Material Characterization & Failure Analysis · 2017. 5. 31. · rate testing. High Strain Rate Tensile Testing (HSRT) This proprietary test machine, developed by SES, is capable

s t r e s s e n g i n e e r i n g s e r v i c e s

Plastics & Composites Testing: Material Characterization& Failure Analysis

on the web at www.stress.comCincinnati • Houston • New Orleans • Baton Rouge • Calgary

Plastic Fatigue

Plastics applications involving cyclic loading are common in machinery-related situations. SES has developed a costeffective approach to generating fatigue data that alsoenables the study of mean stress effects. These data can be used in conjunction with predictive analysis methods toestimate product life.

Injection Molding Machine for Molding Test Samples

SES’s 66-ton Aurburg machine can be oriented horizontallyor vertically, offering the capability to do standard injectionmolding and insert molding. Test specimens can be moldedunder a wide range of conditions with the goal of simulatingprocessing conditions that can produce damage in materi-als. This machine is also used for the molding of prototypecomponents.

Laboratory-based material testing and characterization capabilities are the cornerstone of Stress Engineering’s plastics, rubber and composites design and predictive analysis services.The fact that we use the data we generate gives us a unique perspective on what specific material data and information is needed to design the most robustproducts and components. SES uses a wide range of

specialized tools to test and characterize the behaviorof plastics and composites. Data is collected to estab-lish material behaviors and determine which materialsare appropriate to use, and when.

#431

For Plastics, Composite and Elastomer MaterialsTesting & Characterization

Call SES today at 513-336-6701

Dynamic Mechanical Analyzer (DMA)

A DMA measures a wide variety of time- and temperature-dependent mechanical performance attributes on verysmall material samples. Dynamic properties (storage andloss modulus and tan delta for damping) which are impor-tant in product noise and vibration problems, can be meas-ured directly. The machine can also be used to measurecreep, relaxation and recovery. The DMA is capable ofmaking these measurements in several different loadingmodes: tension, compression, bending and shear.

The DMA is also capable of measuring properties over avery large temperature range, -145°C to 600°C, by combin-ing liquid nitrogen cooling on the low end and a high per-formance furnace on the high end. This allows measure-ment of thermal transitions (e.g. glass transition tempera-ture), and provides an efficient process to study materialbehavior over a range of temperatures and strain rates.These data can then be combined through time-tempera-ture super-positioning to create a master curve of materialstiffness, which includes strain rates (both fast-drop impact or slow-creep) that are difficult to measure usingother means.

Elastomer High FrequencyTension/CompressionTest Machine

Depending on the requiredload/displacement, this testmachine is capable ofcycling a test sample up to100 hertz. One of the mostcommon applicationsinvolves testing of elas-tomers or other polymerssubjected to long termcyclic loading.

Creep Testing of Plastics

Time dependent deformation of polymers is a critical designload case for many products. Sustained loads and elevatedtemperatures can acceler-ate creep-related failuremechanisms. SES has morethan 70 creep machines/stations that can be used to measure tensile creepproperties of polymers andcomposites over a widerange of temperatures.

Constant Strain Rate Creep Testing

Most creep testing is load con-trolled, not strain rate con-trolled. SES’s constant strainrate creep machine will operateat a constant tensile strain rateof one micron per hour. Theability to control strain enablesSES to explore damage undercyclic loading and highlyredundant conditions. Also,“slow” damage mechanisms inplastics, such as environmentalstress cracking are better char-acterized by slow constrainrate testing.

High Strain Rate Tensile Testing (HSRT)

This proprietary test machine, developed by SES, is capableof testing at rates on the order of 10,000% per second,capturing how stress, strain and ductility at failure areaffected by high strain rate events, such as drop impact.Very early in the development process this test can be usedto screen candidate material for a particular design appli-cation, or to develop 'material models’ for predicting fail-ure using non-linear finite element analysis methods. SESis unique in combining testing capabilities and predictivestructural modeling.

Biaxial Tensile Testing (for film and thin materials)

Failures in most plastic products occur under multi-axialstress/strain states. The effect of this stress state is toreduce the ductility of the materials, which becomes thelimiting load scenario for design. To collect data for thisimportant material parameter SES developed a BiaxialTensile Test system. This equipment captures the behaviorof film and thin materials under biaxialtension. It is used to evaluate materi-als for drop impact applications andother high strain rate events. The testspecimen thickness is limited to about0.040 inch maximum. For thicker sec-tions a variety of notched specimensare available for producing triaxialbehavior.

Dynatup Instrumented Drop Impact Test Machine

The Dynatup is an instrumented drop impact test machine.It is also used for biaxial testing because it will accommo-date thicker material samples than the Biaxial Tensile Testsystem. This equipment is used to conduct high strain rateductility testing.

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Dynamic Mechanical Analyzer (DMA)

A DMA measures a wide variety of time- and temperature-dependent mechanical performance attributes on verysmall material samples. Dynamic properties (storage andloss modulus and tan delta for damping) which are impor-tant in product noise and vibration problems, can be meas-ured directly. The machine can also be used to measurecreep, relaxation and recovery. The DMA is capable ofmaking these measurements in several different loadingmodes: tension, compression, bending and shear.

The DMA is also capable of measuring properties over avery large temperature range, -145°C to 600°C, by combin-ing liquid nitrogen cooling on the low end and a high per-formance furnace on the high end. This allows measure-ment of thermal transitions (e.g. glass transition tempera-ture), and provides an efficient process to study materialbehavior over a range of temperatures and strain rates.These data can then be combined through time-tempera-ture super-positioning to create a master curve of materialstiffness, which includes strain rates (both fast-drop impact or slow-creep) that are difficult to measure usingother means.

Elastomer High FrequencyTension/CompressionTest Machine

Depending on the requiredload/displacement, this testmachine is capable ofcycling a test sample up to100 hertz. One of the mostcommon applicationsinvolves testing of elas-tomers or other polymerssubjected to long termcyclic loading.

Creep Testing of Plastics

Time dependent deformation of polymers is a critical designload case for many products. Sustained loads and elevatedtemperatures can acceler-ate creep-related failuremechanisms. SES has morethan 70 creep machines/stations that can be used to measure tensile creepproperties of polymers andcomposites over a widerange of temperatures.

Constant Strain Rate Creep Testing

Most creep testing is load con-trolled, not strain rate con-trolled. SES’s constant strainrate creep machine will operateat a constant tensile strain rateof one micron per hour. Theability to control strain enablesSES to explore damage undercyclic loading and highlyredundant conditions. Also,“slow” damage mechanisms inplastics, such as environmentalstress cracking are better char-acterized by slow constrainrate testing.

High Strain Rate Tensile Testing (HSRT)

This proprietary test machine, developed by SES, is capableof testing at rates on the order of 10,000% per second,capturing how stress, strain and ductility at failure areaffected by high strain rate events, such as drop impact.Very early in the development process this test can be usedto screen candidate material for a particular design appli-cation, or to develop 'material models’ for predicting fail-ure using non-linear finite element analysis methods. SESis unique in combining testing capabilities and predictivestructural modeling.

Biaxial Tensile Testing (for film and thin materials)

Failures in most plastic products occur under multi-axialstress/strain states. The effect of this stress state is toreduce the ductility of the materials, which becomes thelimiting load scenario for design. To collect data for thisimportant material parameter SES developed a BiaxialTensile Test system. This equipment captures the behaviorof film and thin materials under biaxialtension. It is used to evaluate materi-als for drop impact applications andother high strain rate events. The testspecimen thickness is limited to about0.040 inch maximum. For thicker sec-tions a variety of notched specimensare available for producing triaxialbehavior.

Dynatup Instrumented Drop Impact Test Machine

The Dynatup is an instrumented drop impact test machine.It is also used for biaxial testing because it will accommo-date thicker material samples than the Biaxial Tensile Testsystem. This equipment is used to conduct high strain rateductility testing.

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provide a quantifiable acceleration factor. These tests areoften done in conjunction with chemical exposure andmechanical loading to understand potential product relia-bility problems resulting from environmental stress crack-ing, mechanical loads or material degradation.

The Walk-in Environmental Chamber makes it possible tocondition and test large components, or significant num-bers of components under extreme environmental condi-tions (20°C to 80°C, up to 100% relative humidity) foraccelerated aging testing.

Accelerated Weathering Testing (AWT)

Extended exposure to UV from sunlight or other sourcescan cause degradation in the structural properties of mostpolymers. Although additives have been developed to slowthe degradation process, they do not eliminate this prob-lem. Ultimately, a manufacturer of products that will beexposed to the weather must test the performance of theircandidate resin systems to 1) make an informed selectionof the best resin, and 2) estimate the life of the product.

Creep Rupture Testing of Composites

High temperature composite creep rupture testing meas-ures a material's ability to support load over time. This testsystem produces a constant tensile load in specimens whilethe time-to-rupture is measured. SES constructed two, ten-station frames that include thermally controlled chambers,which are important because creep rates for polymer-basedcomposites are highly temperature dependent. This tem-perature dependency is used to accelerate testing, and thedata is used in structural calculations to assess design per-formance or to screen candidate materials.

Stress RelaxationTesting

Stress relaxation testframes measure theloss of force when apolymer is subjected toa fixed deformation,which is the reverse ofcreep. This is a common condition for plastic assemblies,where sealing features or snap locks are deformed and thenheld in a fixed position. These data are used to determinethe retention of strength over time. Tests are often run atelevated temperature to accelerate the relaxation process.

Accelerated Aging of Plastics(in-service degradation mechanisms)

Aging tests are conducted in environmental chambers, with elevated temperature accelerating effective time. Thiseffect is based on the Arrhenius equation, which relatestemperature and time. Testing at multiple temperatures can

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provide a quantifiable acceleration factor. These tests areoften done in conjunction with chemical exposure andmechanical loading to understand potential product relia-bility problems resulting from environmental stress crack-ing, mechanical loads or material degradation.

The Walk-in Environmental Chamber makes it possible tocondition and test large components, or significant num-bers of components under extreme environmental condi-tions (20°C to 80°C, up to 100% relative humidity) foraccelerated aging testing.

Accelerated Weathering Testing (AWT)

Extended exposure to UV from sunlight or other sourcescan cause degradation in the structural properties of mostpolymers. Although additives have been developed to slowthe degradation process, they do not eliminate this prob-lem. Ultimately, a manufacturer of products that will beexposed to the weather must test the performance of theircandidate resin systems to 1) make an informed selectionof the best resin, and 2) estimate the life of the product.

Creep Rupture Testing of Composites

High temperature composite creep rupture testing meas-ures a material's ability to support load over time. This testsystem produces a constant tensile load in specimens whilethe time-to-rupture is measured. SES constructed two, ten-station frames that include thermally controlled chambers,which are important because creep rates for polymer-basedcomposites are highly temperature dependent. This tem-perature dependency is used to accelerate testing, and thedata is used in structural calculations to assess design per-formance or to screen candidate materials.

Stress RelaxationTesting

Stress relaxation testframes measure theloss of force when apolymer is subjected toa fixed deformation,which is the reverse ofcreep. This is a common condition for plastic assemblies,where sealing features or snap locks are deformed and thenheld in a fixed position. These data are used to determinethe retention of strength over time. Tests are often run atelevated temperature to accelerate the relaxation process.

Accelerated Aging of Plastics(in-service degradation mechanisms)

Aging tests are conducted in environmental chambers, with elevated temperature accelerating effective time. Thiseffect is based on the Arrhenius equation, which relatestemperature and time. Testing at multiple temperatures can

4 5

be made on a product’s surface, which provides a non-destructive technique for sampling. This tool can be com-bined with a microscope to allow precise selection of meas-urement location, and to identify trace contaminants, ormulti-material structures.

Digital Microscope

Diagnosing plastic failures or inspecting the most minutefeatures of molded plastic parts is essential to the productassessment and failure analysis process. With this specificpurpose in mind, SES uses a digital microscope to inspectand document features and failures. The Keyence digitalscope is very effective at enabling inspection of clear resins,in addition to those with pigment.

Melt Flow Testing

A melt flow measures apolymer's viscosity atelevated temperature.Melt flow rate is a keyspecification provided bymaterial manufacturersto identify how easily thematerial can beprocessed by injectionmolding or extrusion.The melt flow is directlyrelated to molecularweight of a material, sothe test provides a keyindication of durability.The test is also useful fordetermining if a materialhas been degraded dur-ing processing, or if amaterial substitution hasbeen made.

Friction Testing

Real world plastic product design and assembly involvesone component sliding in contact with other components.Friction is always a factor in these situations. SES has developed proprietary friction testing equipment capable of testing over a wide range of conditions.

Water Vapor Permeability

There are many industries where moisture control or gastransmission is critical. Moisture sensitive foods and phar-maceuticals are sealed to achieve the required quality, safety,and shelf life. The Mocon Permatran-W is the benchmarkstandard for measurement of water vapor transmission

rates. When used in conjunction with SES’s environmentalchambers, the Permatran-W is capable of measuring per-meation through films and barrier materials over a widerange of temperature (-70°C to 190°C) and relative humid-ity (10% to 98%). By measuring the permeation rate at theexpected real world conditions, sensible material selectioncan be made.

Fourier Transform Infrared (FTIR)

The FTIR uses an infrared laser to capture a material’svibration pattern at a molecular level, which is a fingerprintof the material’s chemical composition. Each chemical bondin the polymer chain will have unique vibration frequencies.Materials are identified based on the combinations of fre-quencies measured. SES often uses the FTIR to monitor aclient’s resin supply chain, establish material benchmarksand reverse engineer plastic products. Measurements can

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be made on a product’s surface, which provides a non-destructive technique for sampling. This tool can be com-bined with a microscope to allow precise selection of meas-urement location, and to identify trace contaminants, ormulti-material structures.

Digital Microscope

Diagnosing plastic failures or inspecting the most minutefeatures of molded plastic parts is essential to the productassessment and failure analysis process. With this specificpurpose in mind, SES uses a digital microscope to inspectand document features and failures. The Keyence digitalscope is very effective at enabling inspection of clear resins,in addition to those with pigment.

Melt Flow Testing

A melt flow measures apolymer's viscosity atelevated temperature.Melt flow rate is a keyspecification provided bymaterial manufacturersto identify how easily thematerial can beprocessed by injectionmolding or extrusion.The melt flow is directlyrelated to molecularweight of a material, sothe test provides a keyindication of durability.The test is also useful fordetermining if a materialhas been degraded dur-ing processing, or if amaterial substitution hasbeen made.

Friction Testing

Real world plastic product design and assembly involvesone component sliding in contact with other components.Friction is always a factor in these situations. SES has developed proprietary friction testing equipment capable of testing over a wide range of conditions.

Water Vapor Permeability

There are many industries where moisture control or gastransmission is critical. Moisture sensitive foods and phar-maceuticals are sealed to achieve the required quality, safety,and shelf life. The Mocon Permatran-W is the benchmarkstandard for measurement of water vapor transmission

rates. When used in conjunction with SES’s environmentalchambers, the Permatran-W is capable of measuring per-meation through films and barrier materials over a widerange of temperature (-70°C to 190°C) and relative humid-ity (10% to 98%). By measuring the permeation rate at theexpected real world conditions, sensible material selectioncan be made.

Fourier Transform Infrared (FTIR)

The FTIR uses an infrared laser to capture a material’svibration pattern at a molecular level, which is a fingerprintof the material’s chemical composition. Each chemical bondin the polymer chain will have unique vibration frequencies.Materials are identified based on the combinations of fre-quencies measured. SES often uses the FTIR to monitor aclient’s resin supply chain, establish material benchmarksand reverse engineer plastic products. Measurements can

6 7

Plastics & Composites Testing: Material Characterization& Failure Analysis

on the web at www.stress.comCincinnati • Houston • New Orleans • Baton Rouge • Calgary

Plastic Fatigue

Plastics applications involving cyclic loading are common in machinery-related situations. SES has developed a costeffective approach to generating fatigue data that alsoenables the study of mean stress effects. These data can be used in conjunction with predictive analysis methods toestimate product life.

Injection Molding Machine for Molding Test Samples

SES’s 66-ton Aurburg machine can be oriented horizontallyor vertically, offering the capability to do standard injectionmolding and insert molding. Test specimens can be moldedunder a wide range of conditions with the goal of simulatingprocessing conditions that can produce damage in materi-als. This machine is also used for the molding of prototypecomponents.

Laboratory-based material testing and characterization capabilities are the cornerstone of Stress Engineering’s plastics, rubber and composites design and predictive analysis services.The fact that we use the data we generate gives us a unique perspective on what specific material data and information is needed to design the most robustproducts and components. SES uses a wide range of

specialized tools to test and characterize the behaviorof plastics and composites. Data is collected to estab-lish material behaviors and determine which materialsare appropriate to use, and when.

#431

For Plastics, Composite and Elastomer MaterialsTesting & Characterization

Call SES today at 513-336-6701