Meaning
The dynamic measurement of the force and energy required to puncture a plastic specimen using a weighted tup equipped with sensors provides a precise profile of material behaviour under rapid impact. An instrumented drop test measures the full deformation history of the specimen from first contact to total penetration. This method goes beyond simple pass or fail testing by showing the transition from elastic behaviour to failure.
Moulders rely on this data to evaluate how parts will behave in real life crash or drop scenarios.
Data Capture
High-frequency sensors in the load cell of the falling weight record the resistance of the plastic plate during the split-second impact event. During an instrumented drop test the raw force data is integrated over time to generate velocity and displacement curves. This continuous stream of information allows technicians to calculate the energy absorbed at specific points such as the peak load or the initiation of crack propagation.
Having this level of detail makes it possible to distinguish between a ductile ductile failure and a brittle shatter.
Material Assessment
Evaluating the toughness of different polymer formulations requires testing under identical temperature and velocity conditions. The instrumented drop test shows how well a resin holds up against multiaxial stresses. Unlike unnotched Izod or Charpy tests that measure force in one direction this method applies stress across multiple axes which replicates the conditions of a dropped part.
This is especially helpful for evaluating the performance of recycled resins compared to virgin materials.
Moulding Evaluation
The thermal and mechanical history of an injection moulded part can create internal stresses that are invisible to the naked eye. Applying the instrumented drop test to finished mouldings or specimens cut from them reveals the presence of molded-in stress or weak weld lines. If the injection speed was too fast or the melt temperature too low the polymer chains can align in ways that create weak directions in the part.
Tests carried out on different areas of the part can pinpoint where the injection process has created these vulnerable spots. This information allows the moulder to adjust processing parameters like hold pressure and gate location to make the finished parts stronger.
