Mechanical Testing of Polymers, Composites and 3D-Printed Materials

At AdvanSES, we provide mechanical testing of polymers, composites and 3D-printed materials. Our scope is

1) Mechanical Testing of Polymers, Metals and Composite Materials
2) Fatigue and Durability Testing
3) Dynamic Mechanical Analysis (DMA) of Materials and Components
4) Hyperelastic, Viscoelastic Material Testing
5) Data Cards for Input into FEA, CAE softwares
6) FEA Services
7) Custom Tests, NI Labview DAQ

Discover more at http://www.advanses.com

At AdvanSES, we provide a full 360 degree static and dynamic characterization of your materials, parts and components. We measure the tension, compression, shear, vibration and dynamic properties of individual components and sub assemblies in accordance to international standards.

Melt Flow Index Testing

The Melt Flow Index (MFI) is a measure of the ease of flow of the melt of a thermoplastic polymer. A higher MFI value indicates a lower material viscosity, and when comparing polymer materials of the same class and grades, a lower melt flow MFI rate indicates a higher molecular weight that maybe with or without less branching links. Melt flow rate is a measure of the ability of the polymer material to flow under pressure and temperature. Molecular weight provides performance in polymeric materials, the higher the molecular weight, the better the performance. MFI can be used as an important parameter for quality certification and batch to batch quality comparison.

Contact us at [email protected] for your testing needs.

Melt Flow Index Testing at AdvanSES
Melt Flow Index Testing at AdvanSES

ROPS / FOPS Testing and FEA Finite Element Analysis

The ability to test field service conditions in dangerous work areas and simulate these conditions leads to optimized load bearing structures in automotive and allied applications. For better safety of a driver or operator, mining, agricultural and self-propelled machines are equipped with protective structures

AdvanSES provides experimental test facilities to conduct FOPS tests on automotive and construction related machinery.

FOPS ANALYSES CONDITIONS
 
FOPS stands for Falling Object Protective Structure. FOPS are protective devices structure designed to protect operators from items that may fall on a vehicle or machinery when it is being operated. The recognized standard to define the performance requirements for FOPS is ISO 3449 Earth moving machinery – Falling object protective structures. This standard is referenced in other standards for machineries in general also.
ISO 3449:2005 specifies laboratory tests for measuring the structural characteristics of, and gives performance requirements in a representative test for, falling-object protective structures (FOPS) intended for use on ride-on earth-moving machines as defined in ISO 6165. It is applicable to both FOPS supplied as an integral part of the machine and those supplied separately for attachment onto the machine.
 
There are two (2) different levels of FOPS – Level 1 & Level 2.
 
ISO 3449 states the following –
 
Level I impact protection –
Impact strength for protection from small falling objects (e.g. bricks, debris, small rocks) encountered in operations such as highway maintenance, and construction site services.
Level II impact protection –
Impact strength for protection from heavy falling objects (e.g. boulders, rocks) for machines involved in site clearing, mining and overhead demolitions.
 
Level I – withstands 1,365 joules (45kgs Fall at 3.1m drop)
 
Level II – withstands 11,600 joules (227 kgs Fall at 5.2m drop)
 
According to the standard, the weight is let to fall freely onto the vehicle cabin roof ceiling from a definite height. The weight is made of steel or cast steel with a cylindrical or spherical shape. The height of free fall in correlation with the mass of the weight has to provide the impact energy. The levels of energy depend on purpose of the structure. In the current project virtual testing has been carried out for the FOPS using the commercial software package Abaqus®.
 
Figures show the impactors and striker geometry prescribed in the standard for evaluating the vehicle structure.

Contact us for a discussion on your FOPS and ROPS testing and analysis requirements.

Plastics, Rubber, Composites Product Development and Material Testing

One of the most important component of successful product development and failure analysis programs is the ability to simulate actual material behavior. The definition of material card input data into FEA softwares refers to test data that analysts and engineers must enter into FEA CFD softwares. As the complexity of the simulation increases, the accuracy and fidelity of the material card data becomes top priority to the modeling of actual physics of the system.

We provide Hyperelastic, Viscoelastic Material Characterization Testing data Cards for Input into FEA, CAE softwares

AdvanSES Portfolio

1) Mechanical Testing of Polymers, Metals and Composite Materials
2) Fatigue and Durability Testing
3) Dynamic Mechanical Analysis (DMA) of Materials and Components
4) Hyperelastic, Viscoelastic Material Testing
5) Data Cards for Input into FEA, CAE softwares
6) FEA Services
7) Custom Tests, NI Labview DAQ

At AdvanSES, we provide a full 360 degree static and dynamic characterization of your materials, parts and components. We measure the tension, compression, shear, vibration and dynamic properties of individual components and sub assemblies in accordance to international standards.

Mechanical Testing of Composite Materials

A wide range of standardized and non-standardized mechanical tests on composite materials are carried out to characterize these materials. These tests include tension, compression, flexure, shear, impact and fatigue. It is also imperative that mechanical testing of composites requires use of material testing systems that are capable of performing tests in load control, displacement control, and strain control.

One of the main challenges in testing these type of anisotripic materials is also the requirement that a wide range of fixtures be developed to provide various ways of testing the materials under different conditions.

Our testing engineers are familiar with international standards and range of regulatory requirements. We reglarly characterize composites as per ISO, and ASTM specifications.

Mechanical Testing & Performance Assessment

Uniaxial Tension Test (Directional) (ASTM D638, ISO 527):

The stress (ζ) in a uniaxial tension testis calculated from;

ζ = Load / Area of the material sample ……………………………………..(1)

The strain(ε) is calculated from; ε = δl (change in length) / l (Initial length) ……………..(2)

The slope of the initial linear portion of the curve (E) is the Young’s modulus and given by; E = (ζ2- ζ1) / (ε2- ε1) ……………………………………..(3)

No alt text provided for this image

4 Point Bend Flexure Test (ASTM D6272): 

The four-point flexural test provides values for the modulus of elasticity in bending, flexural stress, flexural. This test is very similar to the three-point bending flexural test. The major difference being that with the addition of a fourth nose for load application the portion of the beam between the two loading points is put under maximum stress. In the 3 point bend test only the portion of beam under the loading nose is under stress.

No alt text provided for this image

This arrangement helps when testing high stiffness materials like ceramics infused polymers, where the number and severity of flaws under maximum stress is directly related to the flexural strength and crack initiation in the material. Compared to the three-point bending flexural test, there are no shear forces in the four-point bending flexural test in the area between the two loading pins.

Poisson’s Ratio Test as per ASTM D3039: 

Poisson’s ratio is one of the most important parameter used for structure design where all dimensional changes resulting from application of force need to be taken into account, specially for 3d printed materials. For this test method, Poisson’s ratio is obtained from strains resulting from uniaxial stress only. ASTM D3039 is primarily used to evaluate the Poison’s ratio. Testing is performed by applying a tensile force to a specimen and measuring various properties of the specimen under stress. Two strain gauges are bonded to the specimen at 0 and 90 degrees to measure the lateral and linear strains. The ratio of the lateral and linear strain provides us with the Poisson’s ratio. 

No alt text provided for this image

Flatwise Compression Test as per ASTM D695: 

The compressive properties of 3d printed materials are important when the product performs under compressive loading conditions. The testing is carried out in the direction normal to the plane of facings as the core would be placed in a structural sandwich construction. The test procedures pertain to compression call for test conditions where the deformation is applied under quasi-static conditions negating the mass and inertia effects.

No alt text provided for this image

The test procedures pertaining to compression call for test conditions where the deformation is applied under quasi-static conditions negating the mass and inertia effects.

Modified Compression Test as per Boeing BSS 7260:

Modified ASTM D695 and Boeing BSS 7260 is the testing specification that determines compressive strength and stiffness of polymer matrix composite materials using a loading compression test fixture. This test procedure introduces the compressive force into the specimen through end loading.

No alt text provided for this image

Axial Fatigue Test as per ASTM D7791 & D3479:

ASTM D7791 describes the determination of dynamic fatigueproperties of plastics in uniaxial loading conditions. Rigid or semi-rigid plastic samples are loaded intension (Procedure A) and rigid plastic samples are loaded incompression (Procedure B) to determine the effect of processing, surface condition, stress, and such,on the fatigue resistance of plastic and reinforced composite materials subjected to uniaxial stress for a large number of cycles.The results are suitable for study of high load carrying capability of candidate materials. ASTM recommends a test frequency of 5hz or lower.The tests can be carried out under load/stress or displacement/strain control. The test method allows generation of stress or strain as a function of cycles, with the fatigue limit characterized by failure of the specimen or reaching 10E+07 cycles.The maximum and minimum stress or strain levels are defined throughan R ratio.

No alt text provided for this image

3 Point Bend Flexure Test (ASTM D790):

Three point bending testing is carried out to understand the bending stress, flexural stress and strain of composite and thermoplastic 3d printed materials. The specimen is loaded in a horizontal position, and in such a way that the compressive stress occurs in the upper portion and the tensile stress occurs in the lower portion of the cross section.This is done by having round bars or curved surfaces supporting the specimen from underneath. Round bars or supports with suitable radii are provided so as to have a single point or line of contact with the specimen. The load is applied by the rounded nose on the top surface of the specimen. If the specimen is symmetrical about its cross section the maximum tensile and compressive stresses will be equal. This test fixture and geometry provides loading conditions so that specimen fails in tension or compression.

No alt text provided for this image

For most composite materials,the compressive strength islower than the tensile and thespecimen will fail at thecompression surface. Thiscompressive failure isassociated with the localbuckling (micro buckling) ofindividual fibres.

Summary:

A variety of standardized mechanical tests on unreinforced and reinforced 3d printed materials including tension, compression, flexural,and fatigue have been discussed.

Mechanical properties of 3d printed polymers, fiber-reinforced polymeric composites immensely depend on thenature of the polymer filament, fiber, and the layer by layer interfacial bonding. Advanced engineering design and analysis applications like Finite Element Analysis use this mechanical test data to characterize the materials. These material properties can be used to develop material models for use in FEA softwares like Ansys, Abaqus, LS-Dyna, MSC-Marc etc.

References:

1) Coutney, T.H., Mechanical Behaviour ofmaterials, Waveland, 1996.

2) Dowling, N.E., Mechanical Behaviour of materials, engineering methods for deformation, fracture and fatigue, Pearson,2016.

3) Ian McEnteggart, Composites Testing:Challenges & Solutions.

4) V. Shanmugam et al., The mechanicaltesting and performance analysis ofpolymer-fibre composites preparedthrough the additive manufacturing. PT, 21.

Heat Deflection Temperature (HDT) and Vicat Softening Temperature Testing

HDT stands for Heat Deflection Temperature. The heat deflection temperature of a reinforced or unreinforced polymer material is a measure of polymer’s resistance to distortion under an applied load at elevated temperatures.

Applications of HDT tests include:

1) Identify suitable material for injection molding application.
2) Identify suitable material for elevated temperature application.
3) Identification and grading of materials as per their properties.

The test specification for the HDT is ASTM D 648 and ISO 75.

Factors Influencing Thermal Performance of Polymer Materials

HDT tests typically test for the short term performance of the materials under loads at elevated temperatures. The following factors play a significant part in the performance prediction of the materials under the test conditions.

1) The total time material is exposed to elevated temperatures.
2) The rate of temperature increase.
3) The specimen dimensions and part geometry.

Vicat softening temperature tests are used to identify the temperature at which a needle of specified dimensions penetrates into a plastic material specimen for a specified distance under applied loading conditions. The test specification for the Vicat softening temperature testing is ASTM D1525 and ISO 306.

Compared with the Heat Deflection Temperature (HDT), Vicat softening temperature test measures the temperature at which the specimen loses its stiffness and softens. HDT test measures the temperature at which the specimen loses its load bearing capability. The Vicat softening point is closer to the actual melting or softening point of the polymer. Vicat softening temperature is typically always higher than the HDT for a polymeric material as the penetration load is always higher than a bending load on a material specimen.

Biaxial Tension Extension Testing of Rubber, Elastomers and Polymeric Thin Films

AdvanSES offers biaxial tension testing of rubber, elastomers and polymeric thin films. Biaxial testing is important for hyperelastic and viscoelastic characterization of elastomers and polymers for Finite Element Analysis FEA Applications. 

We carry out tests under the following biaxial tension deformation modes;

1) Single Stretch.

2) Multiple Cyclic Loading.

3) Single Stretch followed by Stress Relaxation Step.

Hyperelastic and Viscoelastic material characterization testing is carried out under the following deformation modes;

  1. Uniaxial Tension Testing
  2. Planar Shear Testing
  3. Volumetric Compression Testing
  4. Uniaxial Compression Testing
  5. Biaxial Tension Testing

AdvanSES offers a choice of different capacities of load cells for biaxial testing high and low hardness materials, non-contact measurements and capacity to mold material test samples. 

Biaxial Tension Extension Testing of Rubber, Elastomers and Polymeric Thin Films

Biaxial Tension Testing of Rubber is a key property for input into FEA softwares like Abaqus, Ansys, MSC Marc, LS-Dyna. Biaxial tensile testing is a non-traditional but highly accurate testing technique for mechanical characterization of soft and hard materials. Typical materials tested in biaxial tension are silicone and natural rubber elastomers, composites, polymeric thin films, and biological soft tissues.

Polymer Testing & Finite Element Analysis FEA

Simulation of plastics and polymers

Application of engineering polymers and plastics are widespread because of the wide range of material properties, and lower manufacturing cost offered by them. Plastics and polymers are also mixed with glass and carbon fibers to increase the stiffness and provide higher load handling capabilities. Polymer Testing & Finite Element Analysis FEA go hand in hand for such material and product development.

Thermosetting plastics are used in the manufacture of hard, high temperature resistanting parts and a matrix for composites is used for strength and stiffness. Elastomers such as natural rubber are used in automotive applications for vibration isolation and load bearing properties.

Material Properties

The first step in non-linear analysis of polymers and plastics is material characterization of these highly time and frequency dependent strain rate sensitive materials.

Finite Element Analysis (FEA)

Finite Element Analysis FEA of polymer testing is critical to understanding the perfomance of polymer materials and their judicious use in industrial products. Design optimization iterations are then carried out to finalize the design for optimum stress-strain distribution and high fatigue life.

Polymers exhibit a combination of elastic and viscous response to deformation forces. At low temperatures the stiff elastic behaviour is dominant. At high temperatures a viscous or fluid like behaviour is exhibited. At room temperatures a combination of viscous and elastic behaviour (Viscoelastic) is exhibited. The challenge is to test, model and simulate this unique behaviour of this class of material so that the complete material property can be mapped on the product.

Izod Charpy Impact ASTM D256, ISO 180

The Izod Charpy impact test is an ASTM and ISO standard method of determining the impact resistance of thermoplatic and composite materials and is an important test for characterization of materials. The test is very much similar to the Charpy impact test but uses different type of specimens for testing. The Izod impact test differs from the Charpy impact test in that the test sample is held in a cantilevered beam configuration as opposed to a three-point bend configuration. Both notched and un-notched  Izod Charpy impact test  provide important material properties.

The testing conditions are governed by many parameters, as below:

  • the dimensions of the usually rectangular cross section of the sample below the notch;
  • the height of the hammer at the start position, determining its velocity at impact;
  • the mass of the hammer which together with the velocity determines its kinetic energy at impact;
  • the sharpness, or tip curvature, of the notch;
  • the temperature of the sample.

Results of impact tests are expressed in terms of:

  • Amount of energy absorbed (N-m) or 
  • Amount of energy absorbed per unit cross sectional area (N-m/cm2)

Applications include:

  • Measure of the energy required to crack the material.
  • Test materials and grade them as per their impact property and use the grading for different applications.
  • Develop new materials suitable for use in automotive and aerospace impact applications.

Fatigue Testing of Materials and Products

AdvanSES offers Fatigue Testing of Materials and Products using a variety of stress and strain controlled testing machines for characterizing field service behaviors of engineering products, medical devices, and automotive aerospace components.

Fatigue testing involves the application of cyclic loading to a test specimen or a product. Unlike monotonic tests in which loading increases until failure, the applied load is cycled between prescribed maximum and minimum levels until a fatigue failure occurs, or until the predetermined number of loading cycles have been applied.

The loading is applied to assess long term fatigue behavior, vibration isolation properties, and observe failure causing mechanisms.

Figure 1: Fatigue and Static Testing Systems at AdvanSES

AdvanSES offers Fatigue Testing of Materials and Products for;

1) Material Samples
2) Full Scale Component Level Testing
3) Measure Material and Product Degradation
4) Elevated Temperature Testing
5) Incorporation of Aging Mechanisms in Testing

Benefits of Fatigue Testing at AdvanSES

With material and product testing at AdvanSES, you can be sure of:

  1. ISO 17025:2017 Accredited Facility
  2. Knowledgable Testing and Engineering Personnel
  3. Commitment to Understanding your Materials and Products
  4. Identify root cause if Required
  5. Short Timelines
  6. Detailed Testing Reports that Help You Make Accurate Decisions

AdvanSES Fatigue Testing Procedure

The AdvanSES approach to fatigue testing of materials and products is as follows;

  • The machine, environment chamber, extensometer, loadcell etc., are all calibrated and verified.
  • The test samples or products to be tested are prepared.
  • The test parameters are set, environment chamber is placed and the test environment is brought upto the required parameters.
  • The machine is started and runs the set cyclic load, stress, strain ranges according to the parameters predetermined for the test samples.
  • The test is run for the set number of cycles and periodically checked, photographed for signs of degradation, fatigue or until failure.
  • Results and further engineering steps are discussed.
  • All relevant test data with information is reported.