The cantilever beam test is a test in which one end of a specimen is clamped, and the load is applied on the free end, causing the material to be under bending stress. It is a very simple yet handy test apparatus that is commonly used in the study of materials science (both dynamic and static properties). ASTM has also standardized practices whereby cantilever beam configuration is used in performing different procedures, such as fatigue testing on plastics, environmental stress-cracking resistance, and flexural strength determination. With these standards, researchers and manufacturers will have the chance to acquire consistent and reliable information to quantify the performance of the material.
Key ASTM Standards
ASTM D671– Standard Test Methods for Flexural Fatigue of Plastics (Using Cantilever Beam Specimens): The main standard that is used to assess the fatigue resistance of plastics is by placing repeated loads on specimens of plastics through bending till failure.
ASTM D790 Standard Test Methods Flexural Properties of Plastics and Electrical Insulating Materials. Although the test method is concerned with the study of such static properties of the material as the flexural modulus and the flexural strength, it is also possible to adjust the test setup to a cantilever beam style.
ASTM D7774 Standard Test Method for Flexural Fatigue Properties of Plastics (Using Uniaxial Cyclic Loading): Another method of testing flexural fatigue is available in D671, though it involves controlled uniaxial cyclic loading.
ASTM D1693 Standard test method of environmental stress-cracking of ethylene plastics is a test method involving a bent strip or cantilever-type configuration to measure the resistance to cracking of both mechanical and environmental effects on the plastics.
Methodology
The ASTM cantilever beam tests start with proper specimen preparation, whereby the specimen must be prepared with standardized dimensions and the same quality of surfaces to remove external variables. One end of the specimen is then firmly clamped so that it serves as the firm support, with the other end free so that the load can be applied. The load applied can be either a static or cyclic load, or it can apply the environmental conditions like temperature and humidity, depending on the objective of the test. In the test, stresses on the specimen are applied as bending forces till failure, crack initiation, or a predetermined number of cycles is achieved. The most important parameters that are monitored throughout the process are displacement, load response, and the number of cycles to failure.
Applications
Cantilever beam testing is predominant in industries where materials undergo stresses that are related to bending in the course of service. It also analyzes the longevity of plastic brackets, clips, and other building components in the automotive industry. It guarantees the strength of hinges, snap-fits, and flexible joints in consumer products. It is applied in the electronics industry to test the functionality of insulation and housing materials that have been subjected to vibrations and repetitive handling.
Importance
Cantilever beam test is very important as there are conditions in real life where materials are subjected to repeated or sustained bending stresses. In contrast to the testing of the static strength of a material, which involves measurements of how much load a material can hold at any one moment, this testing gives insight into the long-term durability and failure behavior of the material under cyclic or environmental stress. Stress levels at which fatigue and cracking tend to take place are often much less than the strength in the static test, and, hence, standardized cantilever beam testing is essential for in-service life prediction.
