Terms to Know in Thermoset Composites

Understanding key terms related to the manufacturing, supply and fabrication of thermoset composites is essential for today’s professionals.

Thermoset composites, known for their durability, heat resistance, and structural integrity, play a crucial role in manufacturing high-performance components.

Explore some of the most important terms and concepts that underpin the world of this advanced material and learn how to navigate this complex and innovative field with confidence.

Whether you’re a seasoned engineer or new to the industry, mastering these terms will enhance your knowledge and ensure you stay informed about the latest advancements and best practices in thermoset composite technology.

Thermoset composites, known for their durability, heat resistance, and structural integrity, play a crucial role in manufacturing high-performance components. In this blog post, we’ll explore some of the most important terms and concepts that underpin the world of this advanced material, helping you navigate this complex and innovative field with confidence.

Whether you’re a seasoned engineer or new to the industry, mastering these terms will enhance your knowledge and ensure you stay informed about the latest advancements and best practices in thermoset composite technology.

 

List of Thermoset Composite Terms

Anisotropy: The property of being directionally dependent, implying different properties in different directions. In thermoset composites, anisotropy is often due to the orientation of the reinforcing fibers, resulting in varying mechanical properties in different directions.

Autoclave Curing: A high-pressure, high-temperature curing process used to fabricate high-performance thermoset composites. Ensures excellent consolidation and void-free parts, commonly used in aerospace and high-end automotive industries.

Chemical Resistance: The ability of a material to withstand exposure to various chemicals without degrading or losing its properties. Thermoset composites often exhibit high chemical resistance, making them suitable for harsh chemical environments.

Co-curing: The simultaneous curing of different components (such as skins and cores in a sandwich structure) in a single operation. Enhances the bond between the components and can streamline manufacturing.

Coefficient of Thermal Expansion (CTE): The rate at which a material expands with an increase in temperature. A low CTE in thermoset composites ensures better dimensional stability under thermal cycling.

Creep Resistance: The ability of a material to resist deformation under sustained load over time. High creep resistance means the material can maintain its shape and structural integrity even when subjected to long-term stresses.

Cure: The process of hardening a thermoset resin through heat, pressure, or the addition of curing agents. Curing transforms the resin from a liquid or soft state into a rigid, solid state.

Degree of Cure: The extent to which a thermoset resin has undergone the curing process. Often expressed as a percentage and affects the mechanical and thermal properties of the composite.

Dimensional Stability: The ability of a material to maintain its dimensions and shape when exposed to varying environmental conditions such as temperature and humidity. Ensures minimal expansion or contraction, preserving the performance and fit of the component.

Fatigue Resistance: The ability of a material to withstand repeated loading and unloading cycles without significant degradation in performance. High fatigue resistance ensures long-term durability under cyclic stresses.

Fiber Volume Fraction: The ratio of the volume of reinforcing fibers to the total volume of the composite material. Affects the overall mechanical properties of the composite, such as strength and stiffness.

Flexural Strength: The ability of a material to resist deformation under load in bending. A measure of the tensile and compressive strength of a material when subjected to a bending force.

Fracture Toughness: The ability of a material containing a crack to resist fracture. Critical for thermoset composites in applications where structural integrity and damage tolerance are important.

Glass Transition Temperature (Tg): The temperature at which a thermoset polymer transitions from a hard, glassy state to a soft, rubbery state. Marks the upper limit of the material’s operational temperature range.

Hardness: The measure of a material’s resistance to deformation, indentation, or scratching. Indicative of the surface durability and wear resistance of the material.

Hygrothermal Aging: The degradation of material properties due to the combined effects of moisture absorption and temperature variations. Essential for predicting the long-term performance of thermoset composites in humid and variable-temperature environments.

Impact Strength: The ability of a material to absorb energy and resist impact without fracturing. High impact strength is essential for applications where the material may be subjected to sudden forces or shocks.

Interlaminar Shear Strength (ILSS): The measure of the shear strength between the layers (laminae) of a composite material. High ILSS is important for the structural integrity of laminated thermoset composites.

Isothermal Curing: The process of curing a thermoset resin at a constant temperature. Helps in controlling the curing kinetics and achieving uniform properties throughout the composite part.

Microcracking: The formation of tiny cracks within the resin matrix of a composite material. Can occur due to thermal cycling, mechanical loading, or environmental exposure, affecting the composite’s mechanical properties and durability.

Post-Curing: The process of heating a thermoset composite part after the initial curing to further enhance its properties. Improves the material’s mechanical strength, thermal stability, and chemical resistance.

Prepreg: Fibers (such as carbon, glass, or aramid) that are pre-impregnated with a thermoset resin matrix in a partially cured state. Used in composite manufacturing to ensure consistent resin content and distribution.

Residual Stress: Stresses that remain in a thermoset composite material after the curing process due to differential shrinkage, thermal expansion, or chemical reactions. Can impact the mechanical performance and dimensional stability of the composite.

Resin Transfer Molding (RTM): A manufacturing process for fabricating thermoset composites where resin is injected into a mold containing dry fiber preforms. Allows for high-quality, complex-shaped composite parts.

Tensile Strength: The maximum stress that a material can withstand while being stretched or pulled before breaking. Indicates the material’s ability to bear loads and resist tension.

Thermal Conductivity: The property of a material that indicates its ability to conduct heat. Lower thermal conductivity is often desirable for applications requiring thermal insulation.

Thermo-oxidative Stability: The resistance of a thermoset composite to degradation at elevated temperatures in the presence of oxygen. Crucial for applications requiring long-term thermal exposure and oxidative environments.

Toughening Agents: Additives used in thermoset resins to improve their toughness and resistance to crack propagation. Common toughening agents include rubber particles, thermoplastic phases, and core-shell particles.

Viscoelasticity: The property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Important in understanding the response to stress, particularly under dynamic loading conditions.

Viscosity: The measure of a fluid’s resistance to flow. In the context of thermoset resins, viscosity is crucial during the processing and molding stages, affecting the ease of impregnation of fibers and the quality of the final composite part.

Wet-out: The process of fully impregnating reinforcing fibers with a resin to eliminate voids and achieve good fiber-matrix adhesion. Proper wet-out is essential for maximizing the mechanical properties of the composite.

Young’s Modulus: Also known as the modulus of elasticity, it is a measure of the stiffness of a material. Defined as the ratio of stress (force per unit area) to strain (proportional deformation) in a material in the linear elasticity regime of the stress-strain curve.