188 10 Failure Theories of a Lamina Maximum Stress Theory 一一一-Maximum Strain Theory 01 Fig.10.6.Comparison of the failure envelopes for the maximum stress theory and maximum strain theory 0102 吃 a)- 十 (10.16) The failure envelope for this theory is clearly shown in Fig.10.7.The advantage of this theory is that there is interaction between the stress com- ponents.However,this theory does not distinguish between the tensile and compressive strengths and is not as simple to use as the maximum stress theory or the maximum strain theory. 0 0 Fig.10.7.Failure envelope for the Tsai-Hill failure theory188 10 Failure Theories of a Lamina Fig. 10.6. Comparison of the failure envelopes for the maximum stress theory and maximum strain theory σ2 1  σF 1 2 − σ1σ2  σF 1 2 + σ2 2  σF 2 2 + τ 2 12  τ F 122 ≤ 1 (10.16) The failure envelope for this theory is clearly shown in Fig. 10.7. The advantage of this theory is that there is interaction between the stress com￾ponents. However, this theory does not distinguish between the tensile and compressive strengths and is not as simple to use as the maximum stress theory or the maximum strain theory. Fig. 10.7. Failure envelope for the Tsai-Hill failure theory