This article focuses on the development of a carbon composite bicycle frame using various experimental methods of structural analysis. Two types of frame specimen were used. The complete frame specimen was tested in accordance with ISO test load cases with the addition of an ergometer test in order to refine the operational strain envelope of such a frame. Resistive strain gauges and optical Fiber Bragg Grating (FBG) sensors were used for this analysis. The FBG sensors were embedded inside the head tube joints during the manufacturing process. The head connection was designed as a geometrically precise form–connection of wound composite tubes, reinforced with a wrap of high-strength unidirectional carbon tapes and carbon fabrics. Additional structural strength laboratory tests were conducted using simplified frame specimens, in order to evaluate the range of the limit case strain ranges. The digital image correlation method was used for the evaluation of the strain distribution in the head tube area. Resistive strain gauges were used for local strain analysis in critical areas. The acoustic emission method was used to detect structural defects before they could influence the stiffness response of the frame. It was found that the joints of the frame tubes are crucial for the strength and safety of the frame. Therefore, attention was also focused on the strengthening of the head tube joint, and on its experimental verification. A positive effect on the strength of the reinforced frame was found by doubling the thickness of the carbon fabric in the head tube joint area.

Structural Health Monitoring (SHM) of composite structures leads to greater safety during operation and reduces the cost of regular inspections. Impact damage detection is an important SHM task. Since impact damage can significantly reduce the lifetime of composite structures, sensors for impact damage are of great interest. Carbon Fiber Sensors (CFSs) can be used to detect composite damage. CFSs are lightweight and compact, and they can be integrated during the manufacturing process. In our study, CFSs were manufactured from three types of carbon fiber tows and were integrated into different layers of the lay-up in order to investigate the influence on impact damage detection. The effect of mechanical loading and temperature change on the measured electrical resistance was investigated during cyclic flexural tests. It was revealed that, it is possible to distinguish between changes in measured signals due to impact and due mechanical loading. The change in the measured electrical signal caused by temperature can be eliminated. CFSs can be used for impact damage detection of a glass fabric composite. A combination of thermography and CFSs as an active heating element also provides good results in the field of impact damage detection

This paper is focused on the design of the health and usage monitoring system (HUMS) of the composite ultra-light aircrafts. A multichannel measuring system was developed and installed for recording of the long-term operational measurements of the UL airplane. Many fiber Bragg grating sensors were implemented into the composite aircraft structure, mainly in the glue joints. More than ten other analog functions and signals of the aircraft is monitored and can be correlated together. Changing of the FBG sensors responses in monitored places and their correlations, comparing with the calibration and recalibration procedures during a monitored life may indicate damage (eg. in bonded joints) and complements the HUMS system.

This paper presents findings on the sensing capabilities of carbon fiber sensors (CFSs) for detecting impact damage in composite structures. New insights are provided into the correlation between stiffness degradation after impact and the measured response of integrated CFSs, placing both recent...

The presented article focuses on the design of composite tank which consists of wound cylindrical part (manufactured by the means of filament winding) which is bonded together with domes (manufactured by spraying or light resin transfer molding - LRTM technology). Composite structure was manufactured from glass/polyester material system by company ACO Industries Tábor . The article describes the possibility of using a bonded joint on cylinder/dome interface. This possibility was experimentally tested on specimens and also numerical simulation of full-scale model (finite element method - FEM) was performed. Developed construction is used for underground water treatment application and it is loaded with both the weight of the retained water and the pressure of the soil and groundwater during its deep burying.

Surface water management is one of the main topics nowadays. The Glass Reinforced Plastic (GRP) surface water treatment tank is one of the important parts of the system chain solution. GRP tanks are placed below the surface, and during the placement process, high loads can occur on the tank structure. The possibility of monitoring loading using sensors is being investigated. Resistive and optical sensors were installed on the surface of the vessel, and verification measurements were performed during the vacuum test of the vessel. The obtained results were compared with the FEM calculation.