FEATURE / BONDED JOINTS Figure 15. Typical damage modes in HEWT coupons. Figure 16. Delamination progression as a function of in HEWT model. Uz Displacement Contours (At 61.39 kN) Uz Displacement Contours Uz Displacement Contours (At 65.21 kN) (At 66.72 kN) pre-test predictions were within 5% of the test data which was a goal of the project. Delamination between the face sheet plies were predicted for this coupon. The progression of delamination as a function of load is presented in Figure 16. Even though splice plates were not analyzed for damage, stresses in them were noticed to reach the allowable limit as the model reached failure. Future work is planned to include a PFA model for the fabric of the splice plates. Hence the PFA was capable of capturing the delamination mode of failure between the face sheet plies and not the net section failure of the splice plates. CONCLUSIONS The NASA Composite Technology for Exploration (CTE) Project is developing and demonstrating critical composite technologies with a focus on composite bonded joints; incorporating materials, design/analysis, manufacturing, and tests that utilize NASA expertise and capabilities. The project has goals of advancing composite technologies providing lightweight structures to support 20 | SAMPE JOURNAL | future NASA exploration missions. In particular, the CTE project is demonstrating weight-saving, performance-enhancing composite bonded joint technology for Space Launch System (SLS)-scale composite hardware. Advancements from the CTE project may be incorporated as future block upgrades for SLS structural components. This paper discussed the sub-element longitudinal bonded joint testing and analysis correlation for a generic space launch vehicle structure called the CTE Point Design. The CTE Point Design is a conical sandwich structure with a 35-degree angle consisting of eight composite sandwich segments joined together with a double lap composite joint. A description of the sub-element joint test coupon design was presented for three coupon configurations to test various critical loading conditions including axial and hoop compression and hoop tension. Longitudinal bonded joint sub-element test articles were fabricated and tested for several loading conditions to test the capability of the joint design for the as-designed loads. The test results show that test failure loads for the composite longitudi- M AY/J U N E 2 0 2 0 w w w. s a m p e . o r ghttp://www.sampe.org