Search

Fiber reinforced thermoplastic composites are gaining popularity in many industries due to their short consolidation cycles, among other advantages over thermoset-based composites. Computer aided manufacturing processes, such as filament winding and automated fiber placement, have been used conventionally for thermoset-based composites. The automated processes can be adapted to include in situ consolidation for the fabrication of thermoplastic-based composites. In this paper, a detailed literature review on the factors affecting the in situ consolidation process is presented. The models used to study the various aspects of the in situ consolidation process are discussed. The processing parameters that gave good consolidation results in past studies are compiled and highlighted. The parameters can be used as reference points for future studies to further improve the automated manufacturing processes.

One of the main downsides of fiber reinforced polymer composite laminates is their susceptibility to impact damage. Many different methods have been devised to either modify or engineer the composites to improve their impact resistance and tolerance. In this chapter, three types of engineered composites and their impact performances are presented and discussed. The engineered composites are (i) composites with core–shell polymer particles, (ii) composites with carbon nanotubes/nanofibers and (iii) composites with thermoplastic film interleaves. Core–shell polymer particles absorb large amounts of energy during impact, thus limit the damage done to the composite laminate. Carbon nanotubes and nanofibers have excellent stiffness and strength, making them suitable for reinforcing the interlaminar regions of composite laminates, leading to improved impact resistance. For composites with thermoplastic film interleaves, thermoplastic films with high intrinsic toughness modify the interlaminar regions of the composite laminate and enhance the overall toughness. The three types of engineered composites exhibit varying levels of improved impact performances compared to the unmodified composites. For each type of engineered composite, its impact response, the strengthening mechanisms and factors affecting its impact performance are deliberated.

The bonding between metal and carbon fiber-reinforced polymer (CFRP) composites is important in structures such as composite risers. Surface treatment of the metal is required to improve the metal-composite bonding. In this study, the effects of two mechanical surface treatment methods on the bonding between carbon/epoxy composites and aluminum are studied. The treatment methods investigated are grit blasting and grooving. Mechanical tests are performed and the test results are used with finite element simulations to study the failure and damage mechanisms at the composite-metal interface. The mechanical response and damage propagation at the metal-composite interface are modeled successfully using surface-based cohesive behavior. The finite element simulations gave insight into the way that the grooving treatment method improved the composite-metal bonding.

A model to estimate the tensile properties of carbon fiber-reinforced polymers (CFRP) based on their moisture contents and molecular structures is formulated and studied. In the proposed model, water molecules absorbed by polymers are considered congregated near the sub-micro-cavities within the polymers. The absorbed water molecules form hydrogen bonds with the polymer molecules and cause the regions around the sub-micro-cavities to have a reduced elastic modulus. The additive group contributions for polymers are used to determine the contributions of hydrophobic and hydrophilic functional groups separately. This enables the effects of water molecules on the mechanical properties of polymers to be quantified and estimated. For CFRP laminae, an additional effect of moisture on the fiber-matrix interface is considered in the calculation of the transverse tensile strength. The tensile properties are calculated using the proposed model agreed well with the experimental values. It is expected that the time and materials required to obtain the mechanical properties of CFRP exposed to humid environments can be reduced with the help of this model.