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Based on the surface analysis of carbon fiber, an epoxy resin matrix with good wettability to carbon fibers had been developed and studied, and the influence of winding tension on the interface and mechanical properties of the composite were studied. The surface morphology of carbon fiber and the active functional groups of sizing agent were analyzed. In order to form a good interface combination, the wettability between carbon fibers and epoxy resin matrix was characterized by dynamic contact angle. The winding tension played an important role in the mechanical properties of composites. Therefore, a kind of carbon fiber reinforced composites, Naval Ordnance Laboratory (NOL) rings were fabricated using different winding tensions. Particularly, when the winding tension was 30 N, the interfacial bonding between carbon fibers and resin matrix was the most compact and firm. The tensile strength and interlaminar shear strength (ILSS) of NOL rings reached high values, 2712 MPa and 75 MPa, respectively.

The addition of polyamide veil (PAV) to the interlaminar area of carbon fiber (CF) fabric/epoxy composites can effectively increase their toughness with high accuracy. Vacuum-assisted resin infusion (VARI) was used to fabricate composite structures. VARI was applied to obtain a PAV, which is an interleaf between fabric piles of CFs. The thermoplastic PAV was dissolved in epoxy when the PAV was cured at high temperature. A phase-separated morphology with a PAV-rich secondary phase was formed during the curing process. Experimental results indicated that compression after impact (CAI), which is the average value of CAI, increased by threefold when two layers of PAV were added. The thermal and mechanical characteristics of the composite were analyzed and compared at room temperature and high-temperature wet conditions.

This study demonstrated that the addition of dissolvable polyether sulfone fibers to the interlaminar area of carbon fiber/epoxy composites can effectively increase the toughness with very high accuracy. Resin film infusion (RFI) is used to fabricate composite structures. RFI was applied to obtain polyether sulfone as an interleaf of chopped fibers between fabric piles of carbon fibers. The thermoplastic polyether sulfone fiber dissolved in the epoxy when it was cured at a high temperature. A phase-separated morphology with a polyether sulfone-rich secondary phase was formed during the curing process. Experimental results indicated that G Ic, which is the average value of Mode-I fracture toughness, was increased fivefold with the addition of 10 wt% polyether sulfone fiber (with respect to the gross content of the matrix). No detrimental effects were observed in other characteristics such as thermal stability, Young’s modulus, and tensile strength. In addition, the thermal and mechanical characteristics of neat epoxy–polyether sulfone blends were analyzed for comparison.

Novel benzoxazine (BOZ)/bismaleimide (BMI)/2,2′-diallylbisphenol A (BA), with a multiphase structure, was successfully prepared under the catalysis of methyl p-toluenesulfonate (PTSM) through reaction-induced phase separation. The curing reaction of BOZ with BMI and ring-opening polymerization of BOZ under the catalysis of PTSM were studied by Fourier transform-infrared spectroscopy and differential scanning calorimetry analyses, respectively. Mechanical measurements, thermogravimetric analysis, and microanalyses were conducted to assess the toughness and morphology of the composite. The reaction between BOZ and 4,4′-bismaleimidodiphenyl methane (BDM) occurs at a relatively high temperature. The ring-opening reaction of BOZ starts at a low temperature of 100°C because of the catalysis of PTSM. The BOZ/BDM/BA system with an appropriate amount of BOZ significantly improves the impact strength and flexural strength compared with those of the BA/BDM resin. The BOZ/BDM/BA system with PTSM also features high impact strength and flexural strength. Scanning electron microscopy images and energy-dispersive spectroscopy results show that BOZ-rich phase is dispersed in BDM-rich phase in the BOZ/BDM/BA system with PTSM. Thermogravimetric data show that the BOZ/BDM/BA blend with a multiphase structure exhibits superior thermal resistance to those of the BOZ/BDM/BA and BA/BDM resins. The formation mechanism of the ternary system under the catalysis of PTSM is elucidated with Gibbs free energy theory.

A novel bismaleimide matrix resin of amino-polythioetherimide (PTEI-N)/4,4′-bismaleimidodiphenyl methane (BDM)/2,2′-diallylbisphenol A (BA) was prepared. Mechanical measurements, dynamic thermomechanical analysis, thermogravimetric analysis (TGA), and microanalyses were conducted to assess the mechanical properties, thermal resistance, and morphology of the modified resin. Results demonstrate that the addition of PTEI-N has significant effects on the mechanical properties of the BDM/BA system. Compared with the pure BDM/BA resin, the PTEI-N/BDM/BA system markedly improves the tensile strength, flexural strength, and impact strength, given an appropriate amount of PTEI-N. Scanning electron microscopic and energy-dispersive spectroscopic results show that PTEI-N is distributed uniformly in the BDM/BA system, and the interfacial compatibility between the PTEI-N and BDM/BA phase is excellent. TGA shows that the BDM/BA resin continues to exhibit good thermal resistance with a suitable dosage of PTEI-N. These changes in properties are closely correlated with the addition of PTEI-N. The PTEI-N/BDM/BA resin system shows potential applications in many fields.

Graphene oxide (GO) sheets have captured the attention of the scientific community because of its excellent performance and applicability. Hence, studying its reinforcing effects on polyimide (PI) resin is an important research topic. In this study, samples of GO-reinforced PI resin were prepared by hot pressing. The effects of GO as nanofiller on the structure and morphology as well as on the mechanical, thermal, and dielectric properties of the GO/PI resin composites were investigated carefully to provide a practical strategy for the use of the polymer-based composites. The GO nanosheets were dispersed uniformly into the PI matrix by ultrasonication, as illustrated by scanning electron microscopic images (SEM). Compared with pure PI, the GO/PI resin composite loaded with 1 wt% GO showed improved tensile strength by 38.9%, flexural strength by 24.8%, and impact strength by 40.7%. Dynamic mechanical analysis test showed that the addition of GO (1 wt%) increased the glass transition temperature by nearly 9.1°C. In addition, the thermal stability and the dielectric constant were also enhanced by adding only a small amount of GO. This approach provides a strategy for developing simple and cost-effective GO-polymer resin composite materials.

Phenolic cryogel plates (PCPs) and three-dimensional braided glass fiber reinforced phenolic cryogel composite plates (PCCPs) were successfully fabricated by microemulsion-templated sol gel polymerization and freeze-drying methods. Then, pore morphology, mechanical and thermal properties of the composites were investigated. The experimental results showed that the aerogels made by freeze-drying method had the best microstructure. In addition, it was discovered that the compressive and tensile strength of the cryogel plates had equally increased for approximately 8 and 30 times after compounding with glass fiber. Simultaneously, the mechanical properties of the 20 wt% and 25% solid content (PCPs) achieved the optimal value compared with PCPs of other contents. Moreover, it was found that the cryogels had excellent thermostability, and their thermal conductivity decreased with the reducing of the solid contents, what's more, the joining of glass fiber had the increased the composites’ thermal conductivity to some degree. Finally, considering the requirement of low density, good mechanical and thermal performance, the 20 wt% solid content PCCP had the best comprehensive performance compared with others.

Polylactic acid (PLA) based multilayer-structured foam biocomposites were prepared in a three-step process. In step 1, PLA plastic particles mixed with hollow glass beads (HGB) and other additives were blended, pelletized, and foamed and turned into plies using compression moldings. During step 2, the plies were stacked alternately and glued together with glass-fiber cloth reinforced PLA interlayers. The result is a multilayer-structured ply. In step 3, environmental sound-absorbing cotton was spliced on both sides of the ply to obtain the desired foam biocomposites. Then, foam morphology, and both mechanical and acoustical properties of the plies were investigated using a scanning electron microscope, a universal testing machine and a multianalyzer system. Our experimental results indicate that the compressive strength and acoustical properties of the plies made during the first step perform best when the mass fraction of HGB is 15%. We then compared a ply made in the first step with the multilayer-structured ply made in the second step. We found that the mechanical and sound insulation properties became more uniform after the addition of a PLA layer. We also found that the sound-absorbing cotton improved sound insulation by about 30%. The biocomposites achieved the best mechanical and acoustical properties after careful consideration of several factors.

A novel composite of polythioetherimide (PTEI)/bismaleimide (BMI)/2,2′-diallylbisphenol A (BA) was prepared. Mechanical measurements, dynamic thermomechanical analysis, and microanalysis were conducted to assess the toughness and morphology of the composite. Results demonstrate that the addition of PTEI has significant effects on the mechanical properties of the BMI/BA system. Compared with the BMI/BA resin, the PTEI/BMI/BA system significantly improves the impact strength and bending strength, given an appropriate amount of PTEI. Scanning electron microscope (SEM) images and energy dispersive spectroscopy results show that PTEI is distributed uniformly in the PTEI/BMI/BA system and that the interfacial compatibility between the PTEI and BMI/BA phase is excellent. Thermogravimetric and dielectric analyses were also conducted to infer the thermal and dielectric properties of the composite. With a suitable addition of PTEI, the BMI/BA resin still exhibits good thermal resistance and dielectric constant and loss values of the blends still retain good stability in a frequency band from 10 MHz to 60 MHz. All these changes in properties are closely correlated with the addition of PTEI.