Our research focus on enhancing the interface toughness and impaired resistant of fiber composites. We are trying to improve the impaired resistance of fiber composites by incorporating nano particles. One of the most common challenges in fiber composite fabrications is the lack of repeatability.
Through precise control of the fabrication task and quantification of material proportions, we can obtain laminates with very stable mechanical properties. This approach ensures highly repeatable test result across different batch. The WLEB process for fabricating combos is laminates, use the ranking back to remove air bubbles.
Compared to other processes, this process has lot of advantages. It requires simple equipment in both process technologies that is not complicated and the products are also not limited by size or shape. Begin by heating the glass fiber fabric at 60 degrees Celsius for eight hours.
Then paste an isolation film on the acrylic sheet to prevent the resin from bonding. Position the mold in the laying area. Gently mix the resin and hardener for five minutes before placing it in a vacuum chamber to remove air bubbles.
Place a non-porous release film on the mold and secure it with tape. Then lay one peel ply on the non-porous release film. Pour epoxy resin on the film and evenly distribute it throughout using a scraper.
Next, ply the first fiber fabric on the resin. Roll the fabric with a naked roller to ensure bubble removal and complete resin infiltration into the fabric. Again, pour and evenly spread the resin on the fabric using a scraper and continue til all the fabric has been used.
Place a peel ply on the fabric and manually remove air bubbles by scraping in one direction. Lay a perforated release film followed by a breather fabric. Position the suction channel and breathable pad to one side.
Secure a circular heat resistant tape with an acrylic sheet outside the mold and attach the vacuum bag at the top of the device to create a closed space. Apply vacuum for 10 hours at room temperature. Then switch off the vacuum pump and maintain quiescence for 14 hours.
Cure the laminates completely at 80 degrees Celsius for 16 hours before measuring the fiber volume fraction. Comparison of laminates fabricated by the wet hand layup method with and without the vacuum bag process revealed that the vacuum bag assistance, the fiber volume fraction of the laminates increased by 15.78%and their average thickness reduced to 2.11 millimeters. To begin the impact test of glass fiber reinforced polymer or GFRP composite laminates, cut a set of 150 millimeter by 100 millimeter GFRP samples using a high precision cutting machine.
Record the weight and size of each sample. Then mark the positions of the samples using positioning nails in their centers that the impactor can contact for every test. Fix the sample onto the impact support fixture using four rubber tips.
Power on the drop hammer testing machine to conduct the impact test using a drop weight impact tower. After connecting it to the controller, click Home to do the beam reset and then click Before Test. Input the measurement thickness as 2.1 or 2.5 millimeters for WLVB or WL samples respectively.
Set the additional mass to two kilograms and the impact energy to 10 joules. Click start to initiate the experiment. Record the impact response data, such as force, deflection, and energy history.
Remove the sample and document its morphology after the impact. Finally, calculate and compare he data of each sample. Great repeatability of the impact test was evident from the obtained force and absorbed energy curves of samples fabricated by WLVB and WL methods.
The force time curve represented a typical non piercing curve, having a sine wave-like shape. The absorbed energy value increased first with the laminate absorbing and converting the impactor's kinetic energy into its internal energy, and then the value decreased over time, as the laminate released elastic energy to rebound the impactor. The specific absorbed energy of the WLVB sample was larger than that of the WL sample.
The WLVB laminates absorbed 19.48%more specific energy compared to the WL ones. Further, the higher impact energy absorption capacity of WLVB samples was confirmed by their relatively smaller damaged area. To begin the tensile test, using a high precision cutting machine equipped with a diamond cutter, cut 250 millimeter by 25 millimeter samples from the glass fiber reinforced polymer or GFRP laminates.
Measure sample dimensions with a veneer caliper. Attach four aluminum tabs on both ends of the sample using epoxy adhesive to prevent stress concentration. Spray a thin layer of white paint on the front of the sample, followed by spraying black speckles.
Position the sample in the tensile testing machine's center clamps. To set up the image acquisition system, ensure the sample is vertically placed in the middle of the camera shooting area. Adjust the camera focal length and exposure rate to clearly record the spots on the sample.
Next, in Configure Test, set the test speed to 0.5 millimeters per minute. Select specimen data and input the sample's specimen thickness and specimen width before clicking on run test. Click Start and select Accept Current Position to record the load time data.
Remove the sample and record its morphology after the test. Measure the nominal strain of the sample using the tensile test. Using digital image correlation or DIC software, first click Length Scale Image and calibrate the pixel length.
Then click on Reference Image and choose the first image as the reference image. Click deformed image to choose the remaining images as deformed images. Use drawing tools and Select Rectangle to designate the measurement area.
By clicking extensometer, set the extensometer length to 100 millimeters and the angle to 90. Initiate correlation by clicking Processing and Start Correlation. First, divide the load by the cross-sectional area to determine the nominal stress.
Then, combine the nominal strain from the DIC measurement and the nominal stress from the tensile testing machine. Select the slope of the linear segment in the strain stress curve as the elastic modulus and choose the peak value of the tensile force time curve as the strength. Finally, compare the elastic modulus and strength of the samples.
The tensile modulus and strength of laminates fabricated by the WLVB process were higher than those fabricated using the WL process. The WLVB process increased the tensile strength and modulus of the laminates by 17.4%and 16.35%respectively. After the tensile test, both WLVB and WL samples displayed fractures near their central portions.
However, the delamination length of the WL sample is longer than that of the WLVB sample.
