Shaping of Microgeometry for Drilling in Composites

Purpose and goal

The hypothesis is that the damage caused in the composite material during drilling can be reduced with a drill whose cutting edges are fitted with micro-geometry. - How are the micro geometry designed, frequency and amplitude in the wave pattern i.e. size on the geometry? - Need more geometric aspects of the drill geometry to be adapted? - Process parameters of the drilling operation For the current hypothesis testing, the project is not the aim to find optimized parameters but only to establish the existence of strong correlations exist. To that extent, these questions have been answered

Results and expected effects

The project has followed and exceeded objectives in terms of validating the correlations between damages in and around the drilled hole and micro geometry. The hypothesis was verified via experiments that showed cutting of the fibers was enhanced by the presence of micro-geometry on the cutting edges on the drilling tool. The project has also taken the hypothesized from TRL 1 to TRL 3 as well as new ideas on how to produce very accurate holes for H6 H7. Numerous publications have been completed through the project.

Approach and implementation

Initially, a literature study on biomimicry concerning shark and piranha teeth´s micro-geometry. The pattern that was finally chosen was made by a parameter study conducted by FEM. For selection of basic drill geometry, a survey among different drills for making holes in carbon fiber was conducted. A system for determining the damages of the hole was developed this system was based on a scoring system that related hole damage to drill geometry and cutting data. Based on this, a prototype drill with micro geometry based on a basic drill geometry.