This Small Business Innovation Research (SBIR) Phase II project will develop a novel non-contact strain sensor for quality control in production of polymers and fiber-reinforced composites. By measuring residual strains, good parts can be distinguished from bad parts in the production stream. Internal and surface residual strains will be measured by a strain gauge based on the principle of nuclear quadrupole resonance (NQR). A small percentage of tiny additive crystals are blended into the resin during fabrication of the composite. For strain measurement, the composite is irradiated with radio frequencies (RF) to evoke a strain-dependent NQR response from the embedded crystals. Phase I manufactured parts with embedded additive via compression molding. Phase II will build a single-sided strain prototype and measure residual strains in pultruded parts. The NQR-active additive will be introduced into the pultrusion process, and several batches of different types of composites, e.g., fiberglass, will be manufactured. Pultrusion will permit several large batches of samples to obtain the statistics needed to refine the NQR-based quality control method.
Potential commercial applications are expected in many industries, such as civil infrastructure, automotive, sporting goods, aerospace, and many others utilizing composite materials.
