaged edge can reduce impact performance dramatically.

Manufacturing also affects the result. Injection molding conditions, welding, heat treatment, cooling rate, material orientation, and residual stress can all change the way a finished part handles impact.

This is why critical applications often need both controlled material data and a representative component or finished-product test. Standard coupons support comparison and quality control; they do not capture every rib, corner, weld, bond, bearing, fastener, residual stress, or load path in the final assembly.

Which Materials Have High Impact Resistance?

Different material families absorb impact in different ways.

Material family names are only a starting point; grade, processing, temperature and part geometry influence impact behavior.

Polycarbonate

Polycarbonate is widely known for high impact resistance. It is used in protective housings, machine guards, transparent covers, helmets, and other applications where resistance to cracking is important.

ABS

ABS offers a useful balance of impact resistance, stiffness, processability, and surface quality. It is common in equipment housings, automotive parts, appliance components, and consumer products.

High-Impact Nylon

Some nylon grades offer strong mechanical properties combined with useful impact resistance. Reinforcement, moisture content, temperature, and material grade can change performance significantly.

For a broader comparison of nylon and other wheel materials, see Caster Wheel Materials for Industrial Use.

Polyurethane

Polyurethane can combine elasticity, abrasion resistance, toughness, and impact absorption. This is one reason it is widely used in industrial wheels, rollers, bumpers, and protective components.

See polyurethane casters for application-focused wheel options.

Rubber

Rubber can absorb impact by deforming under force. It is useful where cushioning, vibration reduction, and noise control matter.

Thermoplastic rubber and similar resilient materials are also used in wheels and protective parts, including medical caster applications where noise, cushioning, and floor protection matter.

Toughened Steel

Steel can offer very high strength and toughness depending on alloy, heat treatment, geometry, and temperature. It is widely used in structural and industrial parts exposed to impact.

Composite Materials

Composite materials can be engineered to combine stiffness, strength, low weight, and impact behavior. Their performance depends heavily on fiber type, matrix material, orientation, and construction.

No material is automatically the most impact resistant for every application. The right choice depends on the grade, processing history, geometry, temperature, loading rate, environment, cost, weight, wear, and acceptable failure mode. A published value from one specimen and method should not be used to rank unrelated materials under different conditions.

Impact Resistance of Plastic, Rubber, and Metal

Plastic, rubber, and metal behave very differently under impact.

Plastics may be rigid, flexible, brittle, or highly impact resistant depending on the polymer and formulation. Polycarbonate and impact-modified ABS can absorb significant impact, while some hard plastics may crack more easily.

Rubber and elastomers usually absorb impact through deformation. They can compress and recover, making them useful in buffers, wheels, pads, protective parts, and vibration-control applications.

Metals can absorb impact through elastic and plastic deformation. Tough metals may bend before breaking, while brittle metals or poorly treated parts may crack under sudden loading.

The choice depends on what the part must do after impact.

A protective cover may need to remain intact. A rubber bumper may be allowed to deform. A steel bracket may need to resist bending. A wheel may need to absorb impact while continuing to roll normally.

Material selection should therefore focus on the required failure behavior, not only the highest test value.

Hardness, Toughness, and Abrasion Resistance Are Different

Impact resistance is often confused with hardness, toughness, and abrasion resistance.

They are related, but they describe different behaviors.

Hardness describes resistance to indentation, scratching, or surface deformation. A harder material is not automatically more impact resistant. Some very hard materials are brittle and may crack when struck.

For more detail, see Caster Wheel Hardness Explained.

Toughness describes a material’s broader ability to absorb energy before fracture. It includes both strength and the ability to deform. Impact resistance focuses more specifically on sudden or high-rate loading.

Abrasion resistance describes how well a material resists surface wear from rubbing, scraping, or abrasive particles. A material may resist abrasion well but still crack under strong impact.

The practical difference is:

• Hardness:resistance to indentation
• Impact resistance:resistance to sudden shock
• Toughness:overall energy absorption before fracture
• Abrasion resistance:resistance to rubbing and surface wear

A good material choice often requires several of these properties at the same time. For wheel applications, caster wheel materials should be compared as a complete performance balance rather than by one property alone.

Common Applications of Impact-Resistant Materials

Impact-resistant materials are used across many industries.

Common applications include:

• automotive bumpers and interior parts
• protective helmets and guards
• packaging
• construction panels
• equipment housings
• electronics enclosures
• toolboxes
• outdoor furniture parts
• machinery covers
• industrial containers
• warehouse equipment
• material-handling carts
• rollers and wheels
• machine components

The exact material depends on the type of impact.

Packaging may need lightweight plastics that protect products during dropping. Machinery may require metal guards that resist tools or debris. Automotive applications may need a combination of stiffness, energy absorption, weather resistance, and low weight.

Furniture and equipment components may need enough impact resistance to survive transport, assembly, relocation, and everyday use.

Material-handling products often face repeated smaller impacts rather than one dramatic collision. This repeated impact can be just as important for long-term durability.

Why Impact Resistance Matters for Wheels and Casters

Wheels and casters regularly experience impact even when they are not used in obviously harsh environments.

Thresholds and joints create transient loads that depend on speed, wheel size, tread resilience and equipment geometry.

A wheel can hit:

• floor joints
• doorway thresholds
• elevator gaps
• small debris
• ramps
• damaged concrete
• metal strips
• uneven tiles
• potholes
• loading-area transitions

When a loaded caster hits an obstacle, the wheel does not experience only vertical weight. The sudden change in motion creates additional force.

If the wheel or caster does not handle that impact properly, problems may include:

• tread cracking
• wheel-core deformation
• bearing damage
• tread-to-core bond separation
• bent forks
• loosened mounting hardware
• reduced load performance
• sudden wheel failure

Small-diameter wheels usually feel obstacles more strongly because they have greater difficulty climbing over them. Larger wheels generally cross the same obstacle more smoothly.

Impact performance also depends on speed. A caster crossing a floor joint slowly experiences a different load from the same caster hitting it at higher speed.

This is why wheel impact resistance should be considered together with dynamic load and static load, speed, wheel diameter, floor condition, mounting and the stiffness of the complete equipment frame.

Which Caster Materials Handle Impact Better?

Caster materials respond differently to impact.

Wheel materials trade impact cushioning against load support, rolling resistance, wear, noise and floor protection.

Polyurethane wheels often offer a useful balance of load support, abrasion resistance, elasticity, and impact behavior. Softer or more resilient formulations can absorb some surface shock, while harder formulations may reduce rolling resistance.

However, polyurethane formulation, tread thickness, core design, bonding quality, and temperature all affect performance.

Rubber and TPR wheels usually provide better cushioning and vibration reduction. They can be useful where quiet movement and shock absorption matter, although load and wear resistance must also be considered.

Nylon wheels are hard, strong, and efficient on smooth floors. They deform relatively little under load, but their harder structure transfers more impact to the equipment and may feel harsh on rough floors.

Cast iron and steel wheels can handle very high loads and severe industrial conditions, but they offer almost no cushioning. Impact is transferred directly through the wheel, axle, bracket, equipment, and floor.

There is no universal “best impact-resistant caster material.” Heavy duty casters may use polyurethane, nylon, rubber, cast iron, steel, or engineered combinations depending on the actual duty.

The correct material depends on:

• load
• speed
• floor
• temperature
• obstacle height
• noise requirements
• wheel diameter
• service environment

How to Choose Wheels for Impact Conditions

When an application involves repeated impact, begin with the complete operating condition rather than choosing only from the wheel material.

A larger resilient wheel can reduce shock, but the complete caster, mounting and equipment frame still require review.

Confirm the load per wheel, including equipment weight and maximum payload.

Then review the floor. Are there cracks, gaps, thresholds, ramps, debris, or rough concrete? Measure or estimate the obstacles the wheel needs to cross.

Movement speed also matters. Higher speed generally increases impact severity.

Next, consider wheel diameter. A larger wheel usually crosses obstacles more easily and reduces the angle of attack against floor joints.

Tread material should then be matched to the required balance of:

• impact absorption
• rolling resistance
• abrasion resistance
• floor protection
• noise
• load support

The hub and bearing structure also matter. A resilient tread cannot fully protect a weak wheel core, bearing, axle, or bracket.

For severe impact conditions, buyers should review the entire caster assembly rather than simply asking for a “stronger wheel.” The mounting plate, swivel race, fork, axle, bearings, wheel core, tread bond and equipment attachment can each become the limiting element.

How JESS Caster Helps With Impact-Resistant Wheel Selection

JESS Caster helps customers evaluate impact as part of the complete caster application.

For projects involving rough floors, thresholds, frequent movement, or sensitive equipment, we review factors such as:

• total load
• load per caster
• floor condition
• obstacle height
• movement speed
• usage frequency
• wheel diameter
• tread material
• wheel hardness
• hub structure
• bearing type
• caster bracket
• mounting method

A polyurethane wheel may suit one warehouse application, while another project may need rubber for better impact absorption or nylon for lower rolling resistance on a smooth floor.

The correct solution depends on the balance of impact, load, wear, noise, and movement efficiency.

For OEM buyers, distributors, and equipment manufacturers, this application-based approach helps reduce problems such as tread cracking, hub damage, excessive vibration, poor rolling performance, and premature caster replacement.

If your project involves wheels or mobile equipment exposed to impact, contact JESS Caster with the loaded equipment mass, caster layout, wheel diameter, travel speed, floor joints, obstacle height, temperature, duty cycle and failure consequences before confirming the specification.

Conclusion

Impact resistance is the ability of a material or product to absorb sudden impact energy without cracking, breaking, or losing function.

It is not the same as hardness, abrasion resistance, tensile strength, or load capacity. A material can be hard but brittle. It can resist abrasion but still crack under impact. It can have high strength under gradual loading but behave differently when force is applied suddenly.

That is why impact-resistant material selection should consider material composition, temperature, part geometry, thickness, manufacturing quality, impact speed, and real operating conditions.

For wheels and casters, impact resistance becomes especially important when equipment crosses thresholds, floor joints, rough concrete, debris, or loading areas. Wheel material, diameter, bearing, hub, bracket, speed, and dynamic load all influence the final result.

JESS Caster helps buyers select caster solutions based on how equipment actually moves and where impact occurs, not just on one material test value.