There are several measures of strength and it’s handy to have a general understanding of each one because these measurements appear on your 3D printing material’s datasheet, enabling you to compare options. You’ll see measurements for tensile strength and Young’s modus, for example. These measurements relate to the type of force on your part and how the material will withstand the force.

When it comes to materials, all measurements for strength vary depending on the material’s manufacturer, the specific composition of the material, and the printing parameters used. So, note that our charts below are generalizations. For example, not all maraging steels are stronger than all stainless steel, but the strongest maraging steel is stronger than the strongest stainless steel, so it’s higher on our list. Likewise, not all carbon fiber nylons will resist bending more than carbon fiber PEEK materials, but this is usually the case. As you can see, ranking materials by strength is not as clear as it would seem.

Yet another point to consider is environmental conditions on your part. A standard carbon fiber nylon is as strong as a carbon fiber PEEK, but would fall apart in a humid or corrosive environment. All strength data is measured at standard temperature and pressure (STP), but most applications need strength under temperature, UV light, or chemical conditions.

For the measurements below, we used a variety of sources, including the handy Senvol database of 3D printing materials, but always go directly to the material maker’s datasheet for the most accurate information on the latest version of their materials.

Tensile Strength (Resistance to Pulling Apart)

If you’re 3D printing a part where the main force is pulling on the part, such as a type of hook used to lift a heavy object, you’ll want a high tensile strength. Tensile strength refers to the tension or stress a material can take before breaking. Measuring a material’s tensile strength involves literally putting a sample of the material in a vice-like machine and pulling it in opposite directions. In practical terms, this measurement relates to how quickly your part will break or its brittleness. For reference, stainless steel has a tensile strength of 860 MPa, while glass is 33 MPa, and consumer-grade PLA is about 53 MPa.

There are important related terms to tensile strength, such as ultimate tensile strength (UTS), which is the actual breaking point, and tensile yield strength, which is when the material has permanently deformed, in most cases rendering it useless, even if it hasn’t broken yet.

The top materials in tensile strength are metals but don’t count out polymers, especially carbon-fiber or kevlar-filled varieties. These materials are often used to replace metal in applications where the lighter weight of polymers is a benefit.

Flexural Strength (Resistance to Bending)

If your part needs to bend a little to withstand forces without breaking, for example, a 3D printed chair, you’ll want a high flexural strength material. Flexural strength represents the maximum stress a material can withstand before it fails in bending.

The higher the flexural strength, the more resistant the material is to bending or flexing forces. So, if you did want to print something like the chair above, you’d want to select a flexural strength proportional to the amount of force you expect on your chair — and probably not the material with the highest flexural strength. The chair pictured above was printed in a PLA with a flexural strength of 102 MPa.

Don’t confuse this with flexural modulus, which is how much a material will resist bending or its stiffness. Parts with thin walls, such as tubes or containers, would benefit from high flexural modulus to prevent buckling under external forces.

Tensile Modulus (Elasticity)

Elasticity (also known as Young’s modulus, tensile modulus) evaluates the elasticity of a material, which is a ratio between the deformation of a material and the power needed to deform it.

Typical TPU filament, for example, has a low tensile modulus of around 70 MPa (very elastic), while most PEEK filament has a high tensile modulus of 3,720 MPa (not elastic). In material selection, elasticity is one of the measurement considerations often used alongside strength. Another measure that’s important if you want to determine how far your part can stretch without breaking is “elongation at break”, which is usually a percentage of the part representing the change in length of the sample at the point of breaking. For example, a TPU might have an elongation at break of 400%.

Below we list the top most elastic materials for 3D printing, but it’s important to note that 3D printing resins, which can be very elastic, typically don’t provide their chemical recipe. Some products claim to be a type of TPU or that they are “silicone-like”, but it’s only when looking at the material data sheet that you can get a sense of their true elasticity, listed under tensile modulus.

Impact Strength & Hardness

Impact strength (also known as Izod or Charpy impact strength or, generally, as toughness) is your part’s ability to withstand fracturing if you drop it or how it will resist breaking or cracking when force is applied. Think, 3D printed bicycle helmet. You’ll see these measurements of force in either joules per square meter (J/m2) or foot-pound per square inch (ft·lb/in2). The Izod test is the more popular method for plastic materials, whereas Charpy is common for metals.

Hardness can seem like a vague term, especially when talking about metals. It can refer to scratch resistance, wear and abrasion resistance, or the part’s ability to be dented. Hardness of plastics is often shown as a Rockwell or Shore value, which can have little to do with a material’s strength or flexibility. Shore hardness is a common term you’ll hear when it comes to polymers, but it’s more general than the measurements above. For example, all elastomers and flexible filaments, such as TPU, would be Shore A, and within the A category, they would have individual values, such as Shore Hardness 95A.