Mechanical and physical testing of composite materials is important to determine and evaluate their properties. These characteristic properties help us understand the deformation characteristics and failure modes which can further be used in design and analysis of end products. Composite material testing is typically carried out by subjecting the material samples to a variety of deformation modes.
1. Uniaxial Tension Test
The uniaxial tensile test is the primary method to evaluate the material and obtain the parameters. Uniaxial tension test is also the primary test method used for quality control various mechanical properties such as the yield strength, Young’s modulus, Poisson’s ratio etc. are obtained. Strain hardening and true stress-strain etc. values can be calculated from the stress-strain curve.
2. Three (3) Point Bend Flexure Test (ASTM D790)
Three point bending testing is done to understand the flexural stress and strain of composite and thermoplastic materials. The specimen is loaded in a horizontal position, so that the compressive stress occurs in the upper portion and the tensile stress occurs in the lower portion of the cross section.
3. Four (4) Point Bend Flexure Test (ASTM D 6272)
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.
4. 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. For this test method, Poisson’s ratio is obtained from strains resulting from uniaxial stress only.
5. Combined Loading Compression Test
ASTM D6641 is the testing specification that determines compressive strength and stiffness of polymer matrix composite materials using a combined loading compression (CLC) test fixture. This test procedure introduces the compressive force into the specimen through combined shear end loading.
6. Axial Fatigue Test as per ASTM D7791
ASTM D7791 describes the determination of dynamic fatigue properties of plastics in uniaxial conditions. Rigid or semi-rigid plastic samples are loaded in tension (Procedure A) and rigid plastic samples are loaded in compression (Procedure B) to determine the effect of processing, surface condition, stress, etc., on the fatigue resistance of plastic and reinforced composite materials.
All of our composite material testing and characterization work is carried out on state of the art electro-mechanical and servo-hydraulic testing machines with stress and strain controls, with contact and non-contact measurement systems.