Torsion impact test

A torsional impact test, developed by the GMC Technical Center, Warren, Mich., was used to compare the relative toughness and impact resistance of structural adhesives. In this test, a 3.6-lb. weight falls in a 20-inch, 90 -arc to impact a one-half inch overlap bonded lap shear positioned at a right angle to the bond. The impact scale reads directly in inch-pounds of force needed to break the bond. Sixty inch-pounds is the limit of the test. Steel and aluminum lap shears severely deform near this limit. Table 4 illustrates the typical values obtained. 

As previously stated, mechanical properties indicate a material s reaction to the application of forces and their values are determined through a series of standard tests. These tests are carried out on small specimens of the material under test until deformed or destroyed. Such tests are referred to as destructive tests. These tests include tensile, compressive, torsion, bend and impact testing and are used to determine the mechanical properties already outlined. 

Two quantities can be measured to describe a material s resistance to crack propagation fracture toughness, IQ, and strain energy release rate, G. Different stress states can be applied, with the most common being the opening mode (Mode I). Materials can also be tested in inplane shear (Mode n) and in torsional shear (Mode III). Testing in these modes typically involves strain rates much lower than those associated with impact teste such as the Charpy and Izod methods. Other methods... 

Comparison of Fluorinated and Unfluorinated HDPE Torsion Test Tensile Test Charpy Impact Test Ballistic Test Degree of Crystallinity Melting Temperature Flow Index... 

Dynamic Mechanical Analysis determines the elastic modulus (storage modulus), viscous modulus (loss modulus) and damping coefficient (Tan 5) as a function of temperature. The test specimens dimension was 3 mm X 13 mm x 20 mm and was the same for those used in the Izod impact test but without a notch. The test specimens were clamped between the movable and stationary fixtures, and then enclosed in the thermal chamber. The frequency, amplitude, and a temperature range of25-220°C were set-up for the material. The analyzer applied torsional oscillation to the test sample while slowly moving through the specified temperature range of 25-220°C. 

Dynamic Mechanical Testing - Film properties such as impact resistance and the cure response of thermosetting resins are conveniently investigated by dynamic measurements in which an oscillatory or torsional strain is applied to the sample with the stress and phase difference between the applied strain and measured stress being determined. In the present study, a Rheovibron Viscoelastometer was used which employed a sinusoidal strain at a... 

ASTM standard specimens and procedures were used for flexure (D-690), compression (D 695), Izod impact and torsional pendulum analysis (TPA). For tension, D1822 tensile impact specimens were substituted for D638 specimens to conserve material. Test specimens were machined from the plates and cylinders using a water cooled dlamond wheel. All the specimens were dried in vacuo at 100°C for three weeks before testing or subsequent postcure treatment. Half the specimens were post-cured for 2 hours at 225°C in vacuo before testing. Selected specimens were Immersed in distilled water at 80°C for 6 weeks for moisture uptake determinations. 

Finite-element methods have also been used to evaluate new test equipment to measure shear strength under impact loads. In the equipment, two rectangular plates, bonded opposite faces of a vertical hexagonal prismatic rod, bear on a firm surface. The top of the central rod is subjected to an impact load. To prove the validity of the method, the maximum shear stress was compared with the impact shear strength, which was measured using a cylindrical butt joint subjected to impact torsional loads (see Tensile tests). 

The mechanical damping of a polymer is related to impact, vibration, and similar dynamic stresses. Although mechanical damping has been correlated with fatigue performance, neither it nor torsion modulus can be used to determine design data, because creep effects are not included in the test. 

The low-temperature testing of fluoroplasties has included tensile, flexural, compressive, torsional and impact determinations. These test results provide a fairly complete profile of the design limitations of the various materials at cryogenic temperatures. These results were obtained using miniature size samples. 

Mechanical Properties. The measurement of mechanical properties is concerned with load-deformation or stress-strain relationships. Forces may be applied as tension, shear, torsion, and compression and bending. Stress is the force divided by the cross-sectional area of the sample. Strain is the change in a physical dimension of the sample divided by the original dimension. The ratio of the stress to strain is referred to the modulus. Stress maybe applied continuously or periodically at varying rates for dilferent tests. The characteristic stress-strain curve, stress relaxation, or impact behavior is very important in determining the applications and limitations of a polsrmer. 

Many of the methods used for characterizing solid materials are applicable to polymers in the solid state x-ray diffraction and crystallography, thermal analyses such as differential scanning calorimetry, mechanical testing for ductility, brittleness, compressive, tensile, and torsional stress-strain relationships, impact, fatigue, creep, etc. 

The HDPE of fuel tanks contains small amounts of fluorine, determined as 0.3-1 g per 10 kg tank, incorporated as a sealant and present as polytetraethylene (PTFE). In Stage 2, to determine the effect of this fluorine, samples of fluorinated and unfluorinated tanks were sawn into small pieces and reground before being formed into injection-moulded test specimens for determination of torsion modulus, and of tensile, impact and ballistic properties. The thermal properties investigated were the degree of crystallinity, melting temperature, and flow characteristics. The measured properties were compared with those provided for in the relevant quality order for new material. 

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