From preparation to final product, manufacturing a bow limb is complex and expensive. The composite manufacturing processes currently most utilized for both vertical bows and crossbows typically produce products with widely varying properties. This variability can lead to internal defects or other failure points such as matrix crazing, delaminiations, fiber pullout, and fiber breakage, any of which could cause product failure. For bow manufacturers, that’s a serious liability, but unfortunately there hasn’t been a reliable and non-destructive method to test for these kinds of defects before a bow leaves the factory.
At Stress Outdoor®, we hypothesized that we could solve this problem using Acoustic Emission Testing (AET) technology. We tested both a “good” bow limb as well as one we created with
intentional volumetric defects, subjecting them both to bending forces while monitoring AE sensors affixed to each limb. The results showed that AET clearly identified the internal defect in the damaged limb, while revealing a clean bill of health for the defect-free limb.
More research is needed, but our experiment shows that AET holds promise as a nondestructive means of product testing, which could help to eliminate limbs with latent defects from the product field all together. The elimination of defective limbs would not only result in much safer products for the end user, but could dramatically reduce the warranty claims and product liability for the manufacturer. The early findings derived from our AE testing could lay the groundwork for continued development of a nondestructive production proof-test where limb quality can be defined and screened before it ever reaches the hands of the consumer.