The effect of shock wave impingement on thin, woven glass fiber reinforced, polymer composite plates.

摘要

High-performance fiber-reinforced polymer (FRP) composites have been increasingly used in many applications over the last 30 years. Their high specific stiffness, specific strength, and energy absorption capacity have made them attractive as replacements for traditional materials. While the dynamic response of homogeneous or monolithic materials has been well documented, the response of FRP composites is still under investigation. Knowledge of the response of FRP composites under this type of loading is essential to evaluating its performance as a structural or protective material. While such information starts to be slowly available, the effects of dynamic thermomechanical extremes such as shock wave loading on the FRP composites is relatively unknown.;The challenge then is to develop a consistent laboratory methodology that allows investigations of the interactions between a FRP composite and a shock wave and eventually testing of such materials for performance evaluations under shock loading.;Measuring the deformation of test specimens caused by shock wave impingement of different intensities was basic to understanding the gross effects on the FRP composites. In early tests, displacement across the diameter of the test specimen was measured after the end of the test giving a static measurement of the permanent deformation. To allow meaningful comparisons between disparate materials subject to different shock wave intensities a method of weighting and normalizing the was developed. The complexity of setting up and running a shock wave test limited the number tests could be performed, so while the results aren't statically robust, the trends observed are useful in comparing or choosing among different materials.;A Time-Resolved Catadioptric Stereo Digital Image Correlation (TRC-SDIC) technique was developed which provide a non-contact, full-field method of measuring deformation over the time span from the impingement of the shock wave including the maximum deformation of the test specimen. The technique has been validated by comparing the results obtained in a static experiment with the results measured by laser displacement sensors. Additional validation of dynamically obtained strain measurements was carried out by using a 13 mm (1/2") thick in-house fabricated composite specimen with embedded strain gauges and piezoelectric sensors. Surface mounted sensors due to the large inertia forces experienced by a test specimen tend to detach from it almost immediately after the shock impact, so very little useful data could be collected.;The present work has created a strong foundation in testing methodology and baseline results in studying the effects of shock wave impingement on FRP composites. It was found that the maximum deformation of the plate occurs immediate after the shock impact and much before the whole loading cycle is completed. The results of permanent deformation have been normalized by using the impulse of the loading force.;Additional work has been focused on the energy exchange between the incoming shock wave and the specimen. Understanding how much energy is associated with the shock reflection, transmission, absorption, or passed through is critical to designing protective systems using FRP composites.