Experimental studies of thin-ply laminated composites

A new processing method was developed for spreading fiber tows to make thin-ply laminated composites. The present method with a constant airflow through sagged fiber filaments can efficiently spread the thick tows without damaging any fibers. This method is robust and easy compared with other available thin-ply methods. The thin plies of thickness less than one-third of the conventional plies can easily be made with the tow-spreading technology.Experiments were performed to evaluate the performance of tow-spread, thin-ply laminated composites. To study the thickness effect of the laminated composites, the test specimens were made with the same material and the same spread tows, but with dispersed and grouped laminations of the plies. Uniaxial tension static and fatigue loadings were applied on both unnotched and open-hole specimens. Impact and compression-after-impact tests were also conducted. From stress–strain curves, acoustic emission counts, X-ray photos, c-scan images and observation of damage modes of failed specimens, it was observed that the thin-ply laminated composites can suppress the microcracking, delamination and splitting damage for static, fatigue and impact loadings without special resin and/or 3-D reinforcements. Therefore, the laminate design can be simplified by using higher strain allowable without a progressive failure analysis.