Effect of notch on quasi-static and fatigue flexural performance of Twill EGlass/Epoxy composite

An experimental study has been conducted to investigate the effect of notch on flexural (quasi-static and fatigue) performance of Twill E-Glass/Epoxy composite. Standard specimens and specimens with different types of notches configuration such as circular holes, transverse ellipse, longitudinal ellipse and slot geometry, have been prepared from plates and are considered for the study. Displacement-controlled bending fatigue tests with stress ratio R of 0.10 have been conducted on the selected specimens and damage in the composite has been continuously monitored through the decrement of bending moment during cycling. S–N curves are generated for the targeted composite material by cycling the coupons until failure and recording the number of cycles-to-failure. The results of un-notched specimens are then compared with those of coupons which have the selected notch geometries. Besides, the residual mechanical properties (flexural strength) of the material have been measured after loading the specimens to a preset number of cycles for coupon loaded at 30% and 45% of the Average Failure Load (AFL). The results are used to compare the rate of material degradation among the different type of notches. Finally, it is observed that different notched geometry behave differently for quasi-static and fatigue loading. For composite component subjected to quasi-static load, the failure is mainly governed by stress concentration (local failure) i.e. the notch size is not a significant factor. Whereas for composite component subjected to fatigue loading, the notch size becomes a dominant factor for failure and results to be more relevant than the stress concentration

Bending fatigue behavior of twill fabric E-glass/epoxy composite

Twill E-glass/epoxy composite was considered for its bending fatigue behavior. Displacement controlled bending fatigue tests with stress ratio R of 0.1 were conducted on standard specimens and damage development in the composite was continuously monitored through the decrease of bending moment during cycling. The specimens were subjected to different fatigue loadings with the maximum loading level up to 75% of the material ultimate flexural strength. Early damage was observed after hundreds of loading cycles causing degradation of material stiffness with cycling. The amount of stiffness reduction was observed to be a function of the magnitude of the fatigue loading applied to the specimen. For some selected specimens, after 1 million cycles, fatigue tests were stopped and residual properties were measured. Different levels of reduction on material strength and elastic modulus were found to depend on the level of fatigue loading. Finally detailed discussion is made to correlate the found fatigue data and obtain general description of the material fatigue behavior useful for composite component design

Effect of notch on quasi-static and fatigue flexural performance of Twill EGlass/Epoxy composite

An experimental study has been conducted to investigate the effect of notch on flexural (quasi-static and fatigue) performance of Twill E-Glass/Epoxy composite. Standard specimens and specimens with different types of notches configuration such as circular holes, transverse ellipse, longitudinal ellipse and slot geometry, have been prepared from plates and are considered for the study. Displacement-controlled bending fatigue tests with stress ratio R of 0.10 have been conducted on the selected specimens and damage in the composite has been continuously monitored through the decrement of bending moment during cycling. S–N curves are generated for the targeted composite material by cycling the coupons until failure and recording the number of cycles-to-failure. The results of un-notched specimens are then compared with those of coupons which have the selected notch geometries. Besides, the residual mechanical properties (flexural strength) of the material have been measured after loading the specimens to a preset number of cycles for coupon loaded at 30% and 45% of the Average Failure Load (AFL). The results are used to compare the rate of material degradation among the different type of notches. Finally, it is observed that different notched geometry behave differently for quasi-static and fatigue loading. For composite component subjected to quasi-static load, the failure is mainly governed by stress concentration (local failure) i.e. the notch size is not a significant factor. Whereas for composite component subjected to fatigue loading, the notch size becomes a dominant factor for failure and results to be more relevant than the stress concentration

Parametric study of hot-melt adhesive under accelerated ageing for automotive applications

The mechanical properties of commercially available hot-melt adhesive,HMA,which is mostly used in automotive applications,have been studied under different environmental and loading conditions, paying particular attention to the ageing effects. Three laboratory accelerated ageing processes were applied to single lap joints (SLJs) of two polypropylene substrates in order to replicate the least favourable environmental conditions in automotive usage. Experimental parametric studies were performed on virgin and aged specimens,investigating the influence of two design factors, the overlap length and adhesive layer thickness,on the load carrying capacity and mode of failure of the SLJ. FT-IR was used to perform qualitative HMA polymer composition analyses. The DSC test was also performed to obtain the thermal behaviour,and the phase transition temperatures of the HMA. In addition,the sliding temperature test was performed in an electronically controlled climatic chamber to understand, by means of tests on SLJs, the temperature resistance of the HMA/polypropylene bonded systems. Results clearly show that depending on the type of ageing process,the strength of SLJ basedon HMAs varies, this enhances a relevant difference with respect to the strength of SLJ based on conventional thermosetting adhesive. Furthermore, the parametric study performed revealed the correlation between the strength of the SLJ and its geometry, which might be taken as a design guideline for this kind of flexible adhesive joints

Influence of hybrid (micro- and nano-) fillers on quasi-static and impact response of GFRP composite

Efficient crashworthiness of composite materials is one of the fundamental issues in design of lightweight vehicles to provide high amount of energy absorption, reducing greenhouse gas emissions, fuel cost, and to achieve consolidation of multiple components. In this paper, the impact behavior of hybrid nano-/micro-modified composite laminates was investigated. The laminates used were symmetric Glass Fiber Reinforced Plastics (GFRP) intended for automotive applications. The hybrid nano-/micro fillers were chosen based on their individual and synergistic benefits/contributions during impact loading conditions. Impact testing at particular energy level was performed using drop-weight impact tests (DWIT).The impact response was evaluated in terms of damage progression by visual observations of the impacted specimens, evolution of the peak force and of the bending stiffness with corresponding absorbed energy. Additionally, the damaged specimens were inspected using dye penetration method. Experimental results revealed that the impact response of GFRP varied based on the type and concentration of the filler. Initial results show that the damage resistance is affected by the unique phenomena caused by the presence of micro-/ nano-fillers. A better understanding of these phenomena and their contributions is essential for design of resulting structural components

Validation of a new nano-modified adhesive joining technology triggered by electromagnetic field, by testing a real component

Nowadays, the importance of recycling and reuse of parts and materials is growing, and the automotive industry is asked to meet stricter and stricter criteria in vehicle design; as a consequence, more significance is given to assembling and disassembling processes. Studies have been carried regarding the possibility to use an innovative technology based on an electromagnetic field in order to join components for the automotive industry. This new method relies on nanoparticles embedded into a hot-melt adhesive matrix: these nanofillers respond to an electromagnetic field by heating and by allowing the adhesive to reach melting temperature, thus causing both the enhancement of polymerization while joining of the components and allowing disassembling of those components. Experimental results show that not only this process is simple, not time-consuming and flexible, but also that, once the components have been assembled, an equally easy disassembling procedure is possible by using similar equipment and operative conditions