Instron’s CEAST 9340 Drop Weight Tester is a floor-standing system designed to deliver
impact energies from 0.30 joules to 405 joules the corresponding falling weights range from 1
kilograms to 37.5 kilograms with a full range of accessories, the system is suitable for many
applications including tensile impact and penetration testing of plates and films, testing of pipes and
small components. This machine consists of three main parts: a turret, a test chamber, and a control
box. The turret is the upper part of the machine inside the turret there are a motorized cross
head positioning system, set of weights to deliver a range of impact energies, changeable tops and
inserts for different applications, anti-rebound system preventing secondary impacts, photocell used
to measure the velocity of the top just before the impact and to activate the top anti-rebound system.
The base is equipped with a thermostatic chamber for specimen conditioning
and testing between -50 degrees c to 100 degrees. The chamber is heated by means of thermal elements.
It is cooled through liquid nitrogen taken from an external tank. Different stands can be used
for testing depending on the application this machine is currently equipped with two stands:
fixed high stand for single specimen support up to 25 millimeters thickness, support stand
for compression after impact testing. The control box is attached to the right side of the turret
and is provided with the remote operation mode including power on emergency buttons
and lcd display impacting of the specimen can be controlled by the control box. CEAST impact
software is used to display and analyze recorded data which is transmitted via data acquisition
system this impact tester will record the load and deflection during the impact event.
These data are essential to understand the impact resistance or impact damage of specimen. In today's
demonstration we will perform a puncture test on a carbon fiber reinforced laminate.
The laminates were manufactured by laying up 20 layers of woven carbon fiber prepreg. Afterwards,
they were vacuum backed and autoclave cured. Each specimen has dimension of 150mmx100mm
and a thickness of 4.3mm. Let us prepare the machine for the test once the
power is on the machine needs to be calibrated to the home position. After that, switch on the data
acquisition system and run software on the pc. Next we need to set up the test method in the software.
The specimen will undertake the puncture test according to ASTM D5628 at room
temperature. The impact energy selected for this testing method is 30 J. The specimen support
has a diameter of 40 mm. 0.5 kilograms of additional mass is added to the top holder for
this impact event. The sampling frequency is 1000 kilohertz the clamping and anti-rebound options
are enabled. In the next step a photocell is adjusted based on the falling height and specimen
thickness. This allows an accurate measurements of the velocity just before the impact. In this case,
the photocell scale must be set at 19mm. Afterwards, the specimen is loaded into the chamber.
Before the test the specimen is automatically clamped. This machine comes with a clamping device
which allows for the clamping of the specimen on the support with up to 3kN
force before the impact. Once all the parameters are determined we can start the test inside the
turret the tap releasing unit first travel to the desired position, then drop the top from that
height. The sample could be partially or fully penetrated. If the penetration of the specimen
is partial, the anti-rebound system will clamp the tap to avoid bouncing. Finally, the tub returns to
the original position and data is transferred to the software. Data can be plotted in many forms,
for example force vs time, force vs displacement, impacted energy and so on. The software has
post-processing function of the results. Now let us examine the impacted sample. There is clearly some
visible damage to both surfaces. Often impacting with lower energies causes invisible internal
damage. To fully investigate the damage tolerance, other techniques such as CT scan are employed.