Abstract High Strength Low Alloy steels (HSLA) for oil and gas pipelines should display high mechanical strength, toughness, ductility and weldability. In this work we studied the influence of quenching and tempering temperature on the yield strength, ultimate tensile strength, percent elongation and hardness of API 5L steel pipes in order to optimize heat treatments to be performed after hot induction bending of the material. The thermal cycles involved soaking temperatures of 880, 920 and 960 °C, cooling water at 15, 23 and 31 °C and tempering at 530, 600 and 670 °C. From this, experimental design techniques were used to reduce the number of experiments. The results from contour maps suggest that soaking temperatures of 910 and 950 °C and tempering between 540 and 610 °C were the most suitable for treatment, regarding mechanical strength. The variation of the water temperature was not significant for the assumed cooling conditions. The prediction regression models of the mechanical properties from the variables involved in the heat treatments showed a good fit between the experimental and predicted results, with correlation coefficient between 0.89 and 0.94.

The giant bamboo fiber is among the strongest in the Bambusa species with a potential for application as engineering material. Its properties have been evaluated but there is limited information on the impact resistance of epoxy composites incorporated with giant bamboo fibers. Therefore, this study evaluated the Charpy impact energy of epoxy matrix composites reinforced with up to 30 vol% of giant bamboo fibers. Specimens with Charpy configuration were press-molded with continuous and aligned giant bamboo fibers reinforcing a DGEBA-TETA epoxy as the composite matrix. The energy absorbed by the composites was obtained in standard impact tests and the fracture surface of ruptured specimens was analyzed by scanning electron microscopy, SEM. The impact energy was found to increase exponentially with the amount of incorporated fiber. SEM observations revealed the mechanism of crack propagation both in the brittle epoxy matrix and in the fiber interface of the composites.

The ballistic performance of a multilayered armor with a front ceramic tile backed by a plate of giant bamboo fiber reinforced epoxy composite was assessed. The ceramic layer spalls the projectile, while the bamboo composite dissipates the remaining energy. Ballistic tests were performed with high velocity ammunition and the projectile penetration was evaluated by the intrusion depth in a clay witness. The average depth value of near 18 mm was found well below the limit specified by the NIJ standard of 44 mm and better than that for aramid fabric composite, about 22 mm, with the same thickness of the giant bamboo composite. The giant bamboo composite acts as an efficient barrier for the fragments originated from the ceramic brittle rupture. For practical application in portable armor for personal protection, the layer of giant bamboo composite presents not only a superior ballistic performance but also lightness and economical advantages over the conventional aramid fabric.