Design of glass/phenolic ballistic composites by implementation of factorial experimental design

The purpose of the study is to assess the applicability of full factorial experimental design in predicting the ballistic strength of glass fiber/phenolic ballistic composites. In the study we used a number of ballistic composites (20 cm x 20 cm) with different thickness and fiber/resin ratio. The composites were made by an open mold high pressure, high-temperature compression of prepreg layers made of plain woven glass fiber fabric and polyvinyl butyral modified phenolic resin. The preparation of the composite experimental samples was done in accordance to 2 2 full factorial experimental design. The areal weight of composites is taken to be the first factor and the second – fiber/resin ratio. The first factor low and high levels are 2 kg/m2 and 9 kg/m2, respectfully and for the second factor – 80/20 and 50/50, respectfully. We used the first-order linear model with interaction to approximate the response i.e. the ballistic strength of the composites within the study domain (2 – 9) kg/m2 x (80/20 – 50/50) fiber/resin ratio. The influence of each individual factor to the response function is established, as well as the influence of the interaction of the two factors. We found out that the estimated first-degree regression equation with interaction gives a very good approximation of the experimental results of the ballistic strength of composites within the study domain.