Composite Testing Services
Test laboratory accredited according to DIN EN ISO/IEC 17025:2005
At its Berlin site, Grasse Zur Composite Testing offers a wide range of material testing according to all common test methods for fiber-reinforced plastics. The testing services are carried out in the DIN EN ISO 17025:2005 accredited laboratory and cover the entire spectrum of material testing. The clients often come from development departments (simulation or new development) or production (incoming goods or production-accompanying quality assurance) in the aerospace, automotive or chemical industries. The focus of the testing services lies equally in the quasi-static (and sometimes strain rate-development) material testing, the cyclical material testing (fatigue tests) and thermal analysis (DSC, DMA, etc.). The tests are carried out in accordance with all common test procedures according to DIN EN ISO or ASTM. Additionally, the employees of Grasse Zur have extensive know-how from many other technical fields.
To determine the quasi-static material properties, tests are carried out on electromechanical testing machines in the force range of 1 to 100 kN. The cyclical material tests are implemented using a servo hydraulic testing machines in the force of 1 to 50 kN. The clamp is tested with flat and round hydraulic cable clamping systems (1 to 25 mm). One-stage and multi-stage fatigue tests on the servohydraulic testing machines can determine Wöhler lines and Haigh diagrams. Extensive test equipment is available for a wide variety of test requirements.
The range of services offered covers the complete field of material testing, from the production of laminates in the VARI process via CNC-controlled test to the execution of material testing. Optional tests include the degree of cure or fiber volume content and the conditioning of specimens and tests at different temperatures. Special test requirements, such as storage in fuels or fractographic examinations of micrographs, are implemented quickly and flexibly. The production and testing of pure resin materials from EP or VE resin systems is offered as well as drop tests for evaluation of splinter protection. Only calibrated measuring equipment is used for the tests. In accordance with aerospace requirements, only strain gauges and Poisson numbers are used to determine the moduli and to ensure accurate measurement of material deformation.
Procedures for Material Testing
After quoting and commissioning, the client receives an order confirmation
The material input is documented according to our accreditation ISO 17025
On the day the material is received, the client will be given a detailed testing timeline
Test Specimen Production
Production takes place with CNC-controlled machines and possibly also includes DMS application
The finished test specimens are measured with calibrated measuring equipment
The material testing is carried out on universal testing machines or analyzers
Preparation of Test Reports
The test reports contain a clear overview of the results and detailed photos
Dispatch of the Tested Specimens
Depending on the order, the shipment of the tested samples is securely packed
At the end of the test project, the client receives a clear summary of the results
Composite Tensile Tests
In the tensile test, the mechanical material properties are determined under quasi-static tensile loading. The tensile test is one of the most commonly used test methods and is also used for composite materials such as carbon and glass fiber reinforced plastic. Basically, a distinction is made between isotropic, anisotropic and orthotropic materials. In the case of anisotropic materials, a fiber breakage load (FB) results in the fiber longitudinal direction (0° fiber orientation) and an intermediate fiber breakage load (IFB) in the fiber transverse direction (90° fiber orientation).
In order to obtain high-quality test results, a precise specimen production is of great importance in this tensile tests. Doppler with a fiber orientation of +/- 45 ° prevents unwanted failure of the specimens in the clamping area (clamping break) due to the lateral force jump. Ensuring very careful processing of the specimen edges is essential in order to avoid complex stress situations and early crack initiation. The use of diamond saw blades or CNC milling machines is state of the art. For carrying out the tests at elevated temperatures, suitable adhesives for the doublers and the strain gauges are used.
Composite Compressive Tests
In the pressure testing of fiber-reinforced plastics, as in the tensile test, a distinction is made between tests in the fiber longitudinal direction (0° fiber orientation) and in the fiber transverse direction (90° fiber orientation). Several methods are available for the tests, which differ in particular in the type of force application (“shear loading”, “end loading” and “combined loading”). The most commonly used method is shear loading, as this most closely simulates the real material load in a component and is very reliable. In the case of end loading, the edge of the test specimen often bursts, since there is an excessively high concentration of stress during this introduction of force.
In order to obtain high quality test results, accurate specimen production is of great importance in the pressure testing of fiber reinforced plastics. Buckling of specimens should be avoided in order to obtain valid test results. By using two independently measuring strain gauges, buckling is determined. Since the strain gauges are very small and must be applied to a free specimen length of only 10 mm, a very precise alignment in the longitudinal direction is required.
Composite Shear Tests
Different methods are established to determine the shear strength. These differ in the type of force application (as comprehensive force over the specimen or as frictional force on the jaw systems) or in the geometry of the test specimen (unnotched, notched, miniaturized). In addition, the established tensile test can be converted into a shear test through a fiber orientation in a +/- 45° direction, and also statements on the shear strength can be determined from the bending test. All established methods can produce reliable results for low shear deformations (<5%) and thus low shear forces.
However, the reliable characterization of high-performance fiber composites is becoming increasingly important. In addition to the established test methods with the shear test according to DIN SPEC 4885, many at Grasse Zur are trained in the BAM Federal Institute for Materials Research and Testing method. With this experience, much higher glides and thus higher strengths can be tested than before.
Composite Bending Tests
The procedures according to DIN EN ISO 14125, DIN EN ISO 178 and DIN 53293 are mostly used for the bending tests on fiber reinforced plastics (FRP) and on sandwich structures (core composites). A 3-point or 4-point load can be used for the bending test. By means of the various test methods for FRP, the bending strength and the flexural modulus are determined under a bending load of the specimen under defined test conditions. The principle of the bending test consists in a two-part bending process, in which the specimen is clamped as a bending beam between two outer supports and loaded via one (3-point) or two (4-point) inner supports. The test is carried out at a constant increasing speed to a given deformation or until the failure of the sample. As a result, the bending stress and the flexural modulus are determined.
When stressing composite or sandwich material, a 4-point bend has an advantage over the 3-point bending test. A 4-point bend has a constant expansion and a bending curve occurs between the inner supports. It should be noted that in the 4-point bending test between the outer and inner supports an additional shear stress occurs. The bearing distances, i.e. the lever arms, are to be selected so that the shear strength of the material is undercut. The test area between the inner supports is free of shear stress.
Composite ILSS Tests
The Short Bend Test Method for Determining Apparent Interlaminar Shear Strength (ILSS) is a modification of the 3-point bend test. The bearing distance is small in relation to the specimen thickness, whereby the specimen is subjected to shear stress. The specimen is a short bar made of a thermosetting or thermosetting matrix with a fiber reinforcement in the 0 ° or 0 ° / 90 ° direction. With apparent interlaminar shear strength, the standard refers to “the maximum shear stress in half the thickness of the specimen at the moment of the first failure”.
The standard indicates limitations of this test method. Depending on the material selection, “the result may be influenced by various couplings such as elongation/bending/twisting etc”. It is possible that the specimen will fail due to bending or plastic deformation. A statement about the actual shear stress at the moment of failure is then not possible. To determine constructive sizes, the method is unsuitable. However, it can be used for material preselection or for quality control. The calculated value is not an absolute value, test results are comparable only within a series. The disadvantage is that the ILSS method requires very small and geometrically simple specimens. With little material expenditure, a qualitative statement about the fiber-matrix bond is generated.
Composite Thermo Analysis
The thermoanalytical test of fiber reinforced plastics plays a large role in the characterization of material properties. In particular to the determination of the matrix dominating material qualities (intermediate fiber fracture) like shear or transverse tensile properties, a complete picture results only through the knowledge of matrix properties. For example, if there is an incomplete cure (Alpha <95%), cure reserves are available, which can significantly increase the compressive strength, especially at elevated temperatures. Also, a determination of the actual and maximum glass transition temperatures Tg is useful, e.g. to be able to determine the influence of tempering and the mixing ratio. There are several methods available, such as DSC or DMA, which provide the information in different physical ways.
Please fill out the following form to send you an offer. If the desired test standard is not listed, please enter the standard in the comment field. For larger test programs, please use the comment field, too. After sending the test request you will receive a non-binding offer from us promptly.