Experimental Investigation of the Interaction of Moisture, Low Temperature, and Low Level Impact on Graphite/Epoxy Composites.
Abstract
Effect of low speed impact damage on composite materials is a new and potentially significant design condition for high performance systems. In metallic structure, damage due to tool drop, small rock impact and hail (while on the ground) did not constitute a damage of major concern. However, composites generally exhibit little inelastic ductility, are sensitive to secondary stresses, and are susceptible to splitting and delamination with cracks often propagating in the fiber direction through debonding. Upon failure, energy absorption is low. Due to these fracture characteristics and the low strain to failure, composite materials generally exhibit lower impact resistance than the metals typically used for aircraft construction. Environmental exposure may aggravate the deleterious effects of impact damage. It is well known that the mechanical properties of a polymeric matrix are susceptible to environmental degradation. Matrix cracking resulting from impact, loading or thermal cycling may provide pathways for moisture which can enter by laminar flow much more rapidly than by diffusion upon subsequent exposure to high humidity environment. Detrimental effects may also be expected because the internal tensile stress in the matrix increases with decreasing temperature, promoting crazing and the formation of microvoids.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1980
- Accession Number
- ADA097706
Entities
People
- K. N. Lauraitis
- P. E. Sandorff
Organizations
- Lockheed Martin