Pultrusion Process Development for Long Space Boom Model

Long flexible-boom models were required to develop ground-vibration test methods for very-low- frequency space structures with applications to the proposed Space Station. Pultruded quasi-isotropic composite beams were selected as an option over extruded aluminum alloy structures because of the lower cost potential, the higher specific strength, the flexural properties, and the dynamic similarity considerations. The reinforcement material that was used was biaxial 0 DEG/90 DEG fiberglass roving held in place with knitted polyester yarn such that equal fiber volume in O deg and 90 deg orientations provided nearly equal strength in both longitudinal and transverse directions. An isophthalic polyester resin system was used as the matrix. Continuous lengths up to 270 ft were easily pultruded with biaxial fabric. Tracking problems were encountered with similar unidirectional fabrics. The analyses of processing problems were conducted to determine causes for delamination, scaling, and sloughing. Ultrasonic C-scanning, scanning electron microscope (SEM) examinations, and mechanical testing to failure were conducted. A comparison is made of four different pultrusions with varied matrices and fiber orientations. Test results indicate that the pultrusion process can be used to produce quasi-isotropic composite structures by selective fiber orientation using the knit-locked fabric concept. (MM)