Part two of Why Test Composites touches on finding the right test type for your application. We cover the basics in this article; if you have more specific questions you'd like answered, leave us a comment below.
Composites are complex structures made from a variety of different plastic, metal, and ceramic materials. The mechanical and chemical integrity of composite materials are affected by many variables making property prediction and analysis challenging. Testing is a vital adjunct to analysis, as well as being essential for quality control.
Rheology
The study of the rheological behavior of thermo-plastic based composites is very important for fabrication of end products and plays an important role in determining the material performance related to deformation and flow under the processing conditions. Capillary Rheometers measure the rheological behavior of thermoplastic polymers and composites under processing conditions. Melt Flow Testers measure, with great accuracy, the MFR and MVR - basic data required for thermoplastic quality control in the raw materials field.
Thermo-Mechanical
HDT & VICAT systems are used to characterize the behavior of plastic materials at high temperatures, measuring the heat deflection temperature (HDT) and the Vicat softening temperature (Vicat). These thermal testing systems range from very simple units for quality control labs to more advanced and automated systems.
Tensile
Tensile testing of composites is generally in the form of basic tension or flat sandwich tension testing in accordance with standards such as ISO 527-4, ISO 527-5, ASTM D 638, ASTM D 3039 and ASTM C 297. A range of proven gripping solutions is available for ambient, sub-ambient, and high temperature testing. The gripping mechanisms include manual, pneumatic, and hydraulic actuation. A range of jaw face patterns are available to provide effective gripping of tabbed and un-tabbed specimens. This allows for no slipping under load and no premature failure caused by stress concentrations in the jaws. Hydraulic grip solutions for non-ambient testing place the hydraulic components outside the temperature chamber, for safety and reliability. Adapters are available to allow other accessories, including compression platens, and bend fixtures, to be attached while leaving the grips in place.
Compression
Compression tests can be conducted on plain or “open/filled hole” specimens. Common testing standards include: ASTM D 695, ASTM D 3410, and ISO 14126. Compression fixtures are designed to meet the unique requirements of composite materials providing precise alignment and precision guidance to prevent buckling.
Compression After Impact
Significant advances in damage tolerant composites include the addition of sheets between plies and additives to the resin. A Compression After Impact (CAI) test helps develop and prove these damage tolerant composites and also the repeatability of their performance. A drop tower is required to provide the impact before a compression test is conducted on a testing machine. Standards include: Airbus AITM 1.0010, ASTM D 7136 and D 7137, SACMA 2R-94, and Boeing BSS 7260. Watch a video on CAI.
Flexure
The most common flex testing of composites is 3-point and 4-point bend testing to ISO 14125, ASTM D 790, and ASTM D 6272.
Shear
Interlaminar, rail, in-plane Iosipescu, and flat sandwich in-plane shear tests can be performed to meet standards: ISO 14129, ASTM C 273, ASTM D 5379, and ASTM D 4255. ASTM D 2344 and ISO 14130 can also be met using an interlaminar flexural and shear testing fixture.
Fatigue
An extensive range of dynamic systems accommodates loads from < 1 - 2500 kN, ideal for meeting the fatigue and fracture testing requirements of composite materials – especially in demanding applications such as aerospace and wind power. It’s important to note that the load frames need to provide high stiffness and exceptional alignment that composite testing demands.
Other Mechanical Tests
A variety of other standardized mechanical tests on composite materials are available. Examples include bearing strength tests to ASTM D 5961 and interlaminar fracture toughness tests to ASTM D 5538.
Composites are complex structures made from a variety of different plastic, metal, and ceramic materials. The mechanical and chemical integrity of composite materials are affected by many variables making property prediction and analysis challenging. Testing is a vital adjunct to analysis, as well as being essential for quality control.
Rheology
The study of the rheological behavior of thermo-plastic based composites is very important for fabrication of end products and plays an important role in determining the material performance related to deformation and flow under the processing conditions. Capillary Rheometers measure the rheological behavior of thermoplastic polymers and composites under processing conditions. Melt Flow Testers measure, with great accuracy, the MFR and MVR - basic data required for thermoplastic quality control in the raw materials field.
Thermo-Mechanical
HDT & VICAT systems are used to characterize the behavior of plastic materials at high temperatures, measuring the heat deflection temperature (HDT) and the Vicat softening temperature (Vicat). These thermal testing systems range from very simple units for quality control labs to more advanced and automated systems.
Tensile
Tensile testing of composites is generally in the form of basic tension or flat sandwich tension testing in accordance with standards such as ISO 527-4, ISO 527-5, ASTM D 638, ASTM D 3039 and ASTM C 297. A range of proven gripping solutions is available for ambient, sub-ambient, and high temperature testing. The gripping mechanisms include manual, pneumatic, and hydraulic actuation. A range of jaw face patterns are available to provide effective gripping of tabbed and un-tabbed specimens. This allows for no slipping under load and no premature failure caused by stress concentrations in the jaws. Hydraulic grip solutions for non-ambient testing place the hydraulic components outside the temperature chamber, for safety and reliability. Adapters are available to allow other accessories, including compression platens, and bend fixtures, to be attached while leaving the grips in place.
Compression
Compression tests can be conducted on plain or “open/filled hole” specimens. Common testing standards include: ASTM D 695, ASTM D 3410, and ISO 14126. Compression fixtures are designed to meet the unique requirements of composite materials providing precise alignment and precision guidance to prevent buckling.
Compression After Impact
Significant advances in damage tolerant composites include the addition of sheets between plies and additives to the resin. A Compression After Impact (CAI) test helps develop and prove these damage tolerant composites and also the repeatability of their performance. A drop tower is required to provide the impact before a compression test is conducted on a testing machine. Standards include: Airbus AITM 1.0010, ASTM D 7136 and D 7137, SACMA 2R-94, and Boeing BSS 7260. Watch a video on CAI.
Flexure
The most common flex testing of composites is 3-point and 4-point bend testing to ISO 14125, ASTM D 790, and ASTM D 6272.
Shear
Interlaminar, rail, in-plane Iosipescu, and flat sandwich in-plane shear tests can be performed to meet standards: ISO 14129, ASTM C 273, ASTM D 5379, and ASTM D 4255. ASTM D 2344 and ISO 14130 can also be met using an interlaminar flexural and shear testing fixture.
Fatigue
An extensive range of dynamic systems accommodates loads from < 1 - 2500 kN, ideal for meeting the fatigue and fracture testing requirements of composite materials – especially in demanding applications such as aerospace and wind power. It’s important to note that the load frames need to provide high stiffness and exceptional alignment that composite testing demands.
Other Mechanical Tests
A variety of other standardized mechanical tests on composite materials are available. Examples include bearing strength tests to ASTM D 5961 and interlaminar fracture toughness tests to ASTM D 5538.
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