Surface Treatment of Composites with Bismaleimide Resin-Based Wet Peel Ply for Enhanced Adhesive Bonding Performance

Surface treatment is typically required to improve the bonding performance of carbon-fiber-reinforced composites. Herein, a wet peel ply was prepared using bismaleimide (BMI) resins as a matrix resin. The temperature–heating rate extrapolation method and rheological method were employed to study the reaction characteristics and viscosity-temperature characteristics of the matrix in the BMI wet peel ply. The curing temperatures of the BMI wet peel ply and the BMI prepreg were the same (200 °C), making this wet peel ply suitable for co-curing with the BMI prepreg. After treatment with the wet peel ply, the bonding strength of the BMI composite joint showed a mean shear strength of 35.5 MPa, which was 1.72% higher than that of the sanded composite and 17.5% higher than that of the composite treated with the dry peel ply. In addition, the BMI composite treated with the BMI wet peel ply exhibited good bonding stability with a coefficient of variation of 3.9. After damp-heat aging for 1440 h, the retention rate of shear strength at room-temperature was 82.3%. The relatively loosely woven carrier in the BMI wet peel ply increased the surface roughness of the composite, thus improving the bonding strength.

MANUFAKTUR PANEL MATERIAL KOMPOSIT DENGAN METODE INFUSI RESIN

Pembuatan alat ini ditujukan untuk menghasilkan suatu produk panel rata ataupun bentuk lain yang terbuat dari bahan komposit polimer yang diperkuat serat dengan metode infusi resin. Bahan polimer yang digunakan pada penelitian adalah polimer epoksi Eposchon A&B yang diperkuat serat gelas woven roving 600. Pompa vakum digunakan untuk menginfus resin kedalam cetakan yang telah diisi dengan serat. Trap pot ditempatkan antara selang keluar cetakan dan pompa vakum. Kain teflon dan Peel ply digunakan untuk memudahkan melepaskan produk panel. Lembar plastik vakum digunakan untuk menutup seluruh cetakan dan sisi luar lembar plastik direkatkan pada plat baja menggunakan sealing tape agar cetakan kedap udara. Hasil menunjukkan bahwa produk panel komposit yang diproduksi memiliki kualitas yang baik dengan ketebalan panel yang merata dan void (gelembung udara) yang sangat sedikti pada permukaan panel. Disamping itu, kekuatan tarik dan modulus elastisitas yang diperoleh memiliki nilai yang relatif konstan.

Effect of peer ply and cooling rate on the tensile properties of Al/Gf/PP laminate prepared by hot pressing

The glass fiber-reinforced polypropylene/AA2024 hybrid composite (short for Al/Gf/PP laminate) was prepared by hot pressing with anodized 2024-T3 aluminum alloy as the skin and thermoplastic glass fiber-reinforced polypropylene core as a substitute of thermosetting glass fiber-reinforced polymer (based on epoxy) in order to increase the productivity and reduce the production costs during manufacturing procedure. The effect of peel ply (release cloth) and cooling rate on the laminate was investigated elaborately in this work. The orientation of glass fiber is mainly influenced by the peel ply structure, resulting in the resin’s overflow during hot press. Moreover, different cooling rates due to various cooling methods significantly affected both the degree of crystallization of the matrix and deformation of the metal skin during the curing process. Finally, a new peel ply structure was adopted to prevent the fiber from spilling during hot press process, while bubbles were allowed to flow out normally along with partial resin. Finally, a novel cooling method to reduce the degree of polypropylene crystallization and control metal deformation was proposed.

A new method for ultrasonic detection of peel ply at the bondline of out-of-autoclave composite assemblies

Out-of-autoclave materials have long been an established material system for secondary structural applications; however, recent advancements in material properties allow for more advanced structural applications. Even though certain out-of-autoclave properties have achieved parity with autoclaved cured materials, out-of-autoclave materials are cured at reduced temperatures and pressures resulting in less compaction and homogeneity. The consequence is extraneous ultrasonic signals, due to internal reflections and refractions that cause attenuation, potentially masking defects leading to unidentifiable indications. Advanced algorithms were developed to improve the signal to noise ratio between constituents of similar acoustic impedance in bonded out-of-autoclave carbon fiber reinforced polymer assemblies. Conventional ultrasonic nondestructive testing techniques and analysis software cannot consistently achieve signal to noise ratios that meet quantifiable rejection thresholds of accurately sized peel ply inserts at the bonded interface of composite assemblies. Ultrasonic pulse echo with full waveform capture was used to inspect a reference standard with peel ply inserts placed between the adhesive and three-dimensional-woven fabric preform. The ultrasonic signal was produced by a 64 element array transducer with a central frequency of 2.8 MHz. Waveform post-acquisition analysis with post processing software was used to analyze and enhance the signal response between the peel ply and the bondline resulting in the final algorithm. To verify the results, the signal to noise ratio of each insert was calculated for both the raw and processed data. As the measure of detectability, the method relies on principles of statistical measurement to provide an industry standard signal to noise response of 3:1.

Root Causes Analysis of Disbonds and Unidentifiable Ultrasonic Indications on Composite Materials

To ensure the structural integrity of composite materials, honeycomb sandwich panels must be inspected for defects with through-transmission ultrasonic testing. This study focused on the root causes analysis of disbonds and unidentifiable ultrasonic indications on composite materials. Disbonds is a condition that lack of adhesion between ply and core. Unidentifiable ultrasonic indications define as an unknown defect which can only identified after remove the peel ply. In this study, Minitab 16 and SPSS 16 are used in analyzing the potential causes that influences the disbonds and unidentifiable ultrasonic indications. The root causes of disbonds are core crush and core crack. Core crush and core crack may caused by high localized loads or high compaction pressure. For unidentifiable ultrasonic indications, the root cause is adhesive flood at core. Imperfect compaction pressure leads to the uneven flow of adhesive. For the area have lower pressure, probability for adhesive to accumulate is higher. Pleated or dog ear method can be implemented in bagging process to ensure better compaction mechanism. Operators must be trained and educated for better performance.