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In recent decades, the application of composite materials in aerostructures has significantly increased, with modern commercial aircraft progressively replacing aluminum alloys with composite components. This shift is exemplified by comparing the material compositions of the Boeing 777 and the Boeing 787 (Dreamliner). The Boeing 777 incorporates approximately 50% aluminum alloy and 12% composite materials, whereas the Dreamliner reverses this ratio, utilizing around 50% composites and 12% aluminum alloy. While metals remain advantageous due to their availability and ease of machining, composites offer greater potential for property tailoring to meet specific performance requirements. They also provide superior strength-to-weight ratios and enhanced resistance to corrosion and fatigue. To ensure the reliability of composites in aerospace applications, comprehensive testing under various loading conditions, particularly impact, is essential. Impacts were performed on quasi-isotropic (QIT) carbon-fiber reinforced epoxy panels with stainless steel, round-nosed and flat-ended impactors with rubber discs of 1-, 1.5- and 2 mm thickness, adhered to the flat-ended impactor to simulate the transition between hard and soft impact loading conditions. QIT composite panels were tested in this research employing similar lay-ups often being implemented in aircraft wings and other structures. The rubber discs were applied in the flat-ended impactor case but not for the round-nosed impactor due to the limited adhesion between the rubber and the rounded stainless-steel surface. Impact energies of 7.5, 15 and 30 J were investigated, and the performance of the panels was evaluated using force-time and force-displacement data alongside post-impact ultrasonic C-scan imaging to assess the damaged area. Damage was observed at all three energy values for the round-nosed impacts but only at the highest impact energy when using the flat-ended impactor, leading to the hardness study with adhered rubber discs being performed at 30 J. The most noticeable difference with the addition of rubber discs was the reduction in the damage in the plies nearest the top (impacted) surface. This suggests that the rubber reduces the severity of the impact, but increasing the thickness of the rubber from 1 to 2 mm does not notably increase this effect. Indentation clearly plays a significant role in promoting delamination at low-impact energies for the round-nosed impactors. Full article

High-performance fibers are well-known for their high stiffness and strength under axial tension. However, in their many applications as critical components of textiles and composites, transverse loads widely exist in their normal service life. In this study, we modified a micro material testing system to transverse load single fibers using round-head indenters. By integrating the loading platform with the Scanning Electron Microscopy (SEM) operating at a low-vacuum mode, we visualized the failure processes of fibers without conductive coatings. Post-fracture analysis was conducted to provide complementary information about the fibers’ failure. The energy dissipation was compared with the axial tensile experiments. Three inorganic and two organic fibers were investigated, namely carbon nanotube, ceramic, glass, aramid, and ultrahigh molecule weight polyethylene fibers. Different failure characteristics were reported. It is revealed that the organic fibers had higher energy dissipation than the inorganic fibers under the transverse loading by the round-head indenters. The fiber’s energy dissipation under transverse loading was no more than 17.9% of that subjected to axial tension. Such a reduced energy dissipation is believed to be due to the stress concentration under the indenter. It is suggested that the fiber’s material constituent, structural characteristics, and stress concentration under the indenter should be considered in the fiber model for textiles and composites. Full article